What frequently happens in such cases is that a crack eventually appears where the hardpoint in the structure terminates against the flexible panel.
|Here is an example of what I'm talking about. The two vertical strips of bare plywood on the white topside panel are where I've been stripping paint in preparation for gluing some reinforcing frames on either side of the thwart.|
In the photo above, the boat had very flimsy plywood hull panels, and the the main thwart (painted grey) terminated against the topside panel without any framing to distribute the stresses. Eventually, cracks will appear around the edges and corners of the thwart, because the plywood can move and flex, but the thwart is relatively immovable. This is a very bad example of design. What I was doing as part of this repair job was to strip paint on either side of the thwart so that I could glue and screw in a pair of frames on each side of the boat to distribute the point loads out into the gunwale and the chine joint.
Here is the result with the new frames in position. I do not like this boat, but the panel cracking problem has hopefully been solved.
|The stresses are gently distributed out into the structure, and both ends of the half-frame coincide with a very strong part of the boat's hull.|