Broken Board

 And does anyone have board molds and would like to build one or two for a 56′ cat?

OK, here are the pictures and hypothesis.   The owner reports that he didn’t hit anything and the crash block was not crashed.  Further, the balsa core was not soft nor rotted.  The laminate was triaxial, as was designed.  He thought there was a buckle on one side.

Notice that the balsa is at the faces, but there is foam in the middle.  It looks like Airex or divinycel.  Both in 100 kg density or less have much less shear and compression strength than balsa has.  Recall that the highest shear load in a beam is at the centroid, as is the lowest bending load.  Enough side load could move some of the rigid balsa into and crushing the much weaker foam.  The core is there for shear transfer between the faces.  Look how thin some of the foam layers look.  Crushed.   It looks like the weakest link failed, to me.




4 thoughts on “Broken Board”

  1. It looks like it was pulled apart from the ends (like a piece of paper torn from the ends with no shear). The delamination shows extreme pulling expansion stress. Are you sure that a shark did not bite the lower extremity?

    In other news the world circum got faster to under 50 days by a froggie from the Northern part.

  2. Hi Kurt,
    I have done 2 asymmetrical blades for 65 foot proa Luca Antara from some time ago. Quit similar i suppose.
    Would like to build it, but the transportation is of course a disadvantage. The whole design was an idea and a lot had to be reinforced afterward.
    As I stated after delivery: You get 2 for the price of 3 and Robin Warde understood. His reply: i steal from the rich and give it to the poor.
    Outer skin glass epoxy, reinforcement centre and top carbon, a lot uni-directional and some biax on corecell 80 and 200.
    Molds in Styrofoam, covered with vacuumfoil, epoxy infusion in 2 halves. 2 mm recess in front for reinforcement after glueing 2 halves together with glass-biax

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