http://www.youtube.com/watch?v=fx_H22XHa1M
How To: Hang Gliding Aerotow Weak Links
The material you're using is obviously 130 pound Magibraid (IGFA, performs the same as Greenspot) which suggests you're flying at Wallaby.
I put this together quickly for a friend just using my iPhone camera and it is based upon what I have learned from other pilots, books, and my own experience...
- What have you learned from other pilots, books, and your own experience about the purpose of a weak link? (Fifteen hundred words or less.)
- What books? Just kidding.
...but I would welcome any comments, corrections, or suggestions.
Do you need to waste all that material at the ends? These things are REAL easy to tie from a predetermined length such that there's virtually zero protrusion and waste of material.
Note: This knot can be replaced with the larger grapevine bend (double fisherman's knot) which would probably make it stronger...
- Probably? Based on what?
- Wouldn't making it stronger just make it more dangerous? Donnell Hewett established about 32 years ago that the lighter the weak link the safer it is - and there's been very little disagreement tolerated ever since.
...but I have been using the knot shown in the video for a while and I have never seen the tag end of the lines slip at all.
- Strength and slippage are entirely separate issues. If a knot slips its strength is pretty much irrelevant.
- The Fisherman's Knot doesn't slip in braided (or twisted) line. It jams to the point that it's almost impossible to untie after it's been loaded under tow. So we don't need to be discussing that issue.
- The Grapevine Knot is required for nylon monofilament - which slips like an eel. For pretty much anything else it's a waste of time and material.
- Loop weak links don't fail at the knot which forms them. They fail at one of the two strands at the point at which it exits the bridle. So we really don't need to be talking about the strength of the knot which forms the loop.
My conclusion is that there are no advantages to the bigger knot...
Correct. And a bulkier knot doesn't do anything to help the bridle end clear the tow ring - especially when you're using a weak link three times longer than it should be.
...especially on a rig that is going to be replaced after a few uses anyhow due to wear at the tow ring.
- Is that where it's getting worn? Couldn't have anything to do with...
http://www.flickr.com/photos/aerotowrelease/8305428629/
...it clearing the notch at the end of the spinnaker shackle gate?
- How much does it need to get worn before it's no longer safe to assume that it no longer meets your expectation that it break as early as possible in lockout situations, but be strong and reliable enough to avoid frequent breaks from turbulence?
- After they're worn a bit wouldn't it be a good idea to give them to someone who flies fifty or a hundred pounds lighter than you so that he or she would have similar advantages and expectations?
I make my weak links by starting with a 9 inch length of line.
And you finish with something that's stupidly, wastefully, and dangerously overlength.
Now we just pull it a little tighter...
Why don't you feed the ends in as you're pulling it a little tighter so you can use less material and don't end up with something that looks like crap?
Now we need to attach it to the bridle.
At least you spelled it right.
So, with the knot centered, pass the loop through the bridle three times, keeping the knot centered as shown here.
Yeah, three times dude. You really wanna hide that knot from the main tension in the link and exclude it altogether from the equation.
As every fisherman knows, the knot is the most likely breaking point...
As anyone with any common sense knows, a knot WILL BE the breaking point. And you've got TWO knots in this configuration - the Fisherman's Knot to form the loop and the Triple Lark's Head to install it. So don't go too nuts with wraps pretending to isolate the Fisherman's Knot 'cause the Lark's Head is always gonna be wide open.
...so this rig significantly reduces the pull on the knot.
Does it? What data do you have to support that statement?
I got news for ya...
- If you install the loop using a Single Lark's Head it'll fail at one of the strands at the exit point from the bridle.
- A Double Lark's Head stabilizes the loop on the bridle after it's been loaded.
- A Triple is a waste of time and material.
I haven't broken a link in this configuration, but I'm guessing that if I do, it will be at the end where it connects to the metal tow ring, but not at the knot.
- You're installing this weak link on a BRIDLE end - so it's not connecting to a tow ring. It's connecting to a RELEASE.
- Why don't you break the goddam thing in that configuration - either on the ground or at release altitude in a deliberate lockout? That way you wouldn't have to be guessing about anything.
Fly Safe!
How 'bout YOU fly safe?
- You're almost certainly flying at Wallaby and those assholes don't have a clue what they're doing or talking about. Both their crap equipment and the crap information they put out have gotten lotsa people killed.
- An appropriate hang gliding weak link limits the tow tension to about one and a half time the glider's maximum certified operating weight and that fishing line you're using does that for NO glider - one point or two.
- You haven't done any testing because if you had you'd have found that it doesn't matter much where the Fisherman's Knot is positioned.
- It's a virtual no brainer that you don't have a clue as to what towline tension your precision weak link is limiting you to.
We've got zillions of assholes who can show us clever ways to increase the breaking strength of 130 to 260 - double the ACTUAL figure, but you can count the number of people in this idiot sport who understand the function of a weak link and know how to configure for an appropriate value without getting into double digits.
P.S. Isn't it interesting how, in the entire lunatic history of hang gliding and the standard aerotow weak link there's NEVER ONCE been an idea expressed in any instructions, discussion, video on how to configure a loop of 130 pound IGFA fishing line to break at a LOWER value.
- Isolate the Fisherman's Knot in a:
Double Lark's Head to hide it from the tension.
- Isolate the Fisherman's Knot in a Triple Lark's Head to hide it from the tension even better.
- Read my fourteen page magazine article on how to install a weak link using Wrap and Tie which kicks the Double Lark's Head's ass.
- Use a polypro bridle because, without shock absorption, a Spectra bridle acts somewhat like an impact wrench on the weak link.
- Replace the weak link after:
-- ten tows
-- five tows
-- two tows
- Use a fresh weak link every tow.
Interesting that there's not ONE SINGLE comment or query on how to make one lighter.
- I'm a little girl on the light end of a Falcon 3 145 and it really scares me to be flying the same weak link as that 360 pound T2 over there.
- This my first solo and I don't think it's a good idea for me to be using as heavy a weak link as Davis, Jonny Durand, and Dustin Martin are using. Better start out with something that blows at a quarter of theirs and work my way up as I gain experience.
- I couldn't pry my Bailey open at the pressure the standard aerotow weak link was transmitting. I think I'll position the knot so that it's not hidden from the main tension in the link and excluded altogether from the equation.
- We are confident that with an ultimate load of 130 pounds at the release point, the new GT aerotow release works better than all cable releases that we have experience with. And with an ultimate load of 90 pounds at the release point, we are confident that the new GT aerotow release works better than all cable releases that we don't have experience with.
The new GT aerotow release is designed to be used with a V bridle and a 130-pound green stripe Dacron tournament fishing line weak link. At this time it is not recommended to use this release with a higher value weak link.
- Booming day. Pretty good potential for lockouts. Things could get ugly fast. Better get a spool of eighty pound out on the flight line.
- I locked out and the weak link blew as I was reaching for my release. Needed every bit of the 250 feet I had to recover from the stall. Can somebody tell me a good way to cut the strength in half so I can survive a lockout at 125?
P.P.S. Could be a lot of fun using some of these to fuck with assholes like Davis, Rooney, Kinsley Sykes, Craig Hassan, Paul Hurless - if anybody starts getting bored.
