Mark, You're no doubt seeing an optical illusion. Some people call the difference in the mounting angles between the main wing and the stab decalage. The term was originally (technically) used to describe the difference in the incidence between the main wings on a biplane - the top wing having a slightly lower incidence so as to stall later and increase stability. But the term (applied to the difference in mounting angles of any two surfaces) has stuck and that's OK. In any airframe, there is a horizontal reference line along which the horizontal stabilizer is mounted. The angle between this line and the wing is called the angle of incidence. It is typically about 3 deg + (front of the wing higher) because the wing usually (varies with airfoil) generates enough lift at this angle at cruise to offset gravity and the elevator can operate at the neutral position which has the least drag. A flying stab has no such fixed angle. The stab angle will vary with the CG - which determines how much force is necessary to counter the weight moment. If you'd like to measure the angle that your plane "likes" now:
1. Get your hands on an incidence meter. (a bubble level and protractor is OK) 2. Assemble the plane. 3. Turn your radio on (trans & receiver) so that the stab is in the flying position. 4. Set the whole fuse so that the stab is at 0 deg. 5. Measure the incidence of the main wing. It's probably 2-3 deg positive. Having the CG off is what causes drag because the tail has to generate lift to offset the weight. A split stab/elevator just makes things worse when the geometry is off. A flying stab eliminates that factor. Mark -----Original Message----- From: Mark Miller [mailto:[EMAIL PROTECTED] Sent: Wednesday, August 02, 2006 4:04 PM To: [email protected] Subject: [RCSE] Thinking of 2 Meters Just a general question that has nothing to do with 2 meter planes but sailplanes in general. I had a first flight of a sailplane awhile back. I did the dive test and flew inverted. Felt nose heavy. Took out lead. Did it again...took out lead...did it a few more times. All the while putting in down trim to keep it flying level. I get to the point where I notice that the decilage (sp) is massively wrong. LOTS of down stab to keep the plane flying level. Like 1/4" from zero. Take note that in a dive test it is still pulling up to much. So, the question is should I keep moving the CG back and keep making the decilage further off or do I put the CG so that I have zero or very little decilage angle. BTW...It has a full flying stab. I would think having so much decilage would cause a lot of drag....Opinions? Mark Miller 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 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
