HI Robert

I have been poking about with voltmeters for nearly 60 years now and ohms law has been around for nearly 200 years, as far as dc cicuits go, I have never found that it gives the wrong result.

I know the battery terminal volts fall when on load and can see it with a volt meter, all I am trying to do is to determine how good or bad my ESC is, I think it is not very good, because the voltage drop across it is significant and V * I = W and watts mean, in a circuit with the volts and curent in phase, it gets hotter and if W is big enough it melts, bursts into fire and stops working, not necessarilly in that order.

I do not know what good a watt meter would be in what I am looking at. I did need one when I was invoved in ac circuits, as only a voltmeter and ammeter do not tell you the full story, when the current and voltage are not in phase, as you can have lots of both but not many watts.

Nasraf.

I still think what you are looking at is nothing more than the supply voltage falling under load. When the load comes off, the voltage goes back up.

For example, when your flying a plane and the low voltage cut out trips, you can restart the motor on a lower throttle setting (the lower current being drawn keeps the voltage above the cut off) to get you down safely.

Connecting a wattmeter you see your supply voltage fall and recover in relation to the current being drawn.

Robert

HI Dave M

Thanks for information.

I did a couple of simple tests to look at possibility of the motor polarity being configured incorrectly.

With demand being full forward the motor terminal volts were 10.4, I would estimate from previous measurements that the current on no load ( I.e. boat out of water ) would be approx 8 amps, the battery terminal volts were 11.6.

With demand for full reverse the motor terminal voltage was again 10.4 and same battery volts.

This gives a voltage drop through wiring and ESC of 1.2 volts at 8 amps I.e. a loss of approx 10 watts in both directions. So it appears that my ESC is not particularly direction sensitive and the thermal heating is the same for both cases.

hI nasraf
I have found that modern ESC have a forward and (lower) reverse power rating.
Is it possible that you are running the ESC in reverse mode?
If your Tx ESC channel is not set to normal this may be the case.
I recently came across a similar problem at my club site with a twin prop model. One ESC had been configured via the TX nor/rev switch and was running in reverse. it overheated and burnt out the other was fine.
Hope this helps
Dave

My latest comments are based on the measurements I made in report on 4 th May.

The measurements I took were with a voltmeter on battery terminals and motor terminals and I am confident that most of the voltage drop is across the ESC, this is evident by how hot the unit becomes. I have affixed addiditional heat sinks to the extruded heat sink on the ESC which has probably extended its life.

The recent comments on other blogs on these Hong Honk ESC's indicates there is something wrong with them or they are very wishful thinking on their power handling. My unit is suposed to be capable of running at 100 amps, I think if this was tried it would end up in a puff of smoke. I only run mine at a maximum of about 15 amps and not for long with the additional sink, so far it has survived but I am loosing quite a lot of power.

With regard to your measurement and loss of volts, are you using a wattmeter to display V,A and W ?
Have you considered that it my be associated with the C rating of the battery pack not being able to give up the current quickly enough to give yo the voltage?

I place my wattmeter between the battery and the ESC and its quite an eye opener to see how the supply voltage drops under load.

I put it in the water yesterday and gave it a run with the heavier load in the stern and it runs much better and the bow rises clear of the water and there is no tendancy for water to come over the top. I think now I had better find a new ESC that does not drop 2 volts of the 12 I have at maximum current.

Also thanks to this great site, I had a response from the other side of the world to my request for information on NZ coastal steamers. So I may be able to make some progress on my next project.

Its a long time since last post and just over a year since my first post on the subject.

I have at last finished rear well and fittings, there is a surprising amount of work in the back. I think I have made the hoses a bit bigger than scale and have got the planking size wrong but at the moment will live with it.

The extra weight has moved the c of g back 2 cm to 38 cm from stern.

I have not put it in the water or tested it yet, I hope the extra weight will lift the bow a bit.

I have added photo of new arrangement.

