So I went to some local supply stores today to see what base/clear I could get locally. I have such a large job to do I don't know how much paint I'll need and I figure a local supply would be best, since it might be as little as 2.5 gal or as much as 4, maybe even a little more. Since I'm working in sections (the RV has nice large natural divides on the panels and such) I can dial in on the amount of paint after doing one side.

I'm shooting a Class A RV. I was only going to shoot the painted areas on it until I found thermal cracks in the gelcoat when I removed the dark decals. Long story... but the short of it is I am sanding those out and they are coming out without removing much. I know I will have to spot primer those with high build and block, but the everything else in good shape, I don't have other repairs to do - everything is nice and straight and not pitted.

The gelcoat is in good shape (omitting the cracks I'm removing), the plastic doors and paint are in great shape. The only thing that is not in good shape in the original metallic tan paint on the basement area, much of the clear has delam'd but the paint is still there. That is going to be replaced with solid tan and the white fiberglass is going to be shot white.

Store 1 told me to sand and urethane primer everything with high build, then sand the primer and shoot. Said the primer will act as a sealer, so no sealer coat.
Store 2 told me to epoxy spot primer the spots I sanded the cracks out, sand the whole thing, shoot an extra coat of base on those spots, flash and then coat everything. No sealer.
Store 3 told to me spot primer the spots I sanded out (no mention of type of primer and I forgot to ask), sand everything and spray. No sealer.

I've painted smaller jobs and never got too worked up about the type of primer or learning about sealer because they were small paint overs and didn't need to last outdoors. Since I'll be investing so much into the materials (probably 4 gallons!) on this I want to make sure it is done right... but on the flip side since it is such a large area I don't want to do a bunch of extra work just for overkill and have to sand all that primer if I don't need to. The key here is I'm not trying to so much to have a visually perfect paint job by any means, just one that holds up well. The look is of little consequence compared to reasonable longevity.

So I've been researching like crazy trying to get the best answers and here is what I was able to piece together.

I can probably get away with scuffing up the gelcoat and have the paint hold since they seem to do that a lot with boats and paint direct on gelcoat. But I also have a little plastic and aluminum, some is still good paint some not... but nothing is bare metal or anything.. but I don't know if that will hold up with just sanding the paint a little like I would normally do for a quick part I'm painting.

It sounds like if I want insurance I should primer the whole thing. I wanted to do epoxy primer, one shop said urethane. My research suggests epoxy is superior for my application, so that is one point of contention.

Until now I had never ever known what a sealer was and that you should use one. After learning that a epoxy sealer is just reduced epoxy primer and you can shoot base on it in the curing window without sanding it got me thinking...

One, what is the point of sealer (from sealing stuff off) if it is the exact same thing as the primer? How would it be any different that two coats of primer in terms of sealing bleed through or something... unless it creates a chemical bond with the paint of something because it is applied with curing and that helps?

But more importantly why can't I just epoxy spot primer the spots I sanded the cracks out of to build the surface up and block it, then scuff (sand with 400) the entire RV (gelcoat and the faded and good paint) and then shoot it with sealer (reduced epoxy), then spray base? Will the epoxy not provide extra adhesion when used as a sealer as opposed to a cured a primer?

My logic was, from the way I understand it, is there is no difference between epoxy primer and epoxy sealer besides the flow... so the adhesion benefits and such should be the same, but it will save me from having to sand the epoxy when it shot as a "primer". Perhaps the coating won't be a thick unless I apply it multiple times?

Is that viable or should I just resign myself primering and sanding the whole thing and then spraying base... or should I take the advice I got from the stores and just paint directly over scuffed paint and gelcoat without primer and still probably get similar adhesion?

Thanks

I forgot to ask... any options on Advantage base/clear? Surprisingly, these 3 big shops were rather sparse in the selection of paint systems.

2 of them were pushing Advantage as their mid-line "best value" paint system. One place was pushing mid-tier Matrix that was twice as much as the Advantage but they also just started selling Metalux and said they had good feedback. It was a something like $170/gal though compared to I think $120 or so for the Advantage.

I did a bunch of research and was really hoping to find U-Tech since it seemed like the best paint for the money based on feedback online, followed up by the like of Nason and Prospray, but they didn't carry that either.

If it were mine, I would scuff everything, shoot one coat of reduced epoxy primer, wait about an hour and look things over. If everything is locked down (no blistering, wrinkling, etc.) and you are happy with how it looks, mix up your base and spray your color.

The problem with low end or shop line paints is coverage. Yes they are appealing due to the low prices but you may end up shooting extra coats to get coverage. Also, many of them mix 2:1 rather than 1:1 so you end up with less Ready To Spray (RTS) paint.

You can order ProSpray and have it shipped to you. PM me if you want contact info.
I would also suggest you look into Wanda base as it gets great reviews and covers well. It is also relatively inexpensive.

Look into a Euro Clear coat for hardness and longevity. I would plan on 3 coats of base and 3 coats of clear.

here is just one more opinion for you. spot prime your spots you sanded the cracks out of with epoxy and block these areas until flat. sand the rest of the m/h then shoot epoxy as a sealer. then why don't you use s.s. urethane for the color? I just did the basement area of a 40' m/h. used s.s. for the color, 3 times around and i'm done. with b/c its 3 times around for the color then 3 times around for the clear. the difference between primer and sealer, is that the primer is thicker so you get more build and it usually doesn't go on real smooth. as a sealer its reduced so it goes on thinner and lays out nice and flat. and the sealer bonds just as good as the primer.
Jay D.

