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View Full Version : Rib stitch or rivet spacing on wing



Bugs66
07-12-2004, 03:24 PM
I am starting to get my ducks in a row before I build my D&E wing. Since the D&E wing has stamped ribs - I will most likely use fabric rivets. The ribs are not predrilled so I need to drill them for fabric rivets. Does anyone know the spacing between fabric rivets for the Cub wing? Is it the same as stitched?

Thanks,

Bugs

SuperCub MD
07-12-2004, 08:43 PM
On the wings, 2.5" in the prop wash plus 1 rib, and 3.5" from there out. 5" on the tail.

If the ribs are not drilled yet, I'd just stitch em. Laying out and drilling all those holes is a lot of extra work. And I have been seeing a lot of riveted fabric tearing loose around the rivets through the reinforcing tapes. This is very hard to see unless you look close, if the rivet bumps are not there and the fabric is flat....your attachment has failed. This seems most prevalent in the prop wash area with big motors and big props. To me, it looks like the fabric vibrates under the rivet, the edge of the rivet cuts through the reinforcing tape and fabric. Just an opinion, and food for thought...

And to the other stitchers out there, how many of you stitch the vertical fin? I've seen them not stitched at all, just the top rib stitched, or both ribs stitched. If the lower rib is stitched, it always tears loose anyway in just a few hours, and some times the top rib tears loose too. I usually just stitch the top rib with tight spacing...anybody know what is the best way? The ones with no stitching at all seem to fly just fine....

RedEye
07-12-2004, 10:03 PM
I would have to agree with MD on this one. With a little practice you can learn the stitch. Its not as difficult as everyone thinks. Once you've mastered the stitch it's actually faster than riveting or screws. It also gives you more strenght & looks way nicer !!


MD, I've seen both ways on the vert fin. Myself, I only do the top rib. So far no problems. If memory serves me, the Piper print shows only the top rib being stitched.

T.J.
07-12-2004, 10:03 PM
delete

Bill Rusk
07-12-2004, 10:24 PM
I have heard from a couple of the oldtimers that if you pull the fabric in tight to the vert stab all the way to the fuselage that you will get 8 to 10 MPH. I guess the fat rudder is a drag machine. No proof, just what I've heard. Food for thought.

Bill

Bugs66
07-13-2004, 10:12 AM
Thanks for all the input. I was leaning towards riveting because of the stamped ribs. I don't mind learning to stitch, in fact I want to, but other people told me I'm nuts to stitch stamped ribs. What about the sharp edge on a stamped rib, is that a problem for the stitches? I would debur of course.

Bugs

bob turner
07-13-2004, 01:54 PM
I too would rib-stitch. Protect your sharp edges with a file + tape. Not thick tape; it will show. I have done only a few surfaces with pop rivets, and am not happy with finished appearance.
I stitch vertical fins with two stitches on the upper horizontal, like piper did. Mine always pull out in short order. Then I tried canvas for reinforcement and safety wire for stitch. Same result, except that the safety wire is still in there, and has caused minor blemishes on the finish. I tried aluminum washers of about 3x the size of pop rivets - same result. So next time I'll go back to standard rib stitches, and let them pull out. The dollar patches will still look like the original fabric, and few Cub nuts will notice that they pulled out.

JP
07-14-2004, 05:15 PM
If I recall correctly there was an extended post on this same issue awhile back.

I used Univair stamped and drilled ribs in a rebuild and opted to rivet. It was quick, easy and came out beautifully. I made extra sure that the rivets are in solid, on tape and covered with tape. We'll see how it holds up over time. With the right equipment they aren't half the bother to take out when it is time to recover.

On anything other than stamped and drilled I'd stitch, as most don't have the STC for the rivets. Stitching is pretty strong--I used some of the thread to fix my Tevas and it lasted well over a year.

Cimarron
07-14-2004, 07:52 PM
what is the difference between pop rivets and the FAA? Pop rivets are always working. The pops use a soft aluminum as the main hold. the first time they move any, they are loose and will continue to get worse till they fail.

JP
07-14-2004, 08:26 PM
what is the difference between pop rivets and the FAA? Pop rivets are always working. The pops use a soft aluminum as the main hold. the first time they move any, they are loose and will continue to get worse till they fail.

As it was explained to me by my ap/ia, the grade of the rivet makes a big difference and aircraft grade rivets are just that. The tolerances in the manufacturing process are much finer than off the shelf rivets (that are perfectly fine in most applications). When you compare two "identical" rivets, one aircraft grade and one shop grade, you will see and feel differences in the quality and construction.

Aircraft grade fabric rivets can be obtained inexpensively in bulk from Wicks, Spruce and others. They may only be used where the TC for the aircraft originally had them or where an STC has been approved for their use (i.e. on some of the very nice after-market ribs produced by third party vendors). Only then do you have any assurance that the respective parts have been tested to some degree to ensure that they will do what they say they are going to do.

It's nice to have two excellent options for attaching fabric to ribs when rebuilding a Cub to better than new specs (presuming you are replacing ancient Piper ribs with ribs STCd for rivets). It's a matter of preference and like everything else in Cub Land, there are usually a few different options and ways to do things that fall well within the general ambit of being practical, legal and, most of all, safe.

T.J.
07-14-2004, 11:14 PM
JP:
What "right tool" do you use to take out rib rivets?

diggler
07-14-2004, 11:26 PM
delete

Steve Pierce
07-15-2004, 06:38 AM
I agree with Dig. I hate drilling out pop rivets but I have done it using a small pair of flush cutting dikes to hold the rivet if and when it starts to spin without enlarging the holes. I have read about people using hardware store pop rivets and having the sharp edge wear thru the fabric. However I have rebuilt several wings with pop rivets and have not found any that had gone thru the fabric. I personally prefer stitching but have not seen any problems with pop rivets unless someone got carried away when they drilled the popppers out.

