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#1
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bildan wrote:
- limited in height and distance, i.e. you can't tow to that thermal 10 miles away if there's none nearby The practical reality is that you rarely actually know there is a thermal 10 miles away. If there's lift around, you can find it with a 2000'AGL winch launch - if there's no lift around, why consider an aero tow? This depends on the location. At our site, we seldom can reach a thermal from the winch, and even on those rare days not reliably. So as much as we'd like to use it for cross country launches (heck, it *is* cheaper and more fun!), winch launches are pretty much limited to student instruction. On the other hand, we often *do* know that there's that thermal 10 miles away. First, because it is always there, and second, because of the forming cumulus. But between our site and that thermal, there are 10 miles of sink. Agreed, on most days there eventually will grow thermals near the airfield, but only at noon, when those pilots who did a aerotow have already 2 hours under their belt and are 100 miles away. Agreed, you can fill that gap with a sustainer, but then, you can as well aerotow. Most airports weren't planned by glider pilots! |
#2
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I wonder if one of the new generation winches like the Hydrowinch with
a 4000ft launch would make a difference. Most winch operations I have read about all end with a 2K+ launch which does not give you a lot of time before starting a landing pattern. Just imagine a 4K launch without any lift, it still ends up being a perfect training flight of 15-25 minutes. I really want to go out to Colorado and test out the new prototype and see if it is for real. Too bad they cost so much $$$ $$. |
#3
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flyingmr2 wrote:
I wonder if one of the new generation winches like the Hydrowinch with a 4000ft launch would make a difference. The limiting factor is not the winch, but the rope length which in turn is related to the available runway length. A rough estimate is that the height with no wind is about half the rope length. Here's what you can do with a perfectly conventional tost winch and 3000 meters of spectra rope: http://www.youtube.com/watch?v=-VlRd9-wxQI (note that the altimeter is in meters and the vario im m/s) |
#4
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![]() The limiting factor is not the winch, but the rope length which in turn is related to the available runway length. A rough estimate is that the height with no wind is about half the rope length. Super cool video with an awesome launch. The hydrowinch site says they have enough room on the spool for 10K of Spectra rope. I guess if you have a 10k runway available,. you could get launched into space! Well, not quite, but it would sure seem high compared to a regular 2k launch. |
#5
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flyingmr2 wrote:
if you have a 10k runway available,. you could get launched into space! Well, not quite, but it would sure seem high compared to a regular 2k launch. Just be sure to publish a NOTAM. Nobody expects a winch rope above, say, 3000 feet AGL. |
#6
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On Jan 5, 9:11 am, John Smith wrote:
flyingmr2 wrote: if you have a 10k runway available,. you could get launched into space! Well, not quite, but it would sure seem high compared to a regular 2k launch. Just be sure to publish a NOTAM. Nobody expects a winch rope above, say, 3000 feet AGL. Lets say, just for argument, that a rope below 1500' AGL would not deserve a NOTAM but that over 1500' it would. So how long would the rope be above 1500' on a 3000' launch? My educated guess is that would be 15 - 20 seconds. Would a rope the the 1500 - 3000 foot band for 20 seconds every 10 minutes warrant a NOTAM? A typical light plane at cruise travels about 4000 feet in 20 seconds. Couldn't you just scan the airspace visually out to three miles before starting the launch? It's really quiet at a winch start line so you would probably hear an approaching aircraft. The thing is that winch ropes just aren't in the sky very long. Obviously, there are situations that would require a NOTAM but that's not the case everywhere. |
#7
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bildan wrote:
Lets say, just for argument, that a rope below 1500' AGL would not deserve a NOTAM but that over 1500' it would. So how long would the rope be above 1500' on a 3000' launch? My educated guess is that would be 15 - 20 seconds. 15 to 20 seconds are plenty enough for disaster. But I didn't mean it literally. (Albeit, the 5000 feet launch in the linked YouTube clip did require a NOTAM.) Anyway, I didn't mean it literally, but just wanted to point out that a long rope will interfere with power traffic. This is solvable, of course, if you have a plan and everybody cooperates. But you definitely do need a plan. |
#8
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On Jan 5, 8:46 am, flyingmr2 wrote:
The limiting factor is not the winch, but the rope length which in turn is related to the available runway length. A rough estimate is that the height with no wind is about half the rope length. Super cool video with an awesome launch. The hydrowinch site says they have enough room on the spool for 10K of Spectra rope. I guess if you have a 10k runway available,. you could get launched into space! Well, not quite, but it would sure seem high compared to a regular 2k launch. The question of just how high a winch launch could go has come up several times. There is a small group of extreme kite flyers who have flown L/D ~4 kites up to 30,000 feet using the same Spectra rope used by glider winches. That suggests that launching a glider to the floor of Class A airspace would be possible given enough runway and wind. I expect that someone will do that fairly soon. If the glider can be launched into a 50 knot wind layer, a tension controlled winch would automatically reverse the drum rotation direction and pay out rope - the glider would in effect be a high L/D kite. The possible release height would then depend on the length of the rope, not the length of the runway. |
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