Mark, To Calculate how much your Aluminum Speed Brake will weigh use the following: Calculate the volume of your part by multiplying length x width x thickness Then multiply the sum by .105 Which is the density of aluminum plus a correction factor for fabrication (rivets, primer, etc.) Once you have calulated the base weight, calculate the volume of each hole using Pi x Radius squared x Height (thickness)x .105 Multiply this value by the number of holes you plan on removing. Subtract this sum from the base weight.
so: (6 x 36 x .125)x.105=2.835 (Base) 3.1416 x .140625 x .125 x .105 =0.0058(.75 hole) .0058 x 18 = 0.1044 (hole total) and 2.835-0.1044= 2.7306 lbs (Base minus holes) If you are using 6061-T6, it is 80% weaker than the same thickness 7075-T6. 7075-T6 has a much higher yeild strength, and fatigue allowable. 6061-T6 is excellent for welding, however, it will revert back to "O" condition in the vincinity of the weld. The part could be re-heat treated, but it will revert to condition T-62. Re-heat treatment cannot restore the T6 properties. This .125 flat panel weighs more than twice that of a larger sized .040 panel w/stiffeners would weigh. It has more unsupported panel area, and doesn't have nearly the "I" (as in MC/I, which is the basic engineering formula for bending) that a fabricated panel would have. Do what you want, but please realize that a flat plate will: 1. Weigh more 2. Not be as strong 3. Probably fatigue crack from the panel buckling under the air loads and buffet loads. Even though you're adding holes in to the speed brake, those very holes that you've added to reduce weight and decrease the deployed area with, are going to cause drag when the speed brake is stowed, and they could cause some unwanted handling characteristic. Hope this helps. ===== Scott Cable KR-2S # 735 Wright City, MO s2cab...@yahoo.com __________________________________ Do you Yahoo!? SBC Yahoo! - Internet access at a great low price. http://promo.yahoo.com/sbc/
