It was a super tow to cloud base ~2500'.
With a good winch we might get 1000' max.
1. So either that was a super tow not at your local airfield or a super tow to over a fifteen hundred feet shy of cloudbase followed by a climb to cloudbase.
2. I know that aerotowing is expensive and a royal pain with all the tug driver regulations nowadays but it sure is nice being able to go as high as and wherever you want (and not having to deal with all the rewind issues).
3. Stu Caruk (
http://www.towmeup.com) is probably a real good place to start for a winch. Ain't cheap but my guess is that the more you pay at the beginning the less you're gonna pay down a rather short road.
4. And there's no doubt whatsoever that people have died 'cause people were towing static instead of using a payout winch.
There's some about tow forces I do not understand, at least unable to discuss in correct terminology.
That's key. I overshot a field on my third mountain flight 'cause my idiot "instructor" didn't know the meaning of the word "turnpoint".
The force that took my release did not feel excessive. It did not even feel unsafe.
A weak link blow is SUPPOSED TO BE like a parachute deployment.
1. It should never happen in the course of an average pilot's flying career.
2. With rare exceptions, it should only happen after a pilot has screwed a couple of pooches bigtime.
3. The pilot should be scared shitless just before it happens.
4. The pilot should not expect to live if it happens down low.
Need a number. From your photos my best guess is that the weak link is 5/64 inch / 205 pound Dacron leechline. That's gonna blow at about two hundred pounds - which would be pathetic - and does seem consistent with what you reported feeling.
Zack's crowd is using a loop of 205 Lark's Headed onto the tow ring loop of a three string release. It thus becomes an extension of the tow ring loop so you just ignore it and connect your three string normally. I'll attach his photo.
Zack claims it blows around six hundred pounds and - although I haven't tested it myself - that sounds about right. And that's a pretty good one-size-fits-all number.
I would advise that you connect your remaining release directly to the bridle and duplicate Zack's configuration.
And if you have other ideas for weak links I'll be more than happy to load test them for you if you don't have a test rig.
Something I'd like to know more about as a PL pilot.
Platform, reel-in, foot, static, aero... The weak link has only one function and it only cares about the strength of the glider, not the flavor of the tow. And thus you use the same weak link for your glider, regardless of the flavor of the tow (despite as the crap you/we've been fed).
It might be a safety issue without a weak link.
1. Nobody with half a brain or better advises towing ANYTHING without a weak link. But there's a tradition in hang and para gliding that Donnell seems to have founded that you either use a weak link of one G or less - preferably WAY less - or nothing at all. Nobody ever died from using a two G weak link and a two G weak link is never gonna blow in the real world.
2. I don't really like to see "safety" used in the same sentence with "weak link".
Steve Kroop - 2005/02/09
A weak link is there to protect the equipment - not the pilot. Anyone who believes otherwise is setting himself up for disaster.
Steve's actually pretty clueless on weak links - he's a 130 pound Greenspot clone - and I had to patch up his grammar for that quote - but that does express the issue REALLY WELL. All the weak link can and will do is limit the stress on the glider in the air under positive loading - and it doesn't give a rat's a** what happens to you - or the glider - before or after that predetermined stress limit is reached.
3. Statistically you're never gonna be in a situation in which a weak link of any rating is gonna do you any good. Got a choice between losing the weak link and losing the wheels... Lose the weak link. No brainer.
4. Choice between a weak link of one G or less or no weak link... Again, lose the weak link. No brainer.
But, it's called "topping off the tow", for a reason.
Absolutely no reason to have (or excuse for using) a weak link which will blow while anyone's topping out a tow.
I thought sure the loop of smallest diameter line would have been the "weak link".
Of course you're stepping down the tension with each loop so - not unless it's deliberately designed that way which, in my opinion, would be an idea second in crappiness only to your current configuration.
Start off with 400 pounds towline tension, the tow ring loop transmits 200 to the middle loop which transmits 100 to the trigger loop which transmits 50 of side loading to the pin. In the real world however - due to the stiffness of the material and friction - the numbers drop A LOT FASTER than that and make the release dysfunctional at low tensions. That's usually no BFD but since a barrel release has excellent performance over a huge range - when it's on the end of a bridle, from under four pounds to over seven hundred of towline tension no sweat - I don't see any point to using three-strings. (Plus there's no significant abrasion/wear involved in barrel release actuation.)
...the only one that protected me with a weak link break.
It didn't protect YOU - see above. And if it left you with the impression that it did, it actually accomplished the precise opposite.
I'm thinking the force comes from somewhere and not really line weight or line drag.
Mostly the truck.
