: I won our company's cardboard boat race last year. My boat is 10' 10"
: long.
: It is 12" high. It is 20" wide form the stern to about 6 feet and
: then it tapers to the bow. The bottom of the bow has a 2" taper from
: the bow to about 5' back. The back of the boat has a slight taper. The
: boat weighs about 20 pounds. I have a rough drawing I can email. The boat
: is used on calm water, a little wind, over a 400 yard course with 2-90
: degree turns and 2 45 degree turns. The boat is paddled from the sitting
: position using hand paddles. My competators will copy my last years boat
: so I need some design help to make a faster boat. I am already planning on
: tapering the stern like the bow. Also, is the taper on the botton of the
: bow helpful or should the bottom of the boat be flat? I welcome any
: suggestions!!!

You can increase speed by increasing length which is what you will need to do anyway if you taper the stern thus loosing that volume. I was involved in something similiar once but they were not restricted to cardboard. The winning design was 2 six inch dia tubes trussed together about 2' apart and LOA was around 16'. These sizes are from memory so are not exact, but we found that with the given weight of boat and paddlers (2 in this case) the best draft on the tubes was around half or 3".

If cardboard tubes are okay for your design, then go with that, and put cones on both ends of the tubes. Calculate the displacement needed and make the length to displace that much at half dia of tube. Hope you win!