The hoses were a bit fiddily and are my first attempt as I had used up all the shrink tube I had. I made liner by wrapping 22 swg galvanised Iron wire onto 8 mm screwed rod on my lathe and then shrinking on shrink tube, this gave rise to oversize hoses, although I am not sure what diameter the hoses should be.

Next project is to make a model of a New Zealand coastal steamer of about 1875, the COROMANDEL. Although there must have many hundreds of ships like that built there is very little information on them available so the research is taking some time before construction can start.
I thought that information would have been plentiful in the facilities in Bristol but to my surprise very little is there. if anyone has any info on hull shapes from that time I would be very grateful of any guidance. The reason for my interest is that my great grandfather fell into a dock in Auckland and was drowned whilst he was working on the ship in 1880.

HI
Seems as if it is the ESC. At 15 amps I would not expect there to be much heat from wasted power. Could be you have a faulty unit. if you are in a club see if you can try another ESC to verify. MOSFET resistance is typically 0.005 Ohm so at 15 v should drop 0.075 volts. This is why modern ESC's do not need massive heat sinks that were common with Transistor ESC's.
Hope this helps
Dave

HI Dave

Thanks for comments.

I got out paddling pool as it was nice and sunny and did some checks on voltage drop.

At full load, which I think is about 15 amps the battery terminal ( nearly) volts were 10.4 and motor terminal volts 7.9 thus total drop thro' system 2.5 volts.

My wiring is in 2.5 mm 2 and about 1 metre total length the wire should then give a drop of .22 volts at 15 amps. My connectors are high spec military gold plated so will give very little drop also have fuse, so I would estimate that wiring etc would give total loss of say .4 volts max so ESC is responsible for a bit over 2 volts. This was a far east unit supposedly for 100 amps but it gets very hot at 15 amps so may not be very good. Thus motor power is about 113 watts and esc losses approx. 40 watts.
Perhaps I should get another esc but as they are expensive and the boat goes quite well I think I shall live with it.

As to reducing Ae length I think I will keep it as it is, it seems to work quite well. I did notice that when I applied my voltmeter leads to the wiring this disturbed the motor speed which indicated that the leads were radiating noise. I might try a few experiments next time I take the boat out to see what the range is.

nasraf

Not a good idea to interfere with the aerial length on receivers. The manufacturer will have adjusted the aerial loading to the length of wire to ensure full range is achievable - probably not much of a problem for model boats but it can affect interference from adjacent frequency channels. For sailing I normally route the aerial through the deck/cabin and attach to a high point with a rubber band. For display just pull back into hull.

If you are dropping 2v through your esc you are running a pretty hot model!! it may be extra resistance in too long leads/poor connections/too light (current wise) cable. That sort of voltage drop reminds me of my early transistor controllers, and did they run hot!!

The main problem with the rear well is your rudder(s). I had to shorten mine so it fit beneath the floor.

Good luck
Dane

Thanks Dave for the comments.

So far I have not had any problems with RF interference but I will take your advice to try and keep Ae away from main conductors but if I keep it within the hull there is not much space. is it worth making a whip Ae on cabin roof or will short length give other problems. At 40 Mhz an Ae of half a wavelength is a bit long.

As for leaning due to torque reaction, mine has no tendancy to do it, but I do not expect that I am at your power level. My Lipo is 3 cells which I think is about 11 volts and there is about a 2 volt drop thro the esc.

I hope I can get the new build rear well in old space as drawings and pictures do not show much forward of the tow hook bulkhead, but we shall see.

nasraf

Looks very smart. When you model the rear well you may need to move the battery. Shouldn't matter too much as LiPo's are very light. I notice the aerial is very close to the battery positive lead. it is best to try and keep the high current power leads away from the signal wiring (aerial/servo leads etc) so you may wish to bear this in mind when you do the rear well. As a matter of interest does your model show a tendency to list badly on full power? - mine does with brushless motor and LiPo. Finally LiPo's do not like water so do make sure they are in a dry place in the boat.
Good luck
Dave

I have at last finished making various fittings including the cantilever monitors, which turned out to be more difficult than the pram handle version. I have obtained a victory industry fire boat and this has cantilever monitors so I scaled mind off these, I think they are a bit out of scale and the nozzle part is shorter than the actual units.

