National Aeronca Association Bulletin Board

has any one ever got apoval for rib stiching in sted of screws thanks john info@skysigns.com

I don't think you need a FA to stich the wing. As long as you protect the cord from chafing you should be fine. I plan to stich my Champ when the time comes, and will run a piece of tape along edge of the ribs. FYI: Great Lakes Trainers had stamped aluminum ribs and were stiched.

nkh

What is the advantage of rib-stitching versus PK screws? I've done a little rib-stitching and it was very time consuming, screws seem like they'd be way quicker.

Eric

One advantage is when you or someone else have to disassemble the wing it will be a whole lot easier, just snip with a scissors and you are done. No fighting with broken screws that are corroded in place. You won't have to clean the glue out the small + slot. I also think it looks cleaner.

The Polyfiber manual gives the proper spacing for ribstitching and they give clear instructions on how to do it but for someone who is all thumbs like me it is a tedious process.

Nathan, let the forum know what you come up with, I would like to do it for my wings as well.

Scott

Another (possible) advantage of stitching is that the top and bottom surfaces are connected by the stitches, relieving some stress on the rib. Of course, Champs and Chiefs have been flying with screwed-on fabric for how many years?

I used #4 x 1/4 stainless screws and thin, 1/2-inch diameter, aluminum washers on '57B. All the holes are new, as well. That's another possible feature - no holes in the flange to weaken them. I should say no *additional* holes. Or, are you using new ribs?

Jon

my 11ac wings are rib stiched and signed off with a 337 dtd 7-17-2003. reference to AC 43.13 1B CHANGE 1 CHAPTER 2 SECTION 1, PAR 2-10 AND 2-11. hope this helps bernie

Scott is DEAD ON! They claim it's faster with PK, and it is when installing, but it takes about 4X longer to strip fabric. So it's a trade off, spend time now or later.

As for legality, from the 7AC Service Manual:

Wing Frame:
....
....
Covering:
A new and simplified method of attaching fabric to the wing ribs has been used on the American Champion. 3/4" pinked tape is laid over the fabric and rib and fastened into place with aluminum washers, Number 1-2331, and Number 4 x 1/4" stove head PK screws over which is laid 2" pinked tape doped to the fabric. Or fabric attachment wire (Martin Clips) is placed over 3/4" pinked tape doped in place. The tape and wire are covered with 2" pinked tape doped to fabric. These simplified methods of attaching fabric save many tedious hours of rib stitching formerly required when recovering wings.

It's this last sentence that's your loop hole "These simplified methods of attaching fabric save many tedious hours of rib stitching formerly required when recovering wings. I interpret that as saying "we use to rib stich but found a quicker way" and it does not specifically say you can not stich. It comes down to the IA's interpretation of that last sentance.

I'll keep you informed, but I won't take it out of service for about a year, year and a half. Just got that engine running and need to enjoy it a little.

nkh

Gentelmen,

For all of the good intentions of posters to this thread, a field approval is most definately going to be required. Nathan has made reference to the appropriate portion of the 7AC Service Manual. Unfortuanately, the manual specifys the use of PK screws or pop-rivets and not rib stitching. The indication that these "new" methods of attachment saves time over traditional rib stitching in no way grants the authority to rib stitch. Factory method was PK screws or pop-rivets - period.

That means that we need to figure out a way to get a field approval for rib stitching. Since I was already working on this very issue on behalf of the origional poster of this thread, I have been doing some research. The 7AC was certificated under CAR 4(a). There are 3 relevant paragraphs in CAR 4(a) - 4a.338 which indicates that covering must comply with the requirements of 4a302 and be attached in a manner that will develop the necessary strength with consideration for slip stream effects, 4a.302 which indicates that your materials and workmanship need to be of high grade and 4a.252 which states that proof of strength is not required when standard grades of cloth and methods of attaching and doping are employed.

The Stitts manual indicates that rib stitching is acceptable for attaching Stitts under their process but then says that attachment must be the same as used by the factory or a field approval must be obtained.

AC 43-13 shows rib stitching as an acceptable method of attachment but also states that the methods used by the factory must be followed or a field approval obtained since the change is designated as a major alteration.

I am currently researching the FAA manual 8300.10 to find a basis for field approval. It would appear that CAR 4(a) ~4a.338 should be acceptable but that isn't a done deal yet. I am working with one of the ASI's out of the Northwest Mountain Region to get this figured out for John (and myself as I am currently doing a restoration on 2 7AC's). Personally I think this should be a no-brainer however that term seems to have a different connotation within FAA these days.

I will post to this thread when I get a final answer but do remember that what I find will apply to myself and to John, the origional poster of this thread but not necessarily to persons located within other FSDO Districts. In the mean time, please don't tease yourself into believing that you don't need a 337 - changing the method of attachment from the procedure used by the factory on YOUR airplane is a major alteration. That requires submission of a form 337. Without a clearly defined "basis for approval" (ie; an STC) FAA now wants the 337 submitted for field approval prior to performing the actual work.

It seem that both of the methods of attachment are industry standard. Would this not make the interchange a minor alteration? If you chose to glue the fabric to the ribs with 3M 5200 only I would consider that a major alteration. Due to the fact no information exists on this application.

Industry standard has no impact on this issue with the possible exception of providing an arguement for a basis for approval. This issue is exclusively what method of attachment was used by the factory on the specific model of airplane. In this case, only the pop-rivets and PK screws were used by the factory on the 7AC. Anything else is a deviation and constitutes a major alteration.

Jay,
is there a specific reason you are wanting to rib stitch the wings? If you dont like the screws showing you could use the Martin clip.
Paul

My 7AC had the martin fabric clip my dad used on it in the '60's and between it and the orginal PK holes my ribs are "holy". I plan on rib stitching if I can get a FA. Might as well wake this thread up after a couple of years.

Kevin,
You could re drill the holes for the screws and clip as one solution. There are many opinions here, my solution would be to look up the definition of Major vs. Minor repairs. This should bring some clarity to this subject.
Paul

old sport aviation has a picture of the fabric serarating and wing failing on a great lakes

I may even use the martin clip again. I didn't know that it was still available but I saw it in AS&S catalog. When I uncovered the wings it was snug in the existing holes. I don't know why my dad did not use the pk screws over but between them and the martin clip there are plenty of holes to see. I have no personal experience with the martin clip but you would think that it would utilize the existing pk holes and maybe it was supposed to. My dad may have done it incorrestly but that was in about 1965 when he covered the airplane. It was blown around on a ramp by a hovering military helo and that is the entire damage history.