New planing hull design.
Followers (3)
@AlessandroSPQR The lower the better to some extent, though if you go too low you have to deal with water ingress through the prop tube and may have difficulty in mounting the motor low enough, due partly to how you are going to mount the motor - you will of course deal with this when you are working on your drawings. Many of my Faireys (planing hulls) are 12 degrees which matches the full-size boats and the Swordsman for which I showed the drawing is 11 degrees - this uses a 42mm diameter motor but it is a bigger model than yours at 838mm and so I could use a longer prop shaft to keep the angle down. And lowering the motor then affects the position of the prop and it's clearance. It is all a bit of a balancing act and a compromise - will be interesting to see what you come up with.
As I said, 42mm diameter is bigger than you really need, but your choice obviously, and for that size and bigger the choice of motors becomes less and less and the kV also and so you need bigger (more volts) and more expensive batteries. Whereas the 35mm gives plenty of options. This leads me to believe it would be difficult to find a suitable brushless motor for a big planing model, say over 50"/1270mm, as motors sold for boats don't have a high enough kV to produce a higher enough rpm unless say a pully system is used. Maybe have to look outside of model boat motors?
Anyway, for your research purposes here is a link to Overlander Batteries showing what motors they have. They have a smaller range of outrunners than they used to have, though still suitable for my needs, and have added more inrunners.
https://overlander.co.uk/
Unless you have any specific questions I won't say anymore for now and leave you to get on with your designing!
As I said, 42mm diameter is bigger than you really need, but your choice obviously, and for that size and bigger the choice of motors becomes less and less and the kV also and so you need bigger (more volts) and more expensive batteries. Whereas the 35mm gives plenty of options. This leads me to believe it would be difficult to find a suitable brushless motor for a big planing model, say over 50"/1270mm, as motors sold for boats don't have a high enough kV to produce a higher enough rpm unless say a pully system is used. Maybe have to look outside of model boat motors?
Anyway, for your research purposes here is a link to Overlander Batteries showing what motors they have. They have a smaller range of outrunners than they used to have, though still suitable for my needs, and have added more inrunners.
https://overlander.co.uk/
Unless you have any specific questions I won't say anymore for now and leave you to get on with your designing!
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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@Ronald You certainly would be! There's enough variables as it is! Most of my models are scale/near scale and for the planing models I basically just choose what looks right! I use 3 bladed Standard Scale bronze from Prop Shop. If the optimum is say 35mm diameter I don't think it will make a great deal of difference to the performance if I went 5mm either way as I only want decent not crazy speed. Different for race boats of course as you want to maximise speed or use a big lake where you can use higher speeds.
https://www.prop-shop.co.uk/products.php?cat=standard-scale
For my slower, non-planing models I use the Raboesch 3 Blade Metric props.
https://raboeschmodels.com/product/162-3-blade-metric/
I know some folks experiment with different props; number of blades, diameter and pitch but that is often after they have chosen the motor.
https://www.prop-shop.co.uk/products.php?cat=standard-scale
For my slower, non-planing models I use the Raboesch 3 Blade Metric props.
https://raboeschmodels.com/product/162-3-blade-metric/
I know some folks experiment with different props; number of blades, diameter and pitch but that is often after they have chosen the motor.
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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@ChrisF
Hi Chris, I wanted to write this message after completing the motor-shaft-propeller position drawings, to show you what solutions I'd found to stay under a 10° angle (I know you said 12°).
However, while I was looking for electric motors with the right specifications (I agree with you that the best option is to oversize everything to avoid high temperatures rather than adopt cooling systems), I encountered some problems.
For example, on Aliexpress I find class 42 motors (so with a 42 mm case diameter) 4240, 4250, and 4260, but none with 1000 or 1200 KV; the 42s only reach 700 or 900 KV.
With the outrunner motors I found on Aliexpress, I can't reach the required RPM (with 3S/11.1 Volts I would reach the theoretical maximum of 8880 with 800 KV); And the idea was to power a 3S electric motor even though it supports 4S, so as not to overheat it.
As I said, I'm only looking at the maximum dimensions now, so I'm not researching the 35 class because if a 42 motor fits, I'll be able to fit even smaller ones, like the 35 class ones.
However, I've had trouble finding even 35 class motors with 12,000 KV.
I read the article you linked. It's well-written and very helpful. Many guides give the same advice, but the problem is that no one knows how much power should be required for a given model with certain weight and shape characteristics. If this data were known (which no one does, although someone has tried to draw up indicative tables), it would be easy to do all the subsequent calculations.
I'll continue drawing to show you the various solutions.
If I continue drawing, I can start building even before purchasing the individual components.
Hi Chris, I wanted to write this message after completing the motor-shaft-propeller position drawings, to show you what solutions I'd found to stay under a 10° angle (I know you said 12°).
However, while I was looking for electric motors with the right specifications (I agree with you that the best option is to oversize everything to avoid high temperatures rather than adopt cooling systems), I encountered some problems.
For example, on Aliexpress I find class 42 motors (so with a 42 mm case diameter) 4240, 4250, and 4260, but none with 1000 or 1200 KV; the 42s only reach 700 or 900 KV.
With the outrunner motors I found on Aliexpress, I can't reach the required RPM (with 3S/11.1 Volts I would reach the theoretical maximum of 8880 with 800 KV); And the idea was to power a 3S electric motor even though it supports 4S, so as not to overheat it.
As I said, I'm only looking at the maximum dimensions now, so I'm not researching the 35 class because if a 42 motor fits, I'll be able to fit even smaller ones, like the 35 class ones.
However, I've had trouble finding even 35 class motors with 12,000 KV.
I read the article you linked. It's well-written and very helpful. Many guides give the same advice, but the problem is that no one knows how much power should be required for a given model with certain weight and shape characteristics. If this data were known (which no one does, although someone has tried to draw up indicative tables), it would be easy to do all the subsequent calculations.
I'll continue drawing to show you the various solutions.
If I continue drawing, I can start building even before purchasing the individual components.
Liked by ChrisF
@canabus
Hi Harry, thanks so much for the information.
I didn't have any major problems with permanent magnet brushed motors, either in theory or in practice. We've actually discussed them extensively on several occasions.
Some time ago, I thought it was necessary to summarize some basic concepts for everyone's benefit in the link at the end of this text. Let me know what you think.
As for brushless motors, however, I only have theoretical knowledge.
It's obvious—and this has been reiterated many times—that brushless motors, given the same size and voltage, are much more powerful than brushed motors. I've always used brushed motors because they're much cheaper (in fact, I've gotten many for free), and I didn't need them to be lighter or have greater power.
Now I absolutely have to consider them because I'm building a planing hull.
https://model-boats.com/wiki/147457
Hi Harry, thanks so much for the information.
I didn't have any major problems with permanent magnet brushed motors, either in theory or in practice. We've actually discussed them extensively on several occasions.
Some time ago, I thought it was necessary to summarize some basic concepts for everyone's benefit in the link at the end of this text. Let me know what you think.
As for brushless motors, however, I only have theoretical knowledge.
It's obvious—and this has been reiterated many times—that brushless motors, given the same size and voltage, are much more powerful than brushed motors. I've always used brushed motors because they're much cheaper (in fact, I've gotten many for free), and I didn't need them to be lighter or have greater power.
Now I absolutely have to consider them because I'm building a planing hull.
https://model-boats.com/wiki/147457
Next is to post the best prop/pitch for each motor based upon type of boat being built.
Tugboat vs pleasure cruiser vs speedboat
Maybe I am opening up a can if worms !
Tugboat vs pleasure cruiser vs speedboat
Maybe I am opening up a can if worms !
Liked by ChrisF and AlessandroSPQR and
Useful information there Harry. Good to see that 35mm motors of both types will fit the same mount. So, Alessandro, you can use the 500 - 600 right-angle motor mount as I do, the one Bob uses or some folks use their own design and/or mount in a similar way to aircraft i.e. on a bulkhead or former.
That information clearly shows the different power output for both types and confirms what I said that with brushless, it almost doesn't matter what power output you choose for a given diameter as even the lowest would be more than an equivalent brushed. More power is probably good as heat production goes though as the motor wouldn't be working hard. That's my philosophy; powerful (over-powered) motor, decent ESC and battery and everything stays cool and so no water-cooling. Racing speeds for lap after lap will be a different story though. Worth noting that quoted power outputs for brushless motors are if using the maximum voltage batteries allowed, so really only any good for comparative purposes.
Harry, do you have any planing boats using brushed motors?
Here is another useful article; see the table at the end for suggested brushed motor sizes for different models. I had an 850 and lead-acid battery in my 48 inch Fairey Huntsman 31 and the performance was adequate at best, no pretty poor really! Sold it to a club member who put a brushless motor in it and it performed as it should.
https://www.modelboats.co.uk/1112/but-i-dont-understand-electronics/
That information clearly shows the different power output for both types and confirms what I said that with brushless, it almost doesn't matter what power output you choose for a given diameter as even the lowest would be more than an equivalent brushed. More power is probably good as heat production goes though as the motor wouldn't be working hard. That's my philosophy; powerful (over-powered) motor, decent ESC and battery and everything stays cool and so no water-cooling. Racing speeds for lap after lap will be a different story though. Worth noting that quoted power outputs for brushless motors are if using the maximum voltage batteries allowed, so really only any good for comparative purposes.
