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#51
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On Tue, 28 Oct 2003 10:26:06 -0800, "Gary Boggs"
wrote: I really appreciate all this good input, thank you all for responding. Now for a new twist, one of our members has built a "pay out winch". A pay out winch is a drum with a break on it. The glider hooks up about 200' behind the tow vehicle, and as the glider climbs, the line spools out. Does anybody have any experience with this type of launch? How much runway do you need for this type of launch, how high can you get, ect? Boggs Don't know about that one but car tows generally aren't as good as a winch as the initial accleration is much slower. You are accelerating the car as well as the glider. The winch motor only accelerates the glider and wire. The car doesn't last very long in that sort of duty either. Mike Borgelt |
#52
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Your on your own there I think.
John Galloway At 18:36 28 October 2003, Gary Boggs wrote: I really appreciate all this good input, thank you all for responding. Now for a new twist, one of our members has built a 'pay out winch'. A pay out winch is a drum with a break on it. The glider hooks up about 200' behind the tow vehicle, and as the glider climbs, the line spools out. Does anybody have any experience with this type of launch? How much runway do you need for this type of launch, how high can you get, ect? Boggs |
#53
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"Gary Boggs" wrote in message ... I really appreciate all this good input, thank you all for responding. Now for a new twist, one of our members has built a "pay out winch". A pay out winch is a drum with a break on it. The glider hooks up about 200' behind the tow vehicle, and as the glider climbs, the line spools out. Does anybody have any experience with this type of launch? How much runway do you need for this type of launch, how high can you get, ect? Boggs I've done lots of auto tows and winch launches but no payout winch launches. But, I have done some back of the envelope calculating for payout winches. Payout winches seem to work fine for hang gliders where the towing speeds are far lower than sailplanes. The speeds needed for sailplanes really jack up the numbers. Assuming no wind, (Given enough wind, anything works - even a large stake.) the tow car has to accelerate to the normal towing speed plus the payout rate. The normal glider airspeed at the beginning of the climb will be about 55 - 60 Knots. Correcting this for True Airspeed, depending on density altitude, may be 70 - 75 MPH on the tow car speedometer. To pay out enough wire to make the effort worthwhile, (Say, 2500 feet in 60 seconds) the payout rate will be about 45FPS or 30MPH which brings the tow car speed to 105MPH - a bit fast for my taste. Now the tow car speed will decrease as the glider climbs so the distance required will be less than that covered at 100MPH for one minute. But you have to add in the distance to accelerate and stop the tow car. Juggle the numbers for yourself but it looks like you will need a 12,000 foot runway and really fast car - or lots of headwind. Consider also that a heavy two-seater will demand nearly 250 HP at the tow hook and a wire tension of about 1300 pounds. Your tow car had better be heavy as well as fast. This starts to make a standard winch launch look good. Bill Daniels |
#54
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Beware of the raw statistics.
How about this one: 100% of 2003 US glider fatalities occur after aerotow. Sounds like a good tag line for a winch manufacturer advertisement -bob |
#55
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I was lucky enough to get a kite launch one day. We had about 35 Kts of
wind on the ground, and someone suggested we try a launch. An instructor and I climbed into a Blanick L13, launched ( *very* short run ! ) and climbed to 4300 ft still on the wire. Of course we needed the expert cooperation of the winch driver, who eased off the power as we got about 500 ft, then payed out cable to let us climb. At the end, it was mostly the weight of cable ( single strand high tensile steel wire ) which determined the max height, although there wasnt much wire left on the drum. -- Regards, Adrian Jansen J & K MicroSystems Microcomputer solutions for industrial control "Stefan" wrote in message ... Bob Johnson wrote: Your ability to get 600 m releases with a winch on a 1200 m strip seems extraordinary. It all depends on the wind. With zero wind, the rule of thumb is that you get approximately 1/3 the cable lengh. More with headwind, much more with strong headwind. With extraordirarily strong headwind, you can even kite. (Yes, it has been done.) Stefan |
#56
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"Gary Boggs" wrote in message ... I really appreciate all this good input, thank you all for responding. Now for a new twist, one of our members has built a "pay out winch". A pay out winch is a drum with a break on it. The glider hooks up about 200' behind the tow vehicle, and as the glider climbs, the line spools out. Does anybody have any experience with this type of launch? How much runway do you need for this type of launch, how high can you get, ect? Boggs I have quite a bit -- in hang gliders. It works best with lots of road, runway, or dry lake. We typically got about 2/3 of the paid-out line in altitude. With 6000 feet of 3/16 inch polyprop, we could get 4000 feet. More typically, we'd tow until we hit a thermal somewhere above 500 feet. If you don't have a dry lake handy, you can "step tow". The tow car stops at the end of the road, and turns around (either a U turn or a "Y" turn), as the glider also turns around, being careful not to wrap the rope around the wing. When the glider is more-or-less turned around, the tow car starts again. Rinse, lather, repeat. The downwind run takes much less time. This might not work in sailplanes. In hang gliders, we were using a three-ring release, which doesn't back-release. Tim Ward |
#57
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In article , mowry86
@hotmail.com says... Beware of the raw statistics. How about this one: 100% of 2003 US glider fatalities occur after aerotow. Sounds like a good tag line for a winch manufacturer advertisement Unfortunately, not true: some have occurred after self-launch, and I know there have been some ground launch fatalities (how recently, I can't remember) -- !Replace DECIMAL.POINT in my e-mail address with just a . to reply directly Eric Greenwell Richland, WA (USA) |
#58
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Eggert --
Those are really good numbers for your winch. With V8 300 HP (GMC 454 c.i., 7.4 L), and 5000 ft (1550 m) Plasma line laid out, we are getting the rule of thumb 1/3 cable length releases of 1700 ft (525 m). This is into 10-15 kt wind. Much over that, we leave the Blanik in the barn! BJ Midland, Texas Eggert Ehmke wrote: Bob Johnson wrote: Mr. Ehmke -- Your ability to get 600 m releases with a winch on a 1200 m strip seems extraordinary. Is your cable length just 1200 m also or is it greater than your strip length? That's 1200 m of cable laid out, with a V8 240 HP engine at the other end. What I told is the normal range - with strong wind aligned to the runway we had 750 m (2460 feet) agl with a double seated ASK21. I did not see this launch, but it sounds reasonable. 650 m I have experienced myself. Eggert |
#59
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#60
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Good Morning!
I Think Gary had a similar question or topic here, a year ago or longer. Seems to me, he likes winches, but his club has doubts. I was trained with winch launches to solo in Germany, after I had already learnt to fly airplanes in the US. Subsequently I got into soaring in CO with aerotow, the going thing. Visiting Germany through the years, I realize how much more experience there is about that method. There are many places, where there is winch launch only! There are pilots with two years experience of flying who have never seen an aero tow! One canot make any comparison or have statistics! It all depends who does it, and his knowledge. When I look at modern winches and everything that goes with it, winch launching is really quite complicated and specialized. Take a good Towplane, a good instructor, a talented pilot, and in no time one has a towing operation going. In the US, to start a winch operation, which is as perfect as Oerlinghausen or similar would take a lot. To my knowledge, there is not a decent winch in the US, by comparison to Germany and what they have. Bill Daniels knows his stuff, but I think he is the exeption in the US. As for Gary Boggs, the only thing I can suggest is to go to Germany for a summer and learn the trade. Winches, how to run them, including the infrastructure. (Telephone) On the other hand, with more reasonable selflaunchers coming out, the winch effort may not be the answer anymore in the US. There are enough reasons mentioned in this thread. Happy Halloween |
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