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#21
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I think the difference isn't so much height gained, but back calculating
to horsepower based on a 1 "G" acceleration at the start of the launch. I've flown off a Supacat and while it had good acceleration, it sure didn't match up to the whopper of a winch that was built by the permian soaring association. Talk about a zippy launch! http://members.cox.net/tsample10/SpecialProjects.html By the way, I think this "unified winch design" concept is a really great move. If you have a diesel driving through a fluid flywheel you don't need that much power: we have a Supacat with a 245 hp Deutz V8 aircooled industrial diesel and torque converter (no gearbox). This can launch an ASH-25 or just about any Nimbus. With a 15 m glider, K-21 or Grob you'd expect 1200-1400 ft on a 1000m run in calm conditions and over 2000 ft if its blowing a bit. I'd agree with everything you've said about the specialised nature of a glider winch, the heavy duty engineering and the costs. -- martin@ : Martin Gregorie gregorie : Harlow, UK demon : co : Zappa fan & glider pilot uk : |
#22
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See also: http://www.proximedia.com/local/neth...el/various.htm
Diederik BTW: I have winched twin astirs, fully loaded, k-8's, T-21 tutor and prefects with a 350 hp winch. No problem, it's just how you adjust the throtle Stefan wrote in message ... Not exactly what you asked for, but take a look at http://www.skylaunch.de/album/index.html It's fun and it may give you some ideas. Stefan |
#23
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Yep, it's just not the same when you can match the displacement of an
entire European car engine with the displacement of just 2, maybe 3, cylinders worth of an American big block motor...... tango4 wrote: You have to remember folks that these are American horsepower units. About 2:1 is a good ratio against proper European horses! :-) Ian "Kevin Neave" wrote in message ... Bill, I think you need to revisit your numbers. Here at Nympsfield (UK) we have a Supacat winch with a 250 horse Diesel that easily provides enough power for the biggest gliders on site (DG505, DuoDT, Nimbus3DT) (And pretty scary in a Libelle if the winch driver is *over enthusiastic*) The previous engine was 180 HP, this was a bit marginal for the Heavy Glass, but more than enough for any single seat (We have a 1000m field & regularly get 1500', even nil wind) :-) KN At 15:36 19 March 2004, Bill Daniels wrote: Mark, unfortunately, the physics of a winch launch says that it takes about 1 kWh or 3,600,000 Joules to launch a glider. The peak power demand places yet another constraint on the minimum HP that must be available. Those numbers point to a 400 to 500 HP engine to be able to provide launch service to any glider in the existing fleet. |
#24
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"Marc Ramsey" wrote in message . com... I think the difference is that Bill is considering operating at much higher density altitudes. In the western US, there are many glider operations where summer density altitudes are in the 8000+ foot range. Marc Actually, most of the newer and larger diesels are turbocharged and have electronic controls, including absolute manifold pressure sensors, electronically controlled fuel injectors, and turbos with waste gates. These engines will typically make full rated horsepower and torque at density altitudes above 10,000 feet. Electronically controlled engines also leave open the possibility of controlling the engine without the typical manual input to the foot or hand throttle. The foot pedal in that big diesel behind you on the freeway only has copper wires between the foot pedal and the engine's ECU (electronic control unit). It should be quite possible for someone (like you, Marc) to program such an engine to desired and optimized parameters during each part of the launch for each type of glider, with perhaps a hand control to override the automatic settings. The ECU's on the engines already have cruise control and PTO functions built in, as well as logger functions, fault logging, fail soft ability, etc. Big trucks today have as much electronics as cars. -Bob Korves |
#25
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Bill Daniels wrote:
"Mark James Boyd" wrote in message I'd love to see a winch design that uses a 100hp or less engine, can be easily bolted on the back of an old pickup, and has engine and parts that are low maintenance and (especially engine) easy to acquire (either locally or via shipping). Alternately, how about a "spare tire" that is really a winch drum. a stable sturdy "jack" and some way to route the cable to ensure it winds up nice. Might not work (thoughts of side loads tipping my car over come to mind!), but it sure is fun to play with the thuoght! -- Mark, unfortunately, the physics of a winch launch says that it takes about 1 kWh or 3,600,000 Joules to launch a glider. The peak power demand places Hmmm...so all gliders are alike? A Gapa or Russia REQUIRES the same HP as a ballasted LAK-12 or Nimbus 4? Something 400 pounds vs. 1600 pounds? I know this isn't what you meant... I read the Marske site and saw the (wt lbs) x (wing loading lbs) x .03 = hp and it looked like these mini gliders "needed" about 100 hp. yet another constraint on the minimum HP that must be available. Those numbers point to a 400 to 500 HP engine to be able to provide launch service to any glider in the existing fleet. Although the initial cost of a well engineered winch is high (nearly as much as a tow plane) the long term costs are only a