Hi Roy,
Re: "does 'wandering discussion' mean 'Off Piste'?"
In a manner of speaking yes.
Coz it often causes an avalanche of digressions🤔😉
Doug😎

Hi all I usually make my keels from laminated wood or plywood. The outside surface being vertical. As I have said I also make the cross section like an aerofoil and here the various layers of ply can work for you.

As you sand the rounded fore edge of the keel tapered up to about 1/3rd. the width of the keel and then tapered down to a near point. You will see the contour lines created by removal of the wood layers as sanding progresses. This can help to make the 2 sides symetrical in shape.

Picture shows a trial rudder I made but did not use. You can see the nice contours which you can then match to the other side.

This was 1/8th. ply cut to include a bend in the rudder shaft and then 2 layers each side of 1/16th. ply glued together with any PVA glue and clamped together for 24 hours in a vice.
Roy

re post 41.
Length of keel and weight.
A 20 mph wind has an effect of 1 pound per square foot of sail. Work out the area say 3 square feet.
Find the centre of area of the sails and measure how high that is above the water line. Let us say it is 15 inches. The 3 square feet now changes to 3 pounds and multiplied by the 15 inches gives 45 inch-pounds.

So if the keel weight of 4.5 pounds is chosen it should be 10 inches below the water line and the keel length can then be measured.

It could also be 9 pounds at just 5 inches but the displacement of the yacht would not allow that much weight. So take the all up weight of the yacht and aim to have a keel weight of 40% of this. Then divide this into the inch-pound figure for your yacht.

The area is a bit draw it and see if it looks right. It is a good idea to make an aerofoils section of the keel as well.
Bulb keels are very affective but slabs of lead flashing, low down, making the keel thicker are also effective.
Regards
Roy

Hi Doug does 'wandering discussion' mean 'Off Piste'?
Roy

Hear hear Ron.👍
But I'm puzzled as to why you have put 'Emma Jr' on the Open Forum and not in a Build Blog?
Folks tend to respect a Blog as being more personal than the Open Forum which invites wandering discussion.
Cheers, Doug😎

I am sorry Ron. You are correct

Alessandro,
You used the term
CENTRE OF THE HULL
Possibly lost in translation, does this refer to
CENTRE OF BUOYANCY OF THE HULL?

It is best ABOVE the centre of gravity.
CENTRE OF BUOYANCY will shift as the hull heels over.

Does centre of hull and centre of buoyancy refer to the same thing?

You are correct the righting moment will have to be discovered EMPERICALLY. I am not looking forward to that series of measurements and calculations

Yes, Ross is right, we invaded your topic a bit, sorry Ron.
But by doing so your magnificent work will get more visibility.

My intention was only to reassure Jumpugly. His model will have no problems because, as already said, it has space to spare and does not have sails.
The sails are the big problem because they raise the center of gravity and (especially when the wind is abeam) tilt the ship to one side.

However, in this regard I want to clarify something that many people are confused about. Let's say they don't have clear ideas.
In scale naval models we can more or less easily obtain a "weight stability" (in Italian manuals this term is used when the center of gravity is below the center of the hull).
In reality (with a few exceptions) almost all ships and boats (passenger ships, ferries, motorboats, oil tankers, ocean liners, cruisers, aircraft carriers, destroyers, frigates, corvettes, auxiliary ships, icebreakers, container ships, but also ancient galleons and vessels, as well as naos, caravels, carracks, triremes, liburmes, etc. etc.) only had "stability of form" (in Italian manuals this term is used when the center of gravity is above the center of the hull).
It follows that the righting thrust exists when the metacentric height is positive. In other words, the ship is able to right itself only within a certain angle of heel, not beyond.
Ships with "stability of form" beyond a certain angle will no longer be able to right themselves and will capsize.
Most ships, even in adverse weather conditions, do not suffer dangerous inclinations (except for a few cases in where tragedies occur).

Ross, regarding your fin, I am not able to establish how long it should be, calculations should be made with all the data available (almost impossible to find). It is much easier to do empirical tests.
As you know, the longer the fin is under the keel, the less weight you need to put at the end of it.
If you want less draft you need to increase the weight at the end of the fin or the thick fin (in case the weight is distributed and does not have the final bulb), so as to be able to shorten it.
Logically the weight can be increased within certain limits. Until reaching the waterline.

