constructing new centerboard, pour foam in a mold

[davisr]

There are many of us who are trying to maintain or refit an old boat that would otherwise be lost to time. For everyone out there who is facing the necessity of replacing an old and worn centerboard, I thought it would be helpful to share with you everything I learned in the construction of a new centerboard for my Ericson 25. I destroyed my old board and reverse-engineered it to build the new one. The building of the new one involved making a mold, filling it with pour foam, and then shaping the foam into a foil shape before applying the kevlar, biax, xynole, and 10 ounce cloth. It was a big project, but, in the end, a satisfying one.

Regards,
Roscoe

http://www.ericson25.com/2013/01/centerboard-construction-part-1.html

http://www.ericson25.com/2013/01/centerboard-construction-part-ii.html

http://www.ericson25.com/2013/01/centerboard-construction-part-iii.html

http://www.ericson25.com/2013/01/centerboard-construction-part-iv.html

http://www.ericson25.com/2013/05/centerboard-construction-part-5-kevlar.html

http://www.ericson25.com/2013/05/centerboard-construction-part-6.html

http://www.ericson25.com/2013/05/centerboard-construction-part-7-sanding.html

http://www.ericson25.com/2013/05/centerboard-construction-part-8-xynole.html

http://www.ericson25.com/2013/06/centerboard-construction-part-9-bottom.html

 

[anchorclanker]

Wow, thats a lot of work. I'm sure that's a lot more work than the factory put into it originally, and should last much longer.

 

[davisr]

Yes, it was far more work than I ever imagined it would be. Most of the work involved figuring out how to do it. Now I think I could do it much faster. I suppose the factory faced a similar learning curve.

I must say that having done this, I'm convinced that this was the way they built the original board - pour-foam in a mold that was then planed and sanded by hand into the foil shape. I really can't imagine that they had a foil-shaped mold. I think they had some surfer dude who could do it quickly by hand.

Roscoe

 

[anchorclanker]

Im sure they had a mold. You could easily make one from yours, and that chore would be much less labor intensive than what youve done so far. Once you had a mold you could start cranking them out. However, it is doubtful the factory one would be as clean in profile as they just wouldnt take that much time smoothing it out as nice.

 

[Merlin Clark]

What does the board weigh? I like the hunk of metal, mine has a slab like that and has held up fine (not snapped off) during 45 years of sailing Florida's skinny waters.
Great job!

 

[davisr]

There's a friend of mine who also thinks they used a foil shaped mold, and that might have been the case. I'm incliined, though, for two reasons, to believe that they used a square mold and a surfer dude to shape the squared-off board into a foil shape. First, I believe it would have been difficult to center the steel (with lead plates on either side) within a foil-shaped mold. Secondly, given the speed with which my surfboard-making neighbor shaped my squared-off board into a foil shape with just an electric planer, a rasp, and a large sheet of drum-sander sandpaper, I believe it would have been a relatively small amount of labor for a skiilled surf-board maker back in the 1970s in Souhern California where Ericsons were made. I guess the jury is still out on this one.

As far as the weight is concerned . . . the original board was 150 lbs. This included the two lead plates whiich weighed between 40 and 42 pounds each. Given that I built the board to the original specs (except that I used 3/16 inch steel instead of 1/8) and I reused the lead plates, I would say the board is slightly heavier. I tried to weigh it when I was finished but the Admiral told me I would break her scale if I stood on it while holding that board. So . . . the jury is still out on this one too.

Thanks for the compliments.

Roscoe

 

[vulcan98]

Great details in your write up. Very much enjoyed reading it. That was a huge project to under take, & you stuck with it. Sounds like you live in an area with a large group of skilled folks, love it when folks share their skills and are willing to help.
Again talks for sharing, & what a great write up.

 

[Brian S]

Roscoe, the Left Coast Dart keel is definitely built in a mold. I remember seeing the original prototype build log, including how they built the molds and stuff. I can't find that original build log website, but I'm sure if you contacted Jim Lee, he'd let you know where it is, or send you pics of the keel molds being made: http://www.leftcoast.biz/iWeb/Left_Coast/The_Dart.html

Brian