---------------------------------------------------------- Pietenpol-List Digest Archive --- Total Messages Posted Thu 09/28/17: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:51 PM - deck angle (taildrags) ________________________________ Message 1 _____________________________________ Time: 08:51:32 PM PST US Subject: Pietenpol-List: deck angle From: "taildrags" I thought I'd change the subject line to reflect the actual topic of discussion here ;o) I just reviewed the plans (Orrin Hoopman's 1-19-33 plans, Drawing No. 1) and it calls for 2 degrees of incidence on the wing, achieved by making the rear cabane struts 1" shorter than the front ones. The cabanes on my airplane are not built per plans, but after studying their actual geometry in AutoCAD, when my cabanes are canted back by 3-1/2" from the vertical as they are, my wing incidence is within 1/2 of a degree of what it's supposed to be, or about 1.5 degrees. I can probably get that half-degree back after changing out my main gear tires to the 8.00x6s as I'm planning to do. Now to the broader topic of the deck angle. It has been said by several Piet pilots that they feel like a deck angle of 12.5 degrees is about right. With another 2 degrees of incidence built into the wing, that puts the AOA of the wing in the 3-point landing configuration at about 14.5 degrees. I took the liberty of snipping a small section from Michael Shuck's very interesting paper called "Commentary On The Pietenpol Airfoil", copyright 2004 by Michael, full credit and admiration is here given to Mike for both being a Piet lover and for having tremendous skill in the analysis of airfoils. That snip is attached. Highlighted in yellow is the region of interest, which is the region where the coefficient of lift Cl reaches its maximum... the critical AOA. The first column on the left is alpha, the angle of attack. The second column is the coefficient of lift. Notice that Cl is at its maximum at an alpha of around 14 degrees, and it drops off at higher angles of attack. Hmmm... sounds like the seat-of-the-pants Piet pilots know just as much as the aerodynamicists! My conclusion here is that if a Pietenpol airfoil is operated at a deck angle of 12.5 degrees in the landing configuration, it is just about at the critical AOA and if the airspeed is dropping, the wing will be stalling. Perfect. I don't consciously try to land my airplane tailwheel-first because I generally find that that will cause porpoising to start, but theoretically it would land nearer to full-stall if I held the nose a bit higher than I normally do at touchdown. I'm very interested to do some flight testing in calm morning air with the bigger tires. They are on their way here from Colorado Springs as we speak... -------- Oscar Zuniga Medford, OR Air Camper NX41CC "Scout" A75 power, 72x36 Culver prop Read this topic online here: http://forums.matronics.com/viewtopic.php?p=473188#473188 Attachments: http://forums.matronics.com//files/pietcl_508.jpg ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message pietenpol-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Pietenpol-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/pietenpol-list Browse Digests http://www.matronics.com/digest/pietenpol-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.