I was climbing. No vario, but still climbing good. The tension never dropped.
Then why would you be attempting to release?
It felt like it accelerated to weak link failure.
That WOULD explain the weak link failure.
It was real breezy that day. That might be a factor?
Assuming you're heading into the wind and the driver leaves the hydraulic pressure alone...
1. The tension your glider - and the truck - will be feeling will be constantly increasing as the line feeds off the reel and decreases its effective diameter.
2. You'll start climbing off the platform at about a 70 degree angle. Higher performance (L/D) gliders will climb at higher angles, lower at lower.
3. The tension you'll be feeling will also be constantly increasing as a consequence of line weight - which will work totally against you. It will be as if you're constantly taking on ballast, cause the line to pull off the winch faster and sag down, and pull less forward and more down - thus causing the glider to trim at a lower pitch attitude. The heavier the line the more the sag and the more gas the truck's gonna hafta burn to keep you climbing.
4. The drag of the line - which increases as a consequence of its diameter - will cause the line to bow back and pull off the winch faster and, as is the case with the weight and sag, also pull less forward and more down and also cause the glider to trim more nose down.
5. These two factors - weight and drag - will put you at a lower angle (farther) behind the truck and climbing less efficiently. At some point, even with unlimited runway and line, you're gonna be unable to climb any more.
6. With a headwind - call it 15 mph - your driver's gonna have his airspeed indicator reading exactly the same for launch and climb but his speedometer (groundspeed indicator) is always gonna be reading 15 mph slower.
7. Neither the winch, your glider, nor your weak link are gonna know the difference between no wind and fifteen before you get to the altitude you could on that runway in no wind.
8. But... With the headwind you will be using the runway more efficiently / effectively and reach your no wind max altitude with - let's call it - a third of the runway left over.
9. From that point on, because of ever decreasing reel diameter and ever increasing line length, weight, and drag, your glider and weak link are gonna be feeling ever increasing tension beyond "normal".
Not sure of their top-off procedures but Zack will probably say the pressure is increased at the end of the tow.
Let's not use the terms "pressure" and "tension" interchangeably. Drives me nuts.
TENSION is what the towline is transmitting and the glider is feeling and is expressed in POUNDS.
PRESSURE is what the hydraulic fluid is under, is read off the gauge as POUNDS PER SQUARE INCH, and - as long as the drum is turning - is directly proportional to tension. But there are a lot of variables you gotta plug into the equation to get a rough idea how that translates to tension.
Vehicle slows.
As long as the drum is turning the tension isn't gonna be changing appreciably in the short run (insignificant decrease in reel diameter and increase in line out). If the drum stops turning the tension is gonna drop as the vehicle slows.
I'm not sure if it is possible to over fly the tow vehicle while still climbing with tight line. That kinda sounds like perpetual motion.
1. Throw a thermal, dust devil, or strong gradient into the equation... Yes - You CAN achieve perpetual motion (for long enough anyway).
2. If you start out with enough airspeed you can also continue to climb with a tight line straight over the vehicle - but that's not gonna happen with much line out.
3. And of course you don't wanna fly very far in front of the vehicle with a tight line - climbing or not - 'cause you won't live very long if you do.
Where's Zack?
Haven't heard from him in a bit. That usually means he's on a loaded schedule.
The more experienced PL pros are probably laughing at my ignorance. When I become a pro...
I don't give a rat's a** about how EXPERIENCED any of the PROS - or any other folk - are. In hang gliding pros and experienced people are usually just really really good at doing things really really wrong - and are often just as ignorant and always at least as stupid as they were at the end of Day One. What impresses me is someone who understands the relevant principles. What satisfies me is someone who at least conducts operations consistent with the principles - even if he doesn't really understand them.
There isn't a whole lot in the fundamentals of hang gliding - launching, landing, towing - that benefits much from experience once a little muscle memory skill is developed. Spark just proved that bigtime in the Golden, Colorado LZ a couple of weekends ago.
...I hope I never get too important to talk to students with questions.
Or to assume that you can't learn something extremely valuable about some aspect of aviation from someone who's never been around it before and may have little to no aptitude for it.
And, by the same token, one thing you can rely on like death and taxes... If you're ever in a debate with someone who asks about your experience and/or skill level and/or brings up his - you KNOW you're talking to a total idiot who isn't worth the time of day. NEVER fails.
P.S. I'm not seeing a way to get the photo up - may be a problem with my antique browser. But Bob can probably stick it in later if I send it to him. And anyway, the topic IS "missing release".
Admin Note: Here's the "missing release" that Tad sent to me by email:
- three_string_weak_link.JPG (70.44 KiB) Viewed 7567 times
