: I downloaded the KAPER spreadsheet and yes it takes a number of simplified
: parameters, not the hull shape, that makes one wonder how accurate this
: can be. It may very well be OK but the subtleties of the design are
: entered in a rough way. And maybe that's all that matters.

You can find the history of KAPER on the Internet and also in Winter's Shape of the Canoe. The results were verified using tank tests of a limited number of kayaks, and it was shown at higher speeds not to be completely accurate, so Broze modified the formula (this is the one in the spreadsheet and not in Delft/Free). For Freeship, Martijn decided to limit the resistance calculated to the hull speed, because of the inaccuracy introduced by Broze to account for the difference in what KAPER was producing vs. tank tests at higher speeds.

It's key to understand that resistance prediction programs aren't the end all for resistance, they're a tool to help you design the most efficient craft within your design goals. And they allow a simple and quick comparison between one aspect of kayaks. Sea Kayaker Magazine explains this more elegantly than I have.

: If
: KAPER can't resolve it we need to find fluid dynamics software but frankly
: that is more than what I want to take on now.

Michlet. http://www.cyberiad.net/michlet.htm It's free. Freeship/Delft outputs to its file format, so this makes it easy.

: A sharp chine has some other advantages like cutting through waves without
: much pitch and tracking without much yaw. This will improve the efficiency
: in typical ocean water. So the KAPER numbers are only marginally relevant
: because it is for flatwater without yaw caused by the paddler, I just
: don't want them to be horrible.

CANTRACT is a tracking prediction software that can give you an idea of how your kayak will track and then you can figure out the kind of resistance penalty that you'll run into because of lack of tracking.

: You don't bring in any convincing arguments other than your experience. I am
: really interested in the physics and modeling and would like to know how
: this works out mathematically not intuitively.

John Winter's The Shape of the Canoe. If you don't own it. http://www.greenval.com/Shape_of_the_Canoe.html Ignore the wonky weird symbols that appear between every single letter on the website.

Hope this is helpful.