Harry, do you have any planing boats using brushed motors?
Here is another useful article; see the table at the end for suggested brushed motor sizes for different models. I had an 850 and lead-acid battery in my 48 inch Fairey Huntsman 31 and the performance was adequate at best, no pretty poor really! Sold it to a club member who put a brushless motor in it and it performed as it should.
https://www.modelboats.co.uk/1112/but-i-dont-understand-electronics/
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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Hi All
The standard 540 brush motor weight is about 185 grams and 35mm in diameter.
Depending on the number of turns on the motor is the number of revs.
e.g. 13 turns 32,500 rpm on 7.2 volts (unloaded).
21 turns 20,000
35 turns 13,000
45 turns 9,500
55 turns 7,700
65 turns 7,000
80 turns 5,500
To convert to brushless motor divide the rpm by the voltage.
eg 45 turn brush motor would about a 1250kv brushless motor but the power difference about 90 Watts to 800Watts .
The brushless weight is less by about 50 grams.
The good news is the 35 mm motors both fit the same mount with the same size screw holes.
Battery weight eg a 2400mah 7.2 volt is about 300 grams and a 2S (7.2 volt) 30C is about 140 grams.
Battery size is about the same but the Lipo is a lot thinner.
Battery placement can change the balance point of the boat without trim tabs.
I am not a great fan of trim tabs !!!!!
I use full metal uni-joints between motor and shaft with a bit of grease.
Adding heat shrink tube over them to keep the grease in and cut down the noise.
Harry
The standard 540 brush motor weight is about 185 grams and 35mm in diameter.
Depending on the number of turns on the motor is the number of revs.
e.g. 13 turns 32,500 rpm on 7.2 volts (unloaded).
21 turns 20,000
35 turns 13,000
45 turns 9,500
55 turns 7,700
65 turns 7,000
80 turns 5,500
To convert to brushless motor divide the rpm by the voltage.
eg 45 turn brush motor would about a 1250kv brushless motor but the power difference about 90 Watts to 800Watts .
The brushless weight is less by about 50 grams.
The good news is the 35 mm motors both fit the same mount with the same size screw holes.
Battery weight eg a 2400mah 7.2 volt is about 300 grams and a 2S (7.2 volt) 30C is about 140 grams.
Battery size is about the same but the Lipo is a lot thinner.
Battery placement can change the balance point of the boat without trim tabs.
I am not a great fan of trim tabs !!!!!
I use full metal uni-joints between motor and shaft with a bit of grease.
Adding heat shrink tube over them to keep the grease in and cut down the noise.
Harry
Written some years ago, 2011 in fact (!) but a good article on brushless motors and still relevant in many ways. The power of brushless motors is often given nowadays, certainly as regards those from Overlander Batteries. Not sure how relevant knowing the power is unless you can do complex calculations to determine what a particular model needs. Though if I'm looking at two or more motors of a suitable, similar size I will look at the power output and usually go for the most powerful to be on the safe side as I don't build my models particularly light. But having said that, given the power of brushless motors I don't think you can go far wrong as long as you choose a suitable diameter motor and kV to achieve the rpm required. It doesn't cost much more to over power/err on the side of safety (within reason) a model compared with a full-size boat and that is what I tend to do. In that respect I can't wait to see how my Swordsman performs as that is getting to be a quite heavy boat!
Alessandro, maybe as part of your testing, it would be interesting to see how 35mm diameter motors with widely differing power outputs actually perform?
Actually, I'm going to do a bit of experimenting myself! I think the motor I recommended to you will be better than the one I've got for my Huntsman 31. This was bought some years ago not long after I joined the hobby and is an Overlander Tornado Thumper V3 3548/05 900KV which has a lower kV than I usually recommend and on 3S doesn't really provide enough rpm. I've tried the same in the Huntsman 28 though and that performs well, I rarely use full throttle though as our lake isn't that big but it's fast enough anyway. The motor is powerful at 710 watts and I'm guessing will lose less power than the theoretical 20% between loaded and unloaded that we work on?
https://www.modelboats.co.uk/935/going-brushless/
Alessandro, maybe as part of your testing, it would be interesting to see how 35mm diameter motors with widely differing power outputs actually perform?
Actually, I'm going to do a bit of experimenting myself! I think the motor I recommended to you will be better than the one I've got for my Huntsman 31. This was bought some years ago not long after I joined the hobby and is an Overlander Tornado Thumper V3 3548/05 900KV which has a lower kV than I usually recommend and on 3S doesn't really provide enough rpm. I've tried the same in the Huntsman 28 though and that performs well, I rarely use full throttle though as our lake isn't that big but it's fast enough anyway. The motor is powerful at 710 watts and I'm guessing will lose less power than the theoretical 20% between loaded and unloaded that we work on?
https://www.modelboats.co.uk/935/going-brushless/
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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@ChrisF
Top.
Thank you so much for your long, clear, and thorough answers (just the way I like them).
I find this information incredibly useful.
My next step will be to conduct online market research on the brushed and brushless outrunner motors that emerged from my discussions with you.
From this research, I'll obtain dimensions and weights. With the dimensions of the possible motors, I'll design one or more solutions for the electric motor-shaft-propeller system.
It's possible (and I sincerely hope so) that the design for an electric motor setup will work for several different models. This would allow me to test more than one once the hull is completed.
I'll update you as soon as I have time to draw.
Top.
Thank you so much for your long, clear, and thorough answers (just the way I like them).
I find this information incredibly useful.
My next step will be to conduct online market research on the brushed and brushless outrunner motors that emerged from my discussions with you.
From this research, I'll obtain dimensions and weights. With the dimensions of the possible motors, I'll design one or more solutions for the electric motor-shaft-propeller system.
It's possible (and I sincerely hope so) that the design for an electric motor setup will work for several different models. This would allow me to test more than one once the hull is completed.
I'll update you as soon as I have time to draw.
As you say, you don't need to buy a motor just yet but it might be a good idea to decide on one as a starting point so that you can find out the length of the shaft. They probably don't vary that much but you need to check, as along with the coupling, it determines the position of the motor mount and the length of the prop shaft.
Haven't heard of GARTT but I'm pretty sure that Bob and Harry have used Surpass Hobby. I standardised on Overlander after my first one as I knew I was going to build a number of models and in some cases overlapping. They are also a UK supplier though and have detailed information on their site (so good for reference) but of course the motors are made in China!
Further off, but for ESCs I use HobbyWing Quicrun and Seaking with the Quicrun being used by Harry. Bob has/is using various but is going to try a Shark soon. They don't weigh that much anyway so differences will be pretty insignificant. The heaviest items, as you know being the motor (certainly the bigger diameters like 42mm which you don't really need), battery, prop shaft and servo. The rudder to some extent but still quite light.
Haven't heard of GARTT but I'm pretty sure that Bob and Harry have used Surpass Hobby. I standardised on Overlander after my first one as I knew I was going to build a number of models and in some cases overlapping. They are also a UK supplier though and have detailed information on their site (so good for reference) but of course the motors are made in China!
Further off, but for ESCs I use HobbyWing Quicrun and Seaking with the Quicrun being used by Harry. Bob has/is using various but is going to try a Shark soon. They don't weigh that much anyway so differences will be pretty insignificant. The heaviest items, as you know being the motor (certainly the bigger diameters like 42mm which you don't really need), battery, prop shaft and servo. The rudder to some extent but still quite light.
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by Ronald and AlessandroSPQR
Motors
As regards brushed motors I don't know that much about them and if I wanted to use one I'd have to research first. I came late to the hobby, around 9 years ago, by which time brushless had become well established and largely understood so I didn't see any need to consider brushed. I do have brushed in a couple of plastic ready-to-run boats and they perform well. As long as a motor is chosen that provides the required rpm (around 12k. unloaded) for the battery being used then they are fine. Problem with them years ago is that performance boats needed heavy lead-acid batteries and the performance was often poor. With NiMh and LiPo this isn't the case, certainly with mid-sized models.
Brushless - Yes, outrunners are the best choice for this type of model. Bob has tried an inrunner in one of his - I understand he's going to change it to an outrunner though if he hasn't already? Inrunners can be used with any type of prop but due to their lower torque and potential higher rpm they are more suited to high speed and race boats. The water-jet I bought for one of my future builds uses an inrunner with a water-jacket (as you mentioned) but I wouldn't use one in my type of sports cruiser builds.
I suggested that motor as it will give good performance on 3S/11.1 volts. 1250kV x 11.1v = 13875 rpm unloaded. Loaded = 13875 x 80% = 11100 rpm. This is slightly higher than needed (circa 10k. rpm) so yes, other options are perfectly fine - that's one reason I like brushless, the flexibility. Even higher kV if used on 2S/7.4 volts. Personally I don't like going above 3S (no scientific reason! Though cost comes into it) and that is my common size (apart from my smaller/slower builds) though I'm having to go 4S on Swordsman as the kV is only 800. It is a 42mm diameter motor as it is a heavy boat and I wanted plenty of torque. The kV tends to reduce for bigger diameter motors.
