http://www.hanggliding.org/viewtopic.php?t=27684
glider mods sidewire material
Steve Baran - 2012/12/03 23:32:42 UTC
No, don't even really know much about the stuff. But, I do know that steel has decent chemical resistance along with being able to handle a wide temperature range. It is my guess that nonmetallic materials do not match steel in these areas???
Yeah, Steve, you should probably knit yourself a sail out of stainless steel wool so when you're...
- pouring chemicals on your wires it won't matter if you get some splashing; and
- flying on a hot day you won't have any melting problems.
What I'm mainly concerned about is how FireLine and Spiderwire (F&S for short) last over time and when encountering all those things a glider might go through when in a bag atop a vehicle.
Like what? What happens to it in a bag atop a car that doesn't happen to it when it's used as a main sheet on an ocean race?
How do F&S hold up to pinching forces (such as being caught between a couple of DTs when folding up a glider or during transport)? Are F&S porous? If so what happens when they are wet and then freeze?
Find something REAL to worry about.
It is all that sort of stuff that stainless steel cable has met over time being customer tested that adds to reliability.
When customers test stainless steel cable a little too rigorously it fails and they die. Sometimes in aviation the reliability of the customer is a lot more important than the reliability of a particular material.
I don't think I'd want to use F&S unless it also stood the test of both treatment by the less careful ones of us and went through a lot of in-flight testing.
- See above.
- Flight testing tells you NOTHING. The air isn't the place where cable and line get abused.
Steve Baran - 2012/12/03 23:39:58 UTC
I hope I don't sound critical - at least for being critical sake. But, one must be discerning and think about all those things that wires on a glider can encounter.
Unless they're abused the ONLY thing that wires on a glider can encounter that matters is tension loading.
Change is good unless it comes back to haunt you.
Just like not changing can. And this cult has killed a lot of people because it REFUSES to change any crap that has a long track record.
Think about DDT. It was touted as the cat's meow and then used extensively (and still used in many other countries).
- It wasn't touted as the cat's meow by any responsible biologists. And it's not like some of the downsides - like the extinction of the largest subspecies of Peregrine in the world - weren't pretty fucking obvious long before it was banned in the US.
- These lines have had the hell tested out of them. We know what they'll do - this ain't rocket science.
Something new might look good on paper but not survive the real world test.
Fuck real world tests. On the ground you can test to ten times what could be survived in the air.
Tom Galvin - 2012/12/03 23:54:14 UTC
I don't see stainless steel sidewires being replaced as the default material anytime soon...
And, thanks to assholes like you, I don't see preflight bullshit being replaced by hook-in checks as the default method for preventing unhooked launches.
...but I could see the use of alternate materials for specific design goals. A hike and fly glider being one of them.
So why would Dyneema be acceptable for a glider you hike in but not for one you drive to launch? You planning on establishing a Hike-In Hang Glider Manufacturers Association with reduced airworthiness standards?
Devin Wagner - 2012/12/03 23:54:18 UTC
It's hard to cut with sharp knife so pinching is a non point. Cold and heat within reason, like -30 to 200 F, have no effect. Have yet to find chemical that damages it.
Keep trying. Steve won't be happy until you come up with a reliable solution.
On my fishing rods I get two years out of the line and I leave them in my truck bed in full sun all the time.
Why?
The sun will wreck it but it takes a lot of exposure. Wet is also not an issue. Is your sail an issue when it gets wet?
With water or the sulfuric acid he prefers to use?
JJ Coté - 2012/12/06 04:19:18 UTC
Using synthetic fibers in a recreational flight application? Paragliders do it all the time. And their lines are often in the dirt, and getting wet, and in the snow, and on asphalt, and exposed to UV. I don't hear too many complaints about how the lines don't work, or that they're breaking or anything. Now, sure, they have a lot of redundancy and each line has a comparatively low load on it. But all the concerns about how these fibers might be too delicate seem misplaced.
Seems?
So, would it be safe to try for a HG? My second suggestion would be to use the synthetic to replace the wires in order of increasing loading and importance, seeing how things go, and maybe never getting around to replacing them all:
1) reflex bridles
Reflex bridles were originally 205 leechline. Ever hear of any failures or problems?
2) top rigging
And then take the glider to three Gs negative so that part of the experiment will mean something.
3) front and rear lower wires
Which take absurdly low loads in comparison to what the sidewires see.
4) haulback cables
5) lower side wires
And if you get a few in-flight failures you'll know that it was a bad idea.
What a load of crap. Just do the fuckin' math. If you wanna see if a cable or line is still up to the job then take it off the glider and load test it.
Steve Forslund - 2012/12/06 04:29:38 UTC
Factory Trawlers have long ago given up steel for spectra due to better strength per weight.
Funny... One would think they'd have used polypro - which has a reasonable amount of stretch and can act as a shock absorber and reduce the intensity of the impact load. They really need to get in touch with Russell Brown and Dr. Trisa Tilletti so they can learn how to their job right.
Hell I flew a paraglider today that weighs less then 9 1/2 lbs for wing, harness, reserve, pack and vario. There is a market for lighter simpler hang gliders.
I sure hope they have enough sense to use elastic suspension lines. Without shock absorption, low stretch line acts somewhat like an impact wrench on the canopy.
Jason Boehm - 2012/12/06 04:53:10 UTC
I have seen top rigging on a laminar replaced with PG lines.
Which proves what?
consider though....how many lines are on a PG?.......a rough guess. is 100........and i suspect thats on teh low end
so you are probably seeing 3# per line in 1 gee flight..............NOTHING...
now a HG typically weights about 300# all up, and with the angle of the lines..each line sees about that weight in 1 gee flight..........the loads are 100 times what the PG sees
so while he is seeing virtually nothing in the way of load/stretch....we would see about 100 times that
- Maybe you should get your keyboard fixed so the period key doesn't alternate between staying stuck in the down position in the middles of sentences and not functioning at all at the ends of them.
- Your writing sucks as much as your "thinking" does.
- While you're considering how many lines are used on paragliders don't forget to consider their diameters.
- So you're saying that in straight and level flight flight a sidewire on a three hundred pound glider is feeling about three hundred pounds.
- 3/32 inch wire is rated for under a thousand pounds.
- So tell me how a T2 154 - which is rated to a flying weight up to 360 pounds - can be certified to six Gs. They should be blowing sidewires left and right at the bottoms of normal, well executed loops.
Note...
Way more often than not I clean up the writing of the bozos who post on the Jack and Davis Shows to make it less of a headache to read over here. Devin's posts, for example, wouldn't begin to get him out of a second grade classroom with any kind of standards but I translated to English because he at least had an idea worth listening to. Jason's, on the other hand, deserved to be left as he wrote it.
A couple of comments on the thread - currently up to 41 posts...
NOT ONCE has anyone suggested:
- doing or even mentioned the preflight sidewire load test that's in all the Wills Wing owner's manuals
- periodically pulling a Dyneema side line and testing it to, say, five hundred pounds
In this sport all engineering starts and stops with the glider manufacturer and after that it's all about putting stuff in the air and establishing track records. The science and math is quite consistent with the English.