I ended up fitting the Lipo battery at the rear of the boat in the rear compartment and the boat goes quite well now with a nice big bow wave. I do not think that it will run for a long period but I find that 10 minutes is long enough to amuse me.

The c of g has now moved back a bit to 40 cm from top of stern and mass is approx 3.75 Kg.

I was not able to find any ready made front small vents so I made a couple out of aluminium rod but I am not sure they are correct size.

The next part of the project is to remake the rear well with steps and hoses etc.

Thanks for comments and pictures.

It is interesting to see that 93 was fitted with both types of monitor.

I am very tempted to make a pair of the, what I shall call, the cantilever monitor. The ones I have made are not really like centre fed units and I made it from bits of brass strip soldered together, so I was not able to solder on the pram handles, but stuck them on with epoxy, so not really satisfactory.

After having a good look at HS93's building blog of his reduced size fireboat and the quality of the job, it has made me to be not so satisfied with my efforts so far and I find it quite interesting to do the research and making the fittings in brass.

I am tempted to have a go to buy the kit on e bay and build another from scratch, but I had better not tell her indoors.

The back grounds to the pictures of 93 are interesting, I wonder where they were taken, I see a sunderland in the background of one and a scrap yard around in the other. They are not Mountbatten, I am not that familar with the Portsmouth area but from the little I know, it looks like it may be there from the forts on the hill, the main marine craft unit was at Calshot until it was transferred to Mountbatten at the end of the 1950's I think.

nasraf

nice monitors!
there where two different styles of monitors, the most common reproduced where the sort you have,

Earlier monitors where different, boats 93 and 94 did have a few subtle differences

I am now near to getting the answer to the original question where is the c of g and what is the mass all up.

Found a cheap LiPo charger from HK which seems to work.

Have now made and fitted most of the fittings and managed to make some approximate monitors, only the anchor, tow hook, lifebelts, nav lights to go now. I am not going to fit the winch or hydrant there is already enough stuff on top.

Not tested boat yet in open water with Lipo to cold and Ice.

The answer to my question where is c of g and mass in my case it is 41 cm back from top of stern and total mass approx 4 Kgs.

Some pics as it is to day are added.

nasraf

A long gap since last entry as I have not done much to the boat as it is very cold in my workshop.

Also I started painting the hull, the colours with cellulose spray and then decided to apply a 2 part clear varnish.
This was a mistake, the varnish went on to give a nice smooth glossy finish but as I pulled off the masking tape some of the varnish peeled off with it, there was no adhesion to the colours. I should have known this would happen as I had seen problems in my job with sticking resin paints to oil based paints. So I had to sand the varnish off and some of the celulose. So the colour coats will have to be done again and as it is so cold and "her indoors" is not willing to allow spray painting in the house the painting activities are on hold.

Have been looking at battery weight problem and have purchased a LI Po 2800 mah pack, I am now considering how to charge it without having an explosion or fire. I expect that I am going to have to buy a dedicated charger.

Have also made most of the fittings from brass but have a problem with the monitors as they are quite complicated. Looking at pictures on the site the monitors on the boats look different from the ones shown in the plans, in that they do not seem to have the " pram handles" but rather a rear solid arm. it may be my eyes, the pictures are difficult to see the detail, has anyone any idea if the actual monitors were different, as if they have a solid rear arm they would be a lot easier to make.

nasraf

Nasraf
Thanks for this. I like the principle of mounting the motor to a plate. The plate can then be attached to substantial mounts either side of the motor. I intend to make a base plate with fitted bolts so that I can attach the side bars with lock-nuts. I will make a silicon join between the base and side mounts. I use a brushless motor and need to have an absolutely rock solid mounting. The motor is an out-runner so produces some horrendous gyro effects at speed. The silicon will, I hope, absorb the bumps as the boat leaps about the lake!
Peter
Yes thanks for this. Airflow is very Important with high current motors.
I will let you know how I progress.
Dave

Thanks Peter.

