Designing for Impact – the first one.

Designing for impact has many rules, but just as many exceptions. Here is one. Typically plywood/epoxy is thought of as very poor in resisting impact. And I agree, but here, as with many things, you have to sort out what the goals are.
Here is a picture of the 55′ Sierra Cloud after a jetski impacted it. The kid leaped off early.  The jetski was taken out through the hatch. This is clearly a poor impact resistance. Or is it? Larry did the repair quite easily with a 4 sided scarph replacement piece. The damage was little larger than the front profile of the jetski. 

Consider that if the boat had been built of an impact resisting material such as foam/glass, the jetski probably would not have broken the surface and would have bounced off of it.
But, I am sure the delamination area would have been at least a meter or two in each direction. That would have been a huge repair.  Since the cats can’t sink, breaching the hull is not the worst thing possible.  More on this topic later.

damage7b

2 thoughts on “Designing for Impact – the first one.”

  1. Kurt what would be the extent of damage if the hull was either balsa or cedar strip?

  2. mor or less half way between this plywood and foam/glass. Reichart once showed me samples of bowling ball drops on samples. Will go into that tomorrow.

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