Fabric and paint repair

[KeithO]

I've just purchased a 1982 certified pa-18 150. I have it tied down at Paine Field in Everett waiting for floats and at spot at Kenmore on Lake Washington.

There are some cracks in the finish and on the top of the wings there is some rib stitching showing through the tape in 12 places or so.
The airplane was recovered in 2005 using Stits PolyFiber and finished in Ditzler Durathane DUHS 8080.

I'd like to keep the water out of the wings, so sealing the rib stitching on the top of the wings is a priority. Is it acceptable to use some type of tape like vinyl or perhaps a water sealing tape such as used on RVs as a short term solution?

Longer term, what's the best way to re-tape the rib stitching and fix the cracks in the Durathane?

[stewartb]

Brush some Poly Spray (silver) into the cracks and exposed laces. It’ll look like Frankenstein but it’ll prevent UV destroying the fabric. You may have some success light sanding and adding a color topcoat but old urethane will be difficult. Top coat or not you need the silver.

[Steve Pierce]

I have seen vinyl tape used as a temporary repair. At least brush some Poly-Spray on the exposed fabric like Stewart posted. Stewart system is approved to repair over the urethane paint. I have made patches out of the fabric cut out of the inspection panels and glued over spots with Stewarts glue which has no solvents so it doesn't blister the paint. My daughter is repairing a Sport Cub that went through a barb wire fence. We have a whole wing of donor painted fabric to make patches from. I will post some pictures when I get to the hangar.

[Steve Pierce]

[KeithO]

Thanks everyone for the information. Here is a summary of what I understand as the repair process based on the responses:

- "sunlight proof" vinyl or duct tape is acceptable as a temporary repair.

- Permanently repair as follows:
1) Carefully remove any temporary tape and clean up adhesive
2) Lightly sand repair area. Avoid sanding damage to rib stitching
3) Use silver Poly Spray to cover stitching and any exposed fabric
4) Apply pre-shrunk finishing tape with EkoBond
5) Apply white topcoat that is compatible with existing urethane

Is the procedure above correct?

[Bearhawk Builder]

If you're using Stewarts to make the repair, use their manual. There is an approved process.

[RaisedByWolves]

If you're using Stewarts to make the repair, use their manual. There is an approved process.

Have you ever seen the paint detach from the ecobond? Forming a bubble? I wouldn’t have thought the paint was that strong, but it is.


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[stewartb]

Thanks everyone for the information. Here is a summary of what I understand as the repair process based on the responses:

- "sunlight proof" vinyl or duct tape is acceptable as a temporary repair.

- Permanently repair as follows:
1) Carefully remove any temporary tape and clean up adhesive
2) Lightly sand repair area. Avoid sanding damage to rib stitching
3) Use silver Poly Spray to cover stitching and any exposed fabric
4) Apply pre-shrunk finishing tape with EkoBond
5) Apply white topcoat that is compatible with existing urethane

Is the procedure above correct?

Clean it up and carefully pick off any loose or flaking paint. I’d probably use a little rejuvenator to soften up the undercoatings, dab in some Polyspray, and cover with a close matching top coat to hide it as best I could. No tapes, just cover any exposed stitches and cracks in the coating. Talk to your mechanic about it.

[bob turner]

Well past the statute of limitations: we had a taildragger that had been shot with a thick coat of automobile type catalyzed paint. There were cracks at almost every single rib stitch (well, pop rivet). It was awful.

We needed that airplane in one piece - I scuffed it up really quickly, glued 4” pinked tape over all the ribs with Eko-Bond, then brushed four coats of Eko-Fill for UV protection. I might have spent a total of three hours doing that. Parked it outside. Six months later all was ok, although the thing looked like a zebra.

Then one afternoon I got tired of the zebra look, and shot some junk Butyrate on all the stripes. That made it look lots better. The Butyrate was not in conformance with the STC, but it worked. It stayed outside for another year with no ill effects. One mechanic suggested that the Butyrate could be considered a minor alteration. One could hope. . .

[Marty57]

Thanks everyone for the information. Here is a summary of what I understand as the repair process based on the responses:

- "sunlight proof" vinyl or duct tape is acceptable as a temporary repair.

- Permanently repair as follows:
1) Carefully remove any temporary tape and clean up adhesive
2) Lightly sand repair area. Avoid sanding damage to rib stitching
3) Use silver Poly Spray to cover stitching and any exposed fabric
4) Apply pre-shrunk finishing tape with EkoBond
5) Apply white topcoat that is compatible with existing urethane

Is the procedure above correct?

Hi Keith,
The process of a repair using Stewart Systems is pretty close to what you outlined but a couple differences. I go over repairs as part of the covering and painting seminars I do for SS.

When repairing a surface not covered and painted in SS:

1. Clean and sand the repair area down to the silver. Draw out the area you will be covering with a patch so you don't sand a bigger than necessary area. Be careful not to fuzz the fabric.

2. Cut your patch to match the area you sanded. Apply glue to the area where the patch will be applied and lay in the patch to the wet EkoBond glue in the same manner as applying a doily over an inspection ring. Make sure to get the glue a little (1/8") past the pinked edges of your patch. Work our bubbles with a paper towel to get the patch nice and flat. Apply full strength EkoBond glue over the entire patch, wiping the excess off the patch with a paper towel. When the glue has set for an hour or so, any remaining wrinkles or bubbles under the patch can be flattened out using your iron set at about 240 degrees. Don't use high heat as it will shrink your patch some and your nice round patch will change shape.

3. Let it dry; I like overnight but 3-4 hours would be ok. Apply EkoFill over the patch area. You will need three coats, let it dry between coats. This can easily be done with a foam brush. I like to sand between each coat so it's as smooth as possible. If the sanding produces balls rather than normal sanding "dust" the EkoFill is too wet to sand and needs a little more time.

4. After the EkoFill is dry, paint patch with EkoPrime as it is easy to sand and gives a really nice surface finish. White primer gives it a nice background color for your top coat. The primer is not necessary for the repair but I like the application and finish. EkoPrime can be top coated an hour after application.

5. If this is a minor repair (less than the area of two ribs) you can legally topcoat with whatever is currently on the aircraft. If it is a major repair, the topcoat needs to be EkoPoly Premium from Stewart Systems.

The difference from your outline is not using Polytone in the repair itself; the systems should not be mixed, same with a full covering.

Repairing a surface painted with EkoPoly Premium:

1. Scuff sand the topcoat area that will be repaired with 320 grit sandpaper; draw out the area first.

2. Glue patch on same as above step #2 (just like a doily).

3. Apply three coats of EkoFill

4. Paint with EkoPoly Premium

When I teach fabric work, I recommend that guys make a couple test panels out of 1" x 2"'s and cover and go through all the steps. Paint one panel for every mistake you can think of; too close, too far, to slow, too fast, make a run or a sag. Paint the second for perfection. The perfect one can be cut from the panel and rolled up and stored for pre painted patches should a repair be needed. You can then simply cut a painted patch, and glue it in place; perfect for those little rock holes out in the field. I would then catalyze a little paint when back home and with a small 1/4" brush, paint the pinked edges of the patch so it is tight to the surrounding areas paint around the patch.

Pretty simple and nice that Stewart Systems is STC'd to repair any paint and covering system.

Marty57