I completely agree with luckyduck: it is important to already place the necessary weights (not considered ballast) as low as possible (at least under the waterline).
Since I made the project from scratch I was able to make the choices I wanted and I managed to position the relevant weights as low as possible. I am referring to the two batteries, the motor and the propeller shaft, the large electrical cables, etc. etc.
In this way I managed to obtain a good righting thrust (I cannot say without calculations whether I obtained a "stability of form" or a "stability of weight") even without ballast.
When I then added the 400 gram ballast (in place of the keel) I obtained a truly satisfactory righting thrust.
All empirically.
Doing as luckyduck says is better. Create a stable ship already without ballast (if that is possible).

The other option you have, which I have used in the past, if you have sufficient internal space at the keel level, is to use an oversize battery - the sealed lead acid batteries are a very effective extra weight set on the internal keel, when you also need battery power for winches. I sail my Bristol Pilot Cutter with no external fin/keel weight, as the water needs a smooth hull surface to avoid catching weed.

Yes Ron, Your first drawing is my next calculation, HOW DEEP A FIN KEEL DO I NEED FOR A RIGHTING MOMENT?

I have to find the weight of the final vessel and the ballast required to keep it at waterline and the length of the keel for the righting moment.

I do like your idea of an interchangable keel for different conditions.

I don't think I can get that budget for multiple fin keels past the Auditor-General😉

Alessandro,

Firstly I agree with you and support your discussion of spheres and solid keel.

This brings me to my upcoming delemia on the schooner under construction. It was never my intention to use spheres. My ballast requirements are calculated to be just under 7 kgs. Given the SCALE wind speed it will sail in, a conventional 'in hull' ballast of the full sized vessel will not be sufficient. The model will require a fin or fin and bulb keel below the scale keel to sail properly.

I have acquired (salvaged) sheet stainless steel, with a thickness of 1.72 mm's, enough for a quantity of fin keels. If the stainless steel is formed into a hollow foil-type fin, could this fin be filled with molten lead, to create a weighted stainless steel-lead fin?

The fin would have to be in the scale of 30 cm down, 20 cm length, and average of 1 cm thick. (2 cm at thickest of foil tapering to zero at front and back)

Apologies to Ron for this disruptive entry on his EMMA Jr , Ron, your photos of hollow wooden keel and lead shot inspired this idea

Hi Jumpugly, if you don't have a keel you're right, you can't make any substitutions.
In that case, lead pellets are fine because they have the advantage of distributing themselves well in the desired spaces.
You can also use single lead or brass bars placed in the appropriate points at the bottom of the hold.
However, in your case there are no problems because the model is very large and you don't have sails. The margins of work are wide. It doesn't matter that the ballast of the pellets will have a lower efficiency (about half compared to homogeneous bars) because you have a lot of volume available (so it's not vital to optimize).
Try to position the batteries very low (especially if they are lead).

Thank you very much for your final words.

Great stuff Gentlemen!
I hope and pray that my stone tile idea for my American Scout will stand up well enough for my tub test in a few weeks. (see attached pix). I have my doubts, as any build blog I've found on the internet for this kit says anywhere from 6 to 9 pounds of weight will be needed to keep her upright. Yikes!

Truth be told, after paying close attention to all of your ballast tips here; a brass rod or steel bar stock would have been good for me if this kit actually had a keel. However, a piece of sheet steel or a brass door kick, shaped to my ships flat bottom may be my only option should my tiles fail. We shall see...

Alessandro! The workmanship on your build is OUTSTANDING!!!

😁😀

Greetings to all modelers.

I agree with Roycv in what he wrote in message no. 26 of this topic:
RoyCV wrote: "...The benefit of lead sheet over bb's is that there are no air spaces in between..."

I had already highlighted that the spheres occupy about half the volume of a corresponding parallelepiped. So they are not very effective.
In particular:
They are less effective than a full volume if used as ballast, because (with the same metal or alloy) you get about half the weight by putting pellets instead of using a full geometric shape. The other half will be air.
On the other hand, they are absolutely useless if used as a buoyancy reserve. This is clear because in the event of flooding the water will fill the spaces between the spheres. The weight of the water will cancel (more or less) the thrust of the spheres.

