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User avatar
By raquo
#396977
Thanks all of you for the insightful answers! :thumbsup:

I'm ordering new wires of course, but it's still good to know what amount of discoloration is acceptable (I have other wires with just a couple black dots on their nicos). I've emailed Mike as NMERider suggested asking for advice on this, we'll see what he says.

Red, I cut off the shrinkwrap and tried rubbing off the black stuff with a piece of cloth dipped in alcohol like you've suggested – no result, still there, hard as metal. The nico on the other side wire had grey discoloration, after cleaning with alcohol that discoloration became black just like the photos that I've posted.

And no, I do not land in salt mines or anything like that, just grassy fields in a valley. :)

I did not do the stomp test because I'm sure that the nico will hold the ~50 lb force of this test, it's the higher loads that can happen in flight that I'm concerned about.
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#396979
Rcpilot wrote:What did the folks at Wills Wing have to say about your concern of the issue of work hardening of stainless cable due to performing the side wire load test, red?
Rcpilot,

I just looked in some WW owners' manuals on-line, and I did not see this cable "stomp test" in them.
Can somebody quote a WW owners' manual (or any WW source) calling for that "stomp test?"
I'd like to see what they ask you to do there.
You can download new manuals for your WW glider at their web site.

From a technical standpoint, if a cable is rigged straight and tight, deflecting the cable by a handspan can put enormous loads on the cable. A cable rigged slack can be deflected by a handspan and that will put a relatively small load on the cable. It's a function relating to trigonometry. A weak "stomp test" may tell you nothing useful. A strong "stomp test" can work harden your cables. If the cable deflects far enough to let you grind the cable underfoot against the ground, one "stomp test" can damage an otherwise good cable. These "variables" make the "stomp test" unreliable, and maybe risky, in my opinion. YMMV.

:mrgreen:
#396981
red wrote:
Rcpilot wrote:What did the folks at Wills Wing have to say about your concern of the issue of work hardening of stainless cable due to performing the side wire load test, red?
Rcpilot,

I just looked in some WW owners' manuals on-line, and I did not see this cable "stomp test" in them.
Can somebody quote a WW owners' manual (or any WW source) calling for that "stomp test?"
I'd like to see what they ask you to do there.
You can download new manuals for your WW glider at their web site.

From a technical standpoint, if a cable is rigged straight and tight, deflecting the cable by a handspan can put enormous loads on the cable. A cable rigged slack can be deflected by a handspan and that will put a relatively small load on the cable. It's a function relating to trigonometry. A weak "stomp test" may tell you nothing useful. A strong "stomp test" can work harden your cables. If the cable deflects far enough to let you grind the cable underfoot against the ground, one "stomp test" can damage an otherwise good cable. These "variables" make the "stomp test" unreliable, and maybe risky, in my opinion. YMMV.

:mrgreen:
http://willswing.com/wp-content/uploads ... e_2015.pdf
While pushing up on the leading edge between the nose and the crossbar junction, step on the
bottom side wire with about 75 lbs. of force. This is a rough field test of the structural security
of the side wire loop, the control bar, the kingpost, and the crossbar, and will likely reveal a
major structural defect that could cause an in-flight failure in normal operation.
User avatar
By NMERider
#396984
The same illustrations appear in multiple manuals. This simple test could have easily saved a life recently lost at a NorCal coastal site. It's your lives people. Would you rather rely on urban legend and old wives tales that permeate this sport like a stench or facts from the people who manufacture and test your gliders? The choice is yours. It would be nice if the manuals all showed illustrations of the simple Lift & Tug Hook-in Check too.
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User avatar
By brian scharp
#396985
Not found in any manual.
Mike Lake wrote:Squeezing the front wires together is also a quick and easy test. This is something I've done since the days of bulldog clamps.
A friend watched me do this last year and made it part of his preflight.
Just in time it would seem as his rear wire failed at the keel while still on the ground instead of over a volcano in Lanzarote!
#396986
Rcpilot wrote:
red wrote:Can somebody quote a WW owners' manual (or any WW source) calling for that "stomp test?" I'd like to see what they ask you to do there.
http://willswing.com/wp-content/uploads ... uote]While pushing up on the leading edge between the nose and the crossbar junction, step on the
bottom side wire with about 75 lbs. of force.
[/quote]Rcpilot,

I just stepped on a scale for "about 75 lbs. of force." Given the slack cables of the Alpha, you may not hurt anything, but you may not learn anything useful, either.

It's a rather low-stress test, as described for the Alpha. I believe that a lot of pilots will overdo it, "just to be safe." I also believe that some pilots will postpone replacing their cables, as long as they can pass the "stomp test" as described. Neither option (I believe) is a good one. YMMV.