Water-cooling - if the motor and ESC isn't overworked by say using a prop that is too big then you shouldn't need it. I don't and as he says, Harry doesn't either. Bob does though in most of his models, partly because he has always done and also because, as I mentioned, he uses a motor mount with integral water-cooling along with water-cooled ESC's. So your choice on that - water-cooling does give you a water stream/outlet as per full-sized if you want it though!
Chris
As regards brushed motors I don't know that much about them and if I wanted to use one I'd have to research first. I came late to the hobby, around 9 years ago, by which time brushless had become well established and largely understood so I didn't see any need to consider brushed. I do have brushed in a couple of plastic ready-to-run boats and they perform well. As long as a motor is chosen that provides the required rpm (around 12k. unloaded) for the battery being used then they are fine. Problem with them years ago is that performance boats needed heavy lead-acid batteries and the performance was often poor. With NiMh and LiPo this isn't the case, certainly with mid-sized models.
Brushless - Yes, outrunners are the best choice for this type of model. Bob has tried an inrunner in one of his - I understand he's going to change it to an outrunner though if he hasn't already? Inrunners can be used with any type of prop but due to their lower torque and potential higher rpm they are more suited to high speed and race boats. The water-jet I bought for one of my future builds uses an inrunner with a water-jacket (as you mentioned) but I wouldn't use one in my type of sports cruiser builds.
I suggested that motor as it will give good performance on 3S/11.1 volts. 1250kV x 11.1v = 13875 rpm unloaded. Loaded = 13875 x 80% = 11100 rpm. This is slightly higher than needed (circa 10k. rpm) so yes, other options are perfectly fine - that's one reason I like brushless, the flexibility. Even higher kV if used on 2S/7.4 volts. Personally I don't like going above 3S (no scientific reason! Though cost comes into it) and that is my common size (apart from my smaller/slower builds) though I'm having to go 4S on Swordsman as the kV is only 800. It is a 42mm diameter motor as it is a heavy boat and I wanted plenty of torque. The kV tends to reduce for bigger diameter motors.
Water-cooling - if the motor and ESC isn't overworked by say using a prop that is too big then you shouldn't need it. I don't and as he says, Harry doesn't either. Bob does though in most of his models, partly because he has always done and also because, as I mentioned, he uses a motor mount with integral water-cooling along with water-cooled ESC's. So your choice on that - water-cooling does give you a water stream/outlet as per full-sized if you want it though!
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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Hi Alessandro
A lot to answer so I'll spread them out over a number of posts and in some cases make a short response followed by more detailed ones later as we go along in addition to posts by Harry and Bob who have more experience than me with different motors and props.
Prop Shaft, Prop and Motor Mounting
As I mentioned before ideally you want to aim around 12 degrees for the prop shaft. For that length of boat a 40mm prop is probably the maximum but it wouldn't hurt to allow for 45mm plus the required clearance to the hull. For mounting the motor I mainly use the right-angle alloy mounts (though unfortunately the supplier went out of business and no-one makes the exact same ones) or the nylon equivalents. Considering brushless for now, the mounts will take a number of different sized motors as long as the mounting hole centres are the same - if say you went for a smaller motor of say 28mm diameter you would need a smaller mount with holes closer together. I always make my mounts removeable and so if you did this you could change for different sized motors if required.
I've attached a drawing and photos from my Swordsman build so you can see what I'm talking about. I've used a 5mm prop shaft in that but for smaller builds like yours I use 4mm.
Bob is a big fan of using a different mount, which is water-cooled if needed, and allows him to change motors quickly and easily. But he does glue them in so they may not be suitable for some motors - Bob can provide more information on this.
When producing your drawing the motor position will be influenced by the type of coupling you intend to use. My drawing shows a short coupling though I have standardized on the longer ones with a rubber centre section and if using one of those you need to allow for it. You will note that my motor is quite a long way forward. It could be moved further back by shortening the prop shaft as long as you can accommodate the motor being lower - Bob tends to have his motors further back than me.
I do have one of the motor mounts that Bob uses, possibly for a future build, and I also used it to provide the drawings for Bob's Sprite build.
Chris
A lot to answer so I'll spread them out over a number of posts and in some cases make a short response followed by more detailed ones later as we go along in addition to posts by Harry and Bob who have more experience than me with different motors and props.
Prop Shaft, Prop and Motor Mounting
As I mentioned before ideally you want to aim around 12 degrees for the prop shaft. For that length of boat a 40mm prop is probably the maximum but it wouldn't hurt to allow for 45mm plus the required clearance to the hull. For mounting the motor I mainly use the right-angle alloy mounts (though unfortunately the supplier went out of business and no-one makes the exact same ones) or the nylon equivalents. Considering brushless for now, the mounts will take a number of different sized motors as long as the mounting hole centres are the same - if say you went for a smaller motor of say 28mm diameter you would need a smaller mount with holes closer together. I always make my mounts removeable and so if you did this you could change for different sized motors if required.
I've attached a drawing and photos from my Swordsman build so you can see what I'm talking about. I've used a 5mm prop shaft in that but for smaller builds like yours I use 4mm.
Bob is a big fan of using a different mount, which is water-cooled if needed, and allows him to change motors quickly and easily. But he does glue them in so they may not be suitable for some motors - Bob can provide more information on this.
When producing your drawing the motor position will be influenced by the type of coupling you intend to use. My drawing shows a short coupling though I have standardized on the longer ones with a rubber centre section and if using one of those you need to allow for it. You will note that my motor is quite a long way forward. It could be moved further back by shortening the prop shaft as long as you can accommodate the motor being lower - Bob tends to have his motors further back than me.
I do have one of the motor mounts that Bob uses, possibly for a future build, and I also used it to provide the drawings for Bob's Sprite build.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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Hello
I am using 1250kv motors (only two) in my 40" PT 109 with 37 mm 3 blade props.
Running on 2S 4000 mah Lipo batteries with 80 Amp 2-4S car ESCs.
No water cooling used.
The boat is a bit over scale speed.
Canabus
I am using 1250kv motors (only two) in my 40" PT 109 with 37 mm 3 blade props.
Running on 2S 4000 mah Lipo batteries with 80 Amp 2-4S car ESCs.
No water cooling used.
The boat is a bit over scale speed.
Canabus
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Hi Chris, I'm starting with this last hull; if necessary, I'll make another one with a different shape and proportions.
I want to start studying the positions for the engine and the propeller shaft, as well as its inclination (for now, we're using a single-propeller solution).
I was thinking about installing a three-bladed propeller with a diameter of 42 or 40 mm.
Be careful, it's clear that if I set up the propeller shaft for a 40 mm propeller, I can experiment with smaller but certainly not larger diameter propellers. So for now, I'm considering the larger diameter. I wouldn't go beyond 42 mm. What do you think?
Returning to the motor, in a previous message, you recommended an Overlander Tornado Thumper V3 3542/05 1250 KV.
This is very important to me because I already have a starting point.
Keep in mind that the advice I'm asking you and other ship modelers for right now isn't aimed at immediately purchasing an electric motor, but at studying its size and weight to accommodate it in the project.
Ideally, I'd like to find a position for the propeller shaft and the hull mounting arrangements that allows me to easily try out different types of motors and experiment with them.
BRUSHED MOTORS (should we just eliminate them?)
I know you're not hesitant about choosing brushless motors over brushed ones, but I'm asking you to make an effort to answer this question.
Given that when it comes to fast boats, brushless motors are almost a must for many reasons (high power and RPM that brushed motors can't reach, and low weight despite high power and RPM), I'd like to know if it's still possible to use a brushed motor for a ship model with a planing hull with these characteristics.
The reason is essentially economic, as brushless motors and their ESCs are much more expensive.
I wanted to draw your attention to two types of motors in particular.
How would you evaluate the choice of a 775 class brushed motor at 12V-16.8V powered by 4S LiPo or 12V NiMH, combined with a 42-45mm two-blade plastic or brass propeller (fully submerged)?
To save money, instead of the Graupner, I would choose a lower-cost equivalent. Or I could opt for an even more powerful brushed motor such as an 800 (or 850) class motor, a Graupner Speed 800 12V, or a high-performance industrial equivalent, powered above 12 volts.
BRUSHLESS MOTORS
Speaking of brushless motors, I think the choice should fall on outrunners.
In short, if you agree, I would discard any research into inrunner motors.
The high RPM of these motors, I believe (but correct me if I'm wrong) is incompatible with the choice of a submerged propeller, as in my case. I would have to install a surface propeller, which isn't a solution to my liking and isn't suitable (at least I don't think so) for the hull I've designed.
Well, staying on the subject of outrunner motors, I wanted to ask you: besides the Overlander Tornado Thumper V3 3542/05 1250 KV motor, do you have any other options?
Specifically, how do you rate these outrunner motors?
Brushless Outrunner class 3542 or 4240 (approximately 1000 - 1200 KV)
On Aliexpress, I'm leaning toward a 1200KV 4240 outrunner motor (Surpass Hobby or GARTT).
