DIY fabric repairs

Big Ed

Big Ed

N50247 - '79 Super D
Joined
Jul 20, 2020
Messages
1,938
Location
Tampa, FL
What are the rules and work-arounds for owner performed repairs on fabric?

I am buying a 78 Super Decathlon. The cover and paint are original. It has been hangared since new, but has some rough spots. It needs immediate repairs to several 6 inch tears along longerons near the tail. There are several more touch up repairs that could be done to make it cleaner until I get it recovered in a few years.

When I had a share of a Decathlon before, we had 2 small tears that I fixed by sewing in a patch. My aircraft partner was well connected. He got someone to show me what to do and check my work.

I'd like to fix my new plane. Don't really want to pay full shop fees for what amounts to minor cosmetic work. What kind of supervision do I need? What is the threshold where I can't do my own work? Any other tips?
 
Shhh! Fabric patching is easy. For temporary, there are some really strong adhesive tapes - $$
For light aircraft like the Decathlon, very small fabric patches can be glued on.

While not strictly legal, small patches can usually be glued right over the old finish (rough it up a bit with 320 wet sandpaper). Stits process or Stewarts works fine, but if the aircraft is butyrate, stick with those products for an invisible match.

I had to make some fairly large holes in my beautiful Decathlon fabric to install a Balun on the nav antenna. Let me see if I can get a photo - 17 years ago, and you cannot see the patch!
 
Interested in tape for temporary. Is that safe and legal? Are we talking duct tape, or some kind of aircraft grade stuff?

Right now the plane is in shop for prebuy. There are a few holes that must get patched. But I will probably pay thru the nose if I have it done there. Would love to be able to do a temporary repair, fly it a few months, then do a quality permanent repair once I find a hangar to work in and someone to supervise. Would tape work for that?

The legal issue with glued patches is Vne, correct?

I'll try to get some photos of the tears in mine to see what you think about that.
 
Pics of the damage. Doesn't look like tears but there is about a 6 inch section at the end of each former (stringer? longeron?) where you can shove your fingers inside. Same issue on other side. Current owner moved the plane by putting his hip against that surface and pushing.

Seller is an A&P and has a hangar with workshop about 90 miles away. He is willing to supervise me performing maintenance such as oil changes, fabric repairs, etc. He's not experienced with fabric, in fact I think I have done more than him, so I'll be researching the techniques and going to him with proposed repair methods for approval. First step is buying the Ceconite manual.

Questions:
  1. Safety of flight issue?
  2. Can I assume that tears will grow as fabric flaps in wind?
  3. Sew or glue? (based on Vne > 150, I understand rule is to sew, and I plan to follow the rules.)
  4. Is this a single day project or will it take longer?
  5. Can dope be brushed or must it be sprayed? (Cosmetics be damned)
  6. Viability of tape until I can get materials to repair? Is tape strictly an emergency repair to get home, or is there some period of time that it is acceptable to use for normal use (non-acro)?

tail.jpgfabric damage.jpg
 
If you wish to be strictly legal, you must remove all coatings right down to the clear dope or Poly Brush. I believe Poly Tak, which is now interchangeable with Super Seam Cement, is a "no speed limit" repair. Let me check that. No, tape is not a legal repair, but it sticks as good as the glue does. We have a lot of trouble with the Stearman center section - it is in the slipstream of 220 horses. One of the guys stuck some duct tape up there one day and it stayed longer than my carefully glued patches.
 
Do you think I could baseball stitch those tears, or will it be too hard to do because of the stringer directly behind the tear?
 
This is typed directly from Stits manual 1:

In Nov '71 we successfully completed an extensive test program to obtain FAA approval for POLY TAK cemented seams to substitute for sewn seams for all aircraft regardless of the red line (Vne). A minimum 2" overlap splice, covered with a minimum 2" wide finishing tape, may be used on any area of the wings, and a minimum of 1" overlap splice, covered with a minimum 2" finishing tape, may be used on all other parts of the airframe.

Now here's the grabber:

Patches with Dacron cloth are made by thoroughly cleaning the old surface and overlapping all edges at least two inches using POLY TAK for adhesion. . . . Removing the old POLY TONE pigmented finish is optional. . . .
 
Thanks. How does that interact with the Ceconite and Randolph Dope process? Do I follow the Ceconite process, except use POLY TAK instead of Super Seam Seal, and that allows me to glue instead of sew?

Seems like Stitts Poly is way easier to patch than Ceconite & Dope, which requires removal of finish down to nitrate.
 
Re: your picture
Looks like normal finish cracking to me. You say you can put your finger completely through the fabric.? Too bad you are not here; I would have a patch on those in 20 minutes flat.
Yes, you can brush all coatings on. Minor repairs.

I will look for my Ceconite manual. Original Decathlon fabric is neither - it is a factory process using Dacron.
 
Definitely not finish cracking. I can pry the fabric apart and touch the wood stringer underneath.

Covering is original factory. So where do I get the factory process instructions ... Aircraft service manual? Is it nitrate/butyrate dope like Ceconite process, just without Bellanca paying the STC?
 
