On Fri, 8 Dec 2006, Stuart Buchanan wrote: > - There is no trimming for different flight phases. Vertical speed is > purely controlled by power.
Many trikes has a trim function, just like all non-trainer hang glider has nowadays. (I know the Airborne trike we use for aerotowing has it.) This trim is usually operated by a line, the trim line, which is drawn to the speedbar (on a HG) or on a sidebar (on a trike) and most noticeably it adjusts the tension of the cross beam (which is divided in two parts connected with a hinge at the centerline). (Compare with the "kick" or sheet on a sailboat mainsail.) There are however more functions coupled with the trim than cross beam tension. On kingpost HG's (like your trike), there is something called "luff lines" connected to the trailing edge via the kingpost, on the newer topless hg's there are "sprogs" at the wing tips filling the same function. Luff lines and sprogs act like an elevator trim under certain circumstances, and is primary a safety detail to prevent an uncontrollable dive. The setting of those are also altered along with the trim setting. So the trim on a HG or trikes changes: 1. The camber of the whole wing. (cross beam tension) This affects L/D ratio, stall speed. 2. Apex (follows from sail tension) and dihedral (not much). 3. The elevator trim function of sprogs or luff lines. Your trike may have the cross beam fixed to the keel (can't tell by the photo) and would then be a bit stiffer in handling (but more course stable) than a hang glider with the trim fully loose, but with a floating cross beam (i.e. not connected to the keel) as all hang gliders have today, the first effect of moving the weight to one side (shifting the keel sideways with respect to the cross-beam and wing tubes) is that the wing you move away from gets less camber and the other gets more camber. This in turn makes the outer wing tip fly a bit faster than the inner wing tip, generating some rudder and aileron effect. A hang glider with a non-floating cross beam is rather slow in turns. This difference in camber between the wing halves is less the more the pilot tighten the trim. So we can add a fourth function of the HG trim: 4. Sets the amount of rudder and aileron effect from shifting weight sideways -- indirectly by adjusting the cross beam tension and thus the difference in tension of the trailing edge on each wing half. In short: when circling thermals or coming in for landing, you release the trim, when flying straight between thermals you tighten the trim (fully or to a wanted trim speed). But that is perhaps a bit beside the point -- a trike pilot doesn't have to worry much about L/D ratio, and there is plenty of weight for steering with pure CG shift on a trike. > So, should I use YASim or JSBSim for this project? Or larcsim? The only hang glider model in FG (airwaveXtreme150, a larcsim model) has an invisible motor+propeller attached to it, so we could call it "a trike". It doesn't have a trim function anyway. (I'm quite sure the original has.) ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys - and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Flightgear-devel mailing list Flightgear-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/flightgear-devel
