Fiberglass Reinforced Panels (FRP)

[Nor Cal Mike]

Hi I am writing to report on my use of fiberglass reinforced panels (FRP) as siding on my teardrop trailer. This is not a recent build. Rather it was done when I originally built the trailer 20 years ago. This covering is still going after 20 years without a single leak occuring during that time. The trailer has always been stored outside.

The material is the same stuff used in countless gas station bathrooms across the country. It is the bumpy, shiny white stuff. Instead of having the finished (bumpy) side facing out, I installed it with the smooth back side facing out. A word of caution; When I installed mine, I liked the soft white color of the smooth back side of the panel when it was on my trailer so I just left it as is without any paint. Over a few years the ultra violet waves caused fibers in the surface of the paneling to fray and lift. I was planning to replace the paneling again with the same product but this time I was going to make sure that FRP was painted to protect it from UV light. As a temporary stopgap so that I could use it for one final season I painted the old surface with a couple of coats of Rustoleum white oil based enamel in the roll & tip method. That paint is still going strong a year later so I plan to wait another year before replacing the paneling.

When I originally installed the paneling to the 3/4 plywood body, I used contact cement to glue the paneling in place. I was never satisfied with the result. It hasn't give me any trouble but I can see wavering in the surface that indicates the panel has lifted there. I am not worried about it coming off because it is trimmed in with extruded aluminum all around the edges doors and and window When I do it again, I will use a slow set epoxy resin after quickly running my orbiter sander with a course disc over the tops of the bumps on the shiny side to make sure I get a good bond. So here is a pic of my 20 year old trailer. It was taken at or near Capital Reefs National Park, Utah while on a trip to Northern New Mexico.

[RJ Howell]

A concept I have debated. I like the thought of FRP as a skin, yet does require UV protection (as you said), it's an indoor product, yet fiberglass, doable. Basically I see fiberglassing a unit as a thinner FRP, unless several layers are done. Then comes length of product..

I agree with using resin to adhere, it is fiberglass based after all..

So good to see what you did and sharing what you'd do different! Please do continue!

I'm in process of design and about to start my next build. I have much interest in what, why and how, you would do it differently.

[Nor Cal Mike]

If you can find it in your local I have seen listings online for FRP that has a smooth finished face. I think that shiny surface to be gel coat which should be much more UV resistant. Especially if you wax it on a regular basis. I haven't seen it anywhere around here so assume that I will go back to the same stuff next time a with an outside coating. I am very happy with the white Rustoleum. I think it is more resistant to fading than the same paint of other colors. One could also take a que from fiberglass boat builders and use a quality polyurethane marine paint as an excellent option. It would especially work well by application by the roll & tip method since it will flatten out better after the final brush strokes.

[Nor Cal Mike]

I see FRP as fiberglass in sheet form. It eliminates all of the effort and mess of laying up multiple layers of cloth or mat.Not to mention the work required to bring that fiberglass to a smooth enough surface to be considered finished. The backside surface of FRP is smooth and is ready for paint without sanding.

My corner molding is standard RV extruded aluminum that has slots on each side of the upper surface that accepts a vinyl plastic molding strip which covers the screws for appearance and exposure to the elements. I used high end RV caulking that at about $18 a tube was very spendy 20 years ago. It was worth the cost given that I have had no water intrusions over that time. I thing the standard method for sealing this type of corner trim is to use butyl tape. However I doubt that butyl tape would have lasted 20 years.

The lower front panel is aircraft aluminum sheeting that was given to me as a leftover scrap by a buddy from his teardrop build. It makes a great gravel guard for the front of the trailer. The horizontal strips of extruded aluminum trim down the beltline of the side the side was added by me as insurance for that previously mentioned lack of bond between the FRP panel & plywood. I am convinced that this trim could be eliminated if I used a epoxy resin as an adhesive. But I like the looks of the trim in that if gives a 40's-50's flair to the looks of the trailer.

[PCO6]

… The material is the same stuff used in countless gas station bathrooms across the country. It is the bumpy, shiny white stuff. Instead of having the finished (bumpy) side facing out, I installed it with the smooth back side facing out. …

Nice looking trailer.

Mine has an FRP skin too but the opposite - smooth in & bumpy out. I bought it with modifications and upgrades in mind but this is one that I can't do without tearing it apart. It will have to remain as bumpy out! I can't tell you how many times I wish it was bumpy in & smooth out like yours. It looks fine but it collects dirt under the decals it came with and putting on new graphics is tough. I've ripped off most of the decals and will do the rest. My guess is that if I leave them on too long the sun will give a constant reminder of where they used to be.

[RJ Howell]

Interesting.. My thought was to go bumpy out. May re-think it now...

Very familiar with the product and have a local manufacturer of and runs 5ft wide and 12ft long as standard lengths. Being a tradesman, use it many a time. Never as a skin over XPS or on a trailer!!

I have a pricing quote out now.

[Tomterrific]

Hi Mike,

How did you get the bend for the roof?

I thought about using a 4x8 panel by itself for the walls. Ended up using 5mm Revolution Ply because it was cheap and easier for me to work with. The RPly looks good inside.

