Martin wire and rib stitching

[VictorBravo]

Re: Martin wire and rib stitching

Well 43.13 says its a major, so if you dont have a 337 you can be violated for flying an unairworthy aircraft....stupid paperwork...

Did you mean that 43.13 says it is a major alteration to use another method of fabric attach than what is on the aircraft TC...

or did you mean that 43.13 says it is a major alteration to go from one TC approved method to another method approved on the same airplane TC?

I'd be surprised to hear that they would bitch about switching between two methods approved on the same TC. But I'm not an IA or a legal A&P, so I can very easily be wrong about this.

[Forrest Barber]

Re: Martin wire and rib stitching

Rib stitching a stamped rib does not conform to the TC, can I be any plainer than that statment. It was sad to see so many Award winners are not "technically" airworthy.
The rib stitch allows for the lower portion of the rib to act as the support structure for the upper fabric kind of like an upside down "catinary curtain (sp)" . The stamped rib of course transferred the structural loads to the respective top or bottom of the rib.
Loads do not seem to be the main factor, cutting of the cord could be the problem , I agree that someone needs to develop an STC. I use the "fabriv" method a lot. There is approval to use the rivet.
Since I have Taylorcraft wire and know how to modify Martin wire , it was never a problem. Save as much wire as possible when taking the wings apart.

[Buell Powell]

Re: Martin wire and rib stitching

I used the Martin wire on an F19-it really is nice stainless wire but needs some reshaping. The reason it is longer is that the bend in the clip isn't formed as much and is more rounded instead of the more squared Taylorcraft bend. According to a fellow that makes it-it should be the same distance between the holes as the Taylorcraft wire but the machine is very old and out of adjustment.I just cut a slot in a piece of 3/16 stock for the wire to fit into,threaded the other end for a knob and inserted the wire where the bend is and formed the first one with a twist-installed it, then for the rest -inserted the tool at the bend,pulled snug, and twisted front to rear to make the bend deeper until it was the right length before inserting--with a little practice it didn't take much more time and the wires would lie flat and because the bend was deeper and more squared would stay tight in the hole. Some or the ribs had some damaged holes I had to repair but the reason wasn't because that there was a problem with the wire damaging the rib while it was installed but the people that had removed them at the factory or "Harry's chop shop" just pulled them out instead of being careful when removing them--I have a roll of Taylorcraft wire l bought from e-bay that was advertised as enough to do 2 wings if someone needs it.

[Hank Jarrett]

Re: Martin wire and rib stitching

Anyone have any pictures of the machine that made the Taylorcraft wires? Anyone have any NEW wire that is not pulled out of shape or deformed to help design a new machine? How about correct drawings of the wire as it is supposed to be made, not the messed up used stuff I have for the 45.
Given a bit of information it might be fun to design a fixture or tool to make all the new wire we need as owner produced parts.
Hank

[LostnSpace]

Re: Martin wire and rib stitching

There is some new taylorcraft wire on ebay, item #110432065455, poster says he/she got it when the factory closed, I think the address was in Ohio, O.T.

[Forrest Barber]

Re: Martin wire and rib stitching

The drawings are here, the demand is low but we will consider this project. It takes 150 ft per wing. I have two 150 rolls plus a tangled mess of perhaps 300 ft...

[astjp2]

Re: Martin wire and rib stitching

Wow, I want to rib stitch and everybody on here still wants to use the Unapproved martin wire or try to get someone to get a PMA for the correct wire...

[Laz]

Re: Martin wire and rib stitching

I just finished one wing with the original T-craft wire. No problems. I recoverd the same wings in 1970 and the wire was never a problem. (the plane sat outside for at least 18 years). The wire on E-bay is correct. The man selling it purcased it form the factory in the 80's. I would be concerned about the sharpness of the stamped rib edge. Unlike the prewar which were like cub ribs. Just my two cents.

[dalijohn]

Re: Martin wire and rib stitching

The drawings are here, the demand is low but we will consider this project. It takes 150 ft per wing. I have two 150 rolls plus a tangled mess of perhaps 300 ft...

So Forrest, how could one get a copy of the drawing?

[VictorBravo]

Re: Martin wire and rib stitching

Loads do not seem to be the main factor, cutting of the cord could be the problem

Running a file or "edge breaker" tool over the edge of a stamped rib (so it does not cut the cord) should be a fairly easy STC to get, IMHO. I can imagine walking into the ACO office telling them I need to apply for an STC to de-burr something prior to assembly!

Kevlar thread would solve the problem too, but removing the sharp edge would be better.

The ridiculous part of all this is that all the fabric covering manuals tell you to protect anything with a sharp edge using tape of some sort, and nobody seems to think that this can just apply to the edge of a rib too using that antique concept called common sense. But conformity to TC is a separate matter of course.

A piece of thick cloth "first aid" tape would make this problem completely non-existent from a real-world airworthiness standpoint. Since the stamped rib is symmetrical (load and strength wise), a rib stitch (transferring the tensile load to the opposite side of the rib in compressive load) would be STRONGER than any other method because there are no pull-out loads like there would be on wire, rivets, screws, etc. pulling straight out on the rib flange.

