Skinning your TTT in epoxy and fiberglass

[Oldragbaggers]

Thanks KC. Those are some very kind and reassuring words and I appreciate them very much!!

[48Rob]

Becky,

Thanks.
I understand your method now, and it appears to work well.

I was just curious.

Rob

[HKBB]

This is going to sound awfully dumb, but here goes. I've never worked with either epoxy or fiberglass, but am willing to give it a try. I'm skinning the exterior of my trailer in the next couple of days, and will then be staring the epoxy/fiberglass step in the face. My question is, what is the advantage / disadvantage of finishing the exterior of my trailer in just epoxy vs. fiberglass with epoxy? I've seen posts in the forum where people have done both (or rather, either/or) with success, but haven't found a reason WHY they did one or the other. Other than the foamies crowd, and I'm not brave enough to build one of those!

I'm building a 5x5x10 Benroy. It's a woody. I'v purchased the 6 oz. fiberglass, and West Marine 105/207 epoxy. Due to not knowing how to join thinner sheets of plywood (DOH!), I had purchased 3/4" 5x10 exterior grade plywood for the walls (yes, I know - heavy!), with the exterior skinned in 1/4" thick birch strips. The interior sides will not be skinned at all, due to the 3/4". The top will be skinned in 1/4" luan (as a foundation base), with strips of stained 1/8" bending birch over the top of the luan.

My thoughts are that because of the 3/4", I'm still trying to cut weight as much as possible. If the fiberglass isn't necessary, would just using straight epoxy+varnish be acceptable? Would it make any real difference weight-wise to not use the fiberglass? What about the balance of weight vs. strength from using the fiberglass?



All comments and advice is appreciated.

[Forrest747]

Can we see a picture or two that helps. I am not expert on epoxy and going through it right now. but there are plenty here that know what they are talking about. is your roof on or the walls up. I would look at oldragbaggers website she has just fiberglassed her side and took great pics and notes. you can also look up the desert dawg she has a great set of pics and notes as well.

[HKBB]

The stain is still drying on the wood strips for the sides. Nothing's up yet - I'd planned on fiberglassing/epoxying the sides before getting them up. I was just wondering about the weight vs. strength factor because the sides are going to be 1" thick when all's said and done. Obviously, the top isn't up yet either. I'm trying to plan ahead.

[Wobbly Wheels]

Lena, you'll get a huge boost in strength if you tape the corners (epoxy and 4-6" cloth strips).
If you sheath the entire sides and top in cloth, I doubt you'll improve much on the strength given the beefy construction, but you will seal it completely from water and protect the birch from getting dinged with use. Bare epoxy is brittle and may spider-crack with vibration over time over a large panel without cloth. Sheathing the whole thing in cloth won't add significant weight.
Either way, it will need UV protection which means keeping up the varnish on a bright finish.

I haven't worked with the 207 hardener - given that you're in Tx, I probably would have sent you home with 206 instead.
Epoxy cure times assume 72 degrees working temp, so if you're above that I would definitely suggest mixing small batches till you see how much time you have vs how much you can get done.

Looking forward to your build !

[HKBB]

Wobbly Wheels, thanks for the reply - that's good info to have. I didn't realize that the fiberglass cloth added strength to the epoxy itself, preventing cracking over time. I just thought it added strength to the trailer architecture.

I got the 207 because it's touted to be clearer than many other epoxies. Since I'm building a woody and I want to try (emphasis on TRY!) to get that "glass coat" finish, it's what was recommended by several people. And I do realize from reading in the forums that I'll have to apply a UV inhibitor. I'm bouncing back and forth right now between using the Epiphanes clear gloss varnish, or applying an auto clear-coat. There's pro's and con's to both I understand.

So many options!

As far as the fiberglass goes, I think I'll go ahead and use it. Can't hurt, and if it provides additional integrity to both the trailer architecture and epoxy, as well as improved waterproofing, I'm all for that!

As soon as I can locate my camera (where is that little @#$@#$...), I'll start an actual build thread. Right now, there's not a whole lot to see except 10ft long stained strips of birch all over my garage! I decided to put a second coat on the cherry-stained ones, to deepen the color. So hopefully by Friday I can start laminating the strips onto the sides. A milestone, of sorts, and one I am REALLY looking forward to!

Now where is my camera....

[nevadatear]

I used raka for our woody build two yrs ago. It was my first experience using epoxy and it was a learning process but I was very happy with the results. I did use fiberglass and it is holding up dry nice. I did not use cloth on the tongue box of thin ply. It cracked and broke on the first trip. Added fiberglass and more epoxy and it is holding up great.

[doug hodder]

What are you using for stain? Aniline dyes work really well under epoxy, some of the oil based stains may be prone to failure. As a side note. The 207 is used for top coating wood that is to be finished "bright" or natural wood. It has some UV inhibitors in it already, but still needs to be top coated It gives more UV protection to the wood coloring. The 206 can be used under a painted finish for top coating, but it's main purpose is in construction uses. I used the 207 on both my woodies and my boats, but 206 under the painted tears. I haven't used any cloth on the tears, and only on the hulls on the boats. For what it's worth. Doug

[HKBB]

Doug, I HAD planned on just using the Minwax Finish oil based stain, but fortunately a very nice gentleman on these forums sent me a "study" done of the failure rate of that particular stain under epoxy. Apparently, epoxy (ANY kind of epoxy) seems to not adhere to that particular oil blend very well. I'd love to know why... Good thing he sent it when he did - the next day was my planned "stain-fest".