My take: I believe that we are safer by avoiding cable kinks and avoiding the sharp bending of cables, and with changing cables on a schedule (or as better judgment may require).

Kinking a cable is a "just cause" for replacing that cable immediately. No level of inspection can spot the internal damage done, when a cable is kinked.

WW might appreciate me saying, every pilot should have a new set of bottom cables on hand, in case there is any accidental damage done to these important cables. An old set of undamaged top cables can replace your damaged top cables for a few days (if necessary), while you order and wait for the new top cables. Then, you may miss out on one flying day for a bad cable, but you will not need to miss two.
User avatar
By NMERider
#396988
If Mark Smith had done a simple stress test on the wings of his Wanderer, ultra-light powered sailplane after he'd repaired it, George Worthington may very well be alive today some 4 decades later. What in God's name is the matter with pilots and their absurd excuses for not using simple and readily available and utterly harmless methods of insuring they don't join Rafi Lavin among many others in the hereafter. If you aren't smart enough to avoid grinding your side wire into a rock with the sole of your shoe then please find another sport because you don't belong in this one. Hang gliding isn't for everyone. :roll:
#396989
NMERider wrote:If Mark Smith had done a simple stress test on the wings of his Wanderer, ultra-light powered sailplane after he'd repaired it, George Worthington may very well be alive today some 4 decades later. What in God's name is the matter with pilots and their absurd excuses for not using simple and readily available and utterly harmless methods of insuring they don't join Rafi Lavin among many others in the hereafter. If you aren't smart enough to avoid grinding your side wire into a rock with the sole of your shoe then please find another sport because you don't belong in this one. Hang gliding isn't for everyone. :roll:
Campers,

75 lbs. (34kg) of foot pressure on a slack-rigged wire probably won't hurt anything.

You need to have good confidence in what you fly.
User avatar
By raquo
#396993
Mike Meier got back to me, here's what he said:
Hi Nikita,

That does look like corrosion, and I don’t recall seeing that type of corrosion on nico sleeves before. I’m not sure what would have caused that, but my guess would be that at some point moisture got inside the heatshrink tubing and was trapped there.

I think replacing the wires is prudent, though I suspect that in the condition shown in the photos they would still test to their full rated strength. I don’t have any way to ascertain or estimate how much corrosion of the nico sleeve would cause the wire assembly to be weakened below its rated strength. I’ve never seen a wire failure where the nico itself failed – typically the wire fails where it exits from the nico, and this is the normal failure mode even on a brand new wire that tests to full rated strength. Wire failures in the field are most often the result of a wire that has been severely kinked, often because the wire was tensioned with the thimble cocked on the tang, and then the wire has been weakened by repeated loading after having been kinked. A wire with a severe kink can lose half of its strength after 100 loadings to the equivalent of a one G flight load. Even considering the generally lax maintenance that most hang gliders receive, wire failures in the field are fortunately relatively rare, though they can be catastrophic when they do occur.


Sincerely,

Mike Meier
Wills Wing
I'm replacing the wires with most corroded nicos – side wires and top front wire, as well as the sweep wire which only has a couple black dots on the nicos but is otherwise old even if it looks good. Nicos on some other wires also have a couple small black dots on them, but it seems like overkill to replace those right now. I will re-evaluate those nicos in (the sooner of) three months / 10 hours airtime.
User avatar
By NMERider
#396996
raquo wrote:Mike Meier got back to me....
Thanks you for following through and then following up with information from the source. This is what all pilots should be doing before canvassing the community at large.
#397004
red wrote:Campers,

75 lbs. (34kg) of foot pressure on a slack-rigged wire probably won't hurt anything.

You need to have good confidence in what you fly.
Here is a somewhat-related question. I have a Falcon 4 with only 30 hrs total, but it's 3 years old now (I know I need to fly more). I am meticulous about how I handle the cables, I do this stress test, and the lower side wires are in great shape. My glider is stored indoors with low humidity in the off-season, etc.

I was told that in situations like mine where the replacement schedule is long overdue, but the part is still in great shape and all other factors are considered, that it's an acceptable decision (if I wish) to leave the part (wires in this case) in service. Replacing would certainly be fine, but not necessary simply because of the time that the part has been in service.

The logic is not based on cost savings, but on the possibility of introducing a problem that didn't exist (e.g. installation error on my part) because I was solely honoring time-in-service over other factors. I read a study of aircraft maintenance in WWII that pointed to this as well.