Since ANY of these methods is strong enough for the task by far, the focus should be ease of installation and resistance to abnormal wear... with aesthetics and minimal drag coming in third and fourth respectively.

The ideal "upgrade" situation to me would be to get an STC for dimpling the holes in the flanged rib and using a countersunk pop rivet and a Tinnerman CSK washer. The Tinnerman washer will have more clamping force (area) than even the large head rivets, so it would actually be safer. Flushing it all out would reduce the time required to apply the coatings and working an iron around the rivets since they would be flush. Lots better aesthetics while you're at it, and some microscopic drag reduction in the trans-sonic range.

[N96337]

Re: Martin wire and rib stitching

The ridiculous part of all this is that all the fabric covering manuals tell you to protect anything with a sharp edge using tape of some sort, and nobody seems to think that this can just apply to the edge of a rib too using that antique concept called common sense.

A piece of thick cloth "first aid" tape would make this problem completely non-existent from a real-world airworthiness standpoint. Since the stamped rib is symmetrical (load and strength wise), a rib stitch (transferring the tensile load to the opposite side of the rib in compressive load) would be STRONGER than any other method because there are no pull-out loads like there would be on wire, rivets, screws, etc. pulling straight out on the rib flange.

Exactly my thoughts Bill...and I've done a few Tcraft wings that way. Our FSDO said it's not a biggie and just include it in the 337 for covering, reference AC43-13, and you've got a winner. I've never seen a rib stitch cord cut from the ribs on any I've done. "Hockey" tape is a wonderful thing, and the very best anti-chafe I've found.
JH

[Hank Jarrett]

Re: Martin wire and rib stitching

Bill,
My "barn plane" is a 45 and doesn't actually qualify as a true "Post War" since the wing ribs are stamped sheet aluminum, but are NOT factory production ribs. They were evidently hand made as a proof of concept for the post war production (Forrest, remember the mess when I wanted to buy replacement ribs? Think "Worst hand writing you ever saw".)
The cross section on my prototype ribs has the open edge of the "C" cross section slightly flared OUT and even if the edge was deburred it would still wear through a rib stitch cord. If someone wants to go for a STC make sure you put in that if the edge flares out it must be rolled over so the edge angles slightly in. I don't have access to any production post war ribs to look at and check for the edge configuration, but if they have an outward angle I wouldn't pull a rib stitch cord over it even if it was deburred. I see NO REASON the FAA shouldn't approve rib stitching if the edge is rolled in. There is a small, hand held, 4 roller tool just for rolling edges in (and I would REALLY like one if someone knows where you buy them). A local "old timer" had one and now that I am a local old timer I think I need one too.
That brings me to a minor correction for your post that the FAA might jump on (so just don't say it to them). The stamped rib is NOT symmetrical (in cross section) and that means the loads and strength aren't either. The rib strength IS so much higher than what the rib stitch can apply that in the real world it doesn't matter, but engineers (especially GOVERNMENT engineers) LOVE to show they know something you don't, and may turn you down to prove the point (this assuming the one looking at your application is actually paying attention). A rib stitch does (as you said) pass the load BETTER than the wire, screws or rivets, but all of them are way more than is needed.
If you apply for an STC, just say that you require elimination of all contact of the cord with sharp edges (then you are open to Hockey stick tape (WHAT A GREAT IDEA!!! Make sure you buy it from a PMAed sporting goods store) or by rolling the edge if needed). Talking to the FAA can be like talking to a prosecuting attorney. Don't tell them what they don't ask for, but DO make it safe! I personally think rib stitching is the best method, but I will be using the wires for originality (and it is still more than what is actually needed). I DON'T like rivets. They are easy to do, strong, low profile for reduced drag, look beautiful and......ALMOST IMPOSSIBLE TO GET THE @#%$&*&%@ THINGS OUT FOR THE NEXT RECOVER! Please do the next holder of your piece of aviation history a favor and DON'T use those @)*$@&@# rivets!
Hank

[VictorBravo]

Re: Martin wire and rib stitching

If you apply for an STC,

I just been there and done that, received full PMA three days ago. If you haven't seen the little gadget I STC'd check it out here http://www.ezflaphandle.com

Another possibility for fabric attach woudl be a Tinnerman "clip nut" type of sheet metal nut on the edge of the rib, and a PK screw with a large washer. That would solve the rivet removal issue.

I don't know if there is CSK hardware to make that a reality though.

[Ray36048]

Re: Martin wire and rib stitching

What about the STC to use PK screws in place of the wires. I believe the STC is SA1-217. Does anyone now own this STC?

[birdlegs]

Re: Martin wire and rib stitching

I'm holding a fresh clean rib, there's a .150" edge about 75* from rib top can we place in a roll die and bring this angle to a smidge over 90* no more "edge"?
Brad