Tuesday, December 21, 2010


The centerboard was probably one of the more interesting challenges in building the boat so far. Getting the basic shape was just a matter of taking the measurements off the plans and marking it out on a piece of plywood. Again, I used my router trammel setup to cut the big curve at the one end and the jigsaw for the smaller curves. 

The plans did not have any information on how to shape the centerboard though so it was off to the Internet for another lesson and to solicit advice. A big thanks to everyone who is willing to share and help, it is invaluable to first timers like us. We learned that a good rule of thumb is to shape the centerboard with the trailing edge being half the width of the leading edge. And that the bottom 6-8” of the centerboard should be shaped to a thin edge (we went with ~1/4”). Shaping was done by hand with a plane and basically the shape was determined by “eye balling” it. Plywood really is easy to work with in this way as you can see exactly how many “plys” you have cut through all the way along. The leading edge was rounded over using a router and lightly sanded smooth.

Roughed out centerboard

Taper on bottom edge

With the final shape determined it was on to addressing the two lead weights that keep the centerboard in the water during sailing. We made the holes with a small trammel jig that I have for my router—a vintage original Black & Decker jig from the 60’s? that has only seen service a handful of times. Screws were then drilled on the inside of the holes and the heads left protruding by approximately 5/8”. The molten lead will form around these and keep the lead from falling out as it cools and contracts.

All set to pour the molten lead

A view of the whole centerboard

We had read on the Internet that some people have used old tire weights as a source of free lead. Being frugally minded this seemed like the best way to go, so off to my local Costco to ask them if they would help me out. The guy I spoke with was more than eager to help but a little apologetic that they didn’t have much old lead around that day. Still he filled a little bag for me and off I went as happy as can be. Once home we ran a few calculations to determine exactly how much lead we really needed. It was just a matter of a little geometry and specific weight calculations to determine that we needed almost twice as much as my little bag contained. No troubles though, I just stopped by Costco again the following week and got a little larger bag this time.

Now on to the fun stuff, melting and pouring the lead. Everyone knows that lead isn’t good for you so some precautions are necessary to minimize your exposure to harmful lead fumes. Even though I did grow up in the era of leaded gasoline and the fact that this would be a one time job I decided to take no chances. The lead would be melted outside in a can on a propane burner and a large fan was positioned to blow the fumes downwind and away from me.

Fan and melting pot setup

With everything set up properly I lit the burner and started the melting process. Not much happened at first but then some of the lead started to melt so I added more. Still some of the lead was clearly not melting. A little probing and I realized that some of the non-melted material was the steel section of the lead weights that is used to attach the weights to the tire rim. I started carefully removing these with a pair of pliers. Looking at the rest of the lead mass, some molten and some still in its original state I realized that there are two distinct types of lead weights, ones that are obviously lead and others that seem to be made of another type of material that will not easily melt (these weights are much harder and do not bend easily).

Cauldron of melting lead

This revelation meant that I would not have enough molten lead to pour the two weights in one pour…..so I decided to pack the holes with larger pieces of the non-lead weights and then pour my molten lead around these rather than going through the whole process of securing more lead weights and another pour. Thankfully it worked out perfectly, I used all of the molten lead and both of the holes were full. The actual pour was both rush and terrifying at the same time…I would do it again in a heart beat.

The pour

The finished result

Once the lead was cold I filed the tops until they were smooth to the surface of the centerboard and then used a little bondo to fill in any imperfections on the whole centerboard. To add strength to the centerboard we decided to cover it with 4 oz fiberglass. However, before we could start the fiberglassing I drilled a hole for the centerboard pin and inserted a short section of ½” copper pipe and epoxied it in place. The pipe will serve as a sleeve for the pin and allow the centerboard to rotate freely if we can find the correct sized rod for the pin (I understand that a 9/16” bolt is a perfect match). But, that is a problem for later.

Centerboard with copper pipe epoxied in place

First, we cut the fiberglass cloth to size by wrapping it around the centerboard and marking directly on cloth where to cut. With the cloth cut, we now had to decide how to proceed. Do we try to apply the fiberglass cloth to the entire centerboard in a single application, or do we tackle one side at a time? I could not see how it would be possible support the wet board to do the whole job in a single application so I decided to do one side at a time. With the glass in place, I wet out one side of the glass completely working from the middle to the edges. At the edges I just left them floating beyond the edge of the plywood. When the epoxy dried, I just trimmed off the overhanging hardened cloth with a sharp knife—very slick. The only difficulty I encountered glassing the second side was dealing with the leading edge. What I discovered was that you have to be really careful to keep the glass tight and not to apply too much epoxy or it will run onto the already hardened side. The final step will be to apply another one or two plies of glass cloth to the bottom edge (and maybe the leading edge too) to reinforce this area (note: after the initial glassing there is no fiberglass on the bottom edge). I haven’t finished this step yet but will get around to it in the near future. We also plan to paint the centerboard.

First side glassed

Second side glassed

1 comment:

  1. Impressive developments and my personal commendations concernin valiance regarding lead utilization. I eagerly await the completion of this craft!