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Saturday, January 8, 2011

lightening and boat materials

Aluminum is used with stainless steel copper fiberglass timber and carbon fiber in the construction of boats. I am going to talk about carbon fiber this material has an electrical conductivity 10 times better than aluminum. When using laminates of dissimilar materials special mechanical bonding must be used as the heat transfer is totally different and so is the expansion rates when heated. I have seen where an electric motor was made with internal chemical bonds holding on the permanent magnets failed in a explosion and a total loss of the motors, The people were warned and the motors failed because of this difference in expansion where as mechanical bonding would have made the motors survive. There was a helicopter crash in the North sea caused by a lightening strike and the cause was related to de-lamination of the tail rotor due to the heat and the chemical bond between the leading edge made of aluminum and the carbon fiber blades.  Same goes for the rigging wires on a sailing boat made from stainless steel and attached to carbon fiber boat. Good engineered mechanical bonding is a must. now if you throw in the heat generated during an electrical lightening strike the bond needs to be stronger. Where is this going I'm not sure as I intend to use the drug sub in storm conditions and staying over night. There seems to be a hypothetical danger there and how do you design a system to deal with this in a once in a life time lightening event. I know that all lightening devices fitted to a boat must run down the outside of the Fiber glass hull as the lightening could blow a hole right threw the hull if it were contained with in the hull. Carbon fiber strips could be placed in in the hull during manufacture in the outside layers of the laminate so when the lightening left the hull it would only damage the outer layers of the composite. These are only thoughts and more research needs to be done in this area.

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