In this case, is it better to power it with a 3S LiPo (11.1V) to achieve approximately 11,000 - 13,000 rpm?
WATER COOLING JACKET AND OTHER COOLING SYSTEMS
Having always worked on displacement boats (with low speeds), I've never needed any cooling system, also because I always used oversized motors that weren't at their maximum power.
In the case of the motor you recommended (Overlander Tornado Thumper V3 3542/05 1250 KV) and the motors I mentioned, do you think a cooling system is mandatory?
If so, which one? Should I use it, since we're talking about outrunner motors, not inrunners?
I don't think a cooling jacket can be used for an outrunner motor. What method do you use?
Sorry for the many questions, but I invite you to answer me slowly and calmly.
If you'd like, please send me the commercial links for your options directly.
I want to start studying the positions for the engine and the propeller shaft, as well as its inclination (for now, we're using a single-propeller solution).
I was thinking about installing a three-bladed propeller with a diameter of 42 or 40 mm.
Be careful, it's clear that if I set up the propeller shaft for a 40 mm propeller, I can experiment with smaller but certainly not larger diameter propellers. So for now, I'm considering the larger diameter. I wouldn't go beyond 42 mm. What do you think?
Returning to the motor, in a previous message, you recommended an Overlander Tornado Thumper V3 3542/05 1250 KV.
This is very important to me because I already have a starting point.
Keep in mind that the advice I'm asking you and other ship modelers for right now isn't aimed at immediately purchasing an electric motor, but at studying its size and weight to accommodate it in the project.
Ideally, I'd like to find a position for the propeller shaft and the hull mounting arrangements that allows me to easily try out different types of motors and experiment with them.
BRUSHED MOTORS (should we just eliminate them?)
I know you're not hesitant about choosing brushless motors over brushed ones, but I'm asking you to make an effort to answer this question.
Given that when it comes to fast boats, brushless motors are almost a must for many reasons (high power and RPM that brushed motors can't reach, and low weight despite high power and RPM), I'd like to know if it's still possible to use a brushed motor for a ship model with a planing hull with these characteristics.
The reason is essentially economic, as brushless motors and their ESCs are much more expensive.
I wanted to draw your attention to two types of motors in particular.
How would you evaluate the choice of a 775 class brushed motor at 12V-16.8V powered by 4S LiPo or 12V NiMH, combined with a 42-45mm two-blade plastic or brass propeller (fully submerged)?
To save money, instead of the Graupner, I would choose a lower-cost equivalent. Or I could opt for an even more powerful brushed motor such as an 800 (or 850) class motor, a Graupner Speed 800 12V, or a high-performance industrial equivalent, powered above 12 volts.
BRUSHLESS MOTORS
Speaking of brushless motors, I think the choice should fall on outrunners.
In short, if you agree, I would discard any research into inrunner motors.
The high RPM of these motors, I believe (but correct me if I'm wrong) is incompatible with the choice of a submerged propeller, as in my case. I would have to install a surface propeller, which isn't a solution to my liking and isn't suitable (at least I don't think so) for the hull I've designed.
Well, staying on the subject of outrunner motors, I wanted to ask you: besides the Overlander Tornado Thumper V3 3542/05 1250 KV motor, do you have any other options?
Specifically, how do you rate these outrunner motors?
Brushless Outrunner class 3542 or 4240 (approximately 1000 - 1200 KV)
On Aliexpress, I'm leaning toward a 1200KV 4240 outrunner motor (Surpass Hobby or GARTT).
In this case, is it better to power it with a 3S LiPo (11.1V) to achieve approximately 11,000 - 13,000 rpm?
WATER COOLING JACKET AND OTHER COOLING SYSTEMS
Having always worked on displacement boats (with low speeds), I've never needed any cooling system, also because I always used oversized motors that weren't at their maximum power.
In the case of the motor you recommended (Overlander Tornado Thumper V3 3542/05 1250 KV) and the motors I mentioned, do you think a cooling system is mandatory?
If so, which one? Should I use it, since we're talking about outrunner motors, not inrunners?
I don't think a cooling jacket can be used for an outrunner motor. What method do you use?
Sorry for the many questions, but I invite you to answer me slowly and calmly.
If you'd like, please send me the commercial links for your options directly.
Looking good Alessandro. I think the revised bow is more suitable for a naval craft. The bow will cut through waves at lower speeds until it gets on the plane and will look better with a naval superstructure.
The immersed volume is a good result.
Chris
The immersed volume is a good result.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by hermank and AlessandroSPQR
Hi All
I found the best hull design for straight line and turning is the Spearfish hull.
Built in chine rails and two spray rails each side which finish short of the stern.
Also a curve up in the stern keel which I think helps with the turning.
We clocked my boat at 37KPH !!!
Harry
I found the best hull design for straight line and turning is the Spearfish hull.
Built in chine rails and two spray rails each side which finish short of the stern.
Also a curve up in the stern keel which I think helps with the turning.
We clocked my boat at 37KPH !!!
Harry
Liked by AlessandroSPQR and hermank
You may ask how you press the wrong button, easy if you have fat fingers on a smart phone, deadly combination
Ed
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Good evening to all naval modelers, I've been able to draw very little since last time.
This is the new hull.
I'm a little more convinced than the others, but I don't know if it will be the final one to work on.
It has the following characteristics:
- The ratio between width and length is 1:3.48 (so we're back to the value of 3.5)
- The slope of the bow has been accentuated.
- The transom has a reverse slope (this means the total length is greater than the length at the waterline)
- The shape of the hull (at the waterline it has a wedge shape). That is, it widens towards the stern while the lines on the deck become narrower.
The keel is parallel to the waterline, while the gunwale is sloped and rises slightly towards the bow.
I temporarily imagined a scale of 1:32 for this model.
So the actual hull would have been about 24 meters long.
The proportions are as follows:
Height 120 mm
Length 756 mm
Width 217 mm
Maximum draft 50 mm
Minimum draft 40 mm
The deadrise angle is 21 degrees.
The maximum immersed volume (with 50 mm draft)
is just over 3 dm3.
This is a satisfactory value, considering Chris's valuable information.
The red hull represents the immersed volume.
This is the new hull.
I'm a little more convinced than the others, but I don't know if it will be the final one to work on.
It has the following characteristics:
- The ratio between width and length is 1:3.48 (so we're back to the value of 3.5)
- The slope of the bow has been accentuated.
- The transom has a reverse slope (this means the total length is greater than the length at the waterline)
- The shape of the hull (at the waterline it has a wedge shape). That is, it widens towards the stern while the lines on the deck become narrower.
The keel is parallel to the waterline, while the gunwale is sloped and rises slightly towards the bow.
I temporarily imagined a scale of 1:32 for this model.
So the actual hull would have been about 24 meters long.
The proportions are as follows:
Height 120 mm
Length 756 mm
Width 217 mm
Maximum draft 50 mm
Minimum draft 40 mm
The deadrise angle is 21 degrees.
The maximum immersed volume (with 50 mm draft)
is just over 3 dm3.
This is a satisfactory value, considering Chris's valuable information.
The red hull represents the immersed volume.
Liked by Mike Stoney and hermank and
Hi Alessandro
It is difficult to see if the chine does rise upwards at the bow but I think I can make it out in Picture 4, so yes it is quite subtle. Are the chines rounded or as Bob said a soft chine?
The chines don't rise much on my Fairey Swordsman I suppose - see photo.
For interest also see the photos showing the comparison between my Swordsman 33 and Huntsman 31 hulls. The Swordsman is only 50mm longer but has a wider beam and almost parallel sides. The model is much bigger and heavier which is evident when just moving them around whilst I'm painting.
Chris
It is difficult to see if the chine does rise upwards at the bow but I think I can make it out in Picture 4, so yes it is quite subtle. Are the chines rounded or as Bob said a soft chine?
The chines don't rise much on my Fairey Swordsman I suppose - see photo.
For interest also see the photos showing the comparison between my Swordsman 33 and Huntsman 31 hulls. The Swordsman is only 50mm longer but has a wider beam and almost parallel sides. The model is much bigger and heavier which is evident when just moving them around whilst I'm painting.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by chugalone100 and hermank and
@ChrisF
Hi Chris
you wrote:
"""""""""""""Evening Alessandro - the drawing was primarily for interest and to show how twin prop shafts are often positioned rather than suggesting it was the best hull design for your needs.""""""""
Perfect, that's what I meant and thank you very much, you understood exactly what I needed.
you wrote:
""""""""""Whilst I have provided detailed information on some aspects, for example the vee hull and narrowing on plan as you move towards the stern I've been conscious of not trying to impose my own design preferences on you - not that, that would happen! Like me you ask for and research information and then make your own decisions based on what you want. Quite right!""""""""""""""
We're on the same page.
you wrote:
"""""""""""You don't need to worry about it planing. Anything from a flat bottom to a deep vee will do that, just that the deep vee will do it at a lower point below the water surface than a flatter hull.
I like this about your advice. The very direct approach based on experience. Clear and concise answers. Thank you so much. They are infinitely helpful. I'm taking advantage of your experience (I'm new to planing hulls). You can't understand how useful this simple statement of yours is for me to continue.
