*** Generally speaking higher aspect ratio with either a fixed span or area will equal a reduced wing chord. This will result in reduced reynolds numbers which equals reduced performance for most all airfoils ***
Yes, but also .... what's happening (for a fixed wing span) is a trade off between wing loading and induced drag. Re (at least for DLG chords and up) is a variable but not the dominant one. As you increase aspect ratio (reduce chord for a fixed wing span), induced drag goes down but wing loading goes up. The wing loading will eventually degrade your sink rate more than the aspect ratio improves it. Although the wing weight scales with area, the total weight does not (fuselage, tail surfaces, ancillary equipment). Re will hurt here as well (both Cd and Cl) but it's primarily the loading (except perhaps at very small chords). On the other end, lower aspect ratio gives a lower wing loading but increased induced drag (Cl^2/(Pi * AR). In between there is an optimum - but it will depend on the specific weight, planform limitations etc. You can do this in a spreadsheet by using the induced drag formula, typical airfoil data (a flat plate data set is available from UIUC) and the needed Cl (at each velocity) from the lift equation. For a quick and dirty you can ignore parasitic drag, or just use a constant term for the fuselage. This has been covered several times in RCSD for DLG, 2M and open class simulations. Optimum for typical 2M construction is in the 9-11 AR range. For open it's typically in the 11 -15 AR range. Specifc results depend on airfoil and estimated final weights but these ranges are about right. DLG is more sensitive but appears to optimize in the same range as 2M - probably due to the lighter weights of these ships. The absolute numbers may be off a bit since these calculations aren't well calibrated with real world flight data. But the trends are pretty consistent. Neat project with a nice result. A reasonably straight forward simulation should emulate the general trend reported. - Dave R 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
