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Monday, August 30, 2010

Minding the Gap

We had a great time at the PNW Westsail Rendezvous last weekend. Despite being unable to stay very long. But still, it is always inspiring to meet/talk to fellow owners and sniff around their boats. Even though they are same "models" everyone's boat is different. Owners continually make changes. I am sure we will be the same.

Anyway, speaking of inspiring talks... we chatted with Dave King about his Pacific Cup winning Westsail 32 "Saraband". He said the boat has gained nearly a knot by doing some simple underbody fairing mods to improve laminar flow and reduce drag. As he described it, it sounded quite easy to do, as the mods are not structural. Just simple glass over foam against the existing hull. While not exactly the same thing, this got me thinking about the gap between the skeg and rudder on our W42.

Since we installed the rudder, there is about a 2 inch gap between the skeg and leading edge of the rudder. Enough of a gap that I think would increase drag. If you look at most sailboats in the yard, with skeg hung rudders, the trailing edge of the skeg is often closely molded to receive the rudder. This improves flow and reduces drag. I had been wondering how to fill this gap, or if I should even bother. But one thing Dave kept saying about his mod was "Hey, the boat is already out of the water, and it is an easy project." So, that pushed me over to try something.

After a couple hours on the 3D software, and CNC machine, I had cut a couple shims machined from Coosa fitted and ready to be glued/glassed. I am not sure this will yield a knot gain in speed, but you never know lol.

Modeling the shape of the shim.

Test cut using cheap insulation foam.

Final piece cut from Coosa

Final fit of the shim


Jay Bietz said...


Any thought of making these inserts for the WS 32's? We all have the same problem wit the gap.

Jay Bietz

Jay Bietz said...

Here is how Dave finished off the hull modifications above the water line.

robert said...

Hey Jay,

Sure, on the shims for the W32's. We could probably work something out. I'll just need some dimensions. Email me at if you are serious.

Thanks for the DK link.