Volume 16 No 1 Feb 1965.pdf - Lakes Gliding Club

V.RF. to my car with just a whip ofaerial on the roof was very good, seeingthat the radios we were using, eX-R.A.F.,had only cost £12 10s. each.Ahead I could see a very nice cloudstreet stretching some way on track,When I arrived at its near end I woundthe Ka-6 up and then set off underneathit at 150 km. per hr. on the clock, andnine minutes later the cloud street endedand I was still at the same height. Verynice; I could do with a few more ofthese. In the haze, in the distance, Icould just see Salisbury; all I neededwas three more thermals. The last onePERFORMANCE POLARSGlider Weigbt Col1llideratiOllsOR a really fair comparison betweenF glider types, it is best if the weightsof each are referred to some standard.The first idea that springs to mind is toadopt a standard pilot + parachuteweight of, say, 200 Ib.. and to add this tothe empty weight of each test glider.However, the empty glider weight mayvary widely within ·an actual type rangebecause of slight differences in man\!­facture and because of such things as thevarying moisture content of woodenstructures. The standard performancepolar would thus be different for eachglider. We have therefore decided tostandardise on maximum A.U.W. whichis invariant unless drastic modificationsare made to a glider type.To correct a polar from a givenweight, W" to a new weight W" all thatis necessary is to multiply' the scales ofboth axes by the ratio .,lW, : ";W 2 •We have redrawn the Skylark 3F polargiven in the October issue to allow forour new reference weight. To providesome idea of the magnitude of changein performance of a glider with differentA.U.W.'s, we have plotted two Ka-6curves for a difference in weight of 56 lb.Po1:lrsThe polars published this month areas follows:K·6 CR SChleicher SegelflugteugbauSKYLARK. 3p Slingsby Sailplanes Ltd.SKYLARK. 4 Slingsby Sailplanes Ltd.OLYMPfA 460 . Elliotts of Newbury Ltd.The Ka-6 CR and the Skylark 3Fcurves are from the same source as last44I took up high, too high in fact, but itwas so nice to sit there and let the Ka-6go flat out for the last few miles and toknow that my Diamond was "in the bag"and that the first 500-km. flight in Rhodesiawas over. Time 4.45 p.m.On the ground again, started the longsad wait, listening on the radio as othersgradually got lower and lower and. finallylanding just short. Same old story-"justone more thermal".In Rhodesia the day is not very long;by 6 p.m. it is dark. The conditions haveto be good to fly a long task in such ashort day.time, namely, H. J. Merklein and H.zacher.The Skylark 4 measurements weremade by R. H. Johnson in the U.S.A.and are deemed reliable. The polar obtainsan "A" Category.The Olympia 460 polar, obtained fromG. R. Whitfield, was derived from asingle photographic comparison flightwith a Skylark :2 at three speeds. It thusonly obtains a "B" Category. The 460tested was the prototype with the bulbouswheel fairing and without the skid.We must apologise for last month'spolars not lining up with the centimetr-egraph paper. This was due to the inabilityof the blockmakers to scale~curately.K. H. DoETSCH, D. LAMPARo,Aeronautics Dept., Imperial Collel:e,Prince Consort Rd.• London, S.W.7.EOITORIAL NoTE.-We will not be ableto publish any more of these polars forseveral months.NOTHING BUT THE BEST ....•• IS GOOD ENOUGH FOR YOU* REPAIRS * TEN YEAR INSPECTIONS* OVERHAULS * RE·SPRAYING. ETC.Carried out lit Reasonllble ChargesSouthdown Aero Services LtdLasham AIrfield, Alton, Hants.Telopho.o He