Underbelly plastic cardboard weatherproof, toast?

[Yakherder]

Thought I would chime in on this one as I went through the came process in 2019. When I checked on the trailer in the Spring I found that the Coroplast underbelly was split open and multiple stress cracks in the front to the middle of the wheels.

Took the 2mm factory Coroplast off in the area that needed replacing (the back portion ok for now) by removing the self tapping screws and fender washers.

What I found was a mess of wires and broken heat pipes and knew that this was not going to be a weekend project.

Fixed, repaired the wiring and replaced the heat pipe with metal ones. Purchased 4mm coroplast sheets from a local supplier and 1 1/2" alum angle for the cross member supports. I notched the "L" at the ends so that they slid over the "I" beam of the frame. I overlapped the coroplast by 1" facing rearward to prevent rain/wind getting in and used Gorilla Waterproof Patch and Seal tape to cover the seams as an extra precaution. It comes in a 10' roll and is expensive but really works. I also used it to patch around the holes where the lower drains come out the bottom as well as any other hole I could find that a mouse or fly could get in.

I used the self tapping screws and fender washers in the new coroplast Secured the coroplast to the cross member angle and reused the existing holes in the frame where I could using an awl to line up the holes. Where I couldn't I predrilled holes to accept the screws.

As of today underbelly looks like I just put it on and the tape is holding strong. I've attached some pics.

I feel for anyone who has to tackle this job. There are lots of loose things in that underbelly. More like a Pandora's Box.

[Lloyd]

Looks like you did a nice job. Also good write up and the pics to go along.

[MarkCO]

Nice work Yakherder.

[Aceallenk]

I thought I was done with the underbelly yesterday but thought of a better support system for the center of the front 4 sheets so I redid them this morning. It only took a few hours so I'm really glad I redid them and more than confident they won't come ripping off at 60mph going down a highway bucking a 30mph wind type thing. Yea it took a strong 8 days probably, and worked minimum 6-8 hours per day. Of course there was a few trying moments getting a clear prospective of what to do with the black and gray drain pipes till I remembered to step it, and cover that with coroplast. Then run a little gorilla tape on the corners (not that it's necessary as it's screwed every 7".) I added a couple picture, not sure how well you can see stuff but from my view underneath it look night and day over the factories dragging bag they install.

[Aceallenk]

Forgot to give the jiffy marker a wash on the one sheet before taking pictures, oh well, I'm sure we'll be the only people that'll see that, lol...

[Yakherder]

Great job. Looks like it is buttoned up good and tight. Looks like you measured twice and cut once for the lower drain pipes as well. Mine were cut a little large and had to use Gorilla tape to keep the mice out.

As for the marker - it is not a flaw, it's an accent.

[Lloyd]

Nice job! you're right, it looks a 100% better then the factory job.

[Aceallenk]

Yakherder, Yea this was one of those times i can give a little thanks to all the sheets of Gyprock I hung over my lifetime. Another thing is I used clamps to get my first sheet running square, as i was betting the trailers frames ran true and they did. I know the pictures are a tad difficult to get a real good perspetive of the overall job but theres isn't a bigger gap than a 1/8" and no chance a mouse will just walk into a new home, but they can chew there way in. In the low spots like the bottoms of the drain pipe I made a small hole for any water to drain, the other I just didn't gorilla tape the lowest spot. The fresh water drain I didn't caulk the coroplast around the bung so if any water enters it can drain. Lots of little thing to consider, aside from mice. Probably the only way water might enter between the coroplast and the frame is while driving in rain, and I don't want to caulk anything as it creates another issue when you need to get back into the bottom for future unknown reasons..

[MarkCO]

Originally Posted by Aceallenk

Probably the only way water might enter between the coroplast and the frame is while driving in rain, and I don't want to caulk anything as it creates another issue when you need to get back into the bottom for future unknown reasons..

I used 1/2" foam weather seal on the front of the frame to keep water out. Also making access panels for get back in for repairs if needed. But I am doing mine really slow over several months at least.

[Yakherder]

I used the rubberized waterproof gorilla tape along the front edge and along the outside edge of the frame on the ones I replaced. When I took the old coroplast off I noticed that the factory had only used a bead of caulk along the inside edge which just flaked off. There was no real seal in the first place. It is good to have some way for any water that does get trapped in the underbelly. Water, either from rain while driving or puddles to having a leak in one of the tanks has to have a way to drain out or the whole underbelly can fail.

In my case, I still have the rear section to replace, at some point, and there is still lots of escape for water on the inside.

How did you install the coroplast around the Black/Gray tank pipes? In one of your pictures Al, there are pipes coming out horizontal and are fully exposed underneath. My trailer is very similar to yours and my pipes come out at an angle with the holes through the coroplast cut in a long oval. Did you change anything from the original or was yours like this from the factory.
I would like to know as I think yours would be a better setup.

[Aceallenk]

"Yakherder" That's how they are from factory, and mine looked the same as yours with the long oval hole for the drain pipe in the old coroplast. I just cut there factory crap away and installed my new coroplast using the step method , never removed anything from the tanks, and never loosened a clamp. I used some 2x6 cut from 3" to 5" over 31" these are placed on each side of the pipe. the center is held in place by running metal strapping to a 3/4"x 1 1/2" x 12" strip of wood slipped in above the trailers factory cross rails. this is a tricky thing to achieve because of the design of the tank with those crossrails, Then the 3" part of that 2x6 is held to the frame rail cause I covered those cut pieces of 2x6 from rail to rail with 3/4' x1 1/2" x71" with clear pine. This is the step, you add a piece of 3/4x3/4 clear pine towards the top of each piece of 2x6 for the ceiling part of the step, and the bottom the step is the bottom of the 3/4x 1 1/2 that you ran rail to rail. It'll be as solid as a brick **** house The fresh water was so much easier. maybe I'll go fabricate a few pieces of wood and coroplast and take a picture before I clean the shop today, It'll maybe give a clearer ideal..

[Aceallenk]

Yakherder, I'll give a couple photos of my sewer step, imaging the end where sewer pipe is 4-5" high also supported at top with that metal strap, using another 1x2 between the cross-rail and tank-support. (there is nothing to anchor that metal strap too, so you make an anchor spot using 1x2 sliding it above the tank and neighboring cross member, friction fit. Screw strap to this.) Now on the other end of this angled/tapered 2x6 about 31" long where it tapers down to about 3" and the 1x1 1/2" extends out under the framerail just screwed to the bottom of the frame rail with self tapping 1/4' bolt. This step is going nowhere now. I think will give a better understanding type thing, this isn't built to scale, just an adeal if how it works type thing.

[Yakherder]

Thanks. I copies over your pictures to give me a better understanding of what you did. I'll have a better idea on how to tackle that project one I get the coroplast off that section. I don't think it will be this year with all the events coming up for our family but will have to get to it one of these days.