Just one mod req vent holes in the front of the mount , as it is a fan motor it has to move the air in and out via the front and the back holes , makes a big difference.

peter

Dave M

Please find attached pictures of motor and mounting I have left speed pick up on as I intend to do some measurements in water with a prop.

The mounting consists basically of 2 aluminium blocks 1 inch square 70 mm long with the motor mounting plate 1/8 aluminium sheet screwed on the ends.

My final test results with no grese and silicone oil were at 2, 4 and 6 volts 3.7, 4.6 and 5.5 amps respectively this is only slightly higher than motor on its own so quite a good result.

I have had a look at dc motor theory and for permanent magnet motors the speed should be constant for a given supply voltage with the current varying as the load changes.

A bit of a reply to all

Dave M

I will post a few more pictures of motor mount. I t ended up like this as I wanted to use old IC engine mounting and the material was something I had. I initially I thought it was a bit heavy so drilled some of material away, but now think it is a good solid mounting and to some extent is a heat sink for motor,also makes it easy to get motor in and out.

As to radio I have 40 Mhz unit so may not be troubled by interference, I have increased slot size in coupling so may increase level of RF generated if it is proportional to audio noise level.

thelegos

I am not sure what your mixture is, probably a sort of grease with the vaseline being like the soap. A few days ago I was an advocate of grease but Peter has proved correct in his advocacy of oil, see my test results.

pm devlin

I am joining your club with ball race at motor end, I am going for closed bearing pre packed with lubricant and some oil down the shaft with a plastic bearing at prop end. Mine is made of TUFSET polyurethane because I had some, I will find out if it is OK later and it easy to make others. I am going to try silicone oil squirted up the prop shaft tube, it is very slippery stuff as I found out when I got some on a tiled floor.

Now to the results from tests these are shown in attached photos.

The speed v. voltage graph shows that with no prop load the speed does not vary much for various prop shaft arrangements, this may be due the motor characteristics and back emf, I will have to look at a bit of dc motor theory.

The same tests plotted on Current v volts show a considerable current increase when grease is used as a lubricant, this is confirmed in the fact that the prop shaft tube gets quite warm during the tests.

In the third graph I have plotted the power losses for various motor volts and this shows the bad news for grease especially at high speed.

So no more grease, Peter was correct from the start. I think the tests were worth doing as it has increased my understanding of the subject and I hope of others who are members of this admirable and interesting web site.

when I first did the refurb of my 34" Fireboat, I was advised to fill the shaft with grease. This seemed to be a good idea at the time, but the grease just didnt do any good, as the shaft spun, the grease didnt lubricate as it forms a hollow tube effect inside the outer shaft, if you know what I mean!After a short period of time it overheated and went hard.
On the 2nd refurb, I have used a light oil, with an oiler tube, it works much better as the oil lubricates the shaft. I have a sealed ballrace at the top of the shaft, and a synthetic bearing at the prop end, which is lubricated by the water. These bearings cost pennies from SHG, or www.rcbearings.co.uk. its also far less mess. THe grease just causes drag inside the shaft

It's been interesting to read the various views about lubrication. On some of my boats I've used vaseline mixed into a light froth with sewing machine oil, it seems much less prone than grease to drag and 'caking up' away from the surfaces it is supposed to lubricate and protect. has anybody else heard of or tried this ?

Looking good. I had this type of coupling. Much favoured by the Ic brigade. They do sound horrible and whilst not that good a joint work well. However the metal to metal contact can produce radio interference. I am not familiar with your radio but if it is an early 27Mhz am version you may experience problems, especially at long range. Solutions include earthing the shaft to the bat neg lead to using capacitors. if you have any problems I suggest getting a new link. The ones with brass connections to shaft and motor coupled by a plastic insert work well. I was interested to see you motor mount. I need to make something similar for my brushless motor and believe your set up would work. Be interested to know how it stands up to use on the water.
Dave

First thing, appologies to Peter for not attributing advice on prop shaft to him and thanks to Dave for his comments.

