: for cross sections. The problem is that pointed out by Aaron H. where the
: diagram is somewhat ambiguous as far as the 'knuckle' or secondary chine
: on the gunwale.

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.

: My
: question is: how could being off by 1/2" in this area impact the
: performance? Should I worry about it a lot or will it not be too big of a
: deal?

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."

: If anyone is able to help interpret that diagram, that would be awesome as
: well. Without further clarification, I'm going to assume that on the cross
: sectional view (the one with the numbered sections), the knuckle line
: marks the outside of the center of the knuckle.

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
: actual measurments when compared against his dimensions. Some things
: aren't quite lining up - he says the gunwales are 2.5", but in the
: cross sectional view, the line segment from the top of the gunwale to the
: knuckle is 2.33" according to my method of scaling which appears to
: have worked beautifully with everything else. I considered that the
: discrepancy was a result of the line being from the top corner of the
: gunwale to the top corner of the knuckle, but that distance would actually
: be ~2.03". Go figure.

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.

: The real point is, does it matter?

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