JP
07-15-2004, 07:51 AM
JP:
What "right tool" do you use to take out rib rivets?

TJ, same thing Steve does, and drill straight down slowly with a variable. Also, Wicks sells a really nice rivet remover that does the job:

http://www.wicksaircraft.com/catalog/product_cat.php/subid=1873/index.html

I'm really hoping it will be 20 years before I have to remove every one of those rivets from the wing. :roll:

Bugs66
07-15-2004, 12:29 PM
... I made extra sure that the rivets are in solid, on tape and covered with tape. ...

What kind of tape did you use here? I've also heard about putting masking tape or similar between the rivets to flush them out better.

Thanks for everyones help.

Bugs

JP
07-15-2004, 02:11 PM
... I made extra sure that the rivets are in solid, on tape and covered with tape. ...

What kind of tape did you use here? I've also heard about putting masking tape or similar between the rivets to flush them out better.

Thanks for everyones help.

Bugs

Bugs:

I used aircraft grade reinforcing tape (Stits) over the fabric. I then used a standard shop awl to punch throuh the tape to pre-drilled holes. The next step is to place and pull the rivets. After that I put down a thinned base of Air Tech adhesive and put fabric tape over that, followed by two coats of thinned adhesive. Then you are ready to iron the edges, blow test, prime and paint. The finished product with the Air Tech paint is very flush.

Although I've seen it done, I would most definitely not use masking tape anywhere on a recovering job. The stuff degrades fairly quickly and is a real mess to clean up and remove. Always use the chafe tape recommended in whatever STC process you are using. It is medical tape that has been treated with mildew resistant chemical (i.e. so don't use regular medical tape). On the other hand, Clyde Smith has had good results with clear 3M packing tape as a chafe tape.

The aircraft grade fabric rivets are remarkably flush to begin with and I think you will be very happy with the results absent trying to squeeze some more tape between the rivets and over the reinforcing tape and under the fabric tapes.

SuperCub MD
07-15-2004, 04:30 PM
Note, I should have added that the riveted fabric I have seen tearing loose uses that reinforcing tape that is glorified masking tape with fiberglass in it type stuff. If you use Stitts or Ceconite woven reinforcing tapes, the rivets probably won't pull through. This wimpier reinforcing tape is used a lot with rivets because it is easier to get holes punched in it for the rivets.

If you use rivets, the best I have seen are the ones Superflite sells, I've bought the others from Wicks, etc, which are a lot cheaper, but they are not as well made.

If you inspect a riveted wing, look real close at the fabric around the rivets. A riveted wing should look like it has a bad case of zits. If you look close, and see a place where a zit should be, but the zit is now flush, the attachment has failed under the finish tape. This is not easy to see if you don't know what you are looking for, and there are a lot of planes flying around this way.

The only benefit I can see to rivets over stitching is that mice eat stitching, but don't eat rivets. But if you are not flying your plane enough to keep it from becoming a mouse house, you are doing a great disservice to your plane and yourself. If you use your plane on a seasonal only basis, the rivets would have a advantage.

Bill Ingerson
07-15-2004, 10:02 PM
I just finished reading a book given to me by Spencer Aircraft on how to cover with the Poly-Fiber System. Its a good book and goes into great detail about lacing the fabric to the ribs. Since I just bought a basket case and will rebuild it from the ground up, Im trying to read everything about rebuilding a SuperCub since I will do it all, with the help of certified mechanics and inspecters when needed to sign off. Correct Heat is very important on tapes ect. Call 1 800 424 1160 or www.spenceraircraft.com
and see if you can get this book by Jon Goldenbaum Procedure Manual no. 1 Revision No. 20
Another thought is to contact Stewarts Hangar 21, Inc. Fabric covering and paint, hands on workshop located in Cashmere Washington phone 509 782 3522 ask for Doug Stewart or Dan Stewart both are good fabric specialist and have a simple way of Lacing the fabric to the ribs that is quick and easy. WWW.stewartshangar21.aero Hope this helps some of you out there, I need alsorts of help myself, Im just trying to learn everything I can.

Bill Ingerson
aa.fueler@verizon.net
River Patrol

StewartB
07-15-2004, 11:56 PM
Bill,
Get the video by the EAA on fabric covering. Better yet, PM me an address and I'll send you the copy I bought. Find a Polyfiber distributor and take a weekend covering class. PAK from this site puts them on up here, and the class I took was taught by John Goldenbaum. Covering isn't difficult, but it is very time consuming. And, like many other disciplines, novices spend too much time on the wrong things, and not enough time on the right things. I surrendered and hired my fabric work out. I can do what I do for a living and pay somebody else to cover it cheaper than I can take the time off to do it myself.
SB

JP
07-16-2004, 06:56 AM
Bill,
Get the video by the EAA on fabric covering. ..SB

Say, Bill--to muddy the waters a bit, there are different covering processes and you might want to check out the other thread dealing with them. Just run a search on Stits and Air Tech and you will come up with a lot of good commentary on this site.

If you are doing a recover for yourself, I recommend you give it a go yourself. You can do it and do a great job. If you are doing airplanes for a living, you gotta make a decision akin to what Stewart does as it is somewhat time consuming to cover.

Personally, I love covering airplanes. It isn't difficult and it is very rewarding.