Converting Shoal Keel to Centerboard-Keel

[mcollins07]

I am considering converting a 1977 Irwin 37' Mk III center-cockpit, shoal keel to a centerboard-keel. This production boat was built in both versions. Without measuring, from inside the boat the bilge looks open to the bottom of the keel. I'm not certain where the balast is placed, but I believe it is inside balast. Irwin lists the keel's draft as 4' with 20,000 lbs displacement, and 7,800 lbs balast on both models.

I'd be interested in hearing about other's experience converting to or from a centerboard/keel on any boats.

Any info on how this production centerboard-keel is desinged/built is appreciated also..

[mcollins07]

What is your opinion? Is this a practical project to undertake?

[Hunter25]

It certainly is a possible project, but I do not think the average person is capable of this type of work. The removal of the interior is difficult enough, so is the ballast, construction of the case, board, recasting the new ballast, the structural alterations, modifications to the interior to accommodate the case and other modifications, reassembly of the modified interior, etc. should have you running to hide.

What size budget do you have set aside for this project? How much fiberglassing experience?

[mcollins07]

Thanks for you input. I do have some fiberglass experience, a couple of projects. I am also considering vacuum resin infusion as the technique, so that would require some development work in itself. As for budget, that is what I am trying to determine. I would like to have a budget set aside close to what it would cost to hire it done, before starting such a project.

[mcollins07]

Originally Posted by Hunter25

It certainly is a possible project, but ... construction of the case, ...

The construction of the case it the area I have the most questions. How tight a fit is the case to the board?

I believe the original boards were 50 to 75 pounds, So they must be fiberglass. I'm considering fiberglass and steel for the board, but I'm leaning toward steel. Fiberglass would have a better foil shape. the steel would only be an approximation to a foil. Another concern, is a fiberglass case sufficient to use with a steel board?