You wrote:
""""""""""I know that the drawing is to show the submerged volume, but don't forget that the chine and chine rail will curve upwards at the bow.""""""""""""
So I ask you: why does the drawing seem to you like there's no upward curvature? Is it too subtle?
Hi Chris
you wrote:
"""""""""""""Evening Alessandro - the drawing was primarily for interest and to show how twin prop shafts are often positioned rather than suggesting it was the best hull design for your needs.""""""""
Perfect, that's what I meant and thank you very much, you understood exactly what I needed.
you wrote:
""""""""""Whilst I have provided detailed information on some aspects, for example the vee hull and narrowing on plan as you move towards the stern I've been conscious of not trying to impose my own design preferences on you - not that, that would happen! Like me you ask for and research information and then make your own decisions based on what you want. Quite right!""""""""""""""
We're on the same page.
you wrote:
"""""""""""You don't need to worry about it planing. Anything from a flat bottom to a deep vee will do that, just that the deep vee will do it at a lower point below the water surface than a flatter hull.
I like this about your advice. The very direct approach based on experience. Clear and concise answers. Thank you so much. They are infinitely helpful. I'm taking advantage of your experience (I'm new to planing hulls). You can't understand how useful this simple statement of yours is for me to continue.
You wrote:
""""""""""I know that the drawing is to show the submerged volume, but don't forget that the chine and chine rail will curve upwards at the bow.""""""""""""
So I ask you: why does the drawing seem to you like there's no upward curvature? Is it too subtle?
Liked by chugalone100 and hermank
Evening Alessandro - the drawing was primarily for interest and to show how twin prop shafts are often positioned rather than suggesting it was the best hull design for your needs.
Whilst I have provided detailed information on some aspects, for example the vee hull and narrowing on plan as you move towards the stern I've been conscious of not trying to impose my own design preferences on you - not that, that would happen! Like me you ask for and research information and then make your own decisions based on what you want. Quite right!
You don't need to worry about it planing. Anything from a flat bottom to a deep vee will do that, just that the deep vee will do it at a lower point below the water surface than a flatter hull.
I know that the drawing is to show the submerged volume but don't forget that the chine and chine rail will curve upwards at the bow.
Chris
Whilst I have provided detailed information on some aspects, for example the vee hull and narrowing on plan as you move towards the stern I've been conscious of not trying to impose my own design preferences on you - not that, that would happen! Like me you ask for and research information and then make your own decisions based on what you want. Quite right!
You don't need to worry about it planing. Anything from a flat bottom to a deep vee will do that, just that the deep vee will do it at a lower point below the water surface than a flatter hull.
I know that the drawing is to show the submerged volume but don't forget that the chine and chine rail will curve upwards at the bow.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by chugalone100 and hermank and
Hello all the ship modelers, hello Chris and Bob.
Chris, I drew another hull as soon as I had time.
Of course, I'm not referring to the drawing you sent me, because I could faithfully trace it if I wanted, but I prefer to find a different shape. Your drawing was very helpful, however.
You can see the images of the new shape and the comparison with the other one (in blue).
Here's a summary of the changes:
I further reduced the length-to-width ratio, now the ratio is 3.2.
I redid the keel, which is now parallel to the waterline.
At the same time, the deck line rises toward the bow with a slight slope (less than one degree).
The bow has the same slope, but the waterline (the profile at the waterline) is less sharp and therefore has a larger surface area, resulting in more underwater volume.
I raised the freeboard.
The resulting hull is more likely than the other to plane, even at moderate speeds (at least I think so). It has a submerged volume exceeding 2 dm3 (2 kg of weight), but its shape is not very slender, a bit squat. I'm still not convinced by the result I have in mind.
I'll have to find a compromise between the hull with the aesthetic lines I like (very slender with an aggressive bow and a sharp profile, which, however, could be difficult to control when turning, could have difficulty planing immediately, or could lose control and capsize) and a hull with proportions more suited to motorized navigation at high scale speeds.
It's clear that the chosen prototype will then have to pass practical tests and still prove a failure.
I'll design other prototypes until I find the one I'm most satisfied with (and which will in any case be put to the test).
My next hull will have a steeper bow, a reverse-rake stern, and perhaps I'll return to the 3.5 length/beam ratio. To compensate for the inevitable reduction in submerged volume caused by these changes, I might increase the draft.
In the meantime, any comments or suggestions on the images I've attached are welcome.
Chris, I drew another hull as soon as I had time.
Of course, I'm not referring to the drawing you sent me, because I could faithfully trace it if I wanted, but I prefer to find a different shape. Your drawing was very helpful, however.
You can see the images of the new shape and the comparison with the other one (in blue).
Here's a summary of the changes:
I further reduced the length-to-width ratio, now the ratio is 3.2.
I redid the keel, which is now parallel to the waterline.
At the same time, the deck line rises toward the bow with a slight slope (less than one degree).
The bow has the same slope, but the waterline (the profile at the waterline) is less sharp and therefore has a larger surface area, resulting in more underwater volume.
I raised the freeboard.
The resulting hull is more likely than the other to plane, even at moderate speeds (at least I think so). It has a submerged volume exceeding 2 dm3 (2 kg of weight), but its shape is not very slender, a bit squat. I'm still not convinced by the result I have in mind.
I'll have to find a compromise between the hull with the aesthetic lines I like (very slender with an aggressive bow and a sharp profile, which, however, could be difficult to control when turning, could have difficulty planing immediately, or could lose control and capsize) and a hull with proportions more suited to motorized navigation at high scale speeds.
It's clear that the chosen prototype will then have to pass practical tests and still prove a failure.
I'll design other prototypes until I find the one I'm most satisfied with (and which will in any case be put to the test).
My next hull will have a steeper bow, a reverse-rake stern, and perhaps I'll return to the 3.5 length/beam ratio. To compensate for the inevitable reduction in submerged volume caused by these changes, I might increase the draft.
In the meantime, any comments or suggestions on the images I've attached are welcome.
Liked by SimpleSailor and chugalone100 and
I said previously that the weight of my Huntress 28 is 2.3kg. I've just calculated what the weight of my 1:12 model "should be" based on the weight of the full-sized boat and it works out to 2.15kg. So I'm pretty pleased with that especially as the weight of the full-sized one would increase once passengers, provisions and crates of champagne are taken into consideration.
Chris
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by hermank and AlessandroSPQR
Bob - it was the drawing but as we've said there shouldn't be much difference between builds from the drawing or kit. You know what, looking at the hull whilst painting it I wouldn't be surprised if it did need some ballast! Though it it only sits a bit high I won't bother. As we know for it's length of 33" (838mm) it has a wide beam of 11.4" (290mm) and a vee angle of 24 degrees - it gets away with this because it is so wide! This angle was often used in race boats. Will take me sometime to finish painting the hull as it's two-tone but I'm aiming to get it on the water soon - about 3 weeks I hope.
Alessandro - this actually is an interesting hull for you as it it very similar (though bigger) than your original design in that the beam doesn't narrow much as it approaches the stern and why it has a high submerged volume helped by the very deep vee hull. It has an S shaped bow as there is some flare which extends a small distance along the hull. I didn't really mention this one as I haven't even tried it in the bath yet so don't know how it sits.
Chris
Alessandro - this actually is an interesting hull for you as it it very similar (though bigger) than your original design in that the beam doesn't narrow much as it approaches the stern and why it has a high submerged volume helped by the very deep vee hull. It has an S shaped bow as there is some flare which extends a small distance along the hull. I didn't really mention this one as I haven't even tried it in the bath yet so don't know how it sits.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by chugalone100 and hermank and
Hi Chris.
Don't worry about the provenance too much, I am sure that this advice (given at the time) would apply equally to either of the 33" versions of the Swordsman.
I think we need to get our own 33" replica's into the water this year and find out for ourselves..............
Bob.
Don't worry about the provenance too much, I am sure that this advice (given at the time) would apply equally to either of the 33" versions of the Swordsman.
I think we need to get our own 33" replica's into the water this year and find out for ourselves..............
Bob.
Never too old to learn
Liked by hermank and AlessandroSPQR
Hi Bob - It's from the magazine article but can't remember if it related to the kit or drawing, I'll check tomorrow. But obviously the volume of each would be the same and the weight around the same even with the different constructions. I'm still amazed at the quoted ballast, it's not like it's a tug or something and you certainly don't want to be lugging that around!
It's inspiring me to get mine on the water to see how it sits and performs.
It's inspiring me to get mine on the water to see how it sits and performs.
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by hermank and AlessandroSPQR
@ChrisF Thats an interesting artefact Chris.
Did that little gem come with the original Aerokits Swordsman kit (I don't remember it) or did it come in the Model Boats review of their same size plans that were printed in the 1960's ?
It does seem like a lot of dead weight to "heft" around, but we forget just how light our Classic Model Power Boats were with just a (typical) 10cc glow engine and a small fuel tank of fuel to carry in the hull.
Our current brushless motors and LiPo battery packs with suitable ESC probably weight quite a lot more and should make quite a dent in the suggested additional ballast weight suggested?