few percent as much a tug. A coupla points: well engineered, is limited in how high you can get, and very hard to move around are winch disadvantages. The height is tough to get with any winch (8000 ft sightseeing sled rides ain't gonna happen). But if we assume we'll only fly 500 gross wt. with 6# wing loading, how does this ease the engineering and building costs, and how mobile is this new mini-winch? If we can build four of these things for the price and energy of a 400hp version, is the launch weight limitation less of a disadvantage? How about if we can build eight of these for the same price? How about if we can build 16? Obviously if you fly 1600 lbs of glider, this does you no good. And sure, there are non-recurring engineering costs to making 2, 4, 8, 16 of these. I guess what I'm saying is I'm not gonna see a big winch that launches 1600 lbs at MY gliderport in the next 5 years, but I'm gonna bet I'll see a small, portable, back of the truck winch at Tehachapi at the Vintage Sailplane Rally in about a month... I've also seen pictures and know there are dozens (maybe hundreds) of hugely capable, overengineered (IMHO) winch designs (they seem to all be custom homebuilts). For novelty, I'd like to see the juxtaposed minimalist approach. I've been very impressed by the lighter, smaller gliders I've seen recently. I'm excited about the idea of towing them with a 75 hp towplane. I'd like to see a 100 hp winch, even if it was underpowered, just to see HOW underpowered... The good news is that the total energy consumed for one launch (About 1 liter of diesel fuel equivalent) is tiny compared to any other launch method except bungee launch. (Excluding, of course, the beer you have to provide the bungee crew.) Auto tow's about the same, but without the construction costs, from what I gather. The huge downside (I'm finding out) is that auto-tow takes a HUGE amount of room/runway... A glider winch is a highly specialized piece of machinery that needs the kind of engineering Ulrich is asking for. Please avoid the temptation to cobble some junk together to make a barely workable winch. That sort of thing has given winch launch a bad name in the USA. There's that word "needs" again. ;P Keep in mind you are sharing this thread with ME, an avid experimenter and no stranger to failure... A well run winch operation is very attractive to newcomers to the sport. It shows a lot of ground activity that is visible to the onlookers and the rides are a real thrill. Lets get winching! The only winch I know of on the west coast USA that one can schedule use of is Northwest Soaring an hour east of Seattle. I called them and it's a May-Oct operation at Cle Elum. Fortunately the flights out of San Fran area are $130 round trip, so it'll be cheap to visit there this summer )) . -- ------------+ Mark Boyd Avenal, California, USA |
#26
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In article ,
Ulrich Neumann wrote: (Mark James Boyd) wrote in message news:405aa3e8$1@darkstar... mat Redsell wrote: My statement was very confusing... what I really meant was without the winch I think that we will be in troubles down the road for affordable tows.... And in part I do think that we have taken a wrong road with high wing loading. for example with the Monarch we are able to tow it aloft with 160 lbs of tension at a speed of about 15 mph with a wind down the runway of about 10 mph. This requires a very small rope and small horsepower. http://www.continuo.com/marske/ look under articles for : ultralight design parameters design parameters of the ultralight glider I'd love to see a winch design that uses a 100hp or less engine, can be easily bolted on the back of an old pickup, and has engine and parts that are low maintenance and (especially engine) easy to acquire (either locally or via shipping). Alternately, how about a "spare tire" that is really a winch drum. a stable sturdy "jack" and some way to route the cable to ensure it winds up nice. Might not work (thoughts of side loads tipping my car over come to mind!), but it sure is fun to play with the thuoght! Mark, a 100HP or less winch? What are you trying to launch - kites or RC gliders? The Europeans are replacing their winches powered traditionally by Detroit's finest with big rig Diesels, because ...? Lets get real here. As nice as it sounds to have your own personal winch in the trunk, the reality looks more like you could haul your car around with the winch. But keep the ideas coming. Ulrich Neumann The previous post about the Marske stuff was my reference. Keep in mind that yes, I AM talking about very lightweight gliders (either ultralight or close to it). Not necessarily as interesting to the "soaring enthusiasts" found here, but interesting to me as a "soaring consumer." If you wonder where this push comes from, it's from years of having fellow pilots tell everyone how airplanes cost "tens of thousands of dollars" and take $5000 to learn how to fly. I own a $6000 airplane which one could learn to solo in about 20 flights ($2000). http://www.cse.ucsc.edu/~mjboyd/cfi/GHFCcharter A lot of aviation is overkill. Garmin 430, lights, a starter, flaps, oleo struts, a heater, blah blah blah. And who needs a PPL? Solo is solo. There's no doubt who's flying the thing...where did all this complexity come from? Society, certainly not the aircraft itself... Do we NEED a 245 hp winch? Is it POSSIBLE to launch with something smaller and less hassle? Do we NEED two 40# thrust turbines, or just one and a lighter glider? ;P -- ------------+ Mark Boyd Avenal, California, USA |
#27
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4740' MSL - temperatures in the mid 30s Celcius.
