: . . .I'm looking for some suggestions on what kind of kayaks we should build. . .

: *During Spring vacation we will take over the entire cafeteria for building,
: so we will have plenty of space. But we will only have one week! We can
: build small parts before the vacation, but anything that requires a lot of
: space has to be done during that one vacation week.

: *It would be good if we could build folding kayaks, because we are planning a
: trip to the Sea of Cortez a year from now, and it would be nice if we
: didn't have to rent kayaks there. But folding kayaks seem too challenging.

: I'm thinking we should build doubles because it seems that taking a group of
: high school students out in doubles is safer than taking the same group
: out in singles.

I'm not convinced that is true. It does depend on the group you have. Particularly with rambunctious teens. One person can screw around and capsize the boat, and then you have 2 people who need to be pulled out and dried off: the instigator and his or her victim. With solo boats the only one dampened is the one who deserves to be. I think that you should consider making a few boat with larger cockpits, though, so they can serve to hold a passenger if necessary. You don't need to make all the boats from the same design. A mix of doubles and solo boats is another option.

:I think SOF kayaks are probably better, because we can
: make a lot of the parts before the vacation starts...and then put it all
: together during the vacation.

Well, the frame part is good, but you don't have to cover it with a fabric skin. You can use lightweight plywood panels (1/8th inch thick or even 1/4 inch) to cover the frame instead.

Make the frame and lay over it some plywood strips. You just need ones which are slightly wider than the distance between one chine to the next. Clamp it to the chines temporarily while you mark the right size. Trim it with a utility knife, jigsaw or a handsaw so it is the right size. Apply it with some sealant(acrylic or silicone caulk, or Liquid Nails)) along the full length of the chines, and screw the panel to the chines. Then fit a panel to cover the next gap.

The chines serve as attachment points and with the caulk or sealant running the full length of the chines they also waterproof the joints.

You can have adults scarf the plywood sheets into nearly 16 foot lengths ahead of time to get full length panels, or you can use the 8 foot panels and join them on the boat, backing the joint between the panels, on the inside of the boat, with small plywood pieces that are covered with sealant or a waterproof epoxy or resorcinol glue.

: Looking over this site, I am very intrigued by Tom Yost's FAP designs,
: especially the "Combi" folding double (it would be nice if we
: had some single kayaks for training purposes, and doubles for weekend
: camping trips).

Tom's designs show that there is more than one way to skin a kayak.

: So I have basically two question.

: 1) What kind of kayaks should we build?

I think you should look at designs (like Tom Yost's) which have wood chines fitted around a small number of bulkhead-type frames. The alternative form, which uses many thin ribs, would take a lot longer for a group to do.

Tom makes his frames from a strong plastic, but I think for your costs you should look at cutting yours from exterior-glued plywood. If you make several boats from one design, stack 2 to 4 sheets of plywood and cut duplicate frames at one time.

Let one person make 4 copies of frame 3, and another make the 4 copies of frame 4, and a third person make 4 copies of frame 5, etc. This way you can have all the people working on laying out the lines for a frame at the same time. Once the frames are cut they should be immediately sealed. If you can use epoxy resin, then it is wonderful. If not, then go with a waterborne exterior urethane. You'll still need some ventilation, but it doesn't have the volatile organic thnners which can be cloying in an interior building site, and it cleans up with water.

: 2) Are there any specific designs you would recommend?

The picture below is from Clark Craft's website and shows the interior of one of their doubles. (the deck canvas has not been installed. This one happens to have plywood frames (which I suggested above) so I chose the picture as an illustration. This could be your double. For a solo design they have other designs which are also built around plywood frames.

In a similar vein George Putz's book on canvas covered boats has 2 designs for a model called the "Walrus". He builds his boats around plywood building forms which are NOT part of the finished boat. You build the forms once and you can reuse them many times. With his construction methods you could practially run an assembly line for making frames, which are removed from the building forms before being covered, and then cover them all at once. Or, lay the chines in the building forms and sheathe them with the thin plywood-- skipping many of the steps Putz carefuly outlines.

the reason I suggest designs that use frames over those that use ribs is that if you are thinking of "folding" kayaks for traveling you can adapt some of these boat patterns fairly easily.

You will want to attach the chines or stringers ( depending on what the plan calls them) to the frames so that they can be removed. Be inventive in finding stainless steel fasteners.

You can use the same frames, but you may need to drill a few more holes in them for whatever fasteners you use to hold the chines on.

You will have to make shorter chine pieces, and create some manner of joining them back into longer pieces once you are at your put-in point. You can simply overlap shorter pieces and use bolts and nuts if you wish. Tom makes his chines from aluminum tubing. If you use that instead of wood you may be able to simply stack short pieces of tubing to create your long stringers. The aluminum will cost a bit more than wood for these pieces, though.

Make the kayak skins with one end sewn and the other end equipped with laces. Some designs ask you to satple the fabric to the wood parts of the boat. You don't want to do this. Instead, make the fabric fit around your frame like a pouch. If you sew the area behind the cockpit, you can then draw the fabric around the bow end, and use laces, running through grommets or eyelets, rather than sewing thread, to hold the fabric closed. Fold over the excess ends of the fabric and tuck it inside before you lace up the skin and it will keep out the water.

You want to use a flexible coating on skins which will be removed and rolled up. An elastomeric rubber (latex) roof coating is certainly flexible enugh, and water based -- again no obnoxious smells and water cleanup) An outdoor urethane coating should also work.

This way you ship the kayaks in pieces, assemble the frames with nuts and bolts (no fancy "folding" hardware) and then slide the frames into the skins. Then, kind of like putting your foot in your shoe, you lace up the skins. Assembly time might be an hour or more, but that keeps the students busy, and you would probably spend that much time waiting for a rental firm to fill out the forms otherwise.

I assume you are going to have them make their own Greenland style paddles, too.

If the school keeps the boats for future years, the students should be able to keep their own paddles. Voyageurs would draw their maps on the blades of their canoe paddles. You can do something similar by photocopying a map onto tissue paper or rice paper, and laminating these onto the paddle blades with varnish or epoxy

Hope this helps

PGJ

Clarkcraft's "roomy open double 17"

http://www.clarkcraft.com/cgi-local/shop.pl?type=categ&categ=014&cart_id=