I'm not sure many of us would survive 8g without passing out in a rush of blood to the feet! No, if you're flying at 8g you've already lost the plot!!
I'm more concerned with the instantaneous shock loading that the glider might experience during take-off, landing or clumsy ground handling.
As I am now the proud owner of a 105m roll of non-cosmetic CF cloth (it was cheaper than the 60-odd meters I need if I went for a cosmetic grade CF cloth!) I'll probably use that throughout... for this build. If I'm super enthusiastic (and can find a buyer for my first one(!!) I'll use the lessons learned and try to construct an even lighter one!
My rib experements so far have been trial and error jobs... with a little informed guesswork when it came to reducing the structural dimensions. I do think that the resulting ribs are probably far stronger and a little heavier than they really need to be, so if you find yourself overcome by the need to indulge in a little FEM I'd be delighted to see the results and knock up a couple more test pieces to do a reality check on your numbers!
Phil.
PS - the non-cosmetic CF cloth simply has a thin red tracer running across the 1m wide cloth every 100mm (you can't even see it after curing!) - otherwise it's exactly the same as any other twill cloth.
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 Kenny Andersen
Sent: 03 March 2012 02:03
To: This email address is being protected from spambots. You need JavaScript enabled to view it.
Subject: RE: [Carbondragonbuildersandpilots] Composite Rib Construction & Load Testing
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
