Skip to main content

Cast Lead Bulbs and Ballasts!

Today I finally made my first attempts at casting lead bulbs and ballasts, and it turned out well!

Over a month ago, I made some female molds out of refractory cement. They are now fully cured.

One mold was for torpedo style bulbs for the Sun Winds and Rip Tides. It has two slightly diffferent-sized bulbs in it. The molds I made seemed to just miss the sweet spot. I made one slightly smaller than the other in the hopes that one of the two molds would produce a 4.5 lb. half-bulb for a 9 lb. total bulb. The smaller mold turned out a 3 lb. 5 oz. half-bulb, and the larger one turned out a 4 lb. 14 oz. bulb. However, I think I over-poured the larger one, and if I take better care in my pouring I think it would make a 4.5 lb. half-bulb. So I'm really close!

Yes, I made "half bulbs" instead of a solid bulb with a slot in it. My system for mounting the bulbs is to have an thin inner-core of plywood that the two halves mount onto. 

I also made ballast halves for the Wampum VM. They turned out OK but needed a lot of clean-up. They also seemed to have some bubbles in them somehow. Not sure what I did to cause the bubbles. Too hot? Too cool?

Many, many thanks to Rod Carr for loaning me the casting equipment and supplying the lead! It worked perfectly. Thanks Rod!

I started earlier in the day by putting the cured concrete molds in a COLD oven and then turning it on to 150 and letting it heat up so that the thermal shock of the molten lead would be less likely to crack them. I used refractory cement which should be able to handle it, but just wanted to be sure.

I brushed on a good amount of talcum powder as a release agent. Worked really well.

 Here is my second attempt at the Wampum VM ballasts. Turned out OK.

Below is my second attempt at the Sun Wind HF/Rip Tide HF torpedo bulbs. This one weighs 4 lbs. 14 oz. That may be a touch too heavy, but I think I can now pour one that is closer to 4.5 lbs. for each half-bulb.

Here is how the ballasts will fit onto the Wampum VM keel. They'll need some cleaning up and a lot of filling, but should work just fine. Together they weigh about 11.5 lbs. The original called for 12.



Popular posts from this blog

IOM Sailboat Stand

I made an IOM boat stand! The plans are from David Jensen in Bellevue, WA, USA. I found the plans through someone else's blog here , and a model sailboat club from Australia here . It was pretty straightforward to build. My only contribution to the design is that I laser cut the cradle out of 1/8" Lite Ply. I made eight copies, and then epoxy laminated two sets of four each. Turned out really well. If you wish to laser cut your own set, here is my DWG file . You'll have to have your own laser cutter, or send the job to a laser cutting company like National Balsa . Here are the original plans , and here are the original plans for just the cradle . Thanks to David Jensen!! Note that in the picture below, my boat is not finished! Yikes. You can't see it in this image, but there's a small chuck of self-stick foam behind the bulb to protect the bulb. I'll eventually incorporate some Velcro or a strap of some sort to hold the bulb in place so

IOM Rig Box (IOM Sail Box) plans

So all the cool IOM kids seem to have nice wooden boxes to store their rigs in. This might be my next quick project then, so that I can pretend to be cool too. :-P The rig box images that I've seen online are mostly similar, and would work well, but David Jensen from Bellevue, WA, USA (The same guy who designed a fantastic IOM boat stand I posted about earlier) has a really nice design that he shared on RC Groups . Or if that link doesn't work, the go here and search for " IOM sail box " or " IOM rig box ". It holds three sets of rigs for the A, B, and C rigs. He also has a nifty way to attach his IOM boat stand, with a boat on it, to the rig box. His rig box has wheels attached, so once everything is loaded up he just wheels it to the launch spot. Very nice! There are other sources online. They show different variations of the same type of sail box. Here's a nice looking one . Here's a YouTube video of a really nice one . Wil

A Wooden "Alternative" IOM RC Sailboat

Being forced to stay home due to the Coronavirus quarantine has had a positive impact on my boat building. I still haven't been able to sail my newly completed Vickers V8 IOM, yet have just planked and glassed a wooden Alternative IOM . It only took me eight days. It usually takes a couple weeks. I haven't been motivated to blog about it, but I started planking on 5 April and finished planking last night. Today I sanded and have fiberglassed the outside. The Alternative by Brad Gibson was a challenge to plank due to its up-swept bow and flared sheer near the bow. It turned out okay, but as any builder will tell you, there are goofs all over. One that I only discovered after sanding is a lighter colored plank on the starboard side. It really showed up after fiberglassing as the epoxy brought it out... GAAAAH! How did that get there? The other goofs I'll let you find, but that one is pretty obvious. Here's how it looks so far: Here you can see that mu

IOM Alignment and Measuring Jig (UPDATED)

I need to start to consider how I'll mount the fin and bulb, and get it all straight, so I made a 3D modeled alignment jig: Ian Dundas in Scottland sent me pictures of his setup. I just bought a laser level too! He does amazing work and has been a great help in this project so far. There is also another jig featured on page 14 of the winter 2008 Canadian Radio Yacht Association (CRYA) newsletter that features one. It's by Lawire Neish. Read it here . I took both those designs and made my own version that features sliding cradles for the hull, a fixed waterline sight, proper depth to cradles for the bulb, etc... Most of the parts can be laser cut, and the two end pieces and the base can easily be cut on a tablesaw. It has fixed waterline sights that are 420mm above the top edges of the bulb sliders in the base. The fore and aft cradles can be slid up and down to adjust the waterline of the hull. You'll see that the overall interior length is 1003mm t