To understand why I refer you to the message from about eight months ago in the topic entitled: "29" Double Horse 7007 Flying Fish" in response to CB90. It is the first link at the end of this message.
Since it is a bit difficult to find (the messages of the "build blog", unlike those of the forum, do not have any numbering) I report the full text and the images below:

"""""""""""""""""""""""To guarantee a buoyancy reserve it is not essential that the spheres are glued together.
The important thing is that, in the event of a leak in the hull (or in any case if water is entering the hold) they remain in position to carry out their task.
To do this, they just need to be placed in a closed compartment.
However, in the event of flooding, even if the spheres cannot leave the boat, water will seep in between them.
Geometrically the spheres do not have a total occupation of the volume and the space between them is quite conspicuous.
To understand this, look at the images.
In the second and third attached images a parallelepiped measuring 36 x 24 x 24 mm is represented.
So its total volume will be 20736 mm3.
Let's take into consideration spheres with a radius of 3 mm (diameter 6 mm).
A maximum of 96 spheres of this diameter can fit inside this parallelepiped.
A sphere with a diameter of 6 mm has a volume of approximately 113.1 mm3.
Therefore the volume occupied by all the spheres will be 10858 mm3.
Well if you make a proportion between the volume of the parallelepiped and the total of the spheres you will realize that this is approximately 52.36%.
Logically this proportion is always the same, whatever the number of balls taken into consideration and whatever their diameter.
This means that if water gets between the spheres or if the glue you use is heavier or slightly lighter than the water, you will have reduced (almost halved) the floating effect of the spheres.

In fact I prefer light material but not in spheres. Compact, square shapes that I can cut out. They will fill all the spaces (not leaving them available for water) and will be stuck together without the need for glue.
In any case, if you still want to use the spheres, you could put them in various hermetically sealed bags.
I don't know if I managed to explain myself well with the translation.
I hope so.""""""""""""""""""""""""""""""""""""


=============================================

I also have to say that I like the solution of the embedded ballast (which replaces a piece of wood of similar shape) in the keel itself.
I also adopt this solution (as you can see in message no. 105 of the last attached link) which is a very simple trick to lower the center of gravity as much as possible without resorting to fins under the hull.
Finding message no. In among the 439 total is a bit difficult (I have a tired finger from spinning the wheel of my mouse) so I attach some fairly explanatory photos.

=============================================

https://model-boats.com/blogs/140953#141820

https://model-boats.com/forum/128542

Ron,

I'm working on the fin-tube-threaded-rod right now. (my tube and rod arrived in the mail yesterday). did you take any photos of the fin attachment? You could save me some grief. Thanks
Ross

I sit corrected, (like a Labrador dog, don't 'stand' if U can sit, don't sit if U can lay down!). I still respect the 'player' just as much, & or even more. I know someone with a 'chew wah wah'? I don't know what it 'chew wah wahed', with such a small mouth? Same thing??? 'B J', 'B'ad Dad 'J'oke. 👍 😀.

I remember the sound of Peter Appleyard

And a xylophone, (about the only word, instrument that starts with 'X'). I tryed to spell with a 'Z' for Zylophone. What an unbelievably underrated instrument it is? Like the 'player - music maker - artist - a 'real' musician'! Well done U. 👍 instrument😀.

Are those 'Kettle Drums', (tympani) a joke? BOOM! BOOM!? I'm half deaf from playing Rock 'n' roll drums & half from 'ear canal tumor'. Two elephants fell off a cliff! Boom!, boom! Did you hear the joke about a heart beat? Boom!, boom! I hope You laughed, or at least groaned, was it a half grown, even a Full grown, & or maybe a grown - up? You wouldn't expect ME! to put MY! name to that would you??? & or even my letters???

I bought my drawings from bearospaceindustries.com

Do you have the drawings?!?😜

Further thought, perhaps a new version of the hammer with a long handle which straps on the arm and only uses the hand for guidance?

Roy

Hi Ronald, apart from the restriction of 5 inches of water depth I dislike long appendeges underneath the hull. My photo is my version of getting rid of a 12 inch long keel.
However, there is a great deal of satisfaction whacking a piece of lead into shape! Perhaps avoid doing it on your work bench.

regards
Roy

Frustrations come in, the main thing is you are still active and creating.

Hi Ronald if you can use lead sheet then do. I beat into whatever shape you want with a hammer on metal surface.

The benefit of lead sheet over bb's is that there are no air spaces in between. Someone on a forum once posted that lead shot even quite small size, was the equivalent density as iron/steel.

Small metal pins will hold it in shape while it slides into you keel 'pockets'.

For a similar size yacht (Panache) I would have a wood ply keel 6mm with the outer grain vertical and cut lead sheet out to almost a torpedo shape to attach at the lowest part of the keel. You could also go under the keel as well. Beat it to death and into a smooth shape, the keel should locate into it. Use epoxy to hold it in place and then filler to smooth it over.
When dry and sanded use a 'nappy' or loop of glass fibre cloth to hold it in place with the cloth going to halfway up the keel. Filler and sand smooth and then paint.

