[RCSE] Side winder
Any tips out there on converting a HLG to sidewinder launching? Bob Rice Rocky Mountain Soaring Assn. Denver CO USA RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
[RCSE] SmAC! 2000 Results
Okay folks, Real life has caught up to me with a vengeance, and I haven't had a chance to do a write up of SmAC!2000 yet. Nor have I contacted the raffle winners who's prizes were in certificate form. I hope to accomplish all this over the weekend, honest :-) However, let me heartfully thank all the sponsors and donors who contributed to another successful Temple Hill event. Specifically; - Patton Aircraft http://home.earthlink.net/~pattonacft/ - Frank Cavazos (Boomerang) www.boomerangwings.com - Robert Cavazos - RCAV industries http://members.aol.com/rcav - Metatera http://soaring.freeservers.com/metaterra/ - Dave's Aircraft Works www.davesaircraftworks.com - Pat Bowman http://www.bowmanshobbies.com/ - MAD Aircraft http://www.madaircraft.com/index.html - F3X.com (Bandit) www.f3x.com - Multiplex (Combat Pico Jet) http://www.multiplexrc.com/index.htm - Extreme-Products.com www.Extreme-Products.com - Custom Vinyl Graphics (mailto:[EMAIL PROTECTED]) - Jax Hobbies (Fountain Valley, CA - formerly Gyro Hobbies) - Combatwings.com (RTF Boomerangs) www.combatwings.com And any others I've forgotten in my sleep deprived stupor Cheers, Nathan Woods Webmaster: www.boomerangwings.com Temple Hill Slope Squadron Orange, California http://home.earthlink.net/~windrider007/index.html RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
[RCSE] Wanted used 50 to 60 inch 2ch built up
Helping out a friend to replace a broken 50 inch built up glider. Would prefer one with a wing with leading edge sheeting (top and bottom if available). Receiver and servos can optional (as long as control rods or cables are installed...) Hoping to get one RTF for around $80 to $100, or more if it includes receiver and servos. I live in So Cal area, Orange County. Email me direct: [EMAIL PROTECTED] RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
RE: [RCSE] Results from a HLG launch analysis
Mark, When I did the analysis versus mass (and also versus throw angle) I was aware that assuming a constant throw speed wasn't realistic, however I didn't have a better alternative. I like the approach you've presented and have redone the analysis versus mass and aspect for this throw model. The website has been updated with the new results. http://www.rcmodels.com/clubs/asfcnz/ You're right up to a point in saying that lighter models will inherently launch higher using this model. The results indicate that there is actually an optimal weight for a given design, and if you go much lighter then launch height suffers badly. However, with current construction techniques I don't think you can build down to this weight and still have a model strong enough to throw at full power (at least for a 1.5m span RC HLG). Also, the optimal weight for max launch height increases with wind speed, so now we can justify ballast for HLG's on the basis of launch as well as penetration when the wind gets up. Ciao - Chris ** Chris Kaiser Auckland, NEW ZEALAND http://www.rcmodels.com/clubs/asfcnz/ > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] > Sent: Wednesday, 16 August 2000 7:53 p.m. > To: [EMAIL PROTECTED] > Cc: [EMAIL PROTECTED] > Subject: RE: [RCSE] Results from a HLG launch analysis > > > Chris, > > Nice presentation. > > The only beef I have is the assumption of a given > velocity independent of the glider weight. This > is clearly inappropriate. I think a better assumption > is to assume a fixed muscular energy output, which > would correspond to fixed (maximum) muscle forces > acting over some fixed throwing motion. This energy > shows up as kinetic energy of the glider and the arm > at the moment of release. > >E = 0.5 (m + m_arm) V^2 > > This gives the launch velocity in terms of glider mass m: > >V = sqrt( 2 E / (m + m_arm) ) > > I estimate m_arm = 1 kg as the effective mass of the > hand and forearm, and E = 300 J seems like a reasonable > energy for a strong throw. You can get fancier > and assume that there is also a running speed > which adds to the throw independent of the glider weight. > In this case you would have > > V = sqrt( 2 E / (m + m_arm) ) + V_run > > Whatever. > > In your parametric variation of the glider weight, > I suggest fixing m_arm and E, and set V from one of > the relations above rather than fixing it. You'll find > that lighter gliders launch inherently higher now, > which I think is what most people observe. > > > -- > - Mark Drela > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
[RCSE] Tricks
Howdy all, I have a couple of rather long fuses that I need to install linkage housings for the V-tail's, inside it. Does anyone have any suggestions with their pet method of attaching the tubes? I want to secure them extremely well because these planes will be DS'd hard and I want a minimum of slop. Thanks, Cliff Lindgren RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
[RCSE] Re: mass balancing
Aaron, We really ought to get Mark Drela in on this one! I am over my head, technically speaking. But that doesn't stop me from speculating! I assume by shear center that you mean the effective center of the wing beam - the location that is effectively resisting the wing deflection. This is typically behind the quarter chord, especially on sheeted wings, for several reasons. I believe that there is an attempt, even when locating a discrete spar, to balance wing torsion due to lift offset from the spar on the one hand with wing torsion due to the section moment on the other. The lift one is typically leading edge up (LEU) during high loads whereas the moment one is leading edge down (LED) at high speeds. An upward gust tends to twist the wing LEU for two reasons. First, the lift is in front of the spar, so to speak. Second, the mass CG of the wing is behind the lift also, so any upward acceleration tends to twist the wing LEU. I think that it is primarily this second phenomenon that drives flutter at high speed where the wing loads are low, but accelerations are high. At high speed the upward twist further accelerates the wing upward, leading to more twist and so on until the load is balanced by the wing structure. But there is a phase lag going on so now when the wing reaches the top (accelerating down now) the wing twists down and the cycle repeats. I believe that the phase lag and the relative twist/deflection ratio are sensitive to speed and this is why you see this at high speed. By moving the local CG forward you can decouple the acceleration from the twist and make the problem occur at higher speed or disappear. The spar location is more likely to control the bend/twist interaction in the steady-state case. A wing that is flexible in torsion with an aft (effective) spar location will be at risk for divergence. The more it deflects up (say), the more it pitches up, so the more load and so on. At some critical speed this cycle pumps itself up and the wing clicks off. Mass balancing will not help this problem much. It might help to some extent because near to this divergence speed you can get the wing going with a little bit of flutter. I have done this twice with a Mirage - you get about three cycles of increasing amplitude and then the wing clicks of at the center... Anyway, to answer your question directly, I think that the wing CG wants to be near the local quarter chord, not a the spar location. The idea is to reduce or eliminate the couple between the lift and the mass. I hope that this has added something to the discussion. Regards, Blaine Beron-Rawdon Envision Design San Pedro, Calfiornia, USA -- >From: Aaron Valdes <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: mass balancing >Date: Wed, Aug 16, 2000, 1:15 PM > > > Blaine, > Would you try to match the CG of the local wing section to the quarter > chord (approx lift center), or to the shear center? We have an inherent > problem in that the shear center of our wings is not generally located at > the point where the load is applied. So we have a shear coupling effect. I > agree that moving the cg forward is a good thing, especially if the > structure is displaying instability. This is a very interesting area for > me. I wish I got to spend more time working on aero-elasticity problems. > Any thoughts? > > Aaron Valdes > Aerospace Engineer > TRW Unmanned Aerial Vehicles > (858) 592-4201 direct > (858) 592-4228 fax > > > RCSE-List facilities provided by Model Airplane News. Send "subscribe" and "unsubscribe" requests to [EMAIL PROTECTED]
