Winching - Reverse Auto Tow

Can anyone direct me to Clubs / Web sites using this method of launching - Interested in finding out more about this method, particularly from clubs that operate from gravel/dirt strips

Thank you

John Spargo

We used Mity or Tost weak links at each end of the cable, on quick-release links, and changed them to suit whichever glider was next to be launched. On high throughput evenings, when we had two K13's doing perhaps 30 air experience flights, there was no need to change them of course. For the tow, the truck had the main cable hooked on by a separate towing link, to avoid the stress going through the weak link, drogue, etc. at the truck end of the cable, so only the glider end weak link was operative. The drogue etc. at the truck end were all left connected, and loaded into the back of the tow truck to deliver them back to the launch point..

Chris N.

Heh. I noticed this truck hidden behind the Butts on Saturday, rusting away quietly with brambles growing over it. Realised it was a now disused winch system. Didn't realise it was the one they used to use for auto-tows, though in hind sight should've guessed. Having said that, I hadn't realised the club discontinued auto-tows as recently as the turn of the millennium (I only joined at the beginning of last month).

Nice to see pictures of the thing in all its old glory. Thank-you.

There is a limitation in the initial acceleration that is intrinsic to this launch method, due to the limitation of tyre grip. As solid friction coefficient (i.e. ratio of tangential to normal force) barely exceeds 1, the tow vehicle can't deliver much more force than its own weight. This would result in 1g for the tow vehicle alone, with a glider with a weight about 1/2 the weight of the the tow vehicle you get .66g. If R is the ratio of glider weight to tow vehicle weight. you are limited to 1/(1+R) g. You can get as close to 1g as you want by increasing the weight and power of the tow vehicle, but efficiency would be bad, since most of the power would be used to accelerate the tow vehicle rather than the glider.

One may argue that the initial acceleration is not the most important thing, but I think it is an element of security that it is sufficently quick that the glider has no time for dropping a wing before being airborne.

Maybe this is the reason why Costwold preferred a winch.

Ridgewell, that's the place old Fred had the steam winch. Of course, he was shunned by most BGA types.

There's still a story out there somewhere. Maybe someone will ask around this winter.

Frank Whiteley

'Chris Nicholas'

|Hi Chris,

Remember me? I was an instructor at North Weald from 1972 till 1978 when I went to the LGC (a bad move) and gave up gliding when they refused to ratify my instructor's ticket (I only had 1000 launches instructing and about 20 solo pilots to my credit).

However the winch story is interesting. When I was at the Staffordshire Club in the late 60s I designed(!!) and built a diesel winch which consisted of two old artic tractors , one mounted on the top of the other (looked like a particularly nasty copulation). The lower lorry was for transport and the upper had its wheels replaced by large drums with brakes. You braked one drum and the other ran at twice prop shaft speed using the diff as a gear (didn't half heat up the oil). Worked a treat and was very economical. I never saw anyone else try this method. The SGC called it the 'Winchosaurus' as it certainly looked primeval!

Alistair Wright long retired glider pilot

Frank Whiteley wrote [snip] ' we pulled all of the wire from the drum and found it to be collapsing inward under the strain of launching the Twin Astir and L-13 under more power than the winch had been designed for.'

This happened to another club, and I am concerned it might to us too. What did you do do to fix it - could the ATC-type drum be suitably reinforced to prevent it, or did it need a new drum which would no doubt be of heavier material or with added stiffeners inside?

Chris N.

It was repaired with steel pipe of a suitable diameter and thickness by the late Robyn Pierce-Boby and Larry Green(e?). Since Enstone GC is defunct, I have no idea how to contact Larry. Someone like Ken Sparkes may be able to help with contacting Larry. I don't have the specific details, but the pipe was cut to a suitable length and split into two halves and clamshelled around the existing drums. Once welded into place, it was turned true and balanced. Seemed to do the trick though I originally thought it inelegant and perhaps trickier than just making new drums.

Frank Whiteley