Wooden Boat People
By McKenzieDriftBoat.com
A few questions about wood vs. foam
I am in the process of building a modified Briggs dory from Roger Fletcher's book. It will be about 15'9" at the centerline and a double-ender. The hull is marine grade plywood and is all scarfed together and the frames are built. (Boy, I sure hope this works...)
I am new at building dories, but I have rowed one fairly extensively that my ex owned... The River Gypsy. The Gypsy had a honey-comb kevlar bottom (and partway up the sides) and was stitch and glue construction. I like the idea of a lightweight, durable material for the bottom of the boat, but after putting three large holes in the chine, I'm not sold on this particular material. I also have no idea how to properly fix it... we were on the Middle Fork at the time and just stuffed a bunch of epoxy and wood filler in there and called it good. It was ugly but held out about 90% of the water and as far as I know he has not done anything else to it. The relationship ended at the end of the trip but I was bit by the wooden boat bug, so here I am, and here are a few questions:
-What kind of foam works best for a durable bottom?
-How do you fix it (on and off the river?)
-I don't have much money... can I even afford to consider anything other than wood?
-Is there a cheaper polyurethane alternative?
-Do I even need to bother with chine logs if I use foam?
-Should I use it for the decking and bulkheads to keep the weight of the boat down?
Here's a few pictures: (the first are of my 1" to 1' scale model, and the last is of one of the larger chine holes in the Gypsy)
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photo 1 (4).JPG, 544 KB
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chine hole.jpg, 85 KB
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Replies to This Discussion
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Permalink Reply by AJ DeRosa on
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What's the red stuff showing in the "chine hole" photo? Is that the inner chine fillet?
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Permalink Reply by River Gypsy on
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I don't know exactly... but it kinda looks like bondo!
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Permalink Reply by lhedrick on
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The color is from the phenolic micro spheres in the fillet. They are sold by Raka. A sandable filler mixed into the epoxy to prevent the fillet from sagging.
It would be the inside fillet mixture. They are a redish brown color.
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Permalink Reply by chris towles on
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Looks like the inner chine fillet or some kind of filler. Looks like microbaloons to me.
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I have used microbaloons for fairing mixes in the past but never imagined that they would be used in an area that needs strength. I would have thought that something like chopped fibers, silica or cabasol would be the addative in the chine fillet. I'm just a clueless "wood guy" trying to learn about S$G construction.
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Well, it's in the mix is just to prevent the fillet from sagging along with just enough silica so it can be applied smoothly. Just enough to make the inside chine joint curved. The glass layers on top are what carry the load.
Once upon a time I made the fillets thicker thinking they would be stronger. One of my poor judgment calls. Wasted lots of epoxy and time mixing and like you say, no value at all. Now I only use just enough to create as small a fillet as possible to prevent the glass tape from lifting and pulling air under it.
On big water boats I use many layers. I lap many layers over the chine
bottom 17 ounce bi-axial glass up over and over 3 inches
side glass down and over
another layer of bottom glass up and over.
1 layer 17 ounce biaxial stem to transom
2 layers of 17 ounce bi-axial in the centers section
inside
1 layers 17 bi-axisl stem to transom
2 more layers 17 ounce bi-axial stem to transom
9 layer in all. The fillet material really plays no part.
If I have kevlar I will use that too.
The only problem is the edge build up form all the layers which needs to be filled and faired. Make a hump in the finish but, at least is reasonable tough.
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