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Composite Rib Construction & Load Testing 09 Dec 2013 02:08 #463

Thanks Rick - I figure on cutting my teeth perfecting my resin infusion technique on the smaller parts before tackling the main wing spars (I'll be doing both spars together to save consumables.) I've constructed a 24-foot long work table from three lengths of 2' x 8' x 3/4" white melamine covered chipboard. The melamine takes a nice wax finish and releases the cured parts very nicely, but I'm a little concerned (after looking at your rather expensive 'show-and-tell' spar!) about getting a perfect, vacuum-proof join where the ends of the sheets join each other. I figure I can probably get a good seal by pumping the joins with epoxy resin using a syringe a couple of times and then covering the joins with a wide, heavy duty packing tape. Needless to say... I'll be doing a thorough vacuum integrity test before I open the resin infusion valve!

Phil.



From: This email address is being protected from spambots. You need JavaScript enabled to view it. [This email address is being protected from spambots. You need JavaScript enabled to view it.] On Behalf Of Rick Mullins
Sent: 03 March 2012 01:15
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Subject: Re: [Carbondragonbuildersandpilots] Composite Rib Construction & Load Testing




Great write up Phil.


I played around with vacuum infusion when I built my spar. It sure is beautiful when the fabric is ls pulled down into all the corners and it looks exactly how you want it to. In my case though the bag for a 23 foot spar with 16 holes for vacuum and resin lines was very difficult to seal. My first spar I couldn't use because I had a small hole underneath and the vacuum pulled air through the spar while I was waiting for the resin to set. The second attempt worked better but there was a lot of set up time and lots of waste materials. The third time I just did a normal hand layup and was very careful about controlling the resin. I have a friend that has done a lot of composite work tell me that if you are careful applying the resin, vacuum bagging doesn't save that much weight. I was skeptical but in my case the infusion spar weighed 6 pounds 7 ounces, the hand layup was 7 pounds 3 ounces and was much less work and used much less (expensive) resin. I'm certainly no expert, this was my first attempt at it. But if I build another spar I would probably just do the hand layup. For smaller jobs like the ribs though, I can see how it would give you excellent results.

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