Bob
Did that little gem come with the original Aerokits Swordsman kit (I don't remember it) or did it come in the Model Boats review of their same size plans that were printed in the 1960's ?
It does seem like a lot of dead weight to "heft" around, but we forget just how light our Classic Model Power Boats were with just a (typical) 10cc glow engine and a small fuel tank of fuel to carry in the hull.
Our current brushless motors and LiPo battery packs with suitable ESC probably weight quite a lot more and should make quite a dent in the suggested additional ballast weight suggested?
Bob
Never too old to learn
Liked by hermank and AlessandroSPQR
I am looking forward to seeing all of your calculations transformed into a working power boat hull that planes beautifully Alessandro.
Bob.
Bob.
Never too old to learn
Liked by hermank and AlessandroSPQR
Just checked and my length/beam ratio, 654/217mm at the waterline, is actually just over 3.0 which does surprise me as the H28 doesn't look particularly short and fat! Out of interest I will have to look at the Huntress which is basically the same hull which was extended by 5 feet for the H28. I'll look at the Swordsman 33 as well as that does have a wide beam. All interesting stuff!
I know you like doing your calculations and nothing wrong with that but don't get hung up on them. Whatever you design, being a planing hull, can't differ that much from all the designs and kits that have already been designed over the years which don't have a problem with weight. It tends to be small displacement models like destroyers that you have to be careful with isn't it? As I've said from my own experience, planing hulls are very buoyant and I don't think that even doubling up on components will make much difference. In fact I read the story that came with the release of the 1:12 Swordsman 33 model drawings years ago and it states that 7.5 pounds (3.4kg) of ballast is needed to get it down to the waterline!!! See text. I find that very hard to believe and look forward to trying mine in the bath! I have a feeling it will be fine without any ballast!
I know you like doing your calculations and nothing wrong with that but don't get hung up on them. Whatever you design, being a planing hull, can't differ that much from all the designs and kits that have already been designed over the years which don't have a problem with weight. It tends to be small displacement models like destroyers that you have to be careful with isn't it? As I've said from my own experience, planing hulls are very buoyant and I don't think that even doubling up on components will make much difference. In fact I read the story that came with the release of the 1:12 Swordsman 33 model drawings years ago and it states that 7.5 pounds (3.4kg) of ballast is needed to get it down to the waterline!!! See text. I find that very hard to believe and look forward to trying mine in the bath! I have a feeling it will be fine without any ballast!
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by hermank and AlessandroSPQR
Evening Alessandro - No photos! But 15 degrees makes sense, as I said you could increase to 20 degrees if you want to increase the submerged volume.
Details given of only one motor, but that is much too small - I'm using a bigger motor in my little 420mm long Faun! You need to be looking at something like a 3536/06 1300kV on 3S. Or similar with a minimum of 1100kV to give the required rpm.
https://overlander.co.uk/product/3536-06-1300kv-tornado-thumper-v3-brushless-outrunner-rc-motor/
"Here, with 300 mm of immersion (the 700 mm you mentioned seemed excessive), I would also like an immersed volume of at least 2 kg. That seems like a good compromise with these dimensions." I'm confused by what you mean with those figures?
Chris
Details given of only one motor, but that is much too small - I'm using a bigger motor in my little 420mm long Faun! You need to be looking at something like a 3536/06 1300kV on 3S. Or similar with a minimum of 1100kV to give the required rpm.
https://overlander.co.uk/product/3536-06-1300kv-tornado-thumper-v3-brushless-outrunner-rc-motor/
"Here, with 300 mm of immersion (the 700 mm you mentioned seemed excessive), I would also like an immersed volume of at least 2 kg. That seems like a good compromise with these dimensions." I'm confused by what you mean with those figures?
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by hermank and AlessandroSPQR
@ChrisF
Hi Chris, this photo shows the angle measurements. Since I'm not sure which one you were referring to, I included both.
One is 15°, the other 150° (obviously, since the plane angle is 180°).
Anyway, I think you wanted to know the 15° one.
Here are photos of the only two motors I currently own. I think they're a bit too small for this boat. I didn't buy them for this purpose, and I don't intend to burn them needlessly. Please let me know what you think.
Instructions at the end.
Thanks for sending me the photos of your model. Here, with 300 mm of immersion (the 700 mm you mentioned seemed excessive), I would also like an immersed volume of at least 2 kg. That seems like a good compromise with these dimensions.
Electric motor characteristics
A2212: Internal stator dimensions. Indicates a diameter of 22 mm and a height of 12 mm.
13T: Number of turns. This means the copper wire makes 13 turns around each pole.
1000KV: Speed constant (RPM/V). The motor theoretically rotates 1000 revolutions per minute for every applied volt at no load.
Outrunner configuration: The outer metal case rotates with the shaft.
Power requirements: Supports 2S to 3S LiPo batteries.
Operates at nominal voltages between 7.4V and 11.1V.
Current draw: Supports maximum loads of approximately 12A for 60 seconds.
Hi Chris, this photo shows the angle measurements. Since I'm not sure which one you were referring to, I included both.
One is 15°, the other 150° (obviously, since the plane angle is 180°).
Anyway, I think you wanted to know the 15° one.
Here are photos of the only two motors I currently own. I think they're a bit too small for this boat. I didn't buy them for this purpose, and I don't intend to burn them needlessly. Please let me know what you think.
Instructions at the end.
Thanks for sending me the photos of your model. Here, with 300 mm of immersion (the 700 mm you mentioned seemed excessive), I would also like an immersed volume of at least 2 kg. That seems like a good compromise with these dimensions.
Electric motor characteristics
A2212: Internal stator dimensions. Indicates a diameter of 22 mm and a height of 12 mm.
13T: Number of turns. This means the copper wire makes 13 turns around each pole.
1000KV: Speed constant (RPM/V). The motor theoretically rotates 1000 revolutions per minute for every applied volt at no load.
Outrunner configuration: The outer metal case rotates with the shaft.
Power requirements: Supports 2S to 3S LiPo batteries.
Operates at nominal voltages between 7.4V and 11.1V.
Current draw: Supports maximum loads of approximately 12A for 60 seconds.
Liked by hermank
Interested to see what they are.
I keep referring to my Huntsman 28 as it's not much longer at 711mm and the hull has similarities to the one you are designing. Also it's been on the water so I know how it sits. The draught is 30mm.
I've weighed it and it's 2.3kg.
Chris
I keep referring to my Huntsman 28 as it's not much longer at 711mm and the hull has similarities to the one you are designing. Also it's been on the water so I know how it sits. The draught is 30mm.
I've weighed it and it's 2.3kg.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
@ChrisF
Very interesting thoughts, Chris.
Tonight, in addition to measuring the angle (I don't think I'll be able to make any progress with the project), I'll show you the only two brushless motors I have (hoping to find their construction characteristics as well). I have a lot of brushless motors.
Very interesting thoughts, Chris.
Tonight, in addition to measuring the angle (I don't think I'll be able to make any progress with the project), I'll show you the only two brushless motors I have (hoping to find their construction characteristics as well). I have a lot of brushless motors.
Liked by hermank
One motor, or two or even more? Warning, most of what I'm going to say isn't based on scientific research! Just my thoughts based on logic and commonsense (I hope!)
Unless your planing model is really big, say over 4 foot (1200mm) then for good performance you don't need more than one brushless motor as that will provide all the speed that you need - for a brushed motor you are probably looking at a smaller boat but why go brushed at this size?
So, only reason for two or more motors is for differential steering, or more likely because it's a scale model and the full-size boat has multiple engines.
Twin motors will give you more acceleration (if you need it!) but little more in top speed (unlike with full-size), well usable anyway, as the models we are considering, as opposed to race boats, will be faster than we need and possibly well over scale speed anyway even with one motor if brushless.
Size/power of motors. I'm sticking with brushless here as I don't know much about brushed and information on specific motors seems more readily available like the power output for a specific voltage.
My thoughts are that whatever power a single suitable motor has then twin motors should have say 75% of that each to allow for the additional weight of another motor, prop shaft and rudder. But that's assuming that the suitable single motor isn't providing too much power in which case the % could be reduced!
Reason I say this is that motors are usually chosen for their kV i.e. 1000 revs/volt rather than the power output and I make my choices based on using 3S (11.1v) and around 1100/1300 kV to give sufficient rpm. for good planing performance.
One motor I use is an Overlander 3542/05 1250 kV which has a quoted output of 710w which is quite high compared with some other motors and it could therefore be argued that 50% of this for each twin motor would be perfectly adequate?
Alessandro - perhaps in the interests of scientific evaluation you should build your model with single and twin prop shafts!
Me, I just over-engineer!
Chris
Unless your planing model is really big, say over 4 foot (1200mm) then for good performance you don't need more than one brushless motor as that will provide all the speed that you need - for a brushed motor you are probably looking at a smaller boat but why go brushed at this size?
So, only reason for two or more motors is for differential steering, or more likely because it's a scale model and the full-size boat has multiple engines.
