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PostPosted: Thu Jan 30, 2014 10:55 am 
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Site Rank - Deck Hand

Joined: Sat Nov 23, 2013 12:52 am
Posts: 7
Very nice work for such a tough place to access. I just wanted to add a suggestion for those doing internal hull repairs regarding material choices. I have experimented over the years with layups for molded RC racing planes to creat "hulls" with stiff areas blended to impact resistant zones yet preventing twist and stress failures. While carbon fiber is great for areas you want to be as stiff as steel, it can create stress points at its edges and increase the chance of failure. Blends of S glass carbon and kevlar are available and give you options that are great for hulls. Kevlar is hard to cut but manageable. It provides a highly flexable patch yet with extremely high impact resistant. It is very light as well. Glass is great for bonding and resin up take. For the sides of hulls a blend of the three would likely be superiour to a hard spar. http://shop.fiberglasshawaii.com/ This is just one source of many outlets for fabric mixtures. Your repair above was great for a section that no flex can occur at and your tapering of the carbon thickness is the right idea to avoid focusing stress. If you do use a solid spar I would add a bit of kevlar under it to spread the stress to the hull.
Cheers, Steve


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PostPosted: Thu Jan 30, 2014 11:07 am 
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Site Rank - Old Salt

Joined: Mon May 09, 2005 10:25 am
Posts: 2406
Location: Jersey Shore
Thanks for the positive feedback. This repair/reinforcement is a bit of uncharted territory for me. Minimizing edge stress concentrations was definitely a concern and the reason for generously overlapped patches. If I go with the reinforcing stringers/spars I will likewise use a tapered design where the thickness reduces at the ends in order to minimize stress concentrations.

sm


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