Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Yachts and Sail => Topic started by: big-geoff on May 28, 2006, 09:39:24 pm
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Can any one help me out with this.
The last time I built my own model yacht I was 12 it was carved from a solid block of spruce and has a peice of steel plate for the keel, provided by kindly relative who happend to work in a shipyard etc...
I have plenty of roofing lead, I just need to get some idea as to how I can cast it into the desired form.
Or would it be safer to find an off the shelf solution.
The hull that I am thinking of using is 1.4m in length 320mm beam.
To be perfectly honest I am totaly in the dark as to what is necessary to give me the desired stability without compromising the performance.
There is a wealth of expertise out there but it is no help if you dont know where to find it.
Cheers
Geoff
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Here is a link showing you an approach to making the lead bulb ballast for an International One Metre class of yacht which might give you some ideas.
http://www.anderswallin.net/2003/05/making-a-bulb/
You will see that the mould is CNC machined metal. For a one off some people make a wooden pattern and use it to cast a two piece plaster of paris mould (described a while back I think in the article in Marine Modelling International on the Nimbus Mk 3 IOM yacht). It is absolutely essential that the plaster of paris is completely dry otherwise superheated pockets of steam can lead to an explosion when the molten lead is added. Full protective clothing is imperative especially for the hands/arms and face/eyes. Not a task to be undertaken lightly. A safe approach is to build up the shape by laminating sheets of lead bonded with epoxy.
Alan
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The question is, do you need the stramlined bulb or not?
If not, perhaps using a hollow keel, you just add small pieces until the desired water line is reached and finish off by pouring some epoxy resin over the lead.
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I used NASA aerodynamic profiles to shape a lead weight for my 1m yacht. I won lots of races within our club, so it cant have been too far wrong.
Cant remember where i got the info from though, was a long time ago :-\ Try googling it
I used the wood plug/plaster of paris mould method - finished with a fine file
Ian
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Many thanks
Never thought of making a mould with Plaster of Paris.
My next task it to put the hull in the test tank and add weight until it floats on the desired water line then weigh the weights added.
I can then think on the shape and size of the keel.
Thats 1 more ticked off the list.
Whats left, Mast, rigging, sails
this is going to take some time.
I will post some picture of the hull when I get round to finnishing the painting.
More questions to come.
Geoff
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If you are going the plaster of paris route, use as little water as possible when mixing the plaster. I used too much water, and it took weeks for the mould to dry out enough to risk pouring lead, even had it in the oven at one point. But in the end it produced a good bulb that didn't need much fairing. Having said that, on my next boat I bought a ready cast keel, expensive, particularily the postage, but worth it.
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Ukengineman is very wise to issue the protective clothing warning!
Molten lead can splash and is potentially very dangerous.? The fumes are poisonous also.
When I was a youngster (a couple of years ago) I used to make my own lead weights for fishing.? I had a couple of instances where molten lead actually buried itself into the flesh on my hands.
On one occasion, my hand became sore again after about 12 months and out popped a lead slug about half an inch long! I still carry the scar.? On another occasion I ended up in A&E at Ormskirk having local anasthetic while a surgeon dug aroung inside my knuckle joint with a surgical instrument to remove another lump of lead.
Not much fun! Be careful.
Regards, Malcolm Reade
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I found that when making all my keel weights with the plaster method that if, when you are going to use the mould spray it with your wifes anti stick cooking spray and the plaster seems to leave less marks in the lead and it also falls out of the mould very easily, my weights range from 2.5 kilos for the metre yacht, to 12 kilos for the A class yacht..
Goodluck Roy
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Hi All
Does anyone know if the "Liquid Lead", sold by Howes Models is any good for casting Yacht Bulbs
John
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Hello,
A nice SAFE way of making a Keel bulb, is to laminate one using Lead Flashing.
The Flashing can be cut with scissors, laid out flat and soldered together with a BIG Soldering Iron.
When enough Bulb panels have been cut out and weighed, clamp them all together between two pieces of wood and solder along the panel edges.
A streamlined " Shark " shape can be made by reducing the panel size on each side.
Also make the cutout for the Keel BEFORE soldering the thing together!, just leave a suitably sized gap in the middle.
ALL the bulb panels should be vertical and in line with the Keel.
Rasp the Bulb into shape, check the weight, Filler all the rough bits, Epoxy to the Keel.
Drill some small holes thro the Bulb and Keel, to take Brass Rods to make sure it dont fall off !!.
JayDee. ;D ;D ;D
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Reading JayDee's method set the remnants of my grey matter working. If you don't have a BIG soldering iron but did have a BUTANE TORCH, could you clamp all the sheets together and then blast them with the blowtorch to melt them together a la kebab machine !!
Now I'm starting to feel hungry !
MikeK :'( :'(
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I used two part epoxy and a covering of car body filler. Has lasted two seasons now and shows no sign of wear and tear, apart from the paint.
Cheers
Doug
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Hello,
My soldering iron is 75 Watt, I was very surprised how easy it was to melt the Lead Flashing with it.
I started using cored Solder, but soon found out it was not needed, the Lead flowed very easily and soon smooth surfaces were achieved.
If a Gas torch was to be used I think it would be too hot, Lead melts in a fraction of a second, a flame would place the Lead Bulb in your Shoes !!!.
This is after all, supposed to be a SAFE method!.
JayDee. ;) ;)
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point taken JD
MikeK
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Hi Chaps,
Just a word on melting lead flashing, a propane or butane torch is perfectly acceptable providing it has the right burner (pin point).
We professionals use either oxy/propane or better still oxy/acetylene. The process is called lead burning and is the approved way of joining lead sheet to make flashings. The filler stick is an off cut of lead not solder.
Yours Colin H.
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Hello Colin,
The key word in your post seems to be "Professionals".
The ownership of the correct burner tip would not be very common.
Soldering irons seem to be owned by many people.
While you can perform " Lead Burning ", can the rest of us do it too ??.
I admit, I have only used the Soldering method, but, it is SAFE !!.
JayDee. ( Retired Mechanical Engineer )
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Now, now JayDee, do I detect a hackle or two starting to twitch ? ;) My original remark was made when running through your method in my mind and wondering if you could play a butane torch over the lead, because it has such a low melting point. I certainly take your point about safety, I was thinking more about somebody who had a torch and not a big iron who didn't want the expense for a virtually one - off job.
Hope I havn't started something here !! ;D ;D
MikeK (Retired Navigator and I still get lost !!)
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Hello Mike,
NO problem !.
Just pointing out the general safety aspect.
John. :-[
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Hello Mike,
NO problem !.
Just pointing out the general safety aspect.
John. :-[
Cheers, John
MikeK
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i used the plaster mould for my bulb and i put the mould in the oven for 2 hrs on gas mark 3 to dry her out!! worked great for me,for my mould i used dry wall adhesive not plaster of paris its cheaper from b and q lol!!.
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Hi all, if you are just after a streamlined torpedo shaped lead keel then Graupner do one ( I paid £15.00 ) for it a few years ago and it was for the Libera Ocean kit.
And IOM yacht suppliers do lead keels.
As said above it can be dangerous and there is less and less expertise around for this kind of activity. Otherwise its laminated lead flashing which is quite cheap.
regards Roy