Towline Strength

Be kind to our tug pilots, we cant do without them.
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Trevor
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Towline Strength

Post by Trevor » 16 Sep 2018, 22:04

I’ve been doing a bit of towing with an electric Riot XL and a towline, both of which were given to me. I’ve been asked by the owner of a Bolus Baby Albatross, which weighs about 6lb, what breaking strain would be appropriate for a weak link to be incorporated in his release fitting line.

Is there a rule of thumb for weak link strength vs. glider weight?

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Barry_Cole
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Re: Towline Strength

Post by Barry_Cole » 16 Sep 2018, 23:38

Weak links are a waste of time. Don't bother.......

BC

Tom Pack
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Re: Towline Strength

Post by Tom Pack » 17 Sep 2018, 02:03

275 Paracord for the tow line 100-120’.......braided winch line for the loops at the sailplane end of the line with a heavy duty snap swivel.

john greenfield
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Re: Towline Strength

Post by john greenfield » 17 Sep 2018, 11:59

Buy a 30m length of orange builders line from B&Q or your local hardware shop and tie a loop in one end to go on the tug release and a heavy duty fishing swivel with a snap link on the other. Glider pilots provide whatever they need to go between the swivel and their own release in the nose of the glider.
Do NOT use a weak link....it will only end in tears !!!

AEB
AEB = Aeronautical Energiser Bunny (with thanks to CW)

John Vella
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Re: Towline Strength

Post by John Vella » 17 Sep 2018, 17:17

Trevor, in the 80s when we were aerotowing at Romanway with relatively low powered tugs and sailplanes of all sizes we never saw the need for the full size practice of weak links. We did however have 100% reliable releases.
Regards John.

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Trevor
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Re: Towline Strength

Post by Trevor » 17 Sep 2018, 17:25

Thanks guys. The line I was given seems to work well, so if a glider pilot wants a weak link, it’s up to him to provide it in their release adapter connection. I will though pass on your advice not to bother!

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Ray Watts
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Re: Towline Strength

Post by Ray Watts » 17 Sep 2018, 22:12

Never mind a weak link, just make sure you use the most powerful servo on the release that you can afford, whether it is the tug or the glider and not a retract servo. One day you will have a hang up on tow and you will need it to work immediately without stalling in order to save both models at the same time. A standard servo like a 3001 or a JR 507 won't cut it, they will just stall and make you crash. I would say at least a 10kg pull if not a lot more. My tugs have 20 to 25 kg servo's as I don't want to get sucked into a caught wingtip induced crash.

Ray
It's always calmer indoors :D

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Ray Watts
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Re: Towline Strength

Post by Ray Watts » 17 Sep 2018, 22:25

Like I say, one day you'll need it and no, this isn't photoshoppped, it was my first ever towing sortie about 12 years or more ago
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It's always calmer indoors :D

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Trevor
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Re: Towline Strength

Post by Trevor » 18 Sep 2018, 08:56

Ouch! Point taken Ray. However, I'm not sure I'd react fast enough to save the tug in that situation! As I said, the tug is a battered Riot XL which spent most of its previous life stuck up in the top of a pine tree before it was donated to me for use as a club tug. I'm very impressed with how well it copes. I usually put a 5s LiPo in it instead of the normal 4s when towing and it pulled the 6lb Albatross up without problems. Given it's history, we do tend to worry more about the safety of the gliders than the tug.

On the second tow with the Albatross, there was a violent line snatch a second or so after the glider pilot pulled the release. Post flight inspection revealed that the tow release fitment at the end of the line was missing, as was the brass undercarriage skid, suggesting that somehow the line had snagged on the skid after release. This is what has triggered the glider pilot's interest in a weak link!

SP250
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Re: Towline Strength

Post by SP250 » 18 Sep 2018, 09:22

Ray

That looks just like the attitude my DG600 got into last year, before the retract servo (travelling slowly) released the line.
Nearly finished the repairs now (cosmetics still to do) and did re-maiden it at the Long mynd a couple of weeks ago.
So yes, best advice is strongest/fastest servo in the model on the tow release.

John M

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