Duckworks - Projects
The Online Magazine For Amateur Boat Builders

The Joy of Leading
by Andrew Linn

The Cultus Hehtheht (our PDRacer) will have 2 pieces of wood that hang down into the water: The leeboard (the big one) and the rudder. The leeboard helps control lateral - sideways - movement and the rudder steers the boat. Being wood, these float, and so must be weighted to keep them in the water. click to enlarge
click to enlarge
(click images to enlarge)
As usual, there is math involved. According to websites, the leaded area should be about 7% of the surface area that will be under water. My rudder is 16x20, or 320 sq inches, requiring a cutout of about 22.4 sq inches. I decided to go with a 5x5 cutout for the rudder and a 4x9 cutout for the leeboard (25 sq inches and 32sq inches). I drew the square near the bottom of the leading edge of the rudder and drilled through the corners of the square to make cutting easier.
Cutting couldn't be easier. Take the jigsaw and get going. click to enlarge
click to enlarge
(click images to enlarge)
Lead shrinks as it cools so the websites say to bevel the edges of the cutouts to create a lip the led can grip. I used a 45 degree router bit. I normally hate routers. as a kid of about 6 or 7, my carpenter grandfather told me "Boy, of all the tools in this shop, the one that'll most likely chew you up is this here router." I am 41 years old, and am still terrified of routers.
Finally, the websites suggest driving nails around the perimeter of the cutout to act as anchors. It was easier to drive the anchor nails into the 5x5 hole than the 4x9 hole, but I got them in. click to enlarge
click to enlarge
And here are the pieces, ready for leading. 7% of the wetted area, beveled edges, anchor nails around the perimeter.
I got this lead for free from a tire shop, the guys were more than happy to help. Lead weighs .4lbs per cubic inch, and my rudder / leeboard are about .4 to .5 thick, so for the rudder, I anticipated needing between 4 and 5 lbs of lead. I should have added some padding to this, maybe doubling the amount just to make sure I had enough ready. click to enlarge
click to enlarge This is the foundry. Notice I am outside - lead fumes are poisonous. The crucible is a coffee can with a 3/8 inch hole drilled 3 inches up from the bottom. The heat source is propane and the furnace is the base for my turkey fryer. I like that as a furnace because it has a nice, wide base.
I clamped the rudder to a cookie sheet, intending for the cookie sheet to act as a backstop. There were 2 problems with this: 1) The clamps made for an uneven base which I did not account for - the lead pooled in one corner. 2) The cookie sheet was uneven - especially when heated - and the lead flowed out through gaps.

This was a failed try. I had to pound out the lead and think about what I was going to do.

The next day I tried again. I nailed scrap plywood to the backside of the rudder, making sure it made a good seal. I leveled the whole operation out with more scrap and weighted it down. Notice that the crucible is close to the work area - I didn't want to be hauling a bucket of molten lead all over the place. click to enlarge
click to enlarge
Not a good picture, but once poured, the lead would bubble, probably from smoke or steam being released from the plywood backstop. It didn't splatter much, but it did splatter, so be aware and be careful.
This is what I ended up with. Notice the scorch marks on the backstops and the divots in the lead caused by gas bubbles. Lead melts at something like 480 degrees and paper burns at 451 degrees, so I suggest you pour your lead as soon as it melts - within seconds - to prevent the lead from heating so much the wood catches fire. click to enlarge
click to enlarge
I smeared Elmer's Exterior Wood Putty into the divots and around the edges, then sanded it off smooth with a belt sander. This was probably the stupidest thing I did. If lead fumes are dangerous, ground up bits of lead being kicked off by a belt sander are probably worse.
Here is the finished product - it isn't glass smooth, but it isn't bad, either. If I was doing this for a real racing boat, I would probably fiberglass it in as well. click to enlarge
This leading is completely doable by the backyard boat builder. I didn't have any experience with this before I started. I did some research on the web, asked some questions, and used my head. Dress appropriately - all leather and natural fiber stuff just in case there are spills, eye protection, leather gloves and apron. Do it outside. Use your head. Be careful.