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#31
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SAFE Winch Launching
On Sat, 11 Jul 2009 17:07:50 -0700 (PDT), bildan
wrote: A tension controlled winch will do the opposite - decreasing power in thermals letting lift do the work and increasing it in sink leaving the pilot to control speed with pitch. The pilot sees a very smooth launch regardless of wind or thermals. The winch operator doesn't need to do anything at all. It's wonderful to never need speed signals again. .... yet thousands of clubs in Europe with much, much more winch experience than any club in the US don't see the need for such a system. |
#32
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SAFE Winch Launching
Bills explanation a couple of posts ago is an excellent and simple
description of how it constant tension works and why it would be beneficial. Why don't we in Europe adopt this technology -- quite simply cost. Without private finance of money/time/labour/parts few clubs if any can afford to scrap their current winches and buy the new technology. Dave At 00:29 12 July 2009, Andreas Maurer wrote: On Sat, 11 Jul 2009 17:07:50 -0700 (PDT), bildan wrote: A tension controlled winch will do the opposite - decreasing power in thermals letting lift do the work and increasing it in sink leaving the pilot to control speed with pitch. The pilot sees a very smooth launch regardless of wind or thermals. The winch operator doesn't need to do anything at all. It's wonderful to never need speed signals again. .... yet thousands of clubs in Europe with much, much more winch experience than any club in the US don't see the need for such a system. |
#33
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SAFE Winch Launching
On 12 Jul 2009 10:15:03 GMT, Dave Martin
wrote: Bills explanation a couple of posts ago is an excellent and simple description of how it constant tension works and why it would be beneficial. Why don't we in Europe adopt this technology -- quite simply cost. Without private finance of money/time/labour/parts few clubs if any can afford to scrap their current winches and buy the new technology. If constant tension was really necessary for a good winch launch, many clubs would already have one. But the standard system (Tost, Skylaunch, whatever) is good enough for the majority aof the clubs here. It's definitely nicve to have - but Bill would probably have an easier job if he advertized a more simple and much cheaper winch design to the US clubs... |
#34
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SAFE Winch Launching
Hi,
A tension controlled winch will do the opposite ... yet thousands of clubs in Europe with much, much more winch experience than any club in the US don't see the need for such a system. Some do. When I was trained as a winch driver I was taught to judge cable tension and use that as the input parameter to the control loop. The only way of doing that without special sensors is to look at the cable sag. Works during the main portion of the launch, but is not very accurate of course. I think if the winch, or winch driver, has the means to control tension and the pilot controls airspeed winch launches become more efficient and even safer. Reports suggest that, I have no experience of my own. Also you would propably get much more consistent launch performance across different conditions and much more important, different drivers. Today we get launches like being shot from a carrier deck and the lumbering wingrunner-testing type all in the same day depending on who is manning the winch. The first launches of the day, or after a driver swap, or when conditions change would no longer need to be different than those by a well-adapted driver. I am all for it. Ciao, MM |
#35
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SAFE Winch Launching
At 00:07 12 July 2009, bildan wrote:
If a glider encounters a thermal during a launch, the rope tension will increase which the automatic transmission will see as a "hill" causing it to increase torque to the drum. This increases rope tension still more as it tries to pull the glider down through the thermal. If the glider hits sink, the automatic transmission will slack off the torque just when the glider needs more power. A good winch operator can overcome these to a degree with constant throttle adjustments - if he can tell what is going on in the glider but it's hard, skilled work. It's definitely not "set and forget". A tension controlled winch will do the opposite - decreasing power in thermals letting lift do the work and increasing it in sink leaving the pilot to control speed with pitch. The pilot sees a very smooth launch regardless of wind or thermals. The winch operator doesn't need to do anything at all. It's wonderful to never need speed signals again. I think the difference in design concept between Europe/ USA is that over the years we have leaned to design things which work for a minimal cost. We have tried to avoid the expensive solution designed to kill you. I can think of nothing more dangerous in a winch design than a tension sensitive drive. It may be wonderful to not need signals again, which if you are dead of course you don't need, we prefer the safe option over here even if it means a little more work. |
#36
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SAFE Winch Launching
On Jul 11, 1:34*pm, johngalloway wrote:
