Here's a pic of my lashing. I guess this would be considered the "H" pattern and I am using artificial sinew (70 pound)

: It sounds to me as though your lashings are too loose. If you posted a pic of
: them, it would help us assess the technique you're using. When I do my
: own, I run several strands through the beam and gunwale, then wind around
: the resulting loop to pull it extremely tight. You can see this in some of
: the photos in my "SOF #3" album at the link below. I have never
: noticed any gapping or shifting of the gunwales once the beams are lashed
: in place. While it's true that the skin will hold the boat together,
: relying on that too heavily could lead to problems down the road.

: The material you use for lashing can also make a difference. I only use
: polyester lashing materials, as they don't stretch and aren't affected by
: humidity changes. If you're using Nylon, that may be part of the problem.