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keel


richard

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I am building my keel in plywood - 22 mm thick.

I do not need 3 layers because I can overlap with two layers since there are less pieces.

Do you think that 2 layers, giving 44 mm thickness is strong enough or should I add a 10 mm layer to get to 54 mm (as in the plans)?

What about a small aluminium strip on the keel bottom to protect it?

This is cheap, available, can be screwed on and replaced easily when needed.

Richard

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Plywood keels have been made before. Special attention must be given to attaching the bottom to the keel as the end grain of the plywood does not have the holding ability of solid wood. I think it was Joel in Seattle that documented the process. The allum. strip on the edge sounds ok to me. Good luck with the boat.

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The aluminum strip sounds good, the keel gets banged around some. I am assuming you will be fiberglassing the keel. Are you using marine ply?

There is someone else making his keel out of ply, he would be your best bet for info on thickness. My thought is thicker better, are you building a Weekender? If so you want the weight for stability.

If I had my way, meaning if I build another Vacationer, I would cut a single piece of white spruce for the bottom section of the keel and bolt the stem section in.

The more joints, the more exposed edges, and each accidental oops; the more likely moisture will find a way in, possible rot and possible delamination. The keel is the back bone of the Stevenson design. Your boat will only last as long as your keel. :roll: at least I would not want to replace one. Never heard of anyone who did, may have happened, could happen, too. Not by me I hope.

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Guest Lars Hansen

I am in the middle of the process of building a Weekender in Denmark. Up to now I have only finished the keel and bottom, but I hope to be able to do a little more boatbuilding in the summertime.

I have decided to make the keel a little thicker to make sure the boat will be strong. It is hard to find marine plywood in my local area, so I decided on building a strong keel to compensate for the plywood. On the other hand I think the extra weight in the keel will do the boat good.

Lars

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Richard,

I think you will appreciate having the additional thickness. Not only for the additional weight it gives but in the ability to pull the bottom down to the forward curve of the keel. It will also be quite a bit stronger.

You may want to drop Joel a note and ask him about his method of attaching the bottom to the keel. His went on with no problems that he has spoken about.

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Hi Richard,

I guess only having the two layers would cut down on a lot of cutting.. which would be nice.

I built my plywood keel to the width on the plans.. though thats only because I don't really know what I am doing so just follow the plans. My feeling (completely unsubstatiated) is that materials like ply are so strong in shear that the reduced thickness wouldn't be a problem. I would assume that the thickness in the plans is defined by the common thickness of wood and the desire to have three layers to prevent warping of the wooden keel.

My gut reaction is to prefer three layers as they allows a nice symmetry of the keel system, but the ply is so stable I don't think that any asymmetry in the cuts would cause a problem in a two layer structure.

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another thought.. it was mentioned above that a thicker keel might be good for the extra weight for stability.. but though I haven't tested it I have assumed that plywood floats.. is extra weight in the keel any good if it is made from a material which floats? I would have thought that would destablise the boat more than anything ?

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I am still not convinced about the stability issue Ray, closed cell foam floats, and is heavier than air, but I don't think the stability of my boat would be imporved by strapping a lot of it to the side of the keel... or have i missed the ppoint here completely ?

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Okay, first I built a Vacationer, Lord help me for giving advice about a Weekender. :shock:

The Vacationer is a whale, I can stand at any point on my boat and it won't heel over but a few degrees. ( and I am big enough to......well never mind )

The Weekender is not so tolerant I am told. Try hanging ten off the side rail to test this theory if you will, see how comfortable you feel out there.

My thought is that a keel lighter than the plans call for (I am not sure what the trade off of the wood ratio is, ply vs hard wood) might not be wise.

These boats are not self righting, that is why it is a good idea to keep the weight down low in the structure. A little extra weight in the keel is not going to hurt nothing a little extra sail or seamanship won't compensate for. Positive ballast vs positive ballast, density is the answer I think.

Lars, I have thought about doing the same thing to my Vacationer. An extra slab of Alaskan White Spruce to each side and another layer of 1/2 ply on the bottom. Lots of rocky beaches around these parts. I also sail with a variety of different foresails for the extra thrill. The real sailors on these forums tell me our boats have a basic hull speed for their design, I agree. I just might get there a little quicker :wink: no matter how much my boat displaces in water.

My point is, it is nice when the boat comes back up or resists excessive heel when the wind decides to blow. If the wind wants to be a tease and blow an occasional cats paw, thats okay too, just throw up another sail.

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John wrote:

Richard, how will you deal with the stem and stern attachments? I'm referring to how the three pieces overlap to support each other.

Hi John,

That's an easy one. I uses 2 panels 4' x 8' and made one layer in 3 pieces.

tHan I made the 2d layer, again in 3 pieces, but shifted a bit, so the borders do not coincide.

Richard

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