Gliding; a much better approach.

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autoreply

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Winch launching isn't that common in the US (gliding is neither), so most planes are towed by aircraft. In Europe winch launching is more common, but still is usually limited to 1500' AGL or so, even along the military airbases we use for winching. That might not be enough and for teaching students it's way too short, only a couple of minutes of "free flight".

These guys are changing that:
http://www.youtube.com/v/-Dw6r_1r91M&hl=en_US&fs=1&

A good 9000' of cable, altitude record 5700' (for the time being) and it might very well be realistic to winch up to 10,000' AGL.

The cables are very light plastic since an appropriate steel cable weighs around 1000 lbs at these lengths, dyneema and such are maybe 1/10th of that.

Total operational cost of this system is around 7 euro's a launch (10US$)
 
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bmcj

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Attempting to embed the video (hope it's the right one :gig:):

[video=youtube;dhmXpZUkAAA]http://www.youtube.com/watch?v=dhmXpZUkAAA"]www.youtube.com/watch?v=dhmXpZUkAAA[/video]
 

mz-

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Seems the winch accelerates quickly when the line is released.
 
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kent Ashton

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How is 5000ft of line retrieved without it being everywhere?

Maybe autoreply will provide better info but in my experience, most of the cable is reeled in by the time the glider has climbed up and over the winch at pattern altitude, where the cable automatically releases. The cable has a little parachute on it and the rest of the cable is reeled in as it floats to the ground. In Germany, they used an old VW beetle to haul the cable end back to the launching area.

It is quite a thrill. Sort of like launching off a carrier.
 

autoreply

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I was referring to this vid:
[video=youtube;-Dw6r_1r91M]http://www.youtube.com/watch?v=-Dw6r_1r91M&feature=player_embedded[/video]


Maybe autoreply will provide better info but in my experience, most of the cable is reeled in by the time the glider has climbed up and over the winch at pattern altitude, where the cable automatically releases. The cable has a little parachute on it and the rest of the cable is reeled in as it floats to the ground. In Germany, they used an old VW beetle to haul the cable end back to the launching area.

It is quite a thrill. Sort of like launching off a carrier.
Indeed, especially if the winchdriver is experienced. 400 hp on a 350 kg glider makes for an interesting acceleration, airborne in 20'-30'...


Usually you "use" about half of the length to get the glider up and winch in the rest when the gliders disconnects, indeed, with a parachute to brake a bit. Especially steel cable isn't that cool, 200 lbs of steel falling at a good 80 mph gives quite a mess if you don't pay really good attention to controlling your winchline speed and decelerating before that chute hits the winch. I tried that once and it's like running the 10 tonne winch in a brick wall with 20 mph...

Plastic is much better for that, especially if you go longer.

The main spectacular thing of this is the altitude. Winching altitude on normal airfields is limited to anything between 1000 and 2000'. This method can make teaching pilots way cheaper and be a revolution in teaching students. Don't forget than in most trainers, 5000' amounts to almost half an hour of "free teaching time".

Half an hour for 10 US$ plus the yearly (fixed) expenses of the club (400-800US$ a member) isn't that expensive.
 
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vortilon

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I bet some of that technology is borrowed from the long line fishing industry as well as the monofiliment line. My father designed built and sold high start retrievers for the RC model glider people.
 

autoreply

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@ BCMJ,

Well, not sure whether mine is better, but I though it'd be nice to put a vid of such an extreme flight in. Ofcourse I could have inserted it working the first time I posted in this topic.. ;)


In fact it came from an employee of DSM which is a Dutch chemical factory. When better coatings (it's very UV-sensitive) became available Dyneema was finally deemed practical for winching purposes, while before the pulley wear/UV degradation would have made it too costly since those cables run for about 0.75 US$ per feet...

After a lot of problems (without teflon coatings on anything near the cable inside the winch the cable is gone in 50 launches) they started using it on a bigger scale, only to realise later than you aren't limited to 4000' of cable length anymore. Many of our gliding fields are on military airbases with 10000' or more of runway, while abroad that's very seldom.

I presume those problems aren't typical of RC-gliders because they can handle much bigger loads and their cable lengths are a couple factors lower.

In the future this might have a considerable effect on gliding and especially on teaching students. With typical launch costs this flights are a couple of factors cheaper than even an LSA or microlight per minute while nowadays they're still comparable per unit time.

Another interesting innovation is the hydraulic winch. An engine drives a hydraulic generator so torque and drum speed are completely variable.

Some more info
 

Davefl42

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How about an electric computer controlled winch? could that work better?

Dave
 

bmcj

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How about an electric computer controlled winch? could that work better?

Only a guess here, but I suspect that maintaining a constant pressure, you can maintain a consistant pull force that automatically compensates for anything the glider pilot does. I'm not sure if you could do that easily with electric.
 

autoreply

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Only a guess here, but I suspect that maintaining a constant pressure, you can maintain a consistant pull force that automatically compensates for anything the glider pilot does. I'm not sure if you could do that easily with electric.
It's cable pull indeed that defines the kind of start. The amount of pull however varies during the start (acceleration, rotation and then less and less pull while the glider gets higher) and also varies per type of glider. A 800 lbs ASK-13 (wood) glider for example needs less than half the pull of a ballasted, flapped single seat gliders, while it's as heavy as that ASK-13 and flies around the same speeds during winching.
Mainly because of that automation doesn't work that well, especially because wind and such can't be fully corrected, when you're only measuring cable pull.
 
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