![]() Repeated loading and unloading or even worse, loading one way and then the ' other(reverse axial), rapidly reduces a material's physical integrity and accelerates degradation. Fatigue is a reality of all structures and materials, and eventually culminates in structural failure. Fatigue cracks in a material result from repeated (cyclic) stress. The plywood centerboard did, in fact, wear out - or more accurately - it failed from rolling shear fatigue. Understanding why can help us design and construct components that will perform more efficiently and last much longer. Extensive laboratory testing at Gougeon Brothers, Inc. The answer to "why now - while leading the race?" could have been fate. It was a deep and wide board with a lot of area, and like any rudder or centerboard on a boat that is sailed hard, it was exposed to a fair amount of stress. It was then covered with two lavers of 6-oz woven fiberglass fabric. This centerboard was built of laminated layers of plywood, resulting in a thickness of 2". "Guess it just wore out" was my excuse to myself. When the centerboard of my Searunner trimaran broke in the middle of a windy race around the Black Hole, the question I kept asking was "why now, after working fine all of this time, and when we were leading the race?" How to Build Rudder Blades & Centerboards - by J.R. ![]()
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May 2023
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