Thank for you the replies, great info.

About the SS... I thought about it and that was originally going to be the plan because it was cheaper and easier. The main reason for going with B/C is because I was going to make it two tone, and not just a clean break between the basement and the main fiberglass body.

I was going to do a couple simple swooshes to help make it a little more modern like the newer rigs. I was afraid with it being all white except the basement it would look like a fleet bus or something, and nothing wrong with that but I figured if I'm putting the time and money into it I might as well see if I can make it spiffy.

But without clearing over it I did't see how I would be able to two tone it like that with SS without having a lip where the second color was. Not that a lip is the end of the world, it just seemed like it a B/C would be better for that. What I really was originally planning to do was SS the whole thing in white, let cure, scuff, mask the 2nd color, shoot it and then clear the whole thing.

I just thought that was too much sqft to want to scuff a second time and it could be easier to miss a nook or not get spot good enough and if I got poor adhesion it could start a premature failure. That is why I had switched to just working on one section at time at all the way through since it seemed like too much work for me to shoot and setup the 2nd color all by myself in the recoat window. I'm sure I could do it, I would just feel better about having the luxury to do it over a few days. I was going to do one side on day 1, the other on day 2, and then do the front and rear caps on day 3.

Since I'm shooting outside I am building a little structure that will shield the side of it in plastic so I can shoot without as much trash collecting on it.

Pictures would be nice for these nice genital men

So here is what this thing looks like right now. Sorry for the poor pics, the sun was in front of me.



This is not the actual design that will be used, it is just to give an idea of more of the volume and general locations of what areas will be painted white and what areas will be painted tan. It is the best I could quickly work up in the paint program on my PC to help visualize.



I have this mud crack type of cracking in the gelcoat that I have sanded down to the point where you can still see a few hairline cracks but they cannot be felt. It looks like when a egg shell shows hairline fractures but not actually cracked. I am going to epoxy prime and block those spots.



Since I'm not going to be blocking the whole thing be any stretch, just where the repairs were done, I'm thinking it would be easiest to not prime the whole thing and only shoot reduced epoxy as a sealer, let it cure for an hour and shoot paint. I'm not sure about the coats though... on ********** it mentions to only use 1 coat for sealer, but then it also says two can be used. I'd probably like to hit it with two coats of sealer depending on how much it is reduced, but not sure if that is OK.

Now that SS paint was brought up again and I'm getting to the point I need to order paint within the next few days I'm conflicted if I should go for a SS now instead of B/C. It will be cheaper and quicker, but on the flip side I'll have a lot of time invested in this project that I feel like I want to try to get the paint to last as long as possible and I'm not sure how well the SS will hold up against a B/C over the long haul.

So many way to skin a cat and the various pros/cons still have me indecisive about this.

You need to do more to your cracked areas than just sand it smooth.The only way to repair them is to go down to fiberglass possibly add a layer,then reapply gelcoat or polyester spray filler like slick sand.If you just sand them and apply primer they will be back in no time flat just so you know.

Thanks for the reply. The problem is the gelcoat is pretty thin on these panels compared to a boats gelcoat and the cracking originated due to faulty panels. There was a flaw/defect in the process of the Corning panels for a few years and one of those years is when my RV was manufactured. This caused the panels to show this checking/crazing when they were exposed to extreme heat due to dark decals or paint absorbing so much heat from the sun. My cracks only occur where are dark decal was located.

I have ground the gelcoat all the way down in one spot and found the glass to show crazing that looks similar to the cracks in gelcoat, just not opened up like the gelcoat was. The glass doesn't actually have exposed cracks, but you can see where the stresses are, there is staining where the decals bled through into the micro fracture.

I have been told from a few sources the only way to prevent the cracks from reappearing with 100% certainty is to have the faulty panels replaced. I can't really put a layer of glass without cutting out the original glass and I just don't think I have it in me to tackle that right now. Replacing the whole panels is out of the question for this RV right now unless I can find them much cheaper than I have been quoted.

There is a place that is repairing and repainting the panels and so far are holding up from what some other RV owners who have been down this have told me. I couldn't get all the details, but it essentially involved removing the thin gelcoat and building it back up with epoxy. I don't think they were removing any glass from what the people who had it done recall about the process.

From what I understand epoxy is superior in this application because it is stronger and has stronger adhesion to the substrate so it has a better chance of resisting the expansion / contraction cycles.

I have also learned from someone who already had full body paint and just had the surface sanded, filled and sprayed over that the cracks did return to varying degrees over a year or two, but only in the areas where they kept the dark paint. The areas painted white did not reopen since they weren't getting all that heat expansion that causes so much movement in the material.

Since these are not stress cracks in the mechanical sense, and only from thermal expansion, my hope is be keeping all the glass white or a very light tan (or light grey) I can avoid imparting the stress that caused them, and hopefully prevent them from happening again.

Ok then I hope it works out for you.Our shop has done fiberglass repairs on semis,vettes,many motorhomes and 5th wheels and that has been our experience.If you try to bury it with primer it always comes back.