I needed to make an 8oz. keel weight for my Footy sailboat. I didn?t want to go to the trouble to making a plug, a mold, then mess with pouring lead. This is what I came up with (if this is common to most of you, I?m sorry, I thought it was a light bulb moment). This should work for any size or shape bulb you need to build and it?s quick and easy.
I started off with 2oz. of polymer clay (Sculpey, etc.) and 6oz. of lead birdshot, (= 8oz.). Take about 1 ? oz. of the clay and mix in the shot. Work inside a bowl or other container, unless you want vacuum little bitty BB shot off the floor (been there, done that). Knead the shot evenly throughout the clay.
Shape the clay/shot into whatever shape you want, I went for a simi, kind?a, sort?a airfoil shape. It will have a bumpy surface, that?s ok. When I had the shape I wanted, I pushed the keel into the clay, wiggled it around a little, so I would have a little room for adjustment, when I mount it. Remove the keel. Place the bulb on a foil covered baking sheet and bake according to the clay instructions. Because of the thickness, it took about 45 min. @ 275o. Remove from oven and let cool.
Next I took the remaining ? oz. of clay and rolled out a sheet about 1/16 in. thick. Then I covered the ?bumpy? bulb with the sheet of clay. Smooth out clay with your fingers until it?s as smooth as you can get it. Cut out the keel slot with a hobby knife, and then lightly rub any imperfections with your fingertip. When it?s as good as you can get it, bake it again. I did about 25 min. @ 275o. Remove from the oven and let cool.
Sand with fine, then finer sandpaper (easy, remember this is a plastic), until it?s as smooth as a baby?s ___, (well you know). When you?re ready, fill the keel slot about half full with epoxy and push the keel into the slot and brace until the epoxy cures. Clean up any epoxy that oozed out of the slot. Brush on a thin coat of epoxy, prime and paint.
I hope this was a help to some of you.
If you wet your fingers and keep them wet by dipping in a small dish of water when smoothing the unbaked clay, it will help you achieve a really nice smooth finish too.
If you are looking for a product (epoxy) that can be drilled, shaped, sanded and tapped with screw/bolt threads, take a look at JB Weld at your local hardware store. Usually small tubes, two part gray/white mix at 1:1 ratio, and it too can be worked with wet tools, popsicle sticks and fingers. Also very heat and water resistant when cured. I like the fact it can be embedded in foam to provide a drilled and tapped place to attach deck hardware and even multihull cross beams. Have also used in small lawnmower engines to fix tapped holes that were broken out. (You drill/tap after cure!)
Don’t leave home without a set of JB Weld tubes in your repair kit.
Class 3 Landyacht #US-196
I think I got the photo upload figured out. I’m trying to post my Sculpey bulb photos.
Rough “bumpy” bulb out of the oven:
Covered bulb out of the oven:
Sanded, ready for epoxy and mounting:
Very well done!!
Don’t forget to have fun!!!
That is a very cool way to make the weight. I have done somthing different and that was to use an old window sash weight, this is for my home made IOM. Used cedar strips glued and shaped then glassed for the fin? What does everybody think?[:-boggled]
If it works and can me made hydrodynamic, then who’s to really complain. Probably beats having to struggle with pouring lead.
Don’t forget to have fun!!!
Anything other than lead does leave you with more wetted surface and drag.
Though these types of methods are ways to get around the lead pouring problem.
One method I used in the past was to make a rough timber male mould of the weight.
Press it into plastacine to make the female mould and then fill it with lead shot and epoxy resin.
The plastacine is removed and the bulb cleaned up.
I wouldn’t do this now because of the reasons first noted.
I have posted about this before, I made a new lead bulb for my One Metre using Lead sheet.
Called Lead Flashing in the UK, it is used by house builders to seal brickwork joints.
I cut the Lead sheet into the correct sizes and laminated them between two pieces of wood and used a large Soldering Iron to solder them together.
Rasp the bulb to shape and the smooth it all over with some filler.
Use brass screws to fasten the bulb to the Fin, to cut down on corrosion - - -easy!!.
I’ive done similar to Jay Dee before, but instead I stuck the plates together with epoxy and then faired it using epoxy mixed with iron fileings and microbaloons (to stop the stuff running everywhere before it had a chance to go off).
Luff 'em & leave 'em.
Hopefully this picture works, this is the window sash weight
Download Attachment: PANA0379.JPG
My experience of ‘sash weights’ is of a 2" round section by about 12" long rough cast iron ‘pig’ which is now only usefull as raw material for turning parts for model steam engines. By the way your attatchment does not compute, cant download it.
I recently made a couple of ballast bulbs for two ‘Bob About’ Footies using 8oz sea fishing leads. They were of square section and ‘bomb’ shaped. I gently hammered them into round section with a reasonable streamlined shape using a normal claw hammer on the tail of my bench vice then finally smoothed them off using a hardwood mallet on a piece of softwood as the anvil. The slot to take the fin was chisled out using a terminal screw driver and it was bonded in using epoxy and microballons. Absolutely perfect solution. Cost was only ?0.60 each($1.00)and took less than half an hour to do.
When I lived in LA, Calif. I used a 4lb. Cod fishing weight on my Pea Pod. Now that I live in “Small Town”, Oklahoma, it’s kind’a hard to find the lead weights, I was looking for (not much call for deep sea tackle out here), so had to come up with something = Sculpey/birdshot.
Brett is right, anything but solid lead will add surface area and some drag. I’m just a recreation sailor/scratch builder so I won’t even notice the drag, having nothing to compare with. I have to make it up as I go. The nearest R/C racing is about 125 miles from me and there’s only one other person in town that even knows what a R/C boat is.
I’m sure I would be buying a pre-made bulb, if I was into competition racing.
The window sash weight is 12" long 1 and 1/4" thick, I do not have anyone here to race with just building my first iom (winter project) if it work and I enjoy I can always order a lead one. How do you get pictures attached?
That is a pretty clever idea. My approach was more brute force. Down on the “Third Coast” there is no shortage of fishing stuff so I was off to Academy Sports and got 8 oz fishing weights and beat it into shape, drilled a series of small holes down the middle to match the fin thickness and presto. A little filing and sanding to take the hammer marks down and then a thin coat of epoxy to fill it in. A bit more sanding on the epoxy and a weight that works. Raw material cost was maybe a buck.
Download Attachment: [ BAF Keel Ballast2.JPG](http://www.rcsailing.net/forum1/data/bdf_22/200551381317_BAF Keel Ballast2.JPG)
Hope this works. Picture of sash weight used for iom ballast, fin is cedar strips glued together then planed and sanded. Thanks OL GUY
Hey ya’ll, like they say “if it works, don’t fix it”. Kind of funny what we can come up with, when we need to solve a problem.
Any other ways to DIY a keel bulb???
I looked into moldable lead materials years ago, and I found out that you can get LEAD PUTTY. It’s not as dense as pure lead tho. Density about 4g/cc. It’s used for radiation heilding for nuclear reactors, X-ray, & MRI units, etc.
Let me show you the simplest way I have yet found to make FOOTY bulbs which would most proberly also work for larger models.
Take a brass tube, thin walled, approx 12mm…1/2inch dia.
125mm… 5inch long.
Braze a flange on…fill with lead.
Make wooden ends to your shape and glue in…your done.
Comes out around 200grams…6.66 oz