http://www.hanggliding.org/viewtopic.php?t=31738
Calculating weak link strength
Dave Gills - 2014/08/21 18:04:31 UTC
Grove City, Pennsylvania
Hook in weight + Weight of glider x 1.4 = weak link breaking strength.
For me...
175 + 50 x 1.4 = 315 lbs
If I use a weak link on the top (keel) when using a bridal then it is shared tension and divide by 2....Right?
Where does the 1.4 come from?
Does it vary depending on the skill of the pilot or the type of towing you are doing? (scooter, air or payout winch)
Sorry...2 questions in 1 day.
And I did try to search this topic.
- Well before you go about "calculating weak link strength" you need to know what the PURPOSE of the weak link is.
Tost Flugzeuggerätebau
Weak links protect your aircraft against overloading.
Looking at your questions it's obvious that you have no fuckin' clue. Once you understand what the purpose of the weak link is the logic for determining strength falls into place pretty easily.
- Did you check your owner's manual? Should be in there - just like for sailplanes. If it's not then write your manufacturer, ask him what the fuck it should be and why the fuck it's not in the fuckin' manual. And post all the correspondence on The Jack Show.
- The thread that was hanging out immediately below yours from the time you started until Davis bumped it with his ten miles south of useless crap at 2014/08/21 20:30:31 UTC it is called:
http://www.hanggliding.org/viewtopic.php?t=31717
Weak link?
Wouldn't that maybe be a good place to ask around? You can find:
- some sensible and nonsensible statements on the purpose of the weak link
- what:
-- Davis and many of us are currently happy with
-- Michael Farren is using to make sure his glider doesn't get ripped apart
- a reference to how badly you can get fucked up by using a super safe weak link
- some:
-- blatherings by smartass twats who've never had anything of substance to say on anything
-- commentary on the Dark Lord of Trolls and His Minions
Don't we have enough bases covered for you there?
- How 'bout The Davis Show? Jim Keen-Intellect Rooney hasn't been banned from there quite yet, he has an extremely keen intellect, and he'll be more than happy to spend twenty pages telling you he just might know what he's talking about and regaling you with descriptions of track record lengths.
- Go to Quest's website. They've been perfecting aerotowing for twenty years and they certainly have the information you want posted. If not just contact Russell Brown, the Tjaden twins, or Bobby Bailey - who's a fucking genius when it comes to this shit.
- Anything wrong with the excellent book, Towing Aloft, by Dennis Pagen and Bill Bryden?
- What, the fourteen page Higher Education article by Dr. Trisa Tilletti on how to tie a loop of 130 pound Greenspot to put whatever your flying dead center on USHGA's recommendations wasn't enough for you?
- C'mon Davis. You've been dictating weak link strengths since the beginning of time for tens of thousands of flights. Help this guy out. Tell him what you're currently happy with.
- Hey Peter... You're registered on The Jack Show, right?
Hook in weight + Weight of glider...
Weak links have NOTHING to do with flying weights. If you're giving hook-in and glider weight you're thinking about trying to use your weak link as a pitch and lockout protector and emergency release. That kind of "thinking" has gotten a lot of people mangled and killed.
...x 1.4 = weak link breaking strength.
- No. The towline tension that translates to target weak link breaking strength.
- Dark Lord of Trolls here...
http://ozreport.com/forum/viewtopic.php?t=24846
Is this a joke ?
Flyhg - 2011/08/28 12:26:18 UTC
I believe that the 1.5 G thing is something Tad made up.
Everybody thinks mid range weak link strength is something Tad made up. So why don't you ask him?
175 + 50 x 1.4 = 315 lbs
I need to know your glider's maximum capacity - just like it says in the FAA regulations covering hang glider (and sailplane) aerotowing.
If I use a weak link on the top (keel) when using a bridal...
Do me a big favor and use a bridLE.
...then it is shared tension...
- Pressure.
- Yes. If it isn't shared - just like it is on the Dragonfly to put the thrust line where it should be - you're seriously decertifying your glider and setting yourself up with a good option for getting killed.
...and divide by 2....Right?
Wrong. You've got about a sixty degree bridle apex angle and thus a fifteen percent amplification of the split tension. 200 pound towline tension the weak link's feeling 115.
Where does the 1.4 come from?
- Where'd you get it from?
- It's the middle of the FAA legal range. I was its first pusher but that was back in the days before I realized that the FAA guys were also useless lying twats and that the bottom of their legal range was insanely dangerous. So now I bump it up to between 1.5 and 2.0 - depending upon what your glider capacity is and the release capacity.
Does it vary depending on the skill of the pilot...
Of course. If you're really good...
http://farm4.staticflickr.com/3746/13864051003_a820bcf2b8_o.png
http://farm4.staticflickr.com/3713/9655904048_89cce6423a_o.png
37-23223
...you can use a much heavier weak link which will allow you to get into a much steeper climb than the safe stuff that Bill Cummings uses. Then when it breaks you'll be able to respond optimally to keep things safely together.
http://4.bp.blogspot.com/-bRrpHNa68iY/UQ6Pv9gRZyI/AAAAAAAAjTg/Hc22bx5122Q/s2048/20943781_BG1.jpg
Or maybe it works the other way around. Really crappy pilots on the heavy stuff and the ones with the best training on the light ones. I can never remember. Talk to Jim Keen-Intellect Rooney.
...or the type of towing you are doing? (scooter, air or payout winch)
No, the function of the weak link is ONLY to protect the glider from being overloaded and it has shit to do with pilot skill, flavor of towing, or the comfort level of the fuckin' idiot douchebag on the Dragonfly.
Sorry...2 questions in 1 day.
And I did try to search this topic.
Try these locked topics on The Davis Show:
http://ozreport.com/forum/viewtopic.php?t=30971
Zach Marzec
http://ozreport.com/forum/viewtopic.php?t=31052
Poll on weaklinks
Lemme tell ya sumpin', Dave...
Hang gliding's a bit into its fourth decade of practical aerotowing. And the fact that you can't go to scores of sources for an answer to something like this and get the same, consistent, logical answer - just like you've been able to do in sailplaning since the beginning of time - should scare you shitless about getting involved in towing.