On 11 July, 14:36, bildan wrote: On Jul 11, 2:00*am, Derek Copeland wrote: At my club we typically get about 1600ft in no wind and 2000ft launching into a 10 knot headwind. Our standard aerotows are 2000ft, but you can go as high as you like, depending on your needs and the depth of your wallet. This week we were getting as high as 1900' from 3900 feet of rope at 9000 feet density altitude with little wind with the Hydrowinch. *With no gear shifting at all, the Hydrowinch is MUCH smoother than any winch with an automatic transmission. Skylaunches are just like old Gerhleins with new paint - they use exactly the same components. *They are not particularly well controlled since they use road vehicle torque converters and automatic transmissions free to shift gears when they please. *The old junk Gerhleins around most US clubs are probably the only winches in the world worse than a Skylaunch - but they are a LOT cheaper. BTW, notice how Derek has to reply to himself to get any conversation at all? This account of the performance of the Skylaunch winch is, as Bill has repeatedly been told previously elsewhere by pilots who actually operate or launch on Skylaunch winches, utterly false and his obsessive denigration of it is disgraceful. *Our club had a Skylaunch winch for evaluation for six days a couple of weeks ago. *The smoothness of launch is faultless and a vast improvement over Supacat and Tost winches The fact that the automatic transmission can shift gears "when they please" is a complete non issue. *The gear changes up at the start of the launch occur within the first 2-3 seconds (timed by me) and before the glider has rotated into the climb. *The gear changes are completely imperceptible in the glider. *None of numerous pilots on the ground near the winch during launches note the upwards gear changes without being prompted to listen out for them - an even then there was soe debate about whether they could be detected. Occasionally the autobox changes down to second during the mid launch when under load but at no time was any of the many pilots launched aware of any gear change. The operational mechanisms of the Skylaunch are not designed to "control" the launch so it is not surprising that it does not do so. What it does have is an interconnected maximum throttle position guide that takes into account the type of the glider and the headwind component. *This means that each glider is effectively provided with a winch with an appropriately powered engine for itself and the wind conditions in the mid launch. *The winch driver still has to control the start and end of the launch - by advancing the throttle control at an appropriate rate at the start (about 3 seconds IMHO) and backing off the power at the top. *The predictable response of the good old GM V8 to load means that the plot can pull into a steep climb without fear of overspeeding. The new US winches may turn out to be brilliant but Bill's emotional bias invalidates him as an objective reporter in my opinion. John Galloway For the record, I have no financial or managerial connection with either US winch manufacturer but I strongly support and encourage both. Both chose the best solutions based on very careful investigation of winch launch dynamics. Neither chose to spend money on excessively complicated solutions without extremely good cause. Do I have an emotional bias against crappy engineering? Damn right I do - especially when it's being sold as the 'perfect' solution. The use of an automobile engines and automatic transmissions has only one advantage - they're cheap and they 'work' after a fashion but it's far from an ideal solution. There is quite a bit of field data to support this. Once the underlying dynamics is fully investigated, it become clear that this is not the way to go. Automatic transmissions are a particularly evil choice. To repeat yet again, automatic transmissions are highly developed and uniquely adjusted for each vehicle in which they are installed. To transplant them into a glider winch with diametrically opposite requirements brings out the worst in the device. They are designed for a wildly different purpose. People can get used to anything and will learn to compensate for the shortcomings of a winch based on automobile parts. They may not even realize they are compensating unless there is a point of comparison. You may not notice the transmission shifting or tension/speed errors until you launch from a winch that does not shift and automatically adjusts for air motion - then it's a revelation. I strongly suggest doubters read George Moore's article in July Soaring and the following article in the September issue. Thanks to George, we now know EXACTLY how winch physics work. It's no surprise that such knowledge leads to new and better winch designs. |
#37
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SAFE Winch Launching
On Jul 12, 8:45*am, Don Johnstone wrote:
At 00:07 12 July 2009, bildan wrote: If a glider encounters a thermal during a launch, the rope tension will increase which the automatic transmission will see as a "hill" causing it to increase torque to the drum. *This increases rope tension still more as it tries to pull the glider down through the thermal. *If the glider hits sink, the automatic transmission will slack off the torque just when the glider needs more power. *A good winch operator can overcome these to a degree with constant throttle adjustments - if he can tell what is going on in the glider but it's hard, skilled work. *It's definitely not "set and forget". A tension controlled winch will do the opposite - decreasing power in thermals letting lift do the work and increasing it in sink leaving the pilot to control speed with pitch. *The pilot sees a very smooth launch regardless of wind or thermals. *The winch operator doesn't need to do anything at all. It's wonderful to never need speed signals again. I think the difference in design concept between Europe/ USA is that over the years we have leaned to design things which work for a minimal cost. We have tried to avoid the expensive solution designed to kill you. I can think of nothing more dangerous in a winch design than a tension sensitive drive. It may be wonderful to not need signals again, which if you are dead of course you don't need, we prefer the safe option over here even if it means a little more work. Check your geography. Tension controlled winches were developed in Europe. Check your engineering facts. Tension controlled winches are FAR safer than any other alternative. How can a winch be safe when the operator must control glider airspeed with throttle WHEN HE HAS NO KNOWLEDGE OF IT? Actually, Skylaunch indirectly acknowledges this by offering airspeed telemetry as an option. The only reason for this loud controversy is a single English winch manufacturer in who uses cheap American auto parts and sells the product - essentially a 2-drum Gerhlein - for $145,000 USD at last check. It's a great business model as long as there are suckers. People tend to get upset when you point out the Emperor has no clothes. Yes I know it's a MARINE GM V8 but that's the same engine core as used in a pick-up trucks with a few different accessories. Last check, they wholesale for about $2,500. The stock GM TH400 sells for about $1200 USD. |
