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Aug 24, 2019, 03:41 PM
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Test carbon spar

Remember those potholder looms for kids? It gave me an idea...

This is another application I have not seen - an all-carbon truss spar. Using wetted carbon tow (12K in this case), I wove a truss pattern though a set of brads. The idea (Pratt or Warren without verticals truss styles anyway) is to be able to slide ribs into a finished spar unit.

For fun I tried some different patterns with string (second photo). I notice you can take an extra round on the perimeter if you need more thickness.

In practice I found the tension tends to flatten the tow, and this isn't ideal since you'd like more of a round or square section. Despite this the test is very sturdy and certainly benefits from not having any glued joints.

I'm thinking about building a fuselage side like this for my 24" Telemaster. I could use my thickness sander to ensure a flat, uniform surface and make the carbon closer to a square profile.
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Aug 27, 2019, 08:37 AM
Scratch builder
Cool!!! Wetted with what?
Aug 27, 2019, 10:50 PM
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I used West System G-Flex, which is not ideal but what I had on hand. Getting a gallon of 105 resin & 206 hardener tomorrow which everyone swears by. My fuselage side template is ready to go, cut from 1/2" MDF. Looking forward to making something real and getting into my hands and on the scale.

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