: I've decided to partition the 17ft.+ guillemot s&g into three scarfable
: sections, approximately, 6ft.- 5ft. - 6ft. (6-6-6 just didn't sit well for
: me for some reason).

: Is there any advantage in choosing another combination, say 8'-8'-1' or
: 4'-8'-5' for instance?

I suspect that a good many plans for kayaks which are 15 to 15.5 feet long are created with the intention of using the maximum amount from 2 sheets of plywood. Anything longer than that (usually) calls for buying another full sheet.

Think of what uses you might have for the material which you are cutting off. Big pieces of "scrap", say a 4x7 foot panel, would be large enough for quite a few other projects, while small pieces (say 4x2) might be easy to store, but too small for other purposes. If you go 4-8-5 you'll have a 4x4 panel and a 3x4 panel left over. Got any uses in mind for stuff that size? Got a friend who is building a boat who needs to stretch his materials a bit?

If you are making 2 or more boats you can plan your scarfs so that you use 5 full size sheets of plywood for 2 boats. otherwise, you use three sheets for each boat.

By the way, for a 17 foot boat you will need panels which are longer than 17feet. Remember that the wood goes around the outside of the curved hull, while the length is a straight-line measurement up the middle. Depending on the overhangs at the bow and stern, the floor of the boat (the bottom two panels) may be quite a bit shorter. You may only need material 15.5 to 16 feet long for the bottom.

If the cockpit opening is 18 inches long, which is pretty tight--some are much longer, you can make the deck from 4 pieces: A front, a back, and two sides. If you have a peaked deck, you'll use 5 pieces and split the front deck into a left and a right side. The sides along the opening for the cockpit can be very narrow and they can be attached with butt blocks, or scarfed to the rest of the deck, or attached to the deckbeams and supports for the coaming.

Let us suppose that are going to try working with just 2 plywood sheets. You rip off a piece 12 inches wide from each panel, giving you material for the sides, and leaving 2 panels 36 inches wide and 8 feet long. For a 24 inch wide kayak the floor will be made from panels that are about 9 to 11 inches wide, and the deck will need to be about 25-26 inches wide. We rough cut the parts we need, then scarf the floor panels together, and finally trim to the right size. The excess can be used for the deck, and there will be wide areas which can be removed which are suitable for scafing onto the tips of the side pieces, to stretch them to the 17.5 to 18 feet you need. Using butt blocks at the bow and stern not only lets you add those tip pieces easily, but they are smaller there, so they are lighter weight, they don't need to flex there, they give a stronger bow, and the thicker wood is a stronger place to attach carry handles and deck lines.

This doesn't work with all designs, but by carefully laying out your plans on paper--do it to scale on a sheet 0f typing paper, you'll find where the "waste" is, and discover if it can be made to work for you. Don't rule out the possibility of scarfing 1/2-8-8-1/2 to get 17 feet. If all you need to do is recover that 1/2 foot from what would otherwise be scrap, then you'll be saving quite a bit of money. Take a look at the illustration below for how that idea works.

Hope this helps

PGJ