Twin motors will give you more acceleration (if you need it!) but little more in top speed (unlike with full-size), well usable anyway, as the models we are considering, as opposed to race boats, will be faster than we need and possibly well over scale speed anyway even with one motor if brushless.
Size/power of motors. I'm sticking with brushless here as I don't know much about brushed and information on specific motors seems more readily available like the power output for a specific voltage.
My thoughts are that whatever power a single suitable motor has then twin motors should have say 75% of that each to allow for the additional weight of another motor, prop shaft and rudder. But that's assuming that the suitable single motor isn't providing too much power in which case the % could be reduced!
Reason I say this is that motors are usually chosen for their kV i.e. 1000 revs/volt rather than the power output and I make my choices based on using 3S (11.1v) and around 1100/1300 kV to give sufficient rpm. for good planing performance.
One motor I use is an Overlander 3542/05 1250 kV which has a quoted output of 710w which is quite high compared with some other motors and it could therefore be argued that 50% of this for each twin motor would be perfectly adequate?
Alessandro - perhaps in the interests of scientific evaluation you should build your model with single and twin prop shafts!
Me, I just over-engineer!
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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Hi - the angle won't affect how it sits on the water, difficult to know if it will sit exactly parallel to the waterline but I've found that they are usually not far off - in any case ballast can always be used.
Advantage, I think for drawing is that you can see how the sheer and the superstructure will actually look if it's at the right angle rather than bow down a bit.
Plenty of the old kit boats planed Ok on brushed motors. The killer was if they needed a big lead acid battery as often they would then struggle. I have a couple of ready-to-run race boats and a plastic Club 500 that use brushed (that in the Club 500 gets very hot though - battery is a 7.2 volt NiMh).
But I'm sold on brushless and use them in all my builds, even the slow models. I like the engineering and the fact they are more flexible for voltage used - for better performance you can just use a higher voltage battery. Also they will drive a bigger prop.
Many folks who refurbish and upgrade their old models replace the brushed motors with brushless as they found the performance poor.
Advantage, I think for drawing is that you can see how the sheer and the superstructure will actually look if it's at the right angle rather than bow down a bit.
Plenty of the old kit boats planed Ok on brushed motors. The killer was if they needed a big lead acid battery as often they would then struggle. I have a couple of ready-to-run race boats and a plastic Club 500 that use brushed (that in the Club 500 gets very hot though - battery is a 7.2 volt NiMh).
But I'm sold on brushless and use them in all my builds, even the slow models. I like the engineering and the fact they are more flexible for voltage used - for better performance you can just use a higher voltage battery. Also they will drive a bigger prop.
Many folks who refurbish and upgrade their old models replace the brushed motors with brushless as they found the performance poor.
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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@ChrisF
Hi Chris, as soon as I open my PC tonight I'll measure the angle and let you know.
I drew it by eye without measuring it.
Now the fixed point is the 1:3.5 ratio between width and length (or a little closer to 3).
My dilemma now is the keel angle: whether to make it parallel or leave it that way.
But do you think it can't plane with a brushed motor?
I have two brushless motors I can use (I'll show you later), but I wanted to start experimenting with my own brushed motor. I know you're a fan of brushless motors, but do you think brushed motors should be avoided at all costs?
Hi Chris, as soon as I open my PC tonight I'll measure the angle and let you know.
I drew it by eye without measuring it.
Now the fixed point is the 1:3.5 ratio between width and length (or a little closer to 3).
My dilemma now is the keel angle: whether to make it parallel or leave it that way.
But do you think it can't plane with a brushed motor?
I have two brushless motors I can use (I'll show you later), but I wanted to start experimenting with my own brushed motor. I know you're a fan of brushless motors, but do you think brushed motors should be avoided at all costs?
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What angle are you using for the vee? If you need more submerged volume you could increase to 20 degrees if it isn't already.
As my round bottomed Faun has a brushless motor I have had a mad idea to see if I could get it to plane! But I've shelved it as I think it could end in tears!
As my round bottomed Faun has a brushless motor I have had a mad idea to see if I could get it to plane! But I've shelved it as I think it could end in tears!
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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Yes, unfortunately. It used to be quite rare and often after rain so the car would be a right mess. Last few years it's been happening more frequently and especially annoying if you have washed the car the day before!
A ratio of 3.5 sounds good and could be the sweet spot. Surprisingly the Huntsman 28 is around 3.1 but the water-jet project is 3.4.
Inclination - I think it will make a small difference to the submerged volume (slightly worse) but the main thing is that it will more accurately indicate the angle of the chine rail and how the superstructure looks. The line of the deck isn't normally parallel to the waterline.
Sheer (spelt it wrong before) - this is the line between the deck and hull sides running from bow to stern viewed from the side.
A ratio of 3.5 sounds good and could be the sweet spot. Surprisingly the Huntsman 28 is around 3.1 but the water-jet project is 3.4.
Inclination - I think it will make a small difference to the submerged volume (slightly worse) but the main thing is that it will more accurately indicate the angle of the chine rail and how the superstructure looks. The line of the deck isn't normally parallel to the waterline.
Sheer (spelt it wrong before) - this is the line between the deck and hull sides running from bow to stern viewed from the side.
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
Liked by hermank and AlessandroSPQR
@ChrisF
Hi Chris, I didn't think desert sand would reach you in the British Isles.
It sometimes comes here with the Sirocco, but we're facing Africa; you're much further away. Who would have thought?
Thanks for the info on the propellers. I'm thinking of creating space for a 50 mm diameter propeller and then installing one between 35 and 45 mm.
With the finished hull, I could do some empirical testing, which is the fun part.
The width/length ratio of hull no. 5 is 1 to 4, as already mentioned.
I'm designing a new hull with a 3.5 ratio, so on a length of 68/70 cm, I'll have a width of 20 cm.
I went from a length/width ratio of 4 (hull no. 5 you saw in the last attached images) to this one of 3.5 because I didn't want to go all the way to the max right away.
I don't think there are any ratios lower than 3. They range from 3 to 5 for real ones; more rarely with higher values, but almost never below 3.
If you're strongly inclined toward the 3 to 1 ratio, however, let me know.
It's clear that if I want to go from 70 cm in length to 80 cm in length, I can do so by adjusting the scale. Adjusting the scale will also result in a proportional increase in height.
If I want to lengthen it but leave the same height, I'll have to redraw it from scratch.
So, if you're not adamant about the 3 to 1 ratio, let's see how this hull with a 3.5 to 1 ratio turns out. If you'd like, you can give me your personal opinion on this hull, which I'll call "Hull No. 3.5."
You wrote:
"""""Last thing for now. In your drawings, you have the keel angled downwards towards the bow. For this type of boat, the drawings I use/produce usually have the keel parallel to the waterline. This affects how you see the chine, deck/shear, and the submerged volume.
In displacement hulls, I've always preferred the parallel keel (parallel to the waterline).
In planing hulls, however, I've seen that this inclination is very common, and I wanted to try it. Honestly, I don't know what practical differences it will create on a model.
Do you expect substantial differences in behavior, and if so, what?
I'm not sure what you mean here:
""""If you haven't already, something else you need to think about is the shear. Common on planing boats is to run it at an angle along the side of the boat, which then flattens or dips down at the bow. """"""
Hi Chris, I didn't think desert sand would reach you in the British Isles.
It sometimes comes here with the Sirocco, but we're facing Africa; you're much further away. Who would have thought?
Thanks for the info on the propellers. I'm thinking of creating space for a 50 mm diameter propeller and then installing one between 35 and 45 mm.
With the finished hull, I could do some empirical testing, which is the fun part.
The width/length ratio of hull no. 5 is 1 to 4, as already mentioned.
I'm designing a new hull with a 3.5 ratio, so on a length of 68/70 cm, I'll have a width of 20 cm.
I went from a length/width ratio of 4 (hull no. 5 you saw in the last attached images) to this one of 3.5 because I didn't want to go all the way to the max right away.
I don't think there are any ratios lower than 3. They range from 3 to 5 for real ones; more rarely with higher values, but almost never below 3.
If you're strongly inclined toward the 3 to 1 ratio, however, let me know.
It's clear that if I want to go from 70 cm in length to 80 cm in length, I can do so by adjusting the scale. Adjusting the scale will also result in a proportional increase in height.
If I want to lengthen it but leave the same height, I'll have to redraw it from scratch.
So, if you're not adamant about the 3 to 1 ratio, let's see how this hull with a 3.5 to 1 ratio turns out. If you'd like, you can give me your personal opinion on this hull, which I'll call "Hull No. 3.5."
You wrote:
"""""Last thing for now. In your drawings, you have the keel angled downwards towards the bow. For this type of boat, the drawings I use/produce usually have the keel parallel to the waterline. This affects how you see the chine, deck/shear, and the submerged volume.
In displacement hulls, I've always preferred the parallel keel (parallel to the waterline).
In planing hulls, however, I've seen that this inclination is very common, and I wanted to try it. Honestly, I don't know what practical differences it will create on a model.
Do you expect substantial differences in behavior, and if so, what?
