I've been laying out the sea rider forms on poster board and I'm wondering if something isn't right with my frame 4
which is the frame on the forward side of the cockpit.

http://yostwerks.com/SeaRider1.html

The offsets are given in fractional feet so I converted them all to centimeters by multiplying * 12 (in/ft) * 2.54 (cm/in).
This gives the deck ridge HAB at: .833 * 12 * 2.54 = 25.39 cm. The keel HAB for frame 4 is 0.

My first try just blindly working my way back from frame 1, I cut a squarish frame 4:

http://www.antibozo.net/cgi-bin/eric/imglib/prod/image.pl/eric/pictures/Archive/2009_sea_rider/1-resized/IMG_1898.jpg

I end up with a pretty small opening to squeeze my legs through. Only about 6-3/4 inches high at the centerline. Checked
all the HABs and I think they are right. It is approximately 25.4 cm from the keel to the top of the form at the deck ridge.
Looking at the pics of wooden sea rider frames I see that they show a form 4 with a rounded masik-like upper span for
frame 4 so I drew one like that which opens up a little more leg room:

http://www.antibozo.net/cgi-bin/eric/imglib/prod/image.pl/eric/pictures/Archive/2009_sea_rider/1-resized/IMG_1900.jpg

This still has an opening height of about 6-3/4 inch at the centerline but a little more roomy. Not much.

Is frame 4 really supposed to be this tight? Are my measurements completely off somehow?

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Ogata, eric