fiberglass repair and paint questions

jim · #1 08-12-2007, 07:21 PM

Hi,
I am in the process of fitting new fiberglass gear leg and intersection fairings to a flying 6. The cowl is all hinge attachments. The hinges at the bottom of the cowl at the firewall keep breaking so I have decided to use milspec 1/4 turn fasteners there. Before I line up the gear leg fairings I decided I should do the fasteners on the cowl so I can get the best fit possible. I drilled out the hinge from the cowl and now have some holes to fill. I have sanded down the paint and have holes that are up to 3/16 to 1/4 inch diameter to fill. I figured I would glass in a strip of 6 oz cloth to the inside of the cowl and then use microfiber peanut butter paste for the holes and then use a layer of lighter glass on the outside. I am using West Systems epoxy, and figured I would fill with the 403 microfibers, then clamp some wood protected by saran wrap and peel ply to maintain shape. Sound OK??

I have no idea what paint was used on this plane, the primer is the grey/blue looking stuff. I figured I would sand the paint back and try to feather in some primer and paint. The cowl is mostly white. Any suggestions on which paint primer and paint?

Any comments, advice, suggestions from those with experience on these two issues would be appreciated.

Thanks,

jim

RV7Guy · #2 08-12-2007, 08:08 PM

Your repair on the holes sounds fine. I would add, be sure clean thoroughly. I would also add a strip of cloth on the outside as well and blend in with filler 410 micro filler and epoxy.

Regarding the paint, if you have a piece you can take to a auto specialty paint store they might be able to match for you.

jim · #3 08-12-2007, 09:19 PM

Quote:

Originally Posted by RV7Guy

Your repair on the holes sounds fine. I would add, be sure clean thoroughly. I would also add a strip of cloth on the outside as well and blend in with filler 410 micro filler and epoxy.

Regarding the paint, if you have a piece you can take to a auto specialty paint store they might be able to match for you.

Thanks for the reply Darwin, yeah I plan on adding the outside cloth and fair with the 410. As far as cleaning, soapy water or MEK or both?? Any idea what the bluish grey primer may be?

Jim

Scott Will · #4 08-12-2007, 11:04 PM

The primer may be PPG K38. I recently repaired one of my wheel pants and sanded down the primer. It's like you described - bluish, gray.

From the K38 spec sheet:
K 38 is a premium quality 2K primer surfacer for today?s advanced technology finishes. K 38 is a gray, fast drying product which should be used when higher surfacer film builds are required. K 38 offers superior sanding characteristics and excellent gloss holdout. K 38 may also be used as a flexiblized primer surfacer. K 38 can be used over sanded original finishes and/or properly prepared and treated bare steel, aluminum, fiberglass and plastic substrates. K 38 must be mixed with K201 hardener.

jim · #5 08-13-2007, 07:02 AM

Scott,

Thanks for that info, I'll look into the PPG primer.

Jim

DanH · #6 08-13-2007, 12:30 PM

I had a nice chat with a PPG factory rep a few weeks ago. For bare new glass he suggested first spraying DPLF epoxy primer as a tie coat under the K-series urethane primer-fillers. Spray the DPLF and then spray the K as soon as you can, or as he put it, "as soon as you can clean and reload the gun".

I've been experimenting with wiped and squeegeed epoxy methods for sealing glass and eliminating pinholes. I plan a report later, but for now I'd suggest you try it. I've been so impressed with the test parts that I sanded all the DPLF and K36 off a set of wheelpants this weekend so I could start over with an epoxy wipe. The standard K36 spray-sand-cuss-spray-sand cuss method of filling pinholes is history in my shop. It is now reserved for final finishing only.

jim · #7 08-13-2007, 03:41 PM

Dan,

What are you using to wipe the epoxy on? I only have patches of areas to do on the cowl, dont want to sand it all down and start over. Hope I can get a decent looking paint job without having to sand it all off and start over. I also have to touch up the wheel pants some. I may try this wiping method. Would you still use the primer after the wipe?

Thanks,

Jim

logansc · #8 09-28-2007, 10:55 AM

Dan: I am building an F1 Rocket and my hangar mate is building an RV-9. Neither of us has come to the fiberglass finishing point in our projects. Is there a reference you might recommend for us? My empennage, wing, wheel pant, and lower strut fairings are all "mechanically" finished. I'm looking for what to do next. Can you be a little more specific with your suggestion of squeeging on epoxy rather than using one of the more "traditional" methods?

Thanks for your assistance,

Lee...

K?hler · #9 09-28-2007, 11:30 AM

Just to make sure we are all talking about the same thing - I think we're discussing using a squeegy to apply epoxy resin (as opposed to epoxy primer like DPLF which was also mentioned earlier in this thread).

Resins can be applied straight up to properly prepared surface, or mixed with additives like microballoons, cabosil, etc. to make fairing compounds of various viscosities and strengths.

DanH · #10 09-28-2007, 01:38 PM

Starting with bare glass, first sand with 120 or so to remove all the gloss. Working in small sections, use your eyes and fingertips to find all the big pits and open bubbles in the surface, filling each with a dab of epoxy/micro mix. If you spot a thin-skinned bubble just under the surface, go ahead and open it up, then fill it w/micro. Cure and sand; always try to use a block or flexible block, anything to keep the surface flat.

Might need to repeat the process; I always seem to find a few pits I missed. This is also your last chance to correct the shape, cover fasteners, align flanges and seams, whatever.

When you have it looking good, mix a cup of epoxy and grab an ordinary plastic squeegee, the flat plastic kind you find hanging near the Bondo at Bubba's Auto Parts. Slop on some epoxy and start spreading it around, wiping it into the surface with the squeegee as you go. Now squeegee off the excess; scrape off every bit you can.

Wait until that coat tacks up well (not cured, but firm enough that it won't move), then repeat the process again for another coat. The fanatics might do as many as five coats and use very little primer/surfacer later in the process. Two coats will get most of the pinholes. Three coats of West worked well for me, resulting in perhaps one pinhole in three square feet.

Let it cure a day or two, then block sand with 120, just enough to remove the squeegee marks. They won't be deep if you were doing a good job of squeeging off the excess resin. Do not sand through the resin layer.

At this point I like to shoot one cross-coat of epoxy primer for a surface check. It is amazing what you can see the first time you shoot a solid color. If you find a big pit or something, scuff off the primer (but not the resin coat) and fill it with micro. If all you find is a few scattered pinholes, wipe'em with any old spot putty, right over the epoxy primer, and sand it off.

PPG DPLF epoxy primer has a 7 day respray window. After that you gotta wet sand (little too gummy to sand dry), clean, then respray more primer, then shoot your K36/K38. The PPG guy told me to spray the K over the primer as soon as possible, apparently what painters call wet-on-wet application. The primer isn't really wet of course. It flashes off in a 1/2 hour or less.

I've been allowing the first prime coat to cure, then wet-sanding with 320 or 400 to get a slick finish. Later, when I'm set up for real painting, I'll shoot light coats of primer and K36 per the previous paragraph, do some final fine sanding, and shoot color.

The above beats any other method I've tried, including Smooth Prime and repeated spray-on, sand off K36 applications. The epoxy wipe kills pinholes at the root.