Is your fiberglass boat flexing in some areas? If so, should you be concerned about it? Some occasional flexing in non-critical areas may be acceptable. But continual or "cyclic" movement can lead to fatigue, cracking and other symptoms of laminate failure - particularly if it is in a hull surface area.

Such flexing is most obvious over larger, flatter areas. And a fix may be easier than you think. You can quite possibly even do it yourself. One way to increase stiffness in a fiberglass panel is simply to increase its thickness. But you would have to add a lot of fiberglass and resin to notice much of a benefit. What follows is a better approach. First, gain access to the reverse side of the affected area