At 10:27 PM 7/15/2001 -0400, you wrote: >Mark, >I read long time ago that a good way to make the TE thicker and easier >to build is to plot the airfoil for a larger chord and chop off the last >3-6% of the airfoil. This supposedly -almost- does not change the flow >and drag of the airfoil, so the general behavior of the wing will be >very close to the intended. The author claimed that blunt trailing edges >(up to 1% or more thickness at the TE) behave much better then say >rounded ones, so if you MUST have a thick trailing edge, do NOT round >it, leave it square. >Can you comment on this hypothesis, please? >Oleg. > Horner, in his book Fluid Dynamic Drag, reports that simply cutting off the aft end of an airfoil to achieve a finite thickness gives the lowest increase in drag. I am quoting from memory since I had to give back the copy I used for years when I retired so the above may not be exactly correct but I have used this method for the last 25 years. I do remember that some wind tunnel tests on increasing trailing edge thickenss gave a much larger drag increase than reported by Horner. Makes me wonder how the increased thickness was achieved on the wind tunnel models. I would also like to see some modern wind tunnel data on the effects of various methods of increasing trailing edge thickness on airfoil performance. Theory is nice and modern CFD methods are wonderful but I still prefer to rely on good wind tunnel data. I conducted several wind tunnel tests to verify various CFD predictions between 1970 and the time I retired in 1994 and all tests had one thing in common. When the first data was printed out, the researcher responsible for the program always ask "What's wrong with your wind tunnel data?" :-) Chuck Anderson RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