I have now installed new prop shaft arrangement into boat and have taken the opportunity to do some testing. Photos show installation and test set up.

I hade made a chunky dc supply with output capability of at least 30 amps and supplying this with a variac makes quite a good variable power source. The .01 ohm resistor came into use in the set up and current is measured by a DVM reading across across the resistor. The motor terminal volts are monitored by another DVM. Speed is measured by a magnetic pick up on the two screws holding motor half of the coupling, the output being fed to a digital counter.

The motor is a Graupner Speed 700 BB Turbo and I did voltage/current/speed measurements for various configurations, these being;

1 ) Motor on its own I.e. No Load

2 ) Driving the prop shaft with no additional lubrication other than a smear of oil on prop bearing end.

3) Driving prop shaft with tube full of oil.

Oil used approx 30 sae car engine oil.

I have plotted results on graphs and photographed.
It is interesting to note speed does not reduce much with the shaft load for a given motor terminal voltage although the current increase is more significant.

I did not plot oil flled results, for a given terminal voltage the speed did not change much but current was about 0.7 amps greater.

I have not yet tried with shaft full of grease, this to be done later when I have a device to pump it in.

My coupling is not very good it is from the old IC engine installation and is source of a considerable amount of noise, especially with no load on. I think I will keep it like it is as in operation it sounds a bit like an engine, although it may be the cause of some of the loss shown when driving the prop shaft.

just an amp meter will do and listen to revs, yes when you played with big machines grease was not a problem but we are talking about very small amounts of power and the power has to be stored in batteries not down a big wire from a power station believe me we have done rpm / amp test and it is significant the difference enough to push the motor in to over heat if it being pushed try your self

if you want to test do what we do use a gps in boat for speed and a data recorder or transmitter I have just gone over to JetI radio gear so I can get real time feed back but also have a data recorder for 4 channels of info but needs to be downloaded on a pc because it is a bit slow going through the listings, but we have the odd test days and they have paid of Immensely in performance because we know if its better or worse and not guessing especially props. http://www.jetimodel.com/index.php?page=products&old=0&category=6
peter

Thanks Dave for the advice.

I am making similar arrangement to your suggestion with ball race at motor end and plastic bush at prop end.

I have made a steel tube which fits around the old shaft tube at motor end which takes the ball race and lubricant tube. The ball race is 9*4 with 4 mm bore pre lubricated with grease. The spec gives an operating speed up to about 70 K revs so should be a bit of a margin there.

I do not think I agree with your views on grease lubrication, I think that provided you do not put too much in, the moving parts push the grease away and so that if you do not get any churning there should be no significant heating. in the days when I worked for a living, I was involved with an AC generator that ran at 8000 rpm at high temperatures, the bearings were about 3 inch O/D and 1 1/4 inch wide. We had troubles with them, mainly due to problems with the clamping of the inner race. Whenever we took a bearing apart the grease was always pushed away from the balls and cage, in general it appears that in a pre packed bearing the grease only fills about 30 % of the space. As the bearing I am using is pre packed it will not require lubrication, however I shall pump in some grease in the tube to prevent corrosion and to reduce the opportunity for water getting to motor end.

I have made the new drive shaft from 4 mm dia. bright mild steel, because it is cheaper and is easier to machine. I will let you know how it runs when complete, which should be to morrow.

After all the discussion on losses in the system I started making a dynamometer to do some electrical tests with the motor and batteries, but have now decided to leave this until another day as it will take some time.

