Making a trailer tub...

[Veinot]

Would this approach work, building a frame out of 1/2" square stock (I'll ask my cousin what wall thickness to use for a given desired load capacity) and then skinning it with fiberglass cloth and epoxy resin in layers to build it up to the required thickness for the specific load\use? I see a similar technique used with wood\plywood framing to make custom dashes with complex curves and convex shapes so would it work with a metal frame\skeleton to make a simple trailer tub or other structurally sound enclosure?
If yes... Why don't I see it done anywhere? Too expensive? Is there a better way to make one off fiberglass structures without a mould? or does it just look bad without a lot of cosmetic work?

 

[smritte]

Go to teardrops and tiny trailer site.
Some of the guys there layered canvas with fiberglass resin as well as plywood. When I was looking at doing what your asking, they seemed to have the best info.

 

[Veinot]

Go to teardrops and tiny trailer site.
Some of the guys there layered canvas with fiberglass resin as well as plywood. When I was looking at doing what your asking, they seemed to have the best info.

That's a good group, I am a member there as well. Part of my question comes from some of the techniques they use. Since I asked I found out some stuff in my research; First, the the cloth isn't like canvas or nylon where you can stretch it over a skeleton, it will sag into the voids once wetted so you need a backing like plywood. Secondly, building up layers of FB cloth with epoxy isn't exactly cheap.
My goal is to make a trailer tub that was all fibreglass with a steel skeleton support with no plywood lamination. I also found out about C-Flex from the boat building side, it is basically rods of fibreglass suspended in fibreglass cloth that gives it the rigidity to span gaps of 14" or less. So you can build one off fibreglass structures over a frame without a mould, is about 3x more than plywood.

I also saw chloroplast board being used in another project since the epoxy won't stick to it, it was used to make a one off plug. So now I am thinking maybe make the tube out of wood frame with chloroplast (sign board) sides and do 2 or 3 layers of glass cloth and epoxy, pop out the "plug" and build up the inside a bit. Should make a solid FG tub.

I never worked with FG before but it seems the possibilities are endless....

 

[smritte]

I decided not to go with fiberglass when I did mine. I used a metal frame and 10mm paneling. Here's an idea, make the frame and fill the space between the frame with foam type insulation board then glass over that. I used 1" thick on my walls and roof. Looking back, had I fiber glassed over that instead of using the paneling, it would have been stronger.

 

[Veinot]

I decided not to go with fiberglass when I did mine. I used a metal frame and 10mm paneling. Here's an idea, make the frame and fill the space between the frame with foam type insulation board then glass over that. I used 1" thick on my walls and roof. Looking back, had I fiber glassed over that instead of using the paneling, it would have been stronger.

Is this a camper\sleeper or a Utility rig? Do you have pictures? I was thinking about doing this for a modified build of a Mechanics Illustrated camper I found plans for on TnTTT; it looked like a bean was about 12' long, just 6' head room short door. I figured it would just fit a standy wet bath a cook spot and a bed. I thought instead of 2x2 and plywood I could con a cousin into welding up the walls for me in square tubing (steel or aluminium) then filling the vois with 1.5" or 2" foam and then glass it inside and out right over the frame and foam. Mark the frame locations when the glass is still translucent and plot out the walls and cabinets. Glass for strength, sand, paint, install the walls.... anyway I was told the foam would melt when I applied the epoxy.
Just so we are clear I am looking to build a utility trailer tub that is water proof for hauling camping gear and that can double as a light utility trailer. There are a few trailer frames around I was thinking bolting a a fiberglass box onto. I didn't want to use wood but I have seen some good wood examples that have been sealed with epoxy or even bed liner.

 

[smritte]

There's a link in my sig to the build. It is an enclosed trailer and the first I built. My others have been a reworked M-100 and trailers for my ATV's. I had forgotten your were just doing a tub. That's why I suggested the insulation.

I'm gearing up to build another utility trailer for hauling gear around. My plan (so far) is the tub out of aluminum. Light steel frame and the sheet aluminum will be bonded to an aluminum skeleton reinforced with rivets. The box will sit on rubber "body mounts". I may or may not make a removeable top for it. The issue with the top would be mounting the hinges to the aluminum.

My M-100 with a steel lid is under 1k pounds empty (been a while since I weighed it). Loaded with an RTT, fridge and battery is still under 1400. The walls are 12 gauge and the frame is 3/16 with a 3500 axle, 33" tires. I think there's a picture of it in my build thread loaded out.

 

[smritte]

I didn't want to use wood but I have seen some good wood examples that have been sealed with epoxy or even bed liner.

Just spotted this. I waterproofed my wood, epoxy primer and Monsta lined the body. It was easy and using a smooth roller has a very slight texture to it. I chose that because I've used them before and they had the color I wanted.

 

[Veinot]

There's a link in my sig to the build. It is an enclosed trailer and the first I built. My others have been a reworked M-100 and trailers for my ATV's. I had forgotten your were just doing a tub. That's why I suggested the insulation.

I'm gearing up to build another utility trailer for hauling gear around. My plan (so far) is the tub out of aluminum. Light steel frame and the sheet aluminum will be bonded to an aluminum skeleton reinforced with rivets. The box will sit on rubber "body mounts". I may or may not make a removeable top for it. The issue with the top would be mounting the hinges to the aluminum.

My M-100 with a steel lid is under 1k pounds empty (been a while since I weighed it). Loaded with an RTT, fridge and battery is still under 1400. The walls are 12 gauge and the frame is 3/16 with a 3500 axle, 33" tires. I think there's a picture of it in my build thread loaded out.

An M100 or M416 would be ideal bit they are rare and when I do find them they fetch a good price. I looked into replica's but for what is asked for the tubs is only a few hundred less for what I see complete original trailers for. I am also not sure if a fiberglass tub would support roof rack rails for bikes and kayaks like what you can do with the Manly trailers. Part of the reason why I was thinking steel skeleton + fibreglass skin.

 

[smritte]

Fiberglass/steel vs all steel, your looking at 100-150 pound difference. Figure 4 4x8 sheets with some left over. I'm guessing $50 each for 12 ga. $100 for your braces. $50-$100 to have it bent. So...around 400-450 for an M-100/416 steel tub plus however you do your tailgate out of the scraps. That should weigh in about 250 pounds.

 

[Billiebob]

Late to the party but consider neither wood nor fiberglass change size with temperature, steel does. In Florida where temperatures are stable it might not matter, anywhere it snows, that temperature change will create stress as the steel changes but the fiberglass stays stable. With steel you might have to allow for that expansion/contraction change.