>I can use LiftRoll to adjust twist to make it look like an elipse or not, but how do I generate the comparison number from my origional post, IE wing 1 will have min sink of 1 fps and wing 2 will have minimum sink of X fps?
You don't necessarily want an elliptical lift distribution in a real-world model, since that might result in turning behaviour that is a little scary at times if your airfoil selections aren't correct. You're really looking to optimize cruise here, right? (ie min power setting for level flight). Look into the power factor calculation available from xfoil/profili. Flight power is proportional to CD/CL^1.5, but remember that CD is the total airframe drag coefficient, so working with the airfoil Cd along isn't going to give you the full picture. >How do I use LiftRoll to get a wing Cd, Cl given a polar Cl, Cd? Very simple...you can't. It's not designed to be able to give you this information, since at no point does it incorporate actual airfoil data. >In LiftRoll is av/mx Cl the Cl I want to optimize for? That's a planform efficiency number, giving you a measure of how "aggressive" the planform design is. Real-world meaning: a high efficiency number will require a more competent pilot, since upon reaching stall more of the wing will "let go" at the same time. Compromising this measure will result in a model that's easier to fly over a wide range of conditions. >How do I go about guessing an AOA? (Again from the airfoil polar? ) Don't bother...I've already made a sheet that will calculate it for you (overall Cd, wing drag, tail drag etc). You need to know the weight of the model (assuming you're calculating a level flight condition, ie weight=lift required) and you need access to the airfoil polar data from Profili/Xfoil at the appropriate Re# Go to the following link to download the sheet...based off of LiftRoll about 3 yrs ago: http://www.soarcalgary.com/Extras/Articles/Sailplane%20Design%20Spreadsh eet/ Did you have a webpage for your solar project? I've been curious how it was coming along, but the few searches I ran never came up with the webpage that I seem to remember seeing once upon a time. Hope that helps, Adam Adam Till Mechanical Engineer 403-270-9200 (ext 154) 403-270-0399 (Fax) UMA Engineering Ltd. 2540 Kensington Road NW Calgary AB, Canada T2N 3S3 RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED] Please note that subscribe and unsubscribe messages must be sent in text only format with MIME turned off. Email sent from web based email such as Hotmail and AOL are generally NOT in text format
