epoxy and FG questions for redneck truck camper

[MudFlap]

Hello. New member here. Brief "build" thread here: http://www.tnttt.com/viewtopic.php?f=50&t=72813

Just about ready to epoxy and FG the exterior of the camper.

I have no experience with epoxy or FG!

I've spent quite a bit of time reading other threads on this forum and have gathered enough information (and confidence) to convince myself that I. can. do. this.

I've ordered up (but not received) a some Raka 127 thin epoxy and 350 non-blush hardner, plus some 30" 4oz cloth & 3" 6oz tape.

Plan is to:

1. epoxy all surfaces
2. glass seams
3. cloth + epoxy all surfaces
4. glass corners
5. recoat all surfaces a time or two
6. prime and paint

Lots of questions. Most of my questions deal with applying epoxy to these large, flat surfaces (several are ~100 ft^2).

I know that after applying epoxy, it will soon start to cure and become "soft and sticky". At this point, it is recommended to leave it alone until it becomes "hard and sticky". At this point, it can be re-coated. If left to cure too long, it will become "hard and not-sticky". At this point, a re-coat is not possible unless sanded to allow a mechanical instead of chemical bond to previous layer.

What should my strategy be in laying down epoxy on the large sides and top? I'm wondering if I put down a strip of epoxy (and perhaps FG), it might have set up enough by the time I finish one strip that I won't be able to do a second strip due to the need to overlap the two strips.

If I work across the short side, maybe I'll be fast enough to put down second strip before 1st strip gets sticky? I will be rolling the epoxy on with 6" roller.

Or should I just punt, work length-wise and just plan for one strip per session? If I want to keep working, I can move to another side of camper...

[Tom&Shelly]

Hi! We were in the same position, never having used epoxy before, at the start of our build. Long thread

http://www.tnttt.com/viewtopic.php?f=50&t=70278

but if you scroll through, I tried to relate our experience, and some of our questions which led to interesting discussions by experienced users in this forum. Some of the discussion will be a year or more apart, as we did the walls horizontally before erecting them, then later did our roof, including the vertical front.

We also use Raka 127/350 and discovered curing time is much longer at temperatures in the 60's (hours to days) than in the high 70's and low 80's (tens of minutes). We found this out trying to use it in our non-climate controlled garage. (We later bought an electric heater for that reason--so we could work in the Winter.) If you have an air conditioned garage, you can use that to your advantage to control conditions. (I assume you are in heat right now, there in Texas.)

Also, when it is warm, the epoxy kicks much faster in the pot than on the surface. As it cures, it generates internal heat and the concentration in the pot holds the heat in. (I think there will be some photos in our build folder showing it curing yellow when left in the "pot" which is a translucent beer cup. The yellow occurs because it cured hot.)

As you have no doubt seen, lots of differing opinions about ways to apply the epoxy. Probably most work. While we felt a little intimidated at first, I think now either Shelly or I would be very comfortable taking on most projects with glass and epoxy. Just experience; most of our fears never materialized.

Good luck!

Tom

[Tom&Shelly]

Oh ya--also, once the epoxy cured with a glossy surface, I spent days wet sanding it by hand which I was fine with. Seems to be a minority opinion, however, and some here have chided me in a friendly manner--I believe the term was "neanderthal".

You will probably opt for a solution aided by power tools...

To directly answer your question (finally): Given that indication of my building methods, I'd opt for the slower, and more controlled, approach. Shelly's and my experience, and everything we've read, is that there really is no practical difference between getting a good chemical bond between layers of epoxy, and letting a layer cure fully, sanding, and only getting a mechanical bond.

When we do horizontal flat surfaces, our preferred technique is to coat the wood with epoxy, let it cure, sand lightly, then carefully lay out the glass, smoothing any folds. We then coat the epoxy, and come back after it is not too sticky (about a day at 72 deg) and add on more coats. We've done three coats on top of the coated epoxy, to build it up, usually trying to do each coat within a day of the last. Then we let it cure a few days, and I sand. Usually, I'll wish we'd done another coat before the sanding step, but, in the end, we had a perfect teardrop by the time the primer dried.

Tom

[MudFlap]

Hi! We were in the same position, never having used epoxy before, at the start of our build. Long thread

http://www.tnttt.com/viewtopic.php?f=50&t=70278

but if you scroll through, I tried to relate our experience, and some of our questions which led to interesting discussions by experienced users in this forum. Some of the discussion will be a year or more apart, as we did the walls horizontally before erecting them, then later did our roof, including the vertical front.

Wow, what a great job on your TD build, Tom. Very nice.

Here's a small/easy question that one session of experimenting will surely answer for me, but I'll ask anyway:

If you're covering a large area that requires several batches of epoxy to be mixed and applied, how often (if at all) do you change out roller covers/brushes/pan liners/mix buckets?