Note there are different thicknesses available and builders call it Flashing.

The photo shows the before, I used the above method to hold the keel weight in place and it has worked well, absolutely solid.

Hope this helps.
Roy

See the lead Mini-BB’s which were glued inside the fin.

Weight is 1.11lbs

Someone suggested using lead sheet also, though I am not sure how to attach it. Any suggestion for doing it if needed please let me know.

What a great idea.

Letting the clamps hold the parts together and the glue set till the morning before trimming and shaping the front of the fin. Thus far I am pleased with its appearance.

I am trying an idea that occurred to me this weekend. Using a piece of the basswood plywood and form an aerodynamic fin filling it with lead BB shot.

Using some cherry scraps, a pattern was created and cut to form the aerodynamic fin. Next, each piece was carved to match the shape of the hull.

Holes were drilled through the patterns using 2 small finishing nails to hold them in place next to the hull and plywood centre fin.

You can see the sequence in the photos. After the glue sets I will place equal amounts of BB shot inside the form and place a layer of epoxy over them.

Ahahahah, very strong, very funny this one.

heck, I take photos of my house so i remember which one to come back to!

Hi Ronald, I like your solution for the servo.
I also did something similar.
I had difficulty making the world of curves coexist with straight and orthogonal lines and I wanted to make a slightly complicated interlocking system so as not to use screws.
In the end I took photos and videos to remember how to disassemble it, just in case.

I like the idea of the servo system coming out as a single unit👍

Ronald! She’s going to last forever!
Great strong build.
👍🏻😊

After gluing on the rub rails they were shaped and sanded along with the hull.

I removed the RC gear from the interior so the inside and outside could be coated with lots of polyurethane. Next will be the fibreglass cloth on the outside on the hull, I don’t put it on the inside.

Notice the easily removed servos, the panels are removed keeping the servos mounted, this was not a Forethought but it dawned on me when I began dismantling the interior.

It is.
I purchased 20 rods of TIG wire several years ago for around 18AUD and am still going through them. Very handy for creating hooks, pelican hooks, and holding hatches down.

That looks like a positive way to secure the roof

Ross

Yes, I followed Gray Webb’s video instructions on making “RC Sailboat Build DIY Hatch Covers that Fit” found on YouTube.

Yes, I am using another of Gary’s suggestions and that is drilling a small hole to receive a wire that secures the hatch cover. It works well. I use the wire found at Michael’s in the jewelry making section, I know Gary uses stainless steel wire or Tig filler rod but that is only sold locally in a package holding 3 rods. The coated wire is less money and works fine with my vessels.

So Ron,

Are the 'sides' of the roof a simple friction fit on the sides of the cabin?

Mind if I borrow that idea? I'm going to be at that stage (someday). That looks like a good solution, to avoiding hatches. Will you secure it down or will a friction fit be enough to hold it?

28

Your photos and your write-up are definitely appreciated. I tried counting your clamps, I seem to get a different number each time, somewhere in the vicinity of 29 or 30 in the picture

See the New Photos below the clamps are off and the cover is installed.

Very pleased with the 1/16”x8”x12”basswood sheets I bought off of Amazon.

The cabin roof is glued n clamped, when finished it will be one simple lift off to access below deck. No separate hatches or hatch covers.

People have asked me about my plans for enclosing the deck structure. Here are some new photos of the build, but I ran out of basswood to continue with the cabin roof, though you can tell what I am up to on this.

. . . and my solution too. I think it will be fine as is. Do like the double pushrods!!

Rudder servo in and rudder working well.

I am using a HS645MG servo as recommended by Mike Mayberry, Hitec Sales/Team Manager, for sail control. I knew I didn’t have the room for their designated Sail Servo HS765 so after several emails he recommended an alternative for its known torque value.

I have not used Metal Gears before, it is a nosier than other servos I have used. I am wondering if it needs gear grease? Any thoughts?

No the small arm isn’t the one I am using, it’s just there to make the video.
Ron

Very interesting; I built a "full size" Emma, but with the shortened keel as suggested by Gary, but it still hits rocks on the bottom of our pond occasionally. Sails well, though.

I'm currently working (occasionally) on an 80% size Irene, which I'm hoping won't hit bottom.

I'll be interested to see how your Emma develops.

Awesome Ron! And she’s built to last!

Ron, i always enjoy your workshop's "background clutter"🤗

Going really well. I guess she truly is a ‘scratch’ build with plenty of thought and work to make it happen.