Blister repair

[Dirtyfrank]

Hello All,
New to the forum. Just joined to seek advice on DIY repairs on the pitting in my fiberglass. I’ve been researching for days, but every time I find a thread discussing this problem, it stops short of specific recommendations. Please see the pictures below. I believe the underlying issue is the much discussed “bad batch” fiberglass issue from the manufacturer given the age. Not the osmotic blister hypothesis that’s found on boats. These blisters are dry, and furthermore my RV has not been submerged that I know of. I have seen multiple reports that this will be an issue that I will have to chase as long as I own the coach. I’m not replacing the entire panel of fiberglass, nor do I want to take it to a professional given the age and value of the coach, so I’m looking for recommendations on what I can do to give me the most amount of time between repairs. I plan to get as many of the half open chips removed as I can to start. But then, do you think I should try skim-coat something in to fill the chips? Or should I just skip that step and repaint to mask the problem as much as possible. I’ve read some opinions that whatever you fill the chips with will likely pop out again soon. Any advice on specific fillers or paint? Or any useful threads on this topic that I couldn’t find? Thanks .

[Dirtyfrank]

Sorry, thought I specified my coach in my profile. 2003 Brave 36M.

[Wetstuff]

I'm a little surprised nobody picked up on this Frank... Mine is the same parentage, 2002 vintage, but there is not a single similar blister like in your photo. Mine are more like large area water blisters midships. I have an idea about re-laminating the skin but have too many projects.

I saw a really interesting thing in one of my aviation magazines where they made an easy-to-work laminating glue with Gorilla Glue and S-W shrink-free spackle. Easy, compared to sanding traditional epoxy fill.

I would think that would glom onto the fibers I see in the recesses. Then find yourself a small sign shop and let them skin the surface with vinyl. If you are really handy - it may be a new skill you want Youtube to teach you.

Jim

[Dirtyfrank]

Thanks for chiming in Jim! It’s not exactly a common issue with rigs this age, but common enough to find some older discussions online. Relaminating some new filon might be the way I go. But it would involve some pretty heavy duty adhesive that only gives you one shot at placement. Which scares me a bit on something this big. I may just commit to painting every few years too since it’s a fairly easy panel to paint.

[Wetstuff]

Agree, I work alone and I typically 'build' helpers. There some resins that are slow-cure so the dwell time is manageable, but if you can avoid large destruction before construction, that's what I would do. I am a happy painter. Good luck.

Jim

[Dirtyfrank]

Thanks Jim!

[carlwatson]

Your problem can be permanently repaired using fiberglass reenforced Bondo. Of course you will need to repaint, which your planning on any way. If your interested send me a message and I will walk you through it.

[carlwatson]

Grind the gel coat . Wash with vinegar then soap and water then apply the Bondo. Sand prime and paint.

[thataway4]

My expertise is with boating osmotic blistering--although some boats have had similar issues above the waterline. I consider traditional repair to be best: Clean blisters, lightly grind with carbide dye grinder, and then fill with epoxy/medium density filler. Fair with pneumatic file or long boards and sandpaper. Then epoxy primer, and finally 2 part Lineal Polyurethane paint, which should be good for at least a dozen years. Probably longer with clear coat.

The vinyl wrap may well be a more practical suggestion. I am not all that keen on "bond"--but it is used extensively in automotive repair...

[NeilV]

Originally Posted by thataway4

My expertise is with boating osmotic blistering--although some boats have had similar issues above the waterline. I consider traditional repair to be best: Clean blisters, lightly grind with carbide dye grinder, and then fill with epoxy/medium density filler. Fair with pneumatic file or long boards and sandpaper. Then epoxy primer, and finally 2 part Lineal Polyurethane paint, which should be good for at least a dozen years. Probably longer with clear coat.

The vinyl wrap may well be a more practical suggestion. I am not all that keen on "bond"--but it is used extensively in automotive repair...

I would also be inclined to go with a more traditional Marine type Fairing Compound or Gel-Putty instead of a Talcum Powder or Gypsum based Automotive Bondo type Product. If you get a good match you may get away with wet sanding and compounding the Gel-Putty to make it blend without painting it if its just that one corner and not a much larger area.

[Dirtyfrank]

Originally Posted by carlwatson

Grind the gel coat . Wash with vinegar then soap and water then apply the Bondo. Sand prime and paint.

Thanks Carl. Still unsure if we want try to fabricate a new panel to bond overtop, or fill and paint. Though I am personally leaning full and paint, worried that bonding a new panel that size (or even splitting it into 2) might be difficult to get right.

[bruce Dixon]

This caused by moisture being absorbed into the Gel coat. Gel coat is not resistant to moisture. all those microscopic cracks you see are allowing moisture in. the black you see is mildew/mold. is your vehicle worst on the north or south side where it is parked or stored. it's going to be a hard process to fix all the current blisters are going to have ground out and filled sanded done and repainted or sand the whole panel down and vinyl wrap it. heat, moisture, freezing, and Age cause this. You can order a new panel from winnie but than can be expensive. I don't believe there is any way of stopping it just slowing it down. cover up motor home or trailer when not in use protect from UV rain moisture, freeziing.

[carlwatson]

Originally Posted by Dirtyfrank

Thanks Carl. Still unsure if we want try to fabricate a new panel to bond overtop, or fill and paint. Though I am personally leaning full and paint, worried that bonding a new panel that size (or even splitting it into 2) might be difficult to get right.

I say there are people here that have doubts about fiberglass reinforced Bondo which just happens to be 100% waterproof once it's hardened and the filaments that are in it are fiberglass just as in fiberglass roving I've used it on both aluminum and fiberglass bass boats that run 70 miles an hour above and below water line and haven't had a failure yet the stuff is great everybody has their opinion and they're entitled to it but this is fact. The reason for the vinegar wash down and dry out is to kill off the mold. Some people use ammonia that also works black mold is a real problem

[Dirtyfrank]

Originally Posted by thataway4

My expertise is with boating osmotic blistering--although some boats have had similar issues above the waterline. I consider traditional repair to be best: Clean blisters, lightly grind with carbide dye grinder, and then fill with epoxy/medium density filler. Fair with pneumatic file or long boards and sandpaper. Then epoxy primer, and finally 2 part Lineal Polyurethane paint, which should be good for at least a dozen years. Probably longer with clear coat.

The vinyl wrap may well be a more practical suggestion. I am not all that keen on "bond"--but it is used extensively in automotive repair...

We discussed a wrap. But unless the blistering is stopped, they won’t warrant the wrap. Plus it would likely be more than we want to spend.

[Dirtyfrank]

The problem is all the way around the edges. Too many to drill and fill each one, so I’m leaning towards something that can sand off the gelcoat in a reasonable amount of time (belt sander maybe) to get down to bare fiberglass and then refill with a fiberglass resin or some other type of filler and paint.

[Dirtyfrank]

Sorry for the crumby picture. And why do pictures sometimes turn when I upload?