Thanks Bryan! What I did was make a little template cross section of the gunwale and knuckle, and put it on the reference points I'd derived on the computer and drawn on the plywood. They line up perfectly. I'd say that this part of the boat anyway will be within the room of error of the thickness of the survey drawing's line. To minimize error, I typically measured to the center of this line. (I wonder whether the outside or inside dimensions of the drawings are more accurate, even though it really doesn't matter).

I have a photo of the gunwale and knuckle traced onto the plywood which shows it squarely within 1/16". I'll post it tonight when I upload.

: I don't see this ambiguity in the drawing. The drawing clearly shows where
: the gunwale knuckle is. The ambiguity might occur when translating this
: design to Wooden Yost style, so you'll need to figure out where to place
: frames that will reproduce this knuckle. Maybe a foot from each end of the
: knuckle. In theory, if you're able to establish the 25° gunwale angle get
: the right placement on the chine stringer, and use 2.5 inch gunwales, it
: should just fall into place.

: If you want a F1, then you should worry about it. Being off by 1/2", and
: it will be a kayak similar to a F1, but not the F1. What are intending to
: use this kayak for? Will you be surfing with it? From Brian's website,
: "For example, I discovered that if the little 1/2" secondary
: chine is carried past the cockpit it messes up the surfing."

: I'm not sure what you mean by outside of the center of the knuckle. To me it
: looks like the skin becomes free floating and leaves the gunwale at that
: line. Is that what you were thinking?

: It seems closes to the

: There might by some tapering of the gunwales using a block plane like is done
: when building a Cunningham method SOF. Not sure if he does that. Also,
: from the pictures it looks like he rounds the top of the gunwales, so the
: surveying may not be 100% accurate at the top of the gunwale. If I were
: doing it your way, I'd make sure everything lines up from the keel up and
: let the top of the gunwales fall where they may. Or trust the plan and
: profile views over the sectional view. It may be a drafting error.

: Only you can answer this question. Hopefully, you'll find this stuff helpful.
: I want a F1 also.