Hull impact resistance

Anything to do with hull shapes in general (i.e. not specific designs)
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Hull impact resistance

Postby AlexQ23 » Sat Mar 17, 2018 3:05 pm

Hull impact resistance: This matter will probably interest all the available brain in this forum! Classification rules don’t really take puncture resistance of a hull in to account. This is especially true, when you design a new light unit and when you are working with rigid hull material like plywood, carbon fibre or other sandwiches. It could be a great opportunity for us to come with an accurate easy to apply test method and why not a formula or at least a lower value to apply to a specific type of hull. Any idea?

Robert Biegler
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Re: Hull impact resistance

Postby Robert Biegler » Thu Oct 11, 2018 8:43 pm

The common test seems to be to take a standardised shape, with standardised weight, and drop it from a variable height. How pointy the shape is matters. I think it was Gerr who told the story of a boat builder who handed around a lightweight kevlar panel and a claw hammer, inviting people to hit the panel as hard as they could, to demonstrate its toughness. Bashing with the blunt end seemed to make little impression. Gerr turned the hammer round and punched the claw end right through. It might be interesting to test both blunt and sharp impactors. I don't know whether it it more informative to find out what weight of object or height of drop is needed to cause any damage visible from the inside, or whether there should be repeated impacts and extent of damage is assessed. The former is probably easier to measure and therefore more repeatable.

The Gougeon Brothers on Boat Building reports that Kevlar on the inside of plywood was more impact resistant than kevlar on the outside. Sven Yrvind makes a similar comment when it comes to one side of a sandwich core being laminated in glass, the other side in carbon. It was better to have the carbon on the inside.

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