>From my experiences with Libelles. - The ailerons should be rigged to zero deflection in flight. Common trap for new players is slop in the control linkages. When rigging the ailerons on the ground, the weight of the aileron sits the aileron at the bottom end of the control slop. In flight the reduced pressure on the upper surface sucks the ailerons up to the other end of the control slop. So when you set the ailerons to zero on the ground, the sit up in the air in flight. Fixes include having a couple of helpers to gently lift the trailing edges of the ailerons to the top of the slop whilst rigging so that you get zero deflection in flight. Other fix includes working through the linkages and replacing worn bolts, pins, bushes and bearings to reduce the slop.
- Performance losses or gains are really hard to predict. At lower speeds you will definitely have increased induced drag, especially through the gaps at the inboard and outboard ends of the ailerons. At higher speeds you may have some performance gain through the negative flap effect. Find another Libelle and do a side by side comparisson at different speeds on a still morning and see. (The best high speed performance gain you can do is get the wing root fillet mod kit from Streifenader). - Stall speed. Likely to be increased by 1 knot or so. >From memmory all Libelles sit down firmly on the ground: it is inherent in the design of the wing. - Thermalling handling. Libelles are pretty well known to have the ailerons stall out during tight slow thermalling. Having the ailerons up will probably help reduce this somewhat. However, at 45 degrees bank, you are pulling roughly 1.4g. Your stall speed will have increased by the square root of your g force. So 38 kts x square root (1.4) = 45 kts. The answer to your control problems is that you are trying to thermal too slow! From memory you should be at least 48 kts or more for 45 degrees angle of bank. (The best handling mod kit you can get is the winglet mod kit from Streifenader - it also gives you a significant performance boost at low speed). To see the wing root fillet and winglet mods, check out VH-GBP. Anthony > Without laying my hands on the manual it's a bit difficult > to say if up on both ailerons is correct, it could be to > reduce tip stalling. However, I suspect this is not the > case, BUT some (especially older) gliders do mix the > aileron and elevator. > > Is the "up" on the ailerons constant throughout the > elevator movement range (ie does it reduce with stick > forward movement)? > > Regards > SWK > > > ________________________________ > > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On > Behalf Of Richard > Sent: Thursday, 23 March 2006 5:32 PM > To: Discussion of issues relating to Soaring in > Australia. > Subject: [Aus-soaring] Libelle performance > > > Hi > This is my first dip into the discussion group. Its > been great watching from the sidelines. > I have a problem. > My Libelle aileron deflections were found to be out of > whack mid season - max up deflection on right wing 15 deg > rather than specified 20 +/- 1. > I got that sorted through Bob Fox at GCV. > Now in flight and in neutral setting each aileron is > up about 3-4 degree is my estimate as viewed from the > cockpit. > Now thinking about Form 2 this year and would like to > know whether I should get this corrected and what sort of > performance characteristics one can expect from such a > setting, eg stall speed with my 75kg weight plus chute is > about 38 knots; it settles very quickly after round out on > landing and is hard to hold in a 45deg, 45 knot thermaling > turn. Is there a compensating performance gain at higher > speeds? > Any comments will be most welcome. > > Regards > Richard Robinson > VH GBM > > > > ********************************************************** > ************ This email and any file attachments are > confidential and intended solely for the use of the > individual or entity to whom they are addressed. > If you have received this email in error please tell us > immediately by return email and delete the document. > The information in this email expresses the opinion of the > author and does not necessarily represent the views of > ETSA Utilities. > ********************************************************** > ************ > > _______________________________________________ > Aus-soaring mailing list > [email protected] > To check or change subscription details, visit: > http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
