: OK so I admit to it - I have the bug.

Happy to hear that, Bill. :)

: . . . My question to those who have done these is do you use the wider
: spaced SOF forms or do you interpolate the offsets to create
: more closely spaced forms to get a better hull shape?

Either way might work. A little depends on the exact shape of the SOF forms.

The easiest way is if the SOF has ribs instead of forms. just lay your strips over the ribs. They are closely spaced already. if your ribbed boat has 3/8" stringers lashed on to the outside of the ribs, then the outside of the boat built with 1/4" strips will be slightly narrower than a skin boat because of the reduced thickness of the wood strips.

You can reduce this even more by using wood strips which are only 1/16" thick--about the thickness of veneer--if you want a real challenge. Of course matching edges and sanding are going to be delicate jobs,(that is where the cahllenge comes in) but the theory is that actual strip thickness isn't important. The ribs are supporting the strength of the boat (Yup, leave them in), and any glass you put over the wood will be stronger than a canvas, nylon, or polyester skin.With strips this thin you trim them with a sharp knife, and forget about bead and cove edges. Fitting strips is as fast as tracing the trim line with a knife blade, and going over that same line twice with the knife. The excess falls off and you put on the strip.

If you want to remove all the ribs, then you can use 1/8" strips and put on a double layer. You can plank this with the strips going diagonally or straight in line. Or, go with one layer going diagonally and the other layer straight in line. Hull wall thickness is now 1/4", you can remove the ribs, and with this construction fiberglass is optional. Just glue everything together with epoxy or another truly waterproof glue, and paint inside and out with two coats of epoxy.

Again. working with a boat that uses ribs and stringers which are 3/8" to 1/2" thick: To match the outside shape of an SOF, staple or lash foundation strips to the ribs. Make these strips from cheap white construction lumber (spruce, pine, fir, hemlock, whatever), and they can be short lengths. space them an inch or so apart. They can go on the ribs at a 45 degree angle, or straight from bow to stern. Shellac and wax the foundation strips so that your glue doesn't stick to them. the shellac dries fast, and you can just rub on paste wax. This becomes a fair base which you can lay your final strips on. If the SOF uses 3/8" stringers, you can use foundations strips which are 3/16", and cover them with strips which are also 3/16" thick. If your SOF design uses 1/2" stringers then you can use 1/4 inch or 5/16" foundation strips and 1/4" or 3/16" (respectively)for your final strips.

The problem with working from cut plywood forms is that often the shape of the form is made so that the stringers protrude, and the plywood is cut away so that the flexing skin does not come in contact with it. In this case it may actually be easier ( and much faster) to make a plywood skinned boat. Cut long panels of plywood (8 feet long will do, or scarf some longer if you must), Use a lot of clamps, or get a helper to hold this alongside the kayak frame and trace along two adjoining stringers. cut on the line and the plywood panel should ft fine to fill in the space between those stringers. If you want to make a joint in the middle of each stringer, trim down the piece you cut by half the width of that stringer. Work your way around the kayak, fitting plywood pieces between each pair of stringers.

Perhaps you have noticed that the fabric stretched between each stringer (or chine) is a flat surface. replacing it with another flat surface (the plywood) works just fine. use the stringers (chines) as mating surfaces between the plywood panels, or, after getting the plywood to fit, join the plywood panels with wires,pull the pieces off the frame, tighten the wires and replace the chines with a thickened epoxy and fiberglass mix. You now have a stitch and glue kayak based on your SOF plans.

If you want to go with strips instead of plywood, use the SOF frames as a starting point and make slightly smaller ones (scrap lumber will work fine for this) to serve as building frames. I'll try to knock out a prototype of this in the next couple of days and post a picture of it. It is easier to view that describe.

: Is it this simple or should I consider loading the offsets into a CAD
: program and let it do the curve smoothing?

It is even simpler.

actual spacing on the frames does not need to be one foot apart. Strip canoe plans used to space forms 18" or 24" apart. If you have full-length strips and a simple shape, you really only need one frame in the middle of the boat, and bend the strips to meet at the ends! That may not give the most scientific hull shape, but it has worked for years. Any other ribs or frames between the middle of the boat and the ends just support the chines or stringers or wood planks, and serve as center points for changing the direction of their curves.. Thicker chines need fewer supports, hulls with simpler curves need fewer forms. Take a look at how Tom Yost's building plans (yostwerks.com) show shaping a kayak frame's ends and rocker by inserting two forms into a few aluminum tubes, then pulling the center down, and gathering the tubes at the ends of the boat. As the tubes are bent into fair curves they come together naturally. Those two forms define the shape. Adding more forms refines the shape, and supports the length of the stringers.

If your SOF forms are placed as much as 3 feet apart you can build on them as is. just be careful with keeping the edges of your strips together while the glue hardens. this is a case where bead-and-cove-edged strips can be useful. if the forms are 2' to 3' apart (or greater) you might want to use scrap strips to bridge the areas and provide support for your good strips.

Hope this helps

PGJ