I'm not sure what you mean here:
""""If you haven't already, something else you need to think about is the shear. Common on planing boats is to run it at an angle along the side of the boat, which then flattens or dips down at the bow. """"""
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If you haven't already, something else you need to think about is the shear. Common on planing boats is to run it at an angle along the side of the boat which then flattens or dips down at the bow. On many of my models I've averaged out these angles to form a straight line to make building slightly easier but more to simplify planking which I usually do off the model - not a problem with naval vessels though as usually painted. And camber of the deck?
As for props, yes, 2 or three blade. All my builds so far have been scale or thereabouts and I have used 3 blade brass on all of them except one. Full-size use 3 blade and I like a bit of polished brass/bling! The exception is the Huntress with the stern-drive which is 2 blade as will be my outboard build. I arrived at the sizes partly by considering the motor size (though outrunner brushless will turn bigger no problem) but also by what looked right - I didn't want a prop that looked too big. So far performance from all of them is very good and I don't want to go much above scale speeds - I've got race boats for that! My props are: Huntsman 28" and 31" - 35mm dia. M4, Swordsman 33" - 40mm M5. The difference in weight between M4 and M5 prop shafts can be significant. I've used M5 in the Swordsman and bought one for the Huntsman 31 but felt it was too big and heavy so changed it for an M4 which I use in most of my builds.
Last thing for now. In your drawings you have got the keel angled downwards towards the bow. For this type of boat the drawings I use/produce usually have the keel parallel to the waterline. This affects how you see the chine and deck/shear and the submerged volume.
Chris
As for props, yes, 2 or three blade. All my builds so far have been scale or thereabouts and I have used 3 blade brass on all of them except one. Full-size use 3 blade and I like a bit of polished brass/bling! The exception is the Huntress with the stern-drive which is 2 blade as will be my outboard build. I arrived at the sizes partly by considering the motor size (though outrunner brushless will turn bigger no problem) but also by what looked right - I didn't want a prop that looked too big. So far performance from all of them is very good and I don't want to go much above scale speeds - I've got race boats for that! My props are: Huntsman 28" and 31" - 35mm dia. M4, Swordsman 33" - 40mm M5. The difference in weight between M4 and M5 prop shafts can be significant. I've used M5 in the Swordsman and bought one for the Huntsman 31 but felt it was too big and heavy so changed it for an M4 which I use in most of my builds.
Last thing for now. In your drawings you have got the keel angled downwards towards the bow. For this type of boat the drawings I use/produce usually have the keel parallel to the waterline. This affects how you see the chine and deck/shear and the submerged volume.
Chris
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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British weather! Few days ago it was a bit chilly to do much outside and now it's too hot! Being doing some work in the garden and washed that pesky Saharan sand (which is getting increasingly common) off my wife's windscreen so that she could go shopping, but it's 33 deg. now some come in to reply!
I agree on your thoughts to reduce the length to beam ration as it is in the area now of that I was advising against as the model, especially the smaller it gets, will have a tendency to rock more and not turn in a smooth controlled manner. Mentioning size, I think it would also be a good idea to have the length towards the upper end of you limit, say 800/840mm, as this will give you increased buoyancy (not that I'm worried about that!) but also more room to fit the components, especially if you do decide to fit twin prop shafts - a narrow hull/transom will make things more difficult. With twin prop shafts these are usually fitted closer to the keel and not mid-way between the chine and the keel - reason being is that on a tight turn/aggressive driving with a deep vee hull there is a danger that one prop will come out of the water. 800/840 provides a nice size model that handles well and is good for storage and transportation.
I see in your drawing that you do have some narrowing towards the stern and was going to suggest making it a bit more narrow so that the line between the maximum beam and the stern is a more natural curve. But reducing the length/beam ratio will have that effect and you don't want a stern that is too narrow for stability and twin prop shafts if used.
To be continued.
I agree on your thoughts to reduce the length to beam ration as it is in the area now of that I was advising against as the model, especially the smaller it gets, will have a tendency to rock more and not turn in a smooth controlled manner. Mentioning size, I think it would also be a good idea to have the length towards the upper end of you limit, say 800/840mm, as this will give you increased buoyancy (not that I'm worried about that!) but also more room to fit the components, especially if you do decide to fit twin prop shafts - a narrow hull/transom will make things more difficult. With twin prop shafts these are usually fitted closer to the keel and not mid-way between the chine and the keel - reason being is that on a tight turn/aggressive driving with a deep vee hull there is a danger that one prop will come out of the water. 800/840 provides a nice size model that handles well and is good for storage and transportation.
I see in your drawing that you do have some narrowing towards the stern and was going to suggest making it a bit more narrow so that the line between the maximum beam and the stern is a more natural curve. But reducing the length/beam ratio will have that effect and you don't want a stern that is too narrow for stability and twin prop shafts if used.
To be continued.
Scratch building 7 Faireys at a scale of 1:12 and also have 2 built by Dave Milbourn
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Hi Alessandro,
Regarding propellers for your planing hull design.
The size and type of propeller you choose to use should take into account the size of the hull and the amount and type of power available.
Most Classic Model Power Boats use a two bladed propeller and my own favourite power boats that are between 30" and 40" long are mostly driven by an out-runner brushless motor and run on a 45S or a 45X size propeller, but when building or restoring a power boat (of this size) I choose to allow clearance for a 50X propeller as I know this would be the absolute maximum size that I could ever want to use on it....so I keep my options open.
I tend to spend a lot of time testing different propeller types and sizes on my Classic Model Power Boats until I find the one that works best for me on any given model. This is something that I enjoy doing, but I am aware that very few people spend any time doing this - and their boats usually run well enough simply by following the suggested size shown on the plan drawing.
Moulded nylon propellers are inexpensive compared to a custom made brass propeller and so they give the opportunity to experiment with different sizes at an affordable cost. A brass propeller could be added later once the ideal size and pitch has been determined, but I have found that this is not quite as easy as I had hoped, as brass propellers have no movement in the blades as they rotate, and so they work differently to the moulded nylon types that have some "flex" in their blades.
Ultimate performance racing boats often use custom made balanced and sharpened brass propellers that suite them perfectly, but these are not worth considering IMHO for most model power boats and I would suggest that the much less expensive moulded nylon types are more than capable of producing the performance that you would enjoy from your planing hull design.
I like my power boats to go well and to make "white water" - just like their full sized types would - and a two bladed propeller tends to be more aggressive and more suitable for this type of boat than a multi-bladed propeller could be.
3 or 4 bladed propellers are generally (but not always) best suited to scale models where a smoother power delivery is preferred to outright performance.
I have used three bladed propellers on more scale like models previously to give a smoother power delivery, and I have used larger sized 4 bladed and 5 bladed brass propellers on my larger sized tugs in the past when a slower turning prop shaft combined with a torquey motor was preferred.
If your model is anywhere near 1 metre in length, I would suggest starting with a 40 - 45mm moulded nylon propeller - if you are going to power it with a brushless motor. An in-runner motor can benefit from the smaller end of this size range as they are not quite so torquey as a similar sized out-runner would be.
Hope this helps.
Bob.
Regarding propellers for your planing hull design.
The size and type of propeller you choose to use should take into account the size of the hull and the amount and type of power available.
Most Classic Model Power Boats use a two bladed propeller and my own favourite power boats that are between 30" and 40" long are mostly driven by an out-runner brushless motor and run on a 45S or a 45X size propeller, but when building or restoring a power boat (of this size) I choose to allow clearance for a 50X propeller as I know this would be the absolute maximum size that I could ever want to use on it....so I keep my options open.
I tend to spend a lot of time testing different propeller types and sizes on my Classic Model Power Boats until I find the one that works best for me on any given model. This is something that I enjoy doing, but I am aware that very few people spend any time doing this - and their boats usually run well enough simply by following the suggested size shown on the plan drawing.
Moulded nylon propellers are inexpensive compared to a custom made brass propeller and so they give the opportunity to experiment with different sizes at an affordable cost. A brass propeller could be added later once the ideal size and pitch has been determined, but I have found that this is not quite as easy as I had hoped, as brass propellers have no movement in the blades as they rotate, and so they work differently to the moulded nylon types that have some "flex" in their blades.
Ultimate performance racing boats often use custom made balanced and sharpened brass propellers that suite them perfectly, but these are not worth considering IMHO for most model power boats and I would suggest that the much less expensive moulded nylon types are more than capable of producing the performance that you would enjoy from your planing hull design.
I like my power boats to go well and to make "white water" - just like their full sized types would - and a two bladed propeller tends to be more aggressive and more suitable for this type of boat than a multi-bladed propeller could be.
3 or 4 bladed propellers are generally (but not always) best suited to scale models where a smoother power delivery is preferred to outright performance.
I have used three bladed propellers on more scale like models previously to give a smoother power delivery, and I have used larger sized 4 bladed and 5 bladed brass propellers on my larger sized tugs in the past when a slower turning prop shaft combined with a torquey motor was preferred.
If your model is anywhere near 1 metre in length, I would suggest starting with a 40 - 45mm moulded nylon propeller - if you are going to power it with a brushless motor. An in-runner motor can benefit from the smaller end of this size range as they are not quite so torquey as a similar sized out-runner would be.
Hope this helps.
Bob.
Never too old to learn
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