Very good info Scott. However, after I drill the holes, round the corners and possibly reduce it to 6" wide instead of 9", the weight should be more than cut in half. I am sticking with the 1/8" 6061-T6 which will have a lot less complexity and faster to build. Besides, I already have the aluminum cut to size.
Mark Jones (N886MJ) Wales, WI USA E-mail me at [email protected] Visit my KR-2S CorvAIRCRAFT web site at http://mywebpage.netscape.com/n886mj/homepage.html ----- Original Message ----- From: "Scott Cable" <[email protected]> > > --- Mark Jones <[email protected]> wrote: > 1/8" will provide superior strength. 1/16" just did > not sit well with me as I could see it bending under > loads. > Mark, > I think you are still on the "overkill" side, even > with .060. > It would weigh: (@.125 thk =4.25 lbs) > (@.060 thk =2.04 lbs) > Consider this: > 6061-T6 has a Tensile Strength of 42 KSI > 7075-T6 has a Tensile Strength of 78 KSI > > So probably .040 thick 7075-T6 would be more than > adequate. The 7075-T6 is as much as 80% stonger than > the 6061-T6(when comparing same loads and > thicknesses). > > Add stiffening angles to get the required stiffeness > needed to handle panel buckling. You can achieve > expotentially higher stiffeness by adding angles, than > you could ever hope to gain by simply making the part > thicker. > Use solid rivets to attach the piano hinge and > stiffening angles. Commercial, hardware store "pop" > rivets are for non-flight applications. Don't use them > on your airplane. The material they are made from is > hardly airworthy to begin with (I do not wish to get > into some big debate over this issue, so please don't > even go there!). > > Probably 5/32nds spaced at 6 to 8 D (.96 to 1.28)would > suffice to attach the stiffening angles to the speed > brake panel. That means probably 8, 5/32nd fasteners > per stiffener. This would give the attachment > capability of each stiffener approximately 4600 lbs of > shear. > > Probably 5 angles minimum to break up the panel, and > hemming the edge couldn't hurt either. > This would "break-up" the 9 x 36 inch panel into 4, > 9 x 9 panels. Much smaller area when considering panel > buckling. > The stiffening angles should be (obviously) positioned > longitudinally to reduce drag when the speed brake is > in the stowed position. > The stiffening angles probably only need to be about > .50 inch tall and attach with a .75 inch flange. > Again, probably more than overkill. The good news is > that it would only weigh approximately 1.60 lbs. > Bottom line? 1.6 lbs vs 4.25 lbs, A much lighter, and > many times over stiffer panel. > > Another suggestion: make the Speed Brake with a couple > of plys of BID, and co-cure some stiffening angles > onto > the speed brake panel. This would weigh about half of > the .040 7075-T6 version. > > ===== > Scott Cable > KR-2S # 735 > Wright City, MO > [email protected] > > > > > __________________________________ > Do you Yahoo!? > Yahoo! Movies - Buy advance tickets for 'Shrek 2' > http://movies.yahoo.com/showtimes/movie?mid=1808405861 > > _______________________________________ > to UNsubscribe from KRnet, send a message to [email protected] > please see other KRnet info at http://www.krnet.org/info.html