Tt

[Nor Cal Mike]

Hi Tom, The two sides and floor of my trailer are 3/4" marine plywood. The curved section of the roof is 1/4" Marine plywood.Marine plywood sold around here is all made doug fir as far as I know. At least the face plys are fir for sure. To support the 1/4 plywood roof panel, I let-in 1x2 douglas fir strips flatwise across the span at 12" centers. The strips were glued into notches carefully cut into the side panels so that no trim would be required to complete the interior finish. Then it all was covered with the FRP that you see in the pic. I hope that helps.

[GO_C_DAVE]

Hey Mike. I used FRP for my interior cabin and for the hatch. For the simple fact that it has almost no memory. It will bend however you want it to. Without any ( bow back). I was a little scared to use it for the skin. However, now that I’ve read your post... I think it’s time for a new build with FRP. I can find tan or white locally, so let’s see where it leads me. Thanks again.

[saywhatthat]

fiberglass reinforced plastic the key word is plastic This is not like real molded fiberglass. If you have to repair you will see

[Westley]

Yes, it's my understanding that the "P" stands for plastic.

But it's also my understanding that they include polyester resin in the definition of plastic.

So, I thought that in the mfg process, the FRP is made using fiberglass and polyester resin.

I do know that if sanded in prep, FRP and epoxy will stick together super well and bond with cured laminated fiberglass like used in boat making, which I think is cured polyester resin and fiberglass.

I haven't tried bonding FRP with XPS, yet, but I did bond 1708 fiberglass with XPS using epoxy resin. The result seems very strong for just one laminate.

I have a supply of FRP that I scrounged. It's the type used on the roof of the over-the-road trailers. I've used a little of it and find it to be very strong and bonds well. It's quite flexible and about 1/8" thick or less.

I used two of the XPS 150 sheets from Home Depot for the experiment, each 2'x2' X 1" thick. I roughed up the surfaces with a RO sander, 40 grit. The fiberglass/epoxy is in the middle of the sheets of XPS. When cured, I trimmed and squared the edges on my table saw.

With the resulting 2" thick panel is suspended by the edges, laying flat, I can stand on it, bounce, and it holds my 220 lbs just fine.

I don't know if that's a sufficient test or not. There may be other issues with 150 XPS, such as heat and perhaps delamination from stress, or perhaps expansion/contraction from temp changes, leading to delamination. The XPS is not strong stuff, and if there is failure it will be the XPS that gives way, not the epoxy/fiberglass.

[saywhatthat]

just plastic hot rolled with maybe some fiberglass fibers some with plastic fibers . Some siding all plastic with a fiber look rolled in to the back

sanded in prep, FRP and epoxy will stick together super well and bond

just a
mechanical bond

[Westley]

"Mechanical Bond"

That's generally what you get with epoxy, unless the next layer goes on before the under layer hasn't fully cured yet.

It's also why I choose to use epoxy over polyester. I've seen delamination from polyester laid over cured polyester. Thus the mechanical bond failed to hold. Polyester over epoxy is a no-no.

I have not yet seen mechanically bonded epoxy delaminate, whether I use it over cured polyester, cured epoxy, wood.

I have not tried epoxy over what I call "real" plastic, such as the high density stuff, like cutting board. I see no need to try since I expect it will not hold. If I need to use the high density plastic for some reason, I'll use 3M 5200 for that.

For several days now, I've been using some of the FRP I have to mend a fiberglass console for a boat I'm working on. I make a paste from epoxy to glue the FRP to the core, which is all some 40 year old + fiberglass laid up with polyester resin. It works very well. The boat itself was made in 1973. I expect whoever inherits this boat will get another 20 - 30 years out of it.

The FRP I'm using looks to be polyester resin with fiberglass strands mixed in. It's about 1/16" thick, and flexible. I have no way of knowing its shear strength. If I bend it too much it cracks, then it's not too difficult to tear it apart at the crack. In this case I'm not using it for strength, but to flatten surfaces with little weight added, and mend some holes. I know it's some nasty stuff. I definitely use a respirator since I use an angle grinder with a flap disk to clean it up and grind off the excess edges and cut it to fit with a diamond blade on the grinder. I can tell there are lots of fiberglass shards in the stuff that gets on my arms. I use an air compressor to blow it off and away before removing the respirator from my face. I also wear a full face shield when working with any fiberglass.

In addition, I use my random orbital sander mostly and I have it hooked up to a shop vac so 90+ % of the dust is sucked away. it's just the angle grinder/flap disk when I'm in a hurry, and it makes very much dust.

[saywhatthat]

There so many things that call them shelf fiberglass

lots of fiberglass shards in the stuff that gets on my arms

dose it glisten? 99% of what they call fiberglass is not old school spend glass. Try sanding a 63 vet with no shirt.
yes epoxy make a great glue. We have found doing a polyester laid over cured polyester cut some small slots in old glass. faster than drilling holes for more mechanical bond.
Plastic, such as the high density stuff, like cutting board we use as backing dose not stick to polyester

The FRP I'm using looks to be polyester resin

cost is a give a way and the burn test
Where you live has a lot to do with it made from

[tony.latham]

and the burn test

Mike:

Could you expand on that? Do you mean burning the stuff to see what glass is left?



Tony