I would guess that maybe the rollers/brushes/pan can continue to be used across multiple batches, since fresh epoxy is being rotated in/through them over time, but maybe not the buckets since they'll mostly just sit?

While I'm bothering you, how much epoxy did you mix at a time? I bought 16oz mix cups. I think I remember reading that maybe half that is a typical batch size?

Thanks again Tom. Your impressive build thread will continue to keep me busy in the evenings for another few days!

[Pmullen503]

Get the pumps for your epoxy, they are worth every penny. The pumps make it easier to accurately mix smaller batches which is really important if your epoxy has a short working time at the temp you are using it.

If you are using several small batches of epoxy rather that a large batch, then a roller will generally make it through a long covering session. But you must always have several spares. Things happen; you drop it on the floor and it gets dirty, starts to fall apart or the epoxy starts to set up in it, etc. That goes for the rest of the disposables.

[Aguyfromohio]

That's good advice above, use the metered pumps and mix small batches.

It's surprising how fast a larger batch of epoxy can heat up and run away, turning a slow cure into a fast cure.
Last month I bought some West Marine epoxy with their slow hardener (206) and filler (406, then 405) to do some sealing and fairing.
After a couple small batches worked great, I got impatient made a triple batch. Bad move. It got very hot and kicked over in just a couple minutes so I had to throw it away.

I went back to small batches and it was back to a nice slow 20 minute pot life, plenty of working time.

[Tom&Shelly]

Hi! We were in the same position, never having used epoxy before, at the start of our build. Long thread

http://www.tnttt.com/viewtopic.php?f=50&t=70278

but if you scroll through, I tried to relate our experience, and some of our questions which led to interesting discussions by experienced users in this forum. Some of the discussion will be a year or more apart, as we did the walls horizontally before erecting them, then later did our roof, including the vertical front.

Wow, what a great job on your TD build, Tom. Very nice.

Here's a small/easy question that one session of experimenting will surely answer for me, but I'll ask anyway:

If you're covering a large area that requires several batches of epoxy to be mixed and applied, how often (if at all) do you change out roller covers/brushes/pan liners/mix buckets?

I would guess that maybe the rollers/brushes/pan can continue to be used across multiple batches, since fresh epoxy is being rotated in/through them over time, but maybe not the buckets since they'll mostly just sit?

While I'm bothering you, how much epoxy did you mix at a time? I bought 16oz mix cups. I think I remember reading that maybe half that is a typical batch size?

Thanks again Tom. Your impressive build thread will continue to keep me busy in the evenings for another few days!

We use the pumps, but use calibrated beer cups to set the mix ratios (see about a third of the way down the page)

http://www.michneboat.com/Fiberglassing%20-%20101.htm

After some experience, we only mix about 4 oz at a time. Shelly and I do this together, one mixing while the other applies. After pouring in the right amounts in the beer cup (and don't forget the inner cup!) We then stir for 2 minutes. For horizontal surfaces, we just pour a little from the cup right on the surface. We used the plastic lids of macaroni salad containers as disposable roller pans for the vertical surfaces. After the epoxy dried, it cracked right out after bending, and we could use the lids a few times before they broke, or we returned them to their original job (keeping large amounts of bolts in the old containers). I don't recall ever needing more than one roller (white foam worked for us) but as Pmullen says, have a few spares.

Other folks seem to like old credit cards or the like, for spreading.

BTW, we're not very good at this, but it would be a good thing to keep some small (low priority) epoxy jobs handy for after the main jobs, to use up any mixed epoxy. Shelly makes doll house stuff, and so we could always manage to have them ready.

Tom

[pchast]

I've gone so far as to weigh the epoxy and hardener
when using mixes smaller than 1 pump each.
The info is normally available from the manufacturer's
web site.

[MudFlap]

Materials are in, and I'm doing "final" (yeah, right!) sanding. Hope to get started with epoxy/FG soon!

'Nuther question:

The outside of my camper shell has one "inside" corner (behind/above truck cab).

I've rounded all "outside" corners on the camper, and needed to do the same with this "inside" corner. Earlier, I was planning on using PMF, but have since changed my mind and switched to epoxy/FG. So anyway, I used latex caulk to lay in a smooth inside corner in this area. Will that cause any problem with epoxy? I've seen videos where latex caulk is used in a similar manner when using polyester resin, but not sure on epoxy.

If it is a problem, I'll just PMF this corner. I'm actually thinking of PMFing the underside of the "cabover" part of camper for ease of application. Few concerns about water intrusion in this area...

Speaking of PMFing part of camper: I assume that where the two materials meet, it is much better to put PMF over epoxy instead of the other way around. Let me know if I'm off base here...

Thanks.

[OP827]

PMF or latex caulk (which are water based) will generally not stick good to epoxy, so I would avoid that. I guess it is possible to use latex caulk over epoxy and paint epoxy with latex paint, but I'd rather use better quality and compatible materials.

Here are my experience pointers:

For covering large surfaces I covered most of my build large surfaces in close to horizontal position to keep it simple.

