Removing underbelly material, what might I be getting into?

Because of a poor factory frame paint job, I was forced to repaint my frame early and was forced to remove the underbelly covering to do that and it was in one piece. In general these enclosed underbellies are a two edged sword with the biggest downside is that they allow for hiding a plethera of issues and sloppy workmanship. In the end I'm glad I did since I fixed a HOST of issues from dangling wires and ducting to poorly attached and supported holding tanks. In the process I decided to bite the bullet and sectionalize my underbelly so I could easily remove sections and at the same replaced all metal such as screws with either nylon or aluminum material so rust/corrosion would not be such an issue and re routed my gas lines for better under frame access. I took extensive pictures and have described what I did in the following album and the meat is in the captions to each picture. CLICKY

Larry

I've had mine down a few times. I pulled the screws and for any gas lines through the cover I slice a single cut from the line to an edge.

The problem I've found is that on reinstall it's hard to get the old screw holes lined up as the coroplast is fastened around the outside edges and sags in the middle. I overcome this by using a small piece of plywood and a floor jack. The jack and plywood go in the center of the coroplast and lift it up. This takes the sag out of the material and suddenly the screw holes line up again.

Additional excellent advice! Thanks.

All depends...I'm going thru this right now. I've had 3 trailers, all with coroplast bottoms. Two were newer and the self tapping screws weren't rusted solid. This last one was hell on earth but I have no choice.
We drove thru a very heavy deluge in late March on I10. The coroplast was screwed every 6-8 inches. We find out water had gotten in under the frame and coroplast soaking the insulation. I usually loosed the screw with a hand socket then use a drill to back them out. Not this time they were frozen in solid.
I eventually cut around the screw heads and popped the coroplast down.
Due to road salt rust I ground the whole frame bed and ground off the frozen heads. Primered and repainted the frame. Changed out the insulation and when it stops raining I will redrill new holes and use a sealant and aluminum flat bar and 3/4 self tapping screws.
This trailer (bought used) must have been driven a lot in road salt conditions. At least I know now whats under the coroplast. Not a fun job...
Try one or two screws if the come off easy enough you're home free if not it's your call which method you use.

Had a similar problem and had to remove the plastic sheet under trailer. While there I took pictures and put copies in manual. Repaired all the valve seals and replaced sheet from a sign shop (4X8) $20. I cut access holes to change seals again if I have to or to make electrical repairs. I used new screws and large body washers. It was a job, not hard and glad I did.

Many times, if the cable makes a tight curve, it will be difficult to move. So redirecting the cable (straighter) may help free up the movement. Another thought would be to cut the corner out of a ziplock bag. Then thread the cable end through the cut out corner. Next take a zip tie and pull it tight around the corner of the baggie and the cable, to seal it around the cable. Then put some motor oil into a zip lock bag, and position the bag/cable so the oil drips into the outer cable and down through the length of it. Work the cable back and forth a dozen or so times. Let it sit over night. That will lube the cable. In some models of trailers you can do this without needing to go into the underbelly.

The oil in the tank idea, is probably the best way to lube the seals inside of the valve.

You can do more research on it as well online. The correct name of the product is Coroplast (short for Corrugated Plastic)

To service my front gray/black valves (same location on my rig), I cut an 18 in by 18 in square out at the valve location. After servicing my valves, I picked up a 2' x 2' piece of black Coroplast material from a vinyl graphics sign shop near me. I secured it in place with 3/4" self tapping screws (secured to the original underbelly Coroplast) and then taped seams with gorilla tape. Holds and looks great. Now I have a hatch to access valves as I am sure I will need to service them again.
Steve

All excellent idea's! Thank you all!

When I needed to get into the belly and I did not want to drop the black coralast panel completely, I chose to cut a 3 sided opening. I cut the coralast material about 2 ft wide and 2 ft long leaving the uncut side towards the front of the trailer. Then swung down the flap and crawled up in and did what I needed to fix. I then took 2 inch wide wood and cut three pieces 2 ft long. I used screws to screw the wood into the uncut bottom leaving a 1 inch piece of wood exposed so the flap had a place to screw up into. Should any of the screws ever pull out, and I can't see how or why, but having the uncut flap forward the wind from driving will not pull the cut flap open. I have used this method at least 5 times on mine and other trailers without any issues. Fast, easy and cheap.