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#1
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Pullups, I stand corrected!
Lars,
I think you may be forgetting something else. For the same speed of travel, the light glider is using energy faster than the heavy glider. It seems paradoxical, but it is true - look at the loaded and unloaded polars to see that the heavy glider is either: a) travelling faster for the same sink rate, or b) sinking less for the same speed of travel (provided that the speed of travel in both instances is above the crossover point for the polars, the speed this occurs at depends on the wing loading). So, as they zoom upwards during the pull up: a) the light glider is using up its energy faster than the heavy glider, and it has less to start with, and b) the heavy glider is using up its energy slower, and it has more to start with. The heavy glider, of the same type, goes higher. Rgds, Derrick. |
#2
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My god!!!!
The polar for a given glider is reprentative of gliding flight characteristics. Once your nose is pointing up, you are coasting, you are not gliding anymore....so forget about the polar......and at the risk of becoming rude let me add this.........LIFT IS NOT HELPING YOU ANYMORE it may actually pull you away from optimal trajectory. Being the one who started this whole discussion, I am starting to think that I missed a good occasion to shut the F...up! But what the hell!!!! it all started in front of the club house, we're all drinking beer, and I throw The QUESTION!!!!! Immediate answer from everybody the ballasted is actually going wayyyyy higher!!!!!!!! I said that I doubt it, and did a littlle maths (you don,t have to own an eng. degree......which I do ), checked the drag, the only force that could make a difference and came to conclusion the the light glider has an edge, contrary to popular belief. So I came back to my buddies, thinking I was bearing the Good News. I was looked down at ( I am joking ok!!) So short of doing a real test, which is not easy to do "scientifically" I though of posting a message on this forum here!!!!!!!!hell broke loose (I am joking again) but yet I am amazed to see that the "Non-silent" majority is pro-ballasted. One can easily realise how your intuition can mislead you on this ......but yet we have some experimented pilots who are doing the maths to prove their intuition, and they do it in a much scientific way. So I can't wait to see the new sets of equations, and the coasting polar (this is not a joke). we are actally having fun,no? Me I have no proof to offer, and I feel a little obligated, being the one who set the fire. So we are desperatly begging anyone who actually did some testing to come forward and put an end this nightmare ;-), before we start throwing punches at each other!!!!We have alrerady witnessed people using capital letters in their message!!!!! Again, as someone mentionned earlier, please stop throwing ping-pong and golf balls at us. The Cx of a sphere is .42, which makes it the worst aerodynamic shape, an it quickly build a force that will oppose accelaration at a low speed, which is not the case of our beautiful gliders, at he operating speed, ther is not much difference in form (parasite drag), neighter for induced drag for which the heavy will suffer more during the pull-up The debate is not over yet!!!!We need a proof!! BQ "Derrick Steed" a écrit dans le message de ... Lars, I think you may be forgetting something else. For the same speed of travel, the light glider is using energy faster than the heavy glider. It seems paradoxical, but it is true - look at the loaded and unloaded polars to see that the heavy glider is either: a) travelling faster for the same sink rate, or b) sinking less for the same speed of travel (provided that the speed of travel in both instances is above the crossover point for the polars, the speed this occurs at depends on the wing loading). So, as they zoom upwards during the pull up: a) the light glider is using up its energy faster than the heavy glider, and it has less to start with, and b) the heavy glider is using up its energy slower, and it has more to start with. The heavy glider, of the same type, goes higher. Rgds, Derrick. |
#3
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For your convemience, here is two sites that explain lift and drag on
aircrafts, complete with some graph and theory and all. http://www.av8n.com/how/htm/4forces.html and http://www.go.ednet.ns.ca/~larry/bsc/winch/winch.html I hope this help BQ "Todd Pattist" a écrit dans le message de ... "szd41a" wrote: checked the drag, the only force that could make a difference and came to conclusion the the light glider has an edge, contrary to popular belief. I forgot, how did you arrive at this? The light glider has the advantage of being able to slow to a lower stall, but as far as drag goes, the heavy glider has the advantage (in terms of altitude lost) at all times. Todd Pattist - "WH" Ventus C (Remove DONTSPAMME from address to email reply.) |
#4
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In article ,
Stefan wrote: Stall speed isn't the limit. If you go ballistic at the top, i.e. if you push to zero G, then you can slow down to zero km/h if you wish (or to zero knots, if you live in the USA). Sure, but that doesn't help you fly your circuit. -- Bruce |
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