Hello Justin, hello everyone I can add to this discussion by reporting on the effects of an asymmetrically ballasted glider.
During my Pik 20 days one water bag got twisted which all but stopped the dumping of water from one wing and resulted in the opposite wing being about 50 kg heavier. The handling of the glider did not change in the slightest while still airborne. However, during the last third of the ground run it became impossible to keep the wings level. A proper ground loop could only be avoided by applying full wheel brakes when the heavier wing touched the ground. In other words, Noel is right when he says that “Generally a sailplane will not display an imbalance until stalled.” In the above case the stall occurred while already on the ground. Kind regards to all Bernard > On 28 Aug 2017, at 7:07 am, Justin Sinclair <[email protected]> > wrote: > > My only comment having been involved as CFI of a club that has had an > asymmetric balance accident would be that "if" you can pick that you have > asymmetry make sure do a fast landing. > > I am not sure of the speed or flap setting but logic would dictate something > above your normal fully ballasted/slow thermalling speed. The idea would be > to lower the wing onto the ground before you lose aileron effectiveness, but > do not do the traditional stall it on landing otherwise you get a big > surprise as the heavy wing drops first. > > The issue with asymmetry should be structural not aerodynamic. Even if one > wing has 200lts of water in it you average wing can easily develop enough > angle of attack to pull 3G or 600lts/kg, so as long as you have speed/AoA you > will be fine. > > My only other advice would be if you use tape to cover the vent holes instead > of wing sticks make sure you do a proper ABCD walk around just before you > jump in the seat and use any colour tape other than white. > > Justin > > Justin Sinclair > 17 Queen St > Scarborough Qld > > 0421061811 > > On 28 Aug 2017, at 12:18 am, Gary Stevenson <[email protected] > <mailto:[email protected]>> wrote: > >> Hi Noel, >> Tend to agree with you here. >> >> Re “twisted” I am sure that this does not apply only to the bags. Think >> about some of the pilots you know! >> >> You say “Generally a sailplane will not display an imbalance until stalled. >> One wing doesn’t know it’s heavier than its partner until then.” A very >> interesting point, which I have had the misfortune to inadvertently explore >> a little bit, but – thank God – never seriously in the air. >> >> Without doubt the use of water ballast introduced a whole new dimension to >> gliding, as, just co-incidentally Mike B mentioned in a concurrent post. >> However it use is something that should never be treated lightly [groan]. A >> couple of hundred litres of ballast will turn your pussy cat into a tiger: >> In the glide; into a missile ..... almost. Take care that you are not >> lined up on one of your mates. >> >> You say “A number of prototype sailplanes have been lost while testing their >> ability to remain controllable at the stall with max. Imbalance” I have >> never had the chance to own/fly a current “super-ship”, but from the >> literature , they have (as a minimum), inboard tanks, outboard tanks, and >> fuselage tanks. It would seem to me that the situation could become somewhat >> fraught, if the slightest thing goes wrong with the dumping arrangement. >> >> Would any knowable person like to make comment here? >> >> Finally we come to the important practical question of “good ballast bags”. >> It would seem that these are becoming hard to source, due to potential >> liability issues. Who in Australia, or elsewhere, are making new >> replacement bags? >> >> Regards, >> Gary >> >> >> >> >> >> >> >> >> >> >> From: Aus-soaring [mailto:[email protected] >> <mailto:[email protected]>] On Behalf Of Noel Roediger >> Sent: Sunday, 27 August 2017 10:18 PM >> To: 'Anthony Smith'; 'Discussion of issues relating to Soaring in >> Australia.'; 'Gliding Australia Forum' >> Subject: Re: [Aus-soaring] [gfaforum] RE: American Soaring Symposia >> >> Thanks Anthony. >> >> The final question asked of Wil re assymetric water ballast merits further >> comment particularly for those who fly sailplanes with bags instead of tanks. >> >> I believe good ballast bags far outweigh the problems exhibited by rigid >> tanks which often leak into the surrounding structure. >> >> Having said that I don’t know of any “bagged” tank that is not extended and >> held in place by a rear cord. >> >> In reality bags should be held by two cords. One at its rear as is the norm >> but also one at its front to eliminate the possibility of its leading edge >> falling over the aft edge and becoming twisted. >> >> >> >> Regards >> >> Noel. >> >> From: Anthony Smith [mailto:[email protected] >> <mailto:[email protected]>] >> Sent: Sunday, August 27, 2017 6:32 PM >> To: 'Discussion of issues relating to Soaring in Australia.'; 'Gliding >> Australia Forum' >> Subject: [gfaforum] RE: [Aus-soaring] American Soaring Symposia >> >> Part of the Wil Schumann paper is here: >> >> http://www.betsybyars.com/guy/soaring_symposia/72-modif.html >> <http://www.betsybyars.com/guy/soaring_symposia/72-modif.html> >> >> From: Aus-soaring [mailto:[email protected] >> <mailto:[email protected]>] On Behalf Of Ron Sanders >> Sent: Sunday, 27 August 2017 6:22 PM >> To: Gliding Australia Forum <[email protected] >> <mailto:[email protected]>>; Discussion of issues relating to >> Soaring in Australia. <[email protected] >> <mailto:[email protected]>> >> Subject: [Aus-soaring] American Soaring Symposia >> >> Any body got any idea where is can get any of these publications from the >> seventies?? >> Wil Schumann did a clean up of a libelle that i would like to read about >> again. >> >> Ron >> -- >> You received this message because you are subscribed to the Google Groups >> "Gliding Australia Forum" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] >> <mailto:[email protected]>. >> To post to this group, send email to [email protected] >> <mailto:[email protected]>. >> Visit this group at >> https://groups.google.com/a/glidingaustralia.org/group/gfaforum/ >> <https://groups.google.com/a/glidingaustralia.org/group/gfaforum/>. >> >> >> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> >> >> Virus-free. www.avg.com >> <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> >> >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Gliding Australia Forum" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected] >> <mailto:[email protected]>. >> To post to this group, send email to [email protected] >> <mailto:[email protected]>. >> Visit this group at >> https://groups.google.com/a/glidingaustralia.org/group/gfaforum/ >> <https://groups.google.com/a/glidingaustralia.org/group/gfaforum/>. > _______________________________________________ > Aus-soaring mailing list > [email protected] <mailto:[email protected]> > http://lists.base64.com.au/listinfo/aus-soaring > <http://lists.base64.com.au/listinfo/aus-soaring>
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