Towline Strength

Be kind to our tug pilots, we cant do without them.
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Biggles
Posts: 16
Joined: 19 Mar 2015, 17:18
Location: Derbyshire

Re: Towline Strength

Post by Biggles » 20 Sep 2018, 15:51

Fellow Tuggers,
To be contrary: I have used a weak link on my tow line for a number years now. I use 60lb mono filament fishing line which stretches under load but snaps if snagged. It is at the "tug" end of the line and is designed to save my tug, particularly on landing if you come in over a hedge or fence etc. where the trailing line can easily snag. Mine did once and the weak link snapped saving my tug. I tow 6 metre scale gliders with out any problems with this set up although it is essential to take up tow line slack before going "All Out" (which we all do anyway)

I bought a full reel of 50lb line and if anybody wants a metre or two just ask.

The weak link should not be relied upon to save the tug and glider in the situation depicted in the preveous photo. I strongly recommend both tug and glider pilot have their finger's on their release buttons before setting off. I am amazed at the number of glider pilots, some with lovely models, who cannot release quickly in times of stress. If you have to think about where the release switch is, it is allready too late. Anyone hitched up behind my Wilga will hear me shout "finger on button..." before every tow.


Cheers,

John
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Glider Tow tug end.JPG

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Ray Watts
Posts: 176
Joined: 18 Mar 2015, 06:31
Location: Basingstoke

Re: Towline Strength

Post by Ray Watts » 20 Sep 2018, 20:20

Hi John

This isn't personal, just my thoughts.

In the full size world, I believe it is the glider that has the weak link and this is calculated to go with that particular glider.

I see your point about saving the tug if the line snags a fence or anything and I have snagged fences at least 3 or 4 times and been lucky so far. I have the ripped windsocks from the end of the line to prove it. However the problem is when you go to an aerotow event and put yourself forward to tow whatever comes along in the queue, and this can be a 3 and a half kilo woodie like the seagull K8's or a 38 to 40 kilo half scale glider which are becoming increasingly common. In that case your weak link would snap before the glider had even started rolling. Conversely if the weak link was strong enough to withstand the necessary drag of the heavy glider, then it wouldn't snap with a fence snag, so it is a tough call.

Last year at Shrivenham, we tried towing John's Vienna with my Decathlon, but without the take off dolly for the Vienna. I went to full throttle and the Decathlon got airbourne with zero movement from the glider. 3 people pushed the Vienna to start it rolling and we got going. I dread to think what the strain was on the line that day, and if the line had broken, the sudden release of energy on the tug probably wouldn't have done it any good either.

It is all these variables that make towing such a fascination for me and make me want to do it over and over again. You never know what you are going to get next.

Ray
It's always calmer indoors :D

John Vella
Posts: 145
Joined: 20 Mar 2017, 22:09
Location: UK

Re: Towline Strength

Post by John Vella » 21 Sep 2018, 09:03

Ray, just to,clear up a point on full size weak links. You are right that every glider has a colour coded different weak link on winch launch. On Aerotow there is a one strength fits all at the tug end to save the tug . This can break with a snatch in severe turbulence or out of position situations. However in mountain flying in the Pyrenees we did not use weak links. May I suggest in obstacle critical approaches we have dropped the line and done a short circuit with the tug.
Regards John.

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