What does a guy have to do to seal up the underbelly?

I’ve got an 18 3560SS and the underbelