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Composite Rib Construction & Load Testing 09 Dec 2013 02:10 #464

Good work Phil,

I would only say that 8gs is 8gs -- its a severe loading that your aircraft will NEVER see; so, if something supports all of the weight regardless if it twists a bit, it should be fine. To keep the weight down it doesn't have to be perfect under loading, just doesn't have to fail. Also, I think it's worth investigating the use of lighter-weight glass and carbon unidirectional tape. The carbon is actually a bit heavy in some locations. If someone had an electronic (CAD) model, I'd be willing to do some FE modeling of some ribs etc. to optimize the weight.





Also, I wasn't perfectly understanding your first rib (I didn't realize your flanges were so wide) the calculation I made was based on web only, not the whole rib. That's why I was thinking to optimize the weight, and unidirectional tape combined with very thin glass might, in the end, result in some lower weight ribs as well as in some other areas.




Kenny


--- On Fri, 3/2/12, Philip Lardner <This email address is being protected from spambots. You need JavaScript enabled to view it.> wrote:


From: Philip Lardner <This email address is being protected from spambots. You need JavaScript enabled to view it.>
Subject: RE: [Carbondragonbuildersandpilots] Composite Rib Construction & Load Testing
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Date: Friday, March 2, 2012, 7:47 PM




Well now, that's the $64 question! The specific gravity of spruce is around 0.38 (24 lbs/cu-ft) and going on the quick calculation I did for the weight of a spruce root rib (and the measured weight of my CF rib) I reckon the CF version should be about equal weight - possibly slightly lighter given that the CF appears to be considerably stronger than the spruce and therefore the structural dimensions can be reduced in places. Ultimately only time will tell! My interest is in building an all-carbon dragon and eliminating wood from the build entirely. If it's lighter, then woo-hoo! If it's heavier, then boo-hoo... but at least it will be considerably stronger and won't warp in the rain!

Phil.

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