Good advice Peter. Regarding the outer shaft, if the steel inner was bent it is possible that the outer has also been damaged. Replacing the shaft and bearings will only be successful if everything lines up and the shaft can rotate freely with no tight spots. The shafts pictured showing oiling tubes would be ideal - but as Peter advises use a light oil. When you have set it up the running sound should be similar to a well oiled sewing machine. Any rattles, squeaks or vibration should be identified and removed. There are different varieties of stainless steel, 303 grade will rust in time so try for 316 (marine grade) it is much more resilient to rust.

brass is to soft for a shaft, it will break or bend stainless steel is ideal and as for a centre bearing it will only cause problems as whatever lubricant and I DONT recoment anything othere than very light oil wont be able to go to eather end , you can but cheap plastic bearings made from a plastic that is dezined to run in water and not need oil ( aceteal) I usuly put a stainless steel ballrace at the top a 8mm x 4mm x3 and this can be done very simply with a bit of k & S Brass tube 8mm interal size slide over the outer shaft with just the thickness of the bearing sticking out then put a thin oiler tube in to hold it all all the bits can be got from SHG model supply.
any grease will put a load on a high speed motor as there is not enough space in between the inner and outer this will slow your motor and use batterys this mod does not req oil when run in water the oil is for lubricating when on the bench and also to stop the inside of the shaft getting a coating of rubbish that would damage the bearings when pulling the shaft out. we have just beeen running a 14" shaft at 4mm at very high speed in a huntsman and had no whipping.

Thanks for the suggestions putting in a fuse is a good idea that I will incorporate ( I should have thought of this myself )

As for prop shaft, my boat also used to be powered by an IC engine and bearings were worn and it was a bit bent in the middle so at speed I think it touched and was source of quite a lot of noise, I hade made a new bearing at prop end. There is nothing wrong with the outer steel tube and it is a lot of work to take it out and fit a new one, so I thought that it would be a good idea to make a new brass shaft with intemediate bearings along its length. This is what I have done but I think they are a bit too wide so what I am going to do is to reduce their length and to try a moly slip or silicone grease. in the water a bit of heating of the bearings would not be a problem

Hi, don't want to tread on anybody's toes but rather than blow up ESC's, which are expensive, why don't you put a car type fuse in the system, then you have a controllable limit to the current drain. 😊

Reading this thread it occured to me that you may have a bearing problem. Your last post seems to suggest that you do have some concerns. Was this model originally powered by an IC engine? My 34" certainly had been and the shaft and bearings were to put it mildly - worn. I took out both and refitted with new to the same size - bit of a pain I know but well worth the effort. I use locknuts at both ends of the shaft and make sure I have thrust washers at each shaft end. Hope this helps. Dave

A bit of a gap since last post as the house required attention.

Got .01 ohm resistor from RS but then found a small ammeter and shunt I had, so decided to fit this as a fixture in boat to avoid any more accidents with external wires,see picture.

Carried out intial tests with 2 off 6 volt 3.2 ah lead acid batteries (680 gms each ). The boat ran ok but was bow heavy with wash coming over top. So replaced bow battery with NI Mh 6 volt 3.3 ah ( 260 gms ) this gave a better performance.

New far east ECU works ok but although it is rated at 110 amps it gets very hot, even at 16 amps so am going to fit additional heat sink, it is a bit late to water cool it as it would require pipework etc.

Tests using lighter battery were curtailed when the prop fell off in the middle of the lake with no wind for recovery, a nice angler used his rod and line to get the boat back as I did not want to be there all night! Lesson do not use cheap epoxy to attach metal parts.

Prior to trial a did a few tests in paddling pool with following results. I used small spring balance to measure pull.

Motor volts Motor current amps Pull gms

6 7.5 680
8 12 1000
9.5 16 1200

I was surprised at thrust level achieved also volts drop across ecu at max demand, it must be about 2 volts at 16 amps this is 32 watts, it is not surprising it gets hot!

I am making new prop drive shaft with a thread on prop end but am having bearing problems at present. Have got into making items from brass I.e. window frames, mast assy, handrails etc which take some time so have not yet got new prop. or taken pics of boat going.

Maplins have these I THINK it may be the one or is it 0.01ohm


10 Watt Wirewound Resistor
10W W/W 0.1R Code: H0.1
Peter

Thanks for info, I am committed for a bit to a far east ESC as I have ordered it. I have gone for a 110 amp item to give a good margin on current handling capabilities.

Prop size is 35 mm 3 blade I do not know pitch as it is not shown on package.