220 HP winch (and that was when it was new fifteen years ago) We launch Blanik L13, Kestrel 19m etc quite satisfactorily... One advantage of a relatively low power winch is it is simple to drive. With the heavier two seaters and the Kestrel it is a case of roll on full power over four seconds. Leave it there until the time comes to release. OK - we do have 1800m of wire, and we only get 1500' to 2300' AGL. Our conditions are good enough that we seldom need a relight during the middle of the day. Launch after 15:00 and you are taking your chances as always, but I don't think that a couple of hundred feet AGL will make such a difference then anyway. |
#28
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"Mark Zivley" wrote in message
... Yep, it's just not the same when you can match the displacement of an entire European car engine with the displacement of just 2, maybe 3, cylinders worth of an American big block motor...... Not to mention the CO emissions and resource usage ...... Ahh, but what the hell, when all the fish are dead, the sky rains acid, the cows all have two heads and the crops die off because Monsanto decides to modify the wrong gene it won't be our problem! Cynically yours Ian |
#29
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We have had several people writing that they have launched heavy glider X
with a low powered winch. I have done it and so have many others, but this is still not a good idea. There are serious dangers involved. The best way to look at it is to consider power demand and supply. The winch engine should be able to supply all the power the glider demands. If the glider demands more power that is available by pulling up hard, the airspeed will decay quickly. If the pilot knows this is going to happen, he can manage it by controlling the pitch attitude carefully. If he doesn't expect it, the airspeed will decay so quickly that a very dangerous situation will develop. The attempt to launch gliders with a low powered winch gets into who is in control of the launch. I think it goes without saying that who controls the launch should not be in doubt. The majority view is clearly that the winch driver should be in charge. With a low powered winch, the winch driver is in charge early in the launch but as the glider steepens the climb, the power demand exceeds supply and speed control shifts to the glider pilot who now must control airspeed with pitch since the winch is at full throttle. As the glider rises still further and power demands lessen, airspeed control shifts back to the winch driver who must reduce power to prevent over speeding the glider. There are lots of ways this scenario can go badly wrong. The other area where a low powered winch can cause problems is in the initial acceleration. The German Aero Club specifies the maximum distance that a glider can use to reach flying speed to determine the minimum winch power. Specifically, under all conceivable wind, density altitude and weight conditions, a glider must reach Vr (rotation speed) in 40 meters or less - there is no minimum specified. This is a very intelligent specification. The concern driving this spec is that should a glider's wing drop to the ground before reaching flying speed, the resulting ground loop will be very ugly and quite possibly fatal for the glider pilot. These concerns and the desire to get the highest launch possible, has driven winch horsepower higher and higher in recent years. Shortening the accelerate to Vr distance has a powerful effect on the launch height achievable. Many powerful winches have shortened this to less than 20 meters. To summarize, I am advocating generous power reserves to permit the winch driver to maintain control of the launch and to insure the glider reaches flying speed before a wing can drop. Bill Daniels |
#30
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Hi Bill
I respect your views but there are some differences in the way we see things he Firstly please note that I am not advocating underpowered winches. I do however maintain that power is not the most important safety issue in winch launching, and that - for our fleet where the highest wingloading is relatively modest, and the heaviest glider is a Blanik L13 - a winch with 220Hp is adequate. (maybe 250 would be better) Bill Daniels wrote: We have had several people writing that they have launched heavy glider X with a low powered winch. I have done it and so have many others, but this is still not a good idea. There are serious dangers involved. Too low power is dangerous, and we agree entirely that more power is desirable. Interestingly the most recent National Safety meeting addressed winch launching as the primary theme. There were 25 Safety Officers and at least ten Chief Flying Instructors as well as the SSSA Exco present. One thing that became apparent was that there is no optimal power winch. In particular - when launching old designs that are light, high wing with the hook at a considerable vertical displacement from the wing, there have been numerous dangerous launches where the initial acceleration exceeds the control authority on the glider. The example given was launching a Ka8 with the stick hard against the forward stop for most of the launch. Too much