Penthouse Roof Repair (Do I need gelcoat?)

[geoffff]

The fiberglass penthouse roof on my new old van is pretty weathered. It's covered in hundreds of hairline cracks, and there are a couple tiny spots where the gelcoat is completely gone. At some point someone covered it with some kind of liner material that is now cracked and coming off.

I've done a bunch of reading this evening about repairing penthouse fiberglass roofs here on the forum, and am forming a plan of attack. What does this sound like...?

• sand down the paint and clearcoat until the cracks are all gone
• cover small fiberglass holes with epoxy putty. Marine Tex, perhaps?
• roll on Flex Seal over entire top

Do I really need to put gelcoat on before adding flex seal? I read that gelcoat is purely cosmetic. I don't care what the top looks like to passing birds.






Thanks for any advice from your experience!

 

[doublevan2]

I'm not an expert here - but my feeling is "something" needs to fill in gaps and cracks - or any rhino liner or other finish is gonna crack again - just like our county road patches done poorly. Sand all gelcoat off - prime, etc. Thinking epoxy the cracks and holes with fiberglass then sand, and prime, etc. Forseeing all the bouncing around and van flex when off roading just encourages more cracks. Gotta have a good base or you're just throwing good money after bad.

 

[Twoxentrix]

I have to dismiss myself from being an expert as well, but seeing that you're in Seattle you may consider reaching out to a couple Marine shops...may find someone that would/could give you a reasonable price to restore your top. after all, they deal with more fiberglass repair/restoration (and have the tools & considerably more experience) than any other type of auto body shop. At the very least, they'll be able to provide some professional advise (especially since your initial plan includes removing all the gelcoat).

 

[Tadias]

The coating that was placed by former owners is a bit of a problem. It’s probably covering problems in the gel coating and fiberglass and wasn’t the best solution to begin with. What are the chances of getting that off? So I lived on a sailboat for many years and agree with the above post about finding someone who does those repairs routinely. I did all of my own fiberglass work though and if you want to just repair the spots as they come up and you’re not too worried about the gel coat look you could just get a product like west system and I would recommend the 407 filler. Take up the cracked/loose gel coat. Deep scratch the finer cracks you want to fix. Clean well (acetone) use west system w filler, fair and sand, spray paint (unless you plan to take off all the textured coating, gel coating doesn’t make sense to me) and recover w the textured coating if you want a more consistent look. I’d take all that coating off and fix,fair and gel coat personally but that’s me.

 

[geoffff]

Hi, thanks for that info! I will look up those products

I do plan on completely removing the painted on coating. It's not adhering very well, so it needs to come off.

Mostly I am wondering if I sand out the cracks in the gel coat, do I need to reapply gel coat? I read that gel coat is just cosmetic.

I don't want or need the gel coat look. I just want something sturdy protecting the fiberglass.

 

[N147JK]

Mostly I am wondering if I sand out the cracks in the gel coat, do I need to reapply gel coat? I read that gel coat is just cosmetic.

Short answer is "no".. you don't have to use gelcoat. No gelcoat expert here, but I believe gelcoat must be sealed off from the air in order to properly cure, which would be a real hassle for you at home. Easier to just get some decent epoxy and add a thickener as Tadias describes, and just fill spot the voids/defects. No need for paint, unless you want to. The cured epoxy will be just as durable (maybe more so) than the original gelcoat.

 

[gahamby]

The cured epoxy will be just as durable (maybe more so) than the original gelcoat.

Epoxy will not stand up to sunlight. The UV will degrade it. Clean all that bed liner crap off. Grind out all the places the gelcoat has delaminated. Clean the areas with acetone. Get some Evercoat Gel Coat paste and matching pigment. Fair out all the bad spots. That will get you by. Reapplying gel coat is a professional's job. The thing about gelcoat that's been properly mixed and applied is that it doesn't adsorb water like laminating resin. It will buff out real nice. Priming with epoxy and painting with linear poly urethane like Imron, All Grip or Interthane is best and most expensive solution. Again the provence of a professional unless you have experience with such projects. Any structural faults in the roof like saturated wood coring or unreinforced fastener penetrations need to be addressed or you'll just get more cracks.
Good luck with it. GH

 

[geoffff]

OK, this is what I am thinking as my plan moving forward:

• Sand off the current coating
• Sand out the cracks and divots
• Fill these with Marine Epoxy (Marine-Tex?)
• Sand everything smooth
• Paint with Durabak-18 roll-on textured bedliner

Epoxy itself isn't UV-safe, but the Durabak-18 bedliner is, and so should protect it.

I spent some time reading about various traditional RV roof products out there, including:

• liquid rubber EPDM (Liquid Roof): way too soft - I would rip it driving in the trees
• acrylic (Dicor/Heng's): still likely not scratch-resistant to tree branches
• flex-seal: soft
• silicone (GacoMobileRoof): slippery, and doesn't allow for touch-up later

Then I started researching bedliners. Of all the bedliners out there, why am I now thinking Durabak-18?

• I want something UV-safe
• I want roll-on application
• I want something walk-on-it strong, and scratch resistant for tree branches.

I see Raptor Liner is popular here, but I read it sadly isn't UV-resistant without an additional coat of RAPTOR UV Protective Clear Coat. Not necessarily a dealbreaker...

Then I watched this Project Farm guy on Youtube who tests lots of products himself. Great videos! He tested a bunch of bedliner materials, and while Raptor Liner did well, Durabak and Herculiner did the best. And turns out Herculiner isn't UV-safe either.

Only disadvantage of Durabak-18 is the price: $140/gallon. A gallon covers 60 sqft with 2 coats. (My roof is about 60 sqft.)