I had run the arrangement before with no problems and no evident temperature rise in motor or esc.

I have had a look at your test measurements and can see a 700 BB 8.4 volt will draw a lot of current at 12 volts.

I am a bit surprised at the curent consumption of the motor, I did a couple of tests in an unloaded condition, but my current measuring system needs some development so no accurate resulys.

I was trying to be clever and measure the current drawn by my arrangement, but I think in my haste the wiring was not good enough, also prop I think hit bottom of test pool, it is not the first thing I have blown up electrically, in the past it has usually at some one elses cost.

Now I am waiting for ESC I think I will try and put a resistor in the boat wiring to provide a current monitoring system and also as limiter on max current possible. it all depends on if I can get a suitable component from RS.

nasraf

yes we did Peter! its a real learning curve, 50mm motor is cold, 52.5mm, and it overheats (it was a fast 2 mins though!)

Have a look here

http://modelfireboats.com/forum/thread.php?thread=629

there are some comparisons to different props, probably not specific to your set up, but it gives you an idea of the difference a prop makes to the amp draw

think about an electronize speed controler as they can be repaired in the uk so if you smoke it all is not lost as with the Chinese ones
BUT THE MAIN THING IS what size prop are you using???

go for a prop that is a lot smaller than you think you will need and work your way up , buy some cheap Graupner props they are about A£1.25 ea and keep checking the temperature of the motor and ctr-er.
the difference between a fast boat and a smoking boat (literally) can be one size of prop, as we found out recently
(didn't we Paul)

Peter

I have destroyed my Graupner V30 ESC, it seems a bit delicate as I was only running it in the boat in a paddling pool to check on function. I had a ammeter in series with the battery supply and this may have resulted in an intermittent supply with spikes that the electronics did not like. I was hoping to get some figures on motor current consumption but now think I will not repeat activity as it could prove even more expensive than so far.

I have ordered new esc from China so will take a bit of time to come. So tests will have to wait a bit. The tests in pool looked OK and there was considerable thrust from the battery/motor combination.

Thanks Peter

I am hoping to do a test run before next week on unfinished boat and will put results on site with the initial set up. I am not looking for any spectacular performance as basically the boat is for my grandson.

nasraf

Lets Know how you get on, if you feel you need more speed think about upping the volts and going to NIMHS less weight, Paul who is on this site ran this setup on 16 cells , also think about gearing, it made a difference in the motor running cool and Improved run time, it was also very fast.

peter

Thanks for replies it looks like I had better get out and do a bit of testing on the water before I get too far.

I have made a temporary assembly of the bits ( see photos )and done a bit of weighing.

Installation items

Motor Graupner Speed 760 BB turbo nom. voltage 8.4 v.
Home made mounting, it may be a bit heavy, but I used aluminium section I had.

Batteries 6 v 3.2 AH lead/acid gel.

Rx Zebra ZR 106 SF

Servo Zebra ZS S2113

Esc Graupner Navy V30R

Total weight of bits so far 4.42 Kg. I have made a test of c of g position and it is approx. 410 mm from stern top edge.

See pics of arrangement so far.

just to back up HS93's comments, look how low this is from the back, yet at slow speed its almost bow heavy. Esc is in centre section, rx up front, 1 battery pack in centre, and one up front, without the front pack, at speed, the bow is too high out of the water.

Hull seems to sit quite low in the water, until on the plane, then its quite a handful, being narrow its a bit unstable when going fast! (or could be my poor driving! 😀 )

They are a funny boat to set up, what are you using for batteries etc are they in one pack , the reason is after some recent tests with an original boat that is not light we found that at slow speed the nose is quite low but as soon as it goes on the plane you wish you had more weight forward, the best way is to do a test or two before it is finally finished, the backs do sit low when at speed, you will prob find you will need the batteries as near the centre as possible, and the radio gear in the front compartment and speed controler next to motor, its handy if you have a battery that can be split to move about. the boat when sitting in the water changes attitude as soon as it starts moving, just do a few test before you fix everything down.
Peter