Yes. You can find it in the service manual - I have Chapter 11 of the Citabria manual in front of me. Repairs are referenced to AC 43-13, which is on-line, I believe. But you can use the Stits STC for major or minor alterations simply by buying Stits products.

Of note - both the earlier Stits manuals and the Citabria covering instructions allow gluing to wood stringers. You will find folks who argue against that, but it is there, in plain English. Wish I had not given away my 1970 Ceconite manual - it was truly informative, and allowed many things like the Stits manuals. I am almost sure the Super Seam Cement has no speed limit.

Now, all that aside, these things take a terrible beating on the right wing inboard two bays, and underneath the cockpit. It is so bad under the cockpit that those cross-formers will actually break, and then beat the fabric to death. The only cure there is to open it up, re-fasten the cross-members, and maybe even stitch the repair fabric to the existing fabric before finishing. A good curved needle is required, but no fancy stitching is required - just maybe four stitches per inch, then dope them in real good with the Seam Cement or Poly Tak.
 
I'm going to order the 2008 Ceconite Manual from Aircraft Spruce. I'll also grab AC 43-13.

Should I expect to get a service manual with my plane, or is that something I need to chase down and buy?

This informative article from the EAA says the limit for glue-on patches on Ceconite is 150 Vne. Super D's redline at 200, so not going to mess with that. Don't want to wind up like Steve Wittman. I don't mind stitching.
 
Scary. I would go to the source - and remember that these processes have been tightening up over the years, but the original procedure manuals are still approved data. I think the EAA may have omitted some details.

Those little boo-boos back around the tail are not going to do a Steve Wittman on you.
 
Steve discounted the importance of rib stitching, an opinion I'm sure he recanted on during his last flight. Having entire sheets of fabric coming off the top of your wing would fall in the "really bad" category.

Agree that aft fuselage fabric would not have the same results. Look up the Savage Bobber.

As for repairs, I'm hearing almost every "system" name here except Stewart and Oratec. Isn't it important to stay with the system that is installed for chemical compatibility?

I'm sure there's a "you can use this over that, but not the other way around", but I'm no expert.

The fabric on top of my wing has been cut to remove a fuel tank for repair, and it was all brushed back on. I'm guessing the paint used with Stits brushes really nicely because other than it being less faded you couldn't tell it was brushed.

200 Vne, wow. I've really got to get out more.
 
The seller does have the maintenance manual, so I'll get that with the sale.

AC 43-13 is ambiguous about doped-on patches for high Vne aircraft.

Para 2-45 says "2-45. DOPED-ON PATCH REPAIR. An opening not over 8 inches in length in any direction, on an aircraft with a Vne speed less than 150 mph, may be repaired with a 2-inch overlapped and doped patch" (emphasis added). That implies you cannot use a doped on patch repair if the Vne is higher than that.

However, sub para 2-45c says "If the opening is less than 8 inches in length in any direction and the aircraft Vne speed is greater than 150 mph, a 2-inch wide finishing tape should be installed on all sides, centered on the edge of the 2-inch overlap patch."

The way I read that, if under 150 Vne, a 2" overlap patch is sufficient. If over 150 Vne, you have to put 2" finishing tape on the patch edges. The difference in procedure is the finishing tape, not the patch.

I could stitch the tear closed and cover with a 6" finishing tape instead. I'm leaning towards that. No question that is authorized by the AC, as long as I use the correct width finishing tape for the Vne.
 
Big Ed said:
The way I read that, if under 150 Vne, a 2" overlap patch is sufficient. If over 150 Vne, you have to put 2" finishing tape on the patch edges. The difference in procedure is the finishing tape, not the patch.
Click to expand...

I have a piece of new fabric behind the skylight on my CItabria, as there wasn't sufficient overlap on the edge when it was recovered. It's basically from the skylight to the trailing edge of the wing. It is done as described above with a 2" finishing tape over the edge of the patch.
 
Not an expert on Stewarts. I do know that patches glued on anything with Stewarts, and finished with rattle can Dupli-Color, do not peel off. And they look great.
You would have to check their procedure manual, but my impression is their cement is no speed limit, and that it goes on top of anything. Really easy through Eko-Fill. The original tech guy and I had a discussion on legalities - he said they consider it "minor alteration" territory.
 
Finally got some photos - you cannot see the line of demarcation in real life - there is some kind of shadow in the photo, but the repair is on this side of the fin where it joins the fuselage. Glued in patch, refinished in Butyrate, in 2003. It was a big opening; I had to put both hands in and go up the fin to install a Balun. Previous owner had just hooked the center conductor to one ear and the shield to the other - doesn't quite work that way.

DSC02859.webp
 
I got the Ceconite Process Manual and the Factory Service Manual today.

According to the 2008 revision of the Ceconite manual, there is no speed limit and no sewing requirement. The new version of Super Seam cement is much stronger, so overlapped patches are sufficient. As I understand it, the process STC supersedes the guidance in AC 43-13.

Ordered a bunch of supplies from Aircraft Spruce today. Now I need a hangar to work in.
 
There you go. Check to see if they still require removing dope to below the silver. That is usually what makes repairs look awful.

My first cover job was done 100% outside. Have to watch the humidity.
 
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