I did so-called "dry on dry" method similar to kayaks builds when a dry cloth is put down on dry surface and then I mix quite large amount of epoxy, mix it for minimum one and maximum two minutes and then poor over the the middle or the lamination surface like a long strip and then using plastic or metal ~6" or wider drywall knife carefully (so the cloth does not move) distribute the epoxy over the cloth for good saturation. This way I could mix up to a pint of epoxy at a time. Once I did a few surfaces I developed a feel of how much epoxy a large surface would require. If I did a good job the amount (weight) of epoxy was approximately the same as cloth weight. Initially I used pumps, but later I switched to mixing by weight using kitchen scales as it took less time to measure a bigger amount. Pumps work great when you need to mix a relatively small amount quick and waiting time for pump to spring back is not an issue that eats into epoxy working time in a hot summer day.

I would highly recommend timing the epoxy work so that you can laminate and then when epoxy is still "green" but not longer liquid put the second and then third coat to fill the weave. I pored on a surface from a cup and used putty knife to distribute the mix over the area, it was quicker and easier to clean than a brush. All is needed an even surface since epoxy is 100% solids, therefore this knife tool worked for me quite well.

Curing epoxy to full strength will take some time which depends on brand/type of epoxy and curing temperature.

Hope this helps.

[MudFlap]

Yes, thanks for the great info, OP827.

My question wasn't very clear: I've already caulked this "inside corner" with latex caulk over bare plywood to "round" the corner. Is it OK to apply epoxy over this caulk?

If not, I'll probably just apply epoxy/FG up to the caulk (but stop short) and then when I apply the primer and topcoat paint, I might add a strip of fabric down in this area aka PMF.

[Pmullen503]

Yes, you should apply the epoxy and cloth over your caulk. You want those glass fibers to connect your walls and floor. Even if it doesn't adhere to the caulk itself.

For future reference, you should use thickened epoxy to round those inside corners before you apply the fiberglass.

[MudFlap]

Thanks mucho for the excellent tips. I'll be laying my first coats of epoxy tomorrow!

If I could bother the group with a couple more questions:

1. Is "blush-free" (Raka) hardener really free of blush? No concerns about washing blush if I allow to cure between coats (which I'll generally avoid, but not always). If allowed to cure, plan is to do a light sanding, followed by a thorough vacuuming. Will re-coat before previous coat hardens whenever possible.

2. How paranoid (PPE) do I need to be when sanding? Definitely will wear a mask to avoid breathing in dust. What about preventing epoxy dust on skin? I've seen lots of videos where the latter doesn't seem to be a concern, but then again, you can find plenty of videos with people doing pretty dumb things. =)

Thanks again for the great advice!

[Tom&Shelly]

Thanks mucho for the excellent tips. I'll be laying my first coats of epoxy tomorrow!

If I could bother the group with a couple more questions:

1. Is "blush-free" (Raka) hardener really free of blush? No concerns about washing blush if I allow to cure between coats (which I'll generally avoid, but not always). If allowed to cure, plan is to do a light sanding, followed by a thorough vacuuming. Will re-coat before previous coat hardens whenever possible.

2. How paranoid (PPE) do I need to be when sanding? Definitely will wear a mask to avoid breathing in dust. What about preventing epoxy dust on skin? I've seen lots of videos where the latter doesn't seem to be a concern, but then again, you can find plenty of videos with people doing pretty dumb things. =)

Thanks again for the great advice!

We had a few issues with primer chipping off of some epoxied shelves, and the teardrop floor. It's possible it was due to blush, but I'm not convinced. Since then, we added the step of washing it with warm water and detergent right before I start wet sanding. I guess it's possible there was some blush I didn't see, and instead of wet sanding taking it off it merely spread it around, but I'm pretty skeptical.

I'm really terrible about PPE (covid-19 masks strongly excepted). By wet sanding, I figured there wasn't enough epoxy dust in the air to worry about. If I did a lot of dry sanding, I would wear a dust mask.

I'm not worried about cured epoxy dust on the skin. At that point, it's just chemically inert plastic. The problem with dust in the lungs (as I understand it) is that it tends not to ever leave. I've never been sensitive to uncured epoxy on the skin, and get a little careless*, but I've heard an intolerance can build up through exposure, so generally wear latex gloves.

Of course, better to be safe.

Tom

* Then there was the time I fixed a smashed finger-nail with 5 minute epoxy. While sitting there waiting for it to dry, I read the fine print and first noticed it said to avoid exposure to skin. Oh well!

[OP827]

If you are going to sand cured fiberglass into glass fibers then you need a good respirator and also put a liberate layer of talc (baby powder) on your exposed skin areas to prevent glass fiber irritation, it works great (a tip from Atomic). I would always wash the blush off and only then sand if epoxy cured for more than 12 hours in room temperature unless it was covered with peel ply or equivalent to prevent contract with air moisture.