Thoughts? I haven't replaced the lower side wires yet, not because of cost, but because I can inspect them so thoroughly, and they are still in nearly new condition.
#397005
JackieB wrote:....I was told that in situations like mine where the replacement schedule is long overdue, but the part is still in great shape and all other factors are considered, that it's an acceptable decision....
JB - Lives have been saved or lost by either incorrectly servicing a part that didn't really need it or by correctly servicing a part that really did need it. Statistically, the world's pilots will probably live longer by replacing their flying wires with new ones at the manufacturer recommended intervals than by relying upon the "If it ain't broke--don't fix it" mentality of bush pilots who have a shorter life expectancy than their air frames. YMMV.
User avatar
By WA6BD
#397007
NMERider wrote: Rafi Lavin
i miss Rafi, when i am at the fort ~

fly safe ~
By Rcpilot
#397008
WA6BD wrote:i miss Rafi, when i am at the fort
I miss him as well. He was a super fun guy to know and interact with.
User avatar
By NMERider
#397010
Rcpilot wrote:
WA6BD wrote:i miss Rafi, when i am at the fort
I miss him as well. He was a super fun guy to know and interact with.
I never knew Rafi but I'm certain that I'd have been equally fond of him. I was going through my gmail contacts today and found 5 entries for fellow pilots who died since I last did an edit which wasn't that long ago. Only one was due to old age. :(
#397017
NMERider wrote:
JackieB wrote:....I was told that in situations like mine where the replacement schedule is long overdue, but the part is still in great shape and all other factors are considered, that it's an acceptable decision....
JB - Lives have been saved or lost by either incorrectly servicing a part that didn't really need it or by correctly servicing a part that really did need it. Statistically, the world's pilots will probably live longer by replacing their flying wires with new ones at the manufacturer recommended intervals than by relying upon the "If it ain't broke--don't fix it" mentality of bush pilots who have a shorter life expectancy than their air frames. YMMV.
Thanks for your input, NME, and I received a very helpful PM from another experienced .org member as well. I just ordered my new side wires so that I will have them available whether I decide to replace immediately or not.
User avatar
By dbotos
#397052
Do the sleeves have the Nicopress roll mark on the side? On their website, if you go to oval/duplex compression sleeves and select stainless steel as the wire rope material, they have sleeves that are:

1) copper with tin plating
2) straight stainless

The tin-plated copper ones appear to have the roll mark on the side, whereas the stainless did not (which makes sense since it's be much easier to roll mark the softer copper without distorting the rest of the part). Of course, maybe they make special ones for Wills that are copper with nickel plating. Passivated nickel plating would be a good match with passivated stainless wire, galvanically. Passivated stainless on passivated stainless is even better, but would probably take more force to crimp.

Raquo - wanna take a drill bit to one of your old sleeves and see if you hit copper?
User avatar
By dbotos
#397055
I emailed Mike at Wills. He said they are using zinc-plated copper sleeves. Which, on the Nicopress site shows as being compatible with galvanized wire. I thought most glider wires were stainless.

I'm wondering if the zinc plating on the sleeves has a trivalent conversion coating over it. I came across some instances online of "black spot" corrosion when testing trivalent-coated zinc platings.
By Rcpilot
#397064
PM from red:
Rcpilot,

It may seem like I am standing on both sides of the fence, on the Stomp Test. FWIW, I have exactly the same view of Wills Wing, there. They obviously know about Work Hardening of cables, and they have seen enough pilots "stomp test" their cables that they know nobody will listen to them, if they yell STOP IT.

So, what I see instead is that they give a test spec that is essentially meaningless. A glider that fails a 75 lb. cable pressure (which is what is in the manual) tells me only that the pilot was really lucky to survive the last flight on that glider. The realities of Work Hardening (and the resulting loss of Shock Load capability) make any such testing a two-edged sword. This is a case where excessive testing can cause the failure that you wish to avoid.

There really is no one great answer. I wish there was.
Aren't we lucky to have red standing as the last barrier to the deadly misinformation circulating today in fifty thousand Wills Wing glider owner's manuals. Can you imagine the absolute Work Hardening carnage we'd be seeing otherwise? I'd estimate around fifteen or twenty times the zero incidents we've seen to date.
User avatar
By brian scharp
#397070
Rcpilot wrote:What did the folks at Wills Wing have to say about your concern of the issue of work hardening of stainless cable due to performing the side wire load test, red?
red wrote: ...These "variables" make the "stomp test" unreliable, and maybe risky, in my opinion. YMMV...
...I believe...
...I also believe...
...(I believe)...
...My take: I believe...
...WW might appreciate me saying...

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