Fabric Patch

[RCS]

No doubt there are many posts on all aspects of fabric work, however I am trying to understand the best process for my repair scenario... I need to cut a small hole (1" dia) in my ailerons to access and tighten some attachment hardware. the fabric is Superflite and the top coat is Sherwin-Williams Acry-Glo urethane. My questions are: 1) how much larger than my anticipated cut should I remove the coatings and take down to the fabric? 2) can I use a chemical paint stripper to remove the top coat as well as the base coats? 3) what is the best technique to feather the patch into the old finish? Any help will be much appreciated!

[1600vw]

As to the patch its self when I did my repairs I looked in 43.13 for the answers. Anything smaller then a 4 inch square and the patch can be glued into place. If it is bigger then 4 inches, the patch will need to be stitched in place. Something this small, I would make the repair one inch bigger then the hole all the way around the hole. I myself would not use any chemical to remove the paint. I would use sand paper and take the paint down to the weave in the fabric. The stewards system would be used for the repair. Using this method ths repair will be quick and easy. I have done many repairs using this method.

Tony

[1600vw]

I would also have some paint mixed at my local Auto Paint supply house to repaint this. This would then be put into a rattle can and the repair would be painted using this. I have done this type of repair and it looked just like the day I did it 6 years later and some 300 hrs of flight time on it. This airplane was no hangar queen.

[martymayes]

For EAB aircraft do what Tony says on the patching the fabric. AC 43-13-1B Chapter 2 Section 4. If it's a type certificated airplane follow the fabric manufacturer instructions. In either case be mindful that this is a control surface where static balance may be critical.

Good luck with the paint, urethane is tough to spot repair.

[RCS]

Thanks for the feedback - very helpful! I have been hesitant to sand the paint down to the fabric mainly for fear that it would be easy to start abrading the fabric threads. It just seemed to me that the chemical strippers was a more surgical approach. So what is the potential problem with the chemical strippers - what damage can they do?

[Kyle Boatright]

Thanks for the feedback - very helpful! I have been hesitant to sand the paint down to the fabric mainly for fear that it would be easy to start abrading the fabric threads. It just seemed to me that the chemical strippers was a more surgical approach. So what is the potential problem with the chemical strippers - what damage can they do?

Two questions:

1) What will the stripper do to the integrity of the fabric?

2) How far will the stripper wick up under the coatings? Maybe just to the edge where you removed the finish. Maybe it'll wick up much farther and damage the bond.

I doubt anyone has an absolute the answer to either question.

[RCS]

I doubt anyone has an absolute the answer to either question.
Your two questions echo my concerns about the use of a stripper... I was hoping to learn from the experience of others. Maybe like a lot of questions there is no definitive answer, but it never hurts to ask!

[rwanttaja]

I've got urethane on my Fly Baby (Stits Aerothane), and it's a PITA to repair. The Stits manual calls for taking off the paint via manual abrasion (e.g., sanding) when it has to be repaired, unless you can access the inside. Also, I understand that it's difficult for a repair to be able to match the gloss.

You can download the Poly Fiber manual (https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwidvOHZhPTZAhUBwWMKHfSEBWkQFggoMAA&url=http%3A%2F%2Fwww.conaircraft.com%2Fpolyfiber-manual.pdf&usg=AOvVaw1-Ez1bamVH0XYwMTdXEilH) from a variety of places. It's got a second on the Urethane paints, and a urethane section in the repair appendix. I suspect your paint will be similar.

Ron Wanttaja

[1600vw]

What I would do is install inspection rings. You can do this with a covered wing. You lay down some fabric gluing down about one inch of this. Lay your ring down then wrap the fabric back around it. Then glue this down once laid out over the ring. I believe the EAA as a small webinar showing how to install an inspection ring after the wing is covered. If not you can do this yourself if you look at it. Again I would use the Stewart system for is.

[martymayes]

I doubt anyone has an absolute the answer to either question.

Cause it depends on the type stripper used.

[WLIU]

"What I would do is install inspection rings."

Please don't do that on an aileron. Nothing good will result.

Urethane finishes are very resistant to chemical strippers. And the chemicals do attack the poly fabric. And one characteristic of modern fabrics is that they do wick any thin liquids along the weave a long way. The manner of starting a repair advised by the paint manufacturers is to sand the urethane finish off, down to the primer. A drawback of the beautiful urethane finish systems.

The advice on putting what is called a "dollar patch" on the small hole needed to access the fastener, sanding the finish for an inch around that small hole, is the best approach. Cut the patch out with pinking shears.

Yes, I have done that exact repair.

Wes

[1600vw]

"What I would do is install inspection rings."

Please don't do that on an aileron. Nothing good will result.

Urethane finishes are very resistant to chemical strippers. And the chemicals do attack the poly fabric. And one characteristic of modern fabrics is that they do wick any thin liquids along the weave a long way. The manner of starting a repair advised by the paint manufacturers is to sand the urethane finish off, down to the primer. A drawback of the beautiful urethane finish systems.

The advice on putting what is called a "dollar patch" on the small hole needed to access the fastener, sanding the finish for an inch around that small hole, is the best approach. Cut the patch out with pinking shears.

Yes, I have done that exact repair.

Wes

Yes very bad advice to install inspection rings on a control surface. My bad. Thanks for setting this straight or correcting this.

Tony

[Greg Wilson]

Mark back at least 11/2" from the opening, you want 1" min fabric overlap with any type of glued repair. Sand the polyurethane off exposing the silver,U.V. coatings,STOP SANDING when through the color!!, the underlying coatings will be able to be dissolved with M.E.K. Glue on the patch with Super Seam etc. shrink the patch, at least 250* F, NOT over 350* F, refinish with the original type of finish process. Matching the poly top coat will be tough, you cannot "feather" urethane, the best choice to totally hide a repair is to repaint the entire panel.

[RCS]

The detail is really appreciated - thanks!

[Frank Giger]

Seems like Greg is the man on this one!

I think everyone would just roll their eyes at my Weldwood Contact cement on a patch, hit it with an iron in ten minutes, and paint with more household latex system.

That is when it's not in a place where a little duct tape on the inside and a sticker of some kind on the outside isn't possible.

;)

[rwanttaja]

That is when it's not in a place where a little duct tape on the inside and a sticker of some kind on the outside isn't possible.

Psssst... clear plastic shipping tape works nice on the outside. Not as visible as duct tape, but heavier-duty than scotch tape.

Ron "Where's that bonding strip?" Wanttaja

[L16 Pilot]

If it's Superflite the manual has a pretty good section on fabric repair. Basically sand around the hole into the primer and glue the patch with U500 glue. I've never had one come loose.