acceleration is as dangerous as too little. The best way to look at it is to consider power demand and supply. The winch engine should be able to supply all the power the glider demands. If the glider demands more power that is available by pulling up hard, the airspeed will decay quickly. If the pilot knows this is going to happen, he can manage it by controlling the pitch attitude carefully. If he doesn't expect it, the airspeed will decay so quickly that a very dangerous situation will develop. Agreed, and all of our pilots have to learn to control their demands on the winch before going solo. In this respect it would be safer and better to have more power for perhaps 30% of our fleet. Conversely, any piulot who relies on the generous power reserve of the winch to compensate for pulling back too hard is dangerous. I am all for the speed decay to warn the pilot. That way, when the winch falters, he will compensate automatically because he will be used to monitoring and controlling airspeed carefully. The attempt to launch gliders with a low powered winch gets into who is in control of the launch. I think it goes without saying that who controls the launch should not be in doubt. The majority view is clearly that the winch driver should be in charge. Here I differ, the pilot is always in control of his / her destiny. Our process is that the launch marshal controlls the launch process, and the winch driver and pilot must work together. A skilled winch driver is in control at all times within the parameters dictated by physics. If we have a pilot who over rotates and "bends the pole" a number of things will happen. With the exception of the Blanik with its flaps deployed the winch driver will be able to keep the glider above stall speed with full throttle. The winch driver is still in control and may decide that the probability of a maximum tension cable break is dangerously high and elect to reduce power until the pilot takes the pressure off the cable. (even if it results in a low release) If the pilot is being ham fisted the cable will probably break resulting in a dangerous recovery and the possibility of landing damage. This probability is directly proportional to the instantaneous force on the cable, here a powerful winch is a distinct liability. In any event an overzealous pilot is going to get a lecture from the CFI... With a low powered winch, the winch driver is in charge early in the launch but as the glider steepens the climb, the power demand exceeds supply and speed control shifts to the glider pilot who now must control airspeed with pitch since the winch is at full throttle. As the glider rises still further and power demands lessen, airspeed control shifts back to the winch driver who must reduce power to prevent over speeding the glider. There are lots of ways this scenario can go badly wrong. The other area where a low powered winch can cause problems is in the initial acceleration. The German Aero Club specifies the maximum distance that a glider can use to reach flying speed to determine the minimum winch power. Specifically, under all conceivable wind, density altitude and weight conditions, a glider must reach Vr (rotation speed) in 40 meters or less - there is no minimum specified. This is a very intelligent specification. The concern driving this spec is that should a glider's wing drop to the ground before reaching flying speed, the resulting ground loop will be very ugly and quite possibly fatal for the glider pilot. These concerns and the desire to get the highest launch possible, has driven winch horsepower higher and higher in recent years. Shortening the accelerate to Vr distance has a powerful effect on the launch height achievable. Many powerful winches have shortened this to less than 20 meters. IF we were launching twin Astirs, or K21s or other heavy two seater I would concur that you would want more power. But bear in mind that the Blue weak link is easily overcome by a 200-250Hp winch. If that is the heaviest weak link specified you are wasting your time on more power. Again I agree that more initial acceleration is desirable - I HATE slow acceleration launches in my Cirrus because the chance of a wing drop is higher. TO overcome this we use gearing on the winch that increases the effective torque available. To summarize, I am advocating generous power reserves to permit the winch driver to maintain control of the launch and to insure the glider reaches flying speed before a wing can drop. Bill Daniels Generous power reserves are desirable. I am just not convinced that the use of very powerful winches imnproves safety. My experience is that an adequately powerful winch that is tractable and predictable is safe, even if there are compromises on height and initial acceleration. In our mixed vintage and glass setting it would be challenging to have a super powerful winch. My conclusion is that it is desirable to have generous power reserves and good torque for fast acceleration of the heaviest aircraft on the fleet. It is also imperative that the control be adequately calibrated so that power output can be modulated easily for all of the gliders the winch could be expected to launch. Bruce |
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