Anyway, after reading a lot more, talking to manufacturers, and calling my mom (who does take very good care of her sailboat!), I decided that since I didn't know a whole lot about staining evenly on large pieces, I'd play it safe and go with a Gel-stain. Again, by Minwax, but their gel-stains have a different oil composition and solvent ratio. At least, that's what they said when I called them. Just to be sure, I did a test piece, and the West epoxy stuck really well. I was chipping at it with a chisel and it wasn't budging.

I finished staining and am waiting a few days before laminating the decorative strips onto the exterior walls. I'm still trying to decide if I should cut out the doors before laying the strips or after. I'm half afraid that if I do it after, they won't line up when I hang the doors. (Any advice would be appreciated!)

After that, my plan is to apply a coat of CPES and then wait a couple days, then lay out the fiberglass overnight to "form", and then do the West epoxy. When I did the stain/epoxy test, I didn't like the way the brush was skootching the fiberglass around (probably just me with too heavy a hand), so my plan is to roll the epoxy on with epoxy rollers I got from Jamestown Distributors.

Speaking of rollers, I have a question for anybody that can answer it. My mom sent me some rollers, but they're kinda weird looking. Theyre metal, with a bunch of circular ridges going around the center, like an enormous screw. You don't put roller covers on them, apparently, but heck if I know what they are or what theyre used for. Maybe getting bubbles out? I know my mom probably sent them just so I'd have to call her and ask, so I'm not gonna.

HA! In my forties, and still being a donkey's behind.... guess I'll never grow out of bucking my mom!

[KCStudly]

I'm still trying to decide if I should cut out the doors before laying the strips or after. I'm half afraid that if I do it after, they won't line up when I hang the doors. (Any advice would be appreciated!)

HKBB, You might want to consider routing the door in your main panel first, but leave like 4 tabs (or uncut areas) about an inch long near each corner, then strip it as one unit. This way you only have to cut through the short areas, you can use the preliminary cuts to guide your router for the final cuts, and the strips will all line up perfectly.

Just a thought and a variation on techniques I have seen used here before.

[Wobbly Wheels]

They're for rolling the air out of styrene-based layups because a lot of air tends to get trapped in the alternating mat-cloth-mat layers.
Epoxy is normally laid into a single layer of cloth so a squeegee does the job just as well. Those rollers can be helpful in inside corners but I don't use them for epoxy very much personally. If you do use them, clean them right away or they'll be useless next time, though cured epoxy can be softened by boiling them in water.

As far as the brush thing goes, I dab with the brush rather than brushing. It works the epoxy into the weave and doesn't push the cloth around.

my plan is to apply a coat of CPES and then wait a couple days, then lay out the fiberglass overnight to "form", and then do the West epoxy.

According to West's own data, you can thin 105/205 up to 10% to use it as a floodcoat (sealer/primer).
That sounds like what you're using the CPES for ?
If you have enough resin, it might be a good idea on a first project to stick with a single product, especially since you already have the stain as a bit of a wild card.

Then again, it's all a big learning curve and I might be wrong.
$0.02 and all that.

[HKBB]

KC, that is a REALLY good idea! Now why didn't I think of that?

WW, those are exactly what I was asking about. I'd wondered, because I thought they looked like they could almost cut through cloth, and would leave "ridges" in the epoxy.

And mostly, I was thinking that since CPES is a penetrating epoxy, it would fix the stain down in the pores of the wood, and make sure the West had a really good base to stick to. After the near miss with the other oil-based stain, I'm a little nervous about the epoxy not adhering well, even after doing the test piece.

You know, I wonder how much of the "overbuilding" on these trailers is due to the builders' paranoia or uneasiness (like me/mine) about something? Like "will the epoxy stick?" or "won't the walls fall over?" or "won't the chassis frame bend?" I can think of a few dozen questions I had when I first started looking at TD's and all the research and reading I did to try and get an answer that soothed my anxieties.

Of course, there's always new questions and paranoia's... like oil stain and epoxy!

[Wobbly Wheels]

No, the rollers don't cut the cloth. Each ridge acts like a tiny squeegee to press the fibers into the resin and work the air bubbles to the top

You know, I wonder how much of the "overbuilding" on these trailers is due to the builders' paranoia or uneasiness (like me/mine) about something?

Well, when you look at some of the TDs here pushing 1000# and then you have experienced builders coming in under 600...
On such a small platform, there's nothing wrong with overbuilding. It might rival the weight of a production trailer, but as long as you're not overloading your components it's all good.
Shoot for lower weight on the next one.

[Oldragbaggers]

Lena, I have had the best success with my cloth layup by putting the resin on with white high density foam trim rollers. I roll on a small area at a time and squeegee the excess into the adjoining dry area. No need to pay marine store prices, they're available at all the big box stores.



The 4" size works really well for me. Just remember to remove that foam quick and clean off the handle of your roller with acetone as soon as you are done or you will have to throw the whole thing out.