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1.5-ply keel?


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I was about to test-fit the keel and runners tonight, and was lamenting the large bending force that the keel is subjected to at the forwards part of the hull.

This got me to thinking -- is there any reason to not make the keel out of a double thickness of wood epoxied together? Each piece would be able to bend more easily to match the hull curve, and when epoxied would have the same strength as the one-piece keel. This would also reduce the stress on the hull from the keel.

Now, about the 1.5 part. At the stern, the hull is fairly flat. So what I'm thinking of is ripping the keel on my bandsaw (1mm kerf) from the bow to about 24" from the stern, where it will remain one piece. This will also make installation easier, as the keel will still be connected there. It will resemble a really long 2-tine comb.

Thoughts?

Michel

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I would be tempted to scribe and cut the back half of the keel are per the plan instruction, then taper the keel from maybe 2" deep mid hull to say 1/2" deep at the forward end. Visually this would be a nice effect, and the thinner wood will bend nicely with the hull. I might even take that 1/2" keel farther forward to pretect the hull during beachings.

The ply approach will work for sure. It is commonly done on gunwales as well.

Just another opinion.

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Hi Brent,

I'm planning to follow the plan dimensions for the keel + deadwood (ie, 2" thick at the stern). Just looking for a less-stressful way to install it. I've already got the V grooved into the keel and deadwood (plus an innovative way to do that, which I'll describe on my website).

Regarding length of keel: it will follow through to where the centre chine meets the bow transom, which should cover any beach landings. I'll also be adding a 3/4" x 1/8" aluminum wear strip to the bottom of the keel (but not the runners).

I'll want to test-fit the gunwales first, before I decide on whether to use the ply approach for those as well.

Michel

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There is a lot of rocker in the keel, but I thought that it should not be that difficult to install. you could certainly split the forward end to partially laminate, or you could thin down the forward end 1/8".

By the way what thickness is your bottom? If it is 6mm you do not need the outside stringers.

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Hi Graham,

The plywood is 6mm. For the stringers, I was thinking of them more as wear protection than as structural members. I think Charlie did the same on his dinghy -- one on either side of the keel to take the bumps on land.

Also, I'm diverging from the clamping suggested in the plans. Rather than use wood screws into the keel, I'm using #10 through-bolts to hold things while the epoxy cures, then removing the bolts and filling the holes with thickened epoxy. I'm trying to minimize the number of screws in the boat.

Michel

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