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Old 04-05-2012, 11:45 PM   #1
Flying Ant
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Since I've owned my S1S I've never been happy with the rigging so yesterday I took my S1 into a workshop run by the guys who is the local expert on Pitts.

He threw the rigging boards on and found the top wing had dihedral and the bottom ones had a little twist, also the top wing was not level. Then he put the tensionometer on and found that some wires in the same pair had different tensions, one was 650lbs and the other 1000lbs on both sets of flying wires.

So he decided to slacken all the wires and start again, that's when the fun began. The over tensioned wires were assembled dry (no anti-seize on the threads) and had badly galled. Lots of heat, cold and penetrating oil eventually got it out but now I'm up for 2 new flying wires and clevis pins. Of course they are non-standard ones as my S1 was built with 5/16 wires and clevis on both ends so to replace the clevis he'll have to cut holes in the leading edge to get to where they attach to the spar.

So the lesson here... well there are lots but mainly don't over tighten the wires and do lube the threads, especially on stainless steel fittings.

Luckily we found this before I had done anymore than light aeros so the wing is still in good shape.

I don't pretend to be an expert on these things but I'm pretty sure that getting the flying wire setup on these aeroplanes is pretty important, they hold the wings on afterall.

Edited by: Flying Ant



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Old 04-06-2012, 05:45 AM   #2
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I wonder something for some time now : would thread lock fluid (ala loctite) be sufficient against galling ?
Thinking about the butt fittings of my drag wires...



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Old 04-06-2012, 06:54 AM   #3
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Hi Ant

That doesn't look too good. I may have the flying wires you are looking for, what length? They off a project or 2 ago, almost chucked them because they were bizarre.

I will be to Goulburn, via Sydney, next week. I can take them carry on with my favorite domestic carrier?

I've also got some Barry mounts you can have. They are used, off an S2 with about 100 hours.

Lost your email address.

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Old 04-06-2012, 08:28 AM   #4
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Okay, thanks. The wires I need are 5/16 wires that are 70.4 inches long. It's a non standard size, I'll probably have to figure out pretty quickly if they are the right ones as Dave Dent has already ordered them and I'll need to cancel.

I have already got the mounts but thanks anyway.

If you can let me know about the wire sizes and length asap that would be fantastic. I'm sure we can organise them to go on the flight, heck if they fit I'll come and get them

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Old 04-06-2012, 08:34 AM   #5
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Quote:
Originally Posted by Xavier
I wonder something for some time now : would thread lock fluid (ala loctite) be sufficient against galling ?
Thinking about the butt fittings of my drag wires...
I'm not sure but after the trouble I've had I would get the proper stuff. Bruntons have some info on their website and say to use Molybdenum Disulphide grease, I don't think it's hard to find.
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Old 04-06-2012, 02:10 PM   #6
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Hi Anthony,
Well, I discovered Bruntons' advices only recently (and bought some MoS2 grease right away), but my drag wires were already on...I just realize thought that they were only tensionned from the nut side (and only screwed into the butt fitting side without tension), so there might not be any risk there as galling can obviously only form during screwing when too much tension is applied without any mean of lubrication, not once the thread is in and tensionned from outside.

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Old 04-06-2012, 11:09 PM   #7
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FlyingAnt,

<?:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" />I question the method of tension. Pitts manual does not call out using tensionmeter. Pull scale model with 50lbs at 1 1/4 deflection at center point. The only way one would know what the tension using meter, would be to set the wires up with a pull guage (fish gauge) and then get a reading.
I take mine to 50lbs at 1 inch. We have taken them to 100lbs per 1 inch over the years for unlimited flying. Lots of stress transferred all over.
Thoughts from others?



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Old 04-06-2012, 11:37 PM   #8
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http://www.radialengine.com/flywire/index.html


I'd think using a tensio<strike style="font-family: monospace; font-size: medium; ">no</strike>meter would be much more accurate than a pull test.
Best regards,
Brad
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Old 04-07-2012, 12:24 AM   #9
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Brad,
I agree, but what is the eng data to use for the Pitts application. Does 1000lbs = to 1 inch deflection or does 500lbs = 1 inch deflection. I can go to the Stinson or Piper manual and get the data. Curtis never provided this data, only 1 1/4 inch = 50lbs.


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Old 04-07-2012, 01:38 AM   #10
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Ah, I see.

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Old 04-07-2012, 06:12 AM   #11
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The S-1T manual calls out to tension the flying wires using a tensiometer to 675lbs +_75lbs. The tensiometer has markings on it for different readings for different flying wire sizes.

Doesn't Aviat sell tensiometers?

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Old 04-07-2012, 01:07 PM   #12
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I am sure that the problem with galling of the thread on flying wires is because both wire, clevis and nut is stainless steel. Lack of lubricant doesn't make things better of course, but main reason is stainless against stainless. This is never good.
I know Brontons always supply clevis and nuts of stainless steel with the wires, but I do'nt think it is the best idea. I am at least going to use ordinary AN-665 clevices and AN 315 nuts on my wires.
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Old 04-07-2012, 09:07 PM   #13
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Factory Owner's and Maintenance Manuals specify the tension requiring a tensiometer. The S-1 Assembly Manual for home-builders specified the deflection for a spring scale - its been a while since I have seen one of those manuals however there is the same info in Sport Aerobatics magazine of many years ago (also in the IAC Tech Tips Manual from memory) referring to that S-1 Manual.On the same pageis anarticleby Pitts Aviationwhichincludes a copy ofPitts Dwg 41574for the Livingston Wing Rigging Tool. Personally, I avoid stainless hardware for the reasons given so my airplanes always look untidy.
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Old 04-09-2012, 10:28 PM   #14
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This is a problem sailors have on their rigging and its almost always stainless on stainless...just make sure you use a good lube/antiseize and you should be good to go



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