Brodhead Pietenpol Association

Original Posted By: Oscar Zuniga
Tim;The Riblett "612" airfoil is very similar to the NACA 4412 airfoil that has also been discussed here. Both of those airfoils are deeper than the Pietenpol, allowing for lighter spars and ribs, increased volume where a fuel tank can go in the wing, and both of them have less undercamber than the Pietenpol airfoil. With a 60" chord, a 12% airfoil is a bit over 7" deep as compared with the Pietenpol at 4" deep. Mike Shuck has done somewhat of an analysis of them vs. the Pietenpol airfoil and there are some benefits to using one or the other.There is an image of the NACA and Riblett airfoils at http://www.flysquirrel.net/piets/airfoils.jpg and you can see for yourself roughly what they look like. For our purposes, the two are essentially equal and I think either would compare to the Pietenpol airfoil in the same ways.Oscar ZunigaAir Camper NX41CCSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________

Original Posted By: Eric Williams
taildrags(at)hotmail.com wrote:> For our purposes, the two are essentially equal and I think either would compareto the Pietenpol airfoil in the same ways.I am jumping in anew into the airfoil thread out of great interest, and it is likelythat I have missed some of the historical discussion leading up to thispost. So I am asking for "one free dumb question" here to save me a lot of searchingthat I am admittedly poor at.Having just bought a Piet project and staring lovingly at the relationships ina completely subjective vs. objective manner, it seems to me that it is borderingon minimal tail volume with the short tail moment and what is a lot of wingarea for an aircraft this size (I haven't figured out yet if the word "petite"suits here). I think I'll run the numbers on it (like I am sure many of youhave before!) for fun and convince myself one way or the other. But my possibly dumb question is this - is the low tail volume of the Piet planform,and the pitching moment coefficients of most alternate airfoils comparedto the original, an issue that limits freedom with airfoil selection for thePiet? The stock Piet airfoil "looks" like it may have a low pitching moment withit's crude similarity to some flying wing airfoils. I thought I read somewherethat this was a point of concern. Mind you the Baby Ace at our hangar lookslike it had it's tail cropped too. Within limits the lower the tail volume,the narrower the CG margin until you leave the "green zone" and hit the neutralstability regime or worse, and I realize these aircraft fly stably as they are.But it is on my mind.Mike D.--------Piet-builder-who-hopes-to-be-flying-next-summerRead this topic online here:http://forums.matronics.com/viewtopic.p ... __________