By George, I Think I've Got It!

Fussing and fiddling had finally gotten me my OWN design:

• 13 1/2 feet long,
• with 13-inch-high sides for adequate freeboard heavily loaded,
• 26 inches wide at the bottom of the center frame (for a modicum of stability)
• 33 inches wide at  the top of center frame (for modest rocker and not too wide to paddle easily),
• double-ended to be paddle either way and so as not to drag much with ends immersed,
• with exterior chine logs to fasten bottom to,
• inwales to stiffen the sides without adding width,
• canoe-style seats (in addition to the center frame) to help the hull hold its shape

(Exterior chine logs are not only easier to make, but might also help the boat keep from sliding sideways in a breeze.)  Two people can paddle it comfortably.  If someone goes solo, reverse the boat so you're on the forward seat facing aft (the usual "stern" being the new "bow") for better one-person balance.  (Not an idea original to me, by the way.)

I started measuring the sides on ply this morning and came to an abrupt halt: this boat is so close to being a two sheeter!  If I continued, once I cut the 13" sides from the long edges, the resulting <22" wide center is a few inches too narrow to cut the bottom from--the more so because exterior chine logs add 1 1/2 inches to the width of the bottom.  At the same time I sat Stephen on the deck and measured up his side: even one-foot-high sides would make it difficult for him to paddle.  (Granted he wouldn't usually be sitting flat on the bottom, but either on canoe-style seats or cushions.)

The plywood layout plan implied by my original design.  Look at all the wasted wood!

So: reduce the sides to 12 inches.  Still too little left for the bottom--even if I narrowed the center frame to 24", since the ply thickness and chine width must be taken into account. 

Ah--but cutting out the sides leaves three feet or more untouched at one end of one sheet: can I work out a way to get enough of the widest part of the bottom to fit in that few feet?  Lots of drawing, and figuring, and measuring of models later, I have a plan:  keep the bottom of the center frame at 26", making total width of bottom 28" at the middle (assuming 1/4" thick ply and 3/4" wide chine logs).  Take advantage of the stems' rake of 45 degrees (1' in from ends).  Work out how the big end of one ply sheet and the small end of other piece are combined: 4 1/2' total from edges to bottom of stem cuts.  Divide this half, making center of bottom be 15" in from edge of bigger remains piece.  Now turn to the balsa model and figure out how many inches the bottom would narrow in the 27" from middle of bottom to where the bottom would be constricted by cutting the sides.  Leave a teensy bit of slack for the saw kerf and a wandering cut.

Drawing: the overall rectangle is two sheets of plywood laid end-to-end. The sides are cut from the top and bottom edges of the ply, and the two parts of the bottom are cut from the middle beginning at the outside edges.  the leftover bit in the middle of the two ply sheets could form modest decks at the ends, with advantage advantage taken of the wedge-shaped cutouts for aesthetic affect.  The top shows the finished boat in profile and end-on.

DONE--26" full width of bottom would narrow to about 22" at 2' from the middle.  That's a little short of constriction (at 27") and still leaves a bit for errors or a more gradually-narrowing bottom!  The remaining pieces of ply would amount to 3', which (after removing 4" in the middle for a bottom butt strap) could become fore and aft decks of 12" and about 20" on centerline, but much longer on the sides because of the taper of the bottom at the ends.  Little coamings following this inside curve could make this boat look rather pretty!  There should be enough left for side butt straps, and maybe seats!  One final structural test: lining up the joints and framing, the sides are butted together over 1' forward of the center frame, and the bottom is butted together about 2-3 inches forward of the center frame, so no joints align to make a weakness that extends through the entire hull.