#38
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SAFE Winch Launching
On Sun, 12 Jul 2009 10:28:03 -0700 (PDT), bildan
wrote: How can a winch be safe when the operator must control glider airspeed with throttle WHEN HE HAS NO KNOWLEDGE OF IT? It is safe. Period. Even if you don't believe that. All the best Andreas |
#39
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SAFE Winch Launching
On Sun, 12 Jul 2009 12:45:08 +0200, Marian Aldenhövel
wrote: ... yet thousands of clubs in Europe with much, much more winch experience than any club in the US don't see the need for such a system. Some do. Indceed some do - but very, very few. If there really was an urgent need we'd have more than a couple of such winches in Europe by now, don't you agree? When I was trained as a winch driver I was taught to judge cable tension and use that as the input parameter to the control loop. The only way of doing that without special sensors is to look at the cable sag. Works during the main portion of the launch, but is not very accurate of course. But sufficiently accurate, isn't it? Contrary to the believe of some people here it doesn't matter if the speed during the winch launch is 5 kts faster or slower (although the perfect speed certainly increases launch height). I think if the winch, or winch driver, has the means to control tension and the pilot controls airspeed winch launches become more efficient and even safer. Reports suggest that, I have no experience of my own. Efficiency? Definitely. Safety? I doubt it. I havent't been able to find even one accident report that was caused by inappropriate power setting by the winch driver, yet there are comparably many accidents caused by rope breaks or complete power losses of the winch - things that cannot be prevented by tension controlled speed. Also you would propably get much more consistent launch performance across different conditions and much more important, different drivers. Indeed. Nice to have. Today we get launches like being shot from a carrier deck and the lumbering wingrunner-testing type all in the same day depending on who is manning the winch. The first launches of the day, or after a driver swap, or when conditions change would no longer need to be different than those by a well-adapted driver. Typical problem of winch driver training. Once we started to re-train our winch drivers who had problem scontroling the speed, we got rid of this problem. Viele Grüße Andreas |
#40
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SAFE Winch Launching
I would love to fly a tension controlled winch we were launhing today in
to strong head winds increasing rapidly part way up the launch. I can imagine it is better, but I am not an expert. Winch safety is mostly in the hands of the pilot, the winch is not relevant to a good launch, but the trained pilot must be able to react to any scenario. But other nonsense posted here . please help me, ... A standard car auto gearbox has some magic power to automatically adjust the torque to the car wheels on reaching a hill, without changing gear, road speed or engine setting? What magic is that? David. At 18:45 12 July 2009, Andreas Maurer wrote: On Sun, 12 Jul 2009 12:45:08 +0200, Marian Aldenhövel wrote: ... yet thousands of clubs in Europe with much, much more winch experience than any club in the US don't see the need for such a system. Some do. Indceed some do - but very, very few. If there really was an urgent need we'd have more than a couple of such winches in Europe by now, don't you agree? When I was trained as a winch driver I was taught to judge cable tension and use that as the input parameter to the control loop. The only way of doing that without special sensors is to look at the cable sag. Works during the main portion of the launch, but is not very accurate of course. But sufficiently accurate, isn't it? Contrary to the believe of some people here it doesn't matter if the speed during the winch launch is 5 kts faster or slower (although the perfect speed certainly increases launch height). I think if the winch, or winch driver, has the means to control tension and the pilot controls airspeed winch launches become more efficient and even safer. Reports suggest that, I have no experience of my own. Efficiency? Definitely. Safety? I doubt it. I havent't been able to find even one accident report that was caused by inappropriate power setting by the winch driver, yet there are comparably many accidents caused by rope breaks or complete power losses of the winch - things that cannot be prevented by tension controlled speed. Also you would propably get much more consistent launch performance across different conditions and much more important, different drivers. Indeed. Nice to have. Today we get launches like being shot from a carrier deck and the lumbering wingrunner-testing type all in the same day depending on who is manning the winch. The first launches of the day, or after a driver swap, or when conditions change would no longer need to be different than those by a well-adapted driver. Typical problem of winch driver training. Once we started to re-train our winch drivers who had problem scontroling the speed, we got rid of this problem. Viele Grüße Andreas |
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