Teardrops n Tiny Travel Trailers

[quote]"I'm not completely satisfied with my PMF finish, as unique as it is. It did work and is holding up nicely, yet I don't think 'I' saved much vs fiberglassing it. I"m going to glass my next build.”




And again with me... My next build will also have cabinets/compartments made with XPS/fiberglass. This weight savings is huge when working up off a 1/2 pickup base!

The difference between PMF and Fiberglass …. The SANDING !!! Unsanded fiberglass , doesn’t look any better than PMF …

For a Good (acceptable ) Fiberglass finish , you must sand the substrate perfectly flat , apply the glass , then sand that perfectly Flat , fill , then sand more , then paint it ( more sanding) , remembering all the time fiberglass dust is resin and GLASS particles . Wear a mask and protective clothing !!!

PMF is pretty much put it on , go camping … It was NEVER considered to be a beautiful finish , only a pragmatic one … All in how much sanding you like to do … and Cleanup ...

You Choose !!!

I would say that fiberglass adds to structural stability as well. So maybe 2 things different.

apply the glass , then sand that perfectly Flat , fill , then sand more , then paint it ( more sanding) ...

My last build was glassed, primed, and then covered with a urethane bed liner. The sanding was minimal. Now, this was over wood -–not foam-- that had been checked for high and low spots, but plywood is smooth.

I sanded the gloss off the fiberglass surface with a random-orbital sander just to give some tooth for the paint. That was no more than a half-hour. There was no need for filling after this sanding. The epoxy filled the weave. And no "ichies" from the glass since I was not chewing into it.

That was followed by priming, which showed a few low spots.



I filled those places with automotive spot filler. Ten minutes with the orbital? Here's the final surface:



You may think that the texture on the final finish covered blemishes such as cloth weave but that's not true. I was not relying on it to solve issues and I don't think it would have.

Not a lot of sanding.



Tony

P.S. One thing I have been scratching my head about is the PMF texture issue. PMF came out of the canvass covered wood canoe era (I'm guessing '20s through the '60s). Fine boats but they do need some TLC.

You'll note that the canvass surface on those finally made boats show no weave. They have a process of dealing with it. (Which includes sanding and filling.)

There is a huge difference between drop cloth canvas and real cotton duck canvas. The real canvas has a fine uniform texture that could be filled for a smooth finish.

Drop cloths are looser weave with many imperfections. I ran out of duck and covered a door with drop cloth canvas and it really shows.

tony.latham wrote:

apply the glass , then sand that perfectly Flat , fill , then sand more , then paint it ( more sanding) ...

My last build was glassed, primed, and then covered with a urethane bed liner. The sanding was minimal. Now, this was over wood -–not foam-- that had been checked for high and low spots, but plywood is smooth.

I sanded the gloss off the fiberglass surface with a random-orbital sander just to give some tooth for the paint. That was no more than a half-hour. There was no need for filling after this sanding. The epoxy filled the weave. And no "ichies" from the glass since I was not chewing into it.

That was followed by priming, which showed a few low spots.



I filled those places with automotive spot filler. Ten minutes with the orbital? Here's the final surface:



You may think that the texture on the final finish covered blemishes such as cloth weave but that's not true. I was not relying on it to solve issues and I don't think it would have.

Not a lot of sanding.



Tony

P.S. One thing I have been scratching my head about is the PMF texture issue. PMF came out of the canvass covered wood canoe era (I'm guessing '20s through the '60s). Fine boats but they do need some TLC.

You'll note that the canvass surface on those finally made boats show no weave. They have a process of dealing with it. (Which includes sanding and filling.)

Fiberglass over wood is a good choice. The hard wood surface underneath makes the glass much easier to sand. It does make a strong composite material.

Sanding hard fiberglass over soft foam is a different animal all together. You can still peel fiberglass off of foam easily. You get a thin layer of foam attached to the glass so the composite material is limited by how easily the foam separates from itself.

Fortunately, PMF over foam is strong enough for a trailer. It's just has a certain finish.

Pmullen503 wrote:There is a huge difference between drop cloth canvas and real cotton duck canvas. The real canvas has a fine uniform texture that could be filled for a smooth finish.

Drop cloths are looser weave with many imperfections. I ran out of duck and covered a door with drop cloth canvas and it really shows.

I do agree with the Duck Cloth... What a difference! Do wish I had come across it sooner in my first build.

They used a dope for canoe work too. Applied with a stiff, short haired brush to work it into the weave and then smoothed. A final sanding after about a month of dry time, then painted with a toxic paint to keep mildew growth to a minimum. They don't build them like that anymore, most of the items they used are not available anymore due to environmental hazards.

They used a dope for canoe work too.

As in aircraft dope?

There are several commercial canoe builders making them now. Gorgeous boats. That photo above is a new canvassed covered boat. There is also a resurgence of craftsmen building them along with folks re-canvassing the old ones.

I don't know how they are gluing the canvass or filling the weave but the information is out there.

Here's a forum on wood and canvass canoes:

http://www.wcha.org/forums/index.php?forums/wood-and-canvas.6/



Tony

Note: PMF doesn’t have to be UGLY …

GPW wrote:Note: PMF doesn’t have to be UGLY … 8)

Yep! That looks really nice!

JV, best of all , it’s lasted 7 years ( living Outside ) and no signs of giving up yet !!!

I've read and searched several threads relating to fiberglass over XPS and still have questions.

This one IS Fiberglass over XPS, so I'll post herein.

First, has anyone experienced delamination of the fiberglass skin from the 150 XPS core?

If so, was it heat or stress, or unknown?

I have other questions, but this will start. (kiss)

Thanks in advance.

First, has anyone experienced delamination of the fiberglass skin from the 150 XPS core?

Burt Rutan has been designing aircraft manufacture in that method --he calls it "moldless construction"-- for decades.



https://www.airspacemag.com/flight-today/design-by-rutan-133347555/

They don't fail but you'll note they are always painted white.

Tony

That's incredible.

Surfboards are also made by foam coring XPS with fiberglass/epoxy shell.

But I read that if not white, they make sure to not carry it on a roof rack, exposed to sun.

BTW, I can't get the denser XPS here, like the 250. It may be available with special order and/or large batch, but I don't want to go there.