Under side of trailer

[Reddog49]

The underside of our Viking TT has a heavy plactic liner almost the whole length of the unit. I never saw this before this new trailer. Are there anythings I should be aware of with this?

[stahrmcgee]

brulaz wrote:
In some places, my coroplast bends down in the centre around tanks and supports. If travelling on a wet day, water can get in and accumulate in these low spots. Probably not a good thing. Others have (I intend to) cut or drilled some drain holes at these low points.

I got under and looked at our new camper. They are now (at least for Rockwood) putting little circular drains in the lower points to let water/condensation out. Perhaps the manufacturers are listening...:W

[jessjerr1831]

Had this very material blow off the front third of the underbelly 3 weeks ago while bucking very strong head winds. Luckily I have a BIL who has extensive body shop experience so he was able to reattach it. Left it at his place so he could do it in his spare time. He explained to me how he did it but sorry didn't think about taking pictures to see how he did it. I guess I was just surprised to see all of the electrical wires and insulation just hanging in space. I was sure glad I had a roll of gorilla tape along to tape up all the wires.

[Huntindog]

LarryJM wrote:

Huntindog wrote:
I took all of mine down, and installed pipe insulation and heat tape on all of the plumbing.
Then I used a polyisicronate (sp) R7 insulation to insulate the inside of the frame rails and across the bottom,(like a insulated basement) just above where the coroplast is. I added another heat vent right next to the fresh water tank. When I reinstalled the coroplast, I cut it into smaller overlapping sections so that when I need access in the future it will be easy.
This mod was intended for freezing weather, but a side benefit has been in the summer. The AC now can keep it cooler. Propane use has declined dramactically in cold temps as well. To the point that it will pay for itself in short order.

I did something similar, but went a little higher tech with using aluminum angle iron for each coroplast section cross support, all nylon bolts/washers for corrosion prevention and re routed all my propane lines from running across the underbelly to alongside the frame for better protection and to make removing the coroplast sections easier. Like you I also added a lot of additional insulation along with putting in some extra tank supports.

I photographed and documented what I did in the caption in THIS ALBUM

Larry

On mine the factory had used 1x4s across the span of the frame rails to screw the coroplast into.
With sectionalizing it carefully I was able to eliminate most of those, and screw into the truss cross supports. So I got a small weight savings to partially offset some of the rest of the project.
My propane lines were already attached to the frame rails.

[LarryJM]

Huntindog wrote:
I took all of mine down, and installed pipe insulation and heat tape on all of the plumbing.
Then I used a polyisicronate (sp) R7 insulation to insulate the inside of the frame rails and across the bottom,(like a insulated basement) just above where the coroplast is. I added another heat vent right next to the fresh water tank. When I reinstalled the coroplast, I cut it into smaller overlapping sections so that when I need access in the future it will be easy.
This mod was intended for freezing weather, but a side benefit has been in the summer. The AC now can keep it cooler. Propane use has declined dramactically in cold temps as well. To the point that it will pay for itself in short order.

I did something similar, but went a little higher tech with using aluminum angle iron for each coroplast section cross support, all nylon bolts/washers for corrosion prevention and re routed all my propane lines from running across the underbelly to alongside the frame for better protection and to make removing the coroplast sections easier. Like you I also added a lot of additional insulation along with putting in some extra tank supports.

I photographed and documented what I did in the caption in THIS ALBUM

Larry

[thomasmnile]

Main advantages of Coroplast: CHEAP! which explains why it's used and its relatively light weight.

[martipr]

Suggest using Gaffer's Tape to close up access cut outs. Just Goggle it.

[opnspaces]

Probably not a bad idea to drill a hole or two. Just be careful you don't drill into the bottom of the tank above the bulge. :E

[brulaz]

In some places, my coroplast bends down in the centre around tanks and supports. If travelling on a wet day, water can get in and accumulate in these low spots. Probably not a good thing. Others have (I intend to) cut or drilled some drain holes at these low points.

[Huntindog]

I took all of mine down, and installed pipe insulation and heat tape on all of the plumbing.
Then I used a polyisicronate (sp) R7 insulation to insulate the inside of the frame rails and across the bottom,(like a insulated basement) just above where the coroplast is. I added another heat vent right next to the fresh water tank. When I reinstalled the coroplast, I cut it into smaller overlapping sections so that when I need access in the future it will be easy.
This mod was intended for freezing weather, but a side benefit has been in the summer. The AC now can keep it cooler. Propane use has declined dramactically in cold temps as well. To the point that it will pay for itself in short order.

[opnspaces]

If the liner is like plastic corrugated board (cardboard) then it's called Coroplast. Many manufactures use it to claim a sealed and heated underbelly.

I've dropped mine a few times and it's not too bad, But as RoyB states it's a lot of screws. Many people cut access holes in the Coroplast to make repairs, although personally I would not cut any in mine.

I have only two tips:
If you pull the Coroplast down, use a floor jack with a piece of plywood on it to hold it all up while you put the screws in. otherwise is sags in the middle and pulls the edges away so you can't get the screw holes to line up with the frame.

If you cut an access port you will need to use some strong tape to hold it closed and sealed when done. Only cut it on three sides and leave the tongue side of the hole uncut to act as a hinge. That way if the tape fails the wind while driving will constantly blow the port closed.

[mosseater]

When I fixed my water tank earlier this year, I found out there is a vent down into the underbelly from the main heating plenum. I suppose there are enough holes in the floor to help get some circulation. Never knew it before. Isn't technically a "heated underbelly". Or is it???

[skipnchar]

All trailers with "enclosed belly" have this "coroplast" liner. It's purpose can be to help insulate the belly so passive heat from the furnace acts as a tank eater of sorts. Some are heavily insulated and work very well. Without them furnace based tank heaters are pretty much worthless.

[RoyB]

I have this under my Fifth Wheel trailer but not under my OFF-ROAD POPUP trailer.

Really helps keeping things clean from road debris and helps with keeping things from freezing up.

Some folks will modify certain areas under the trailer they want to get easy access too by cutting a door in the underbelly membrane so to speak that can be opened and then put back in place.

Removing the underbelly membrane will require removing a whole bunch of screws (Maybe hundreds) on the ones I have looked at.

I am always running cables for projects so what I did was install some PVC flexible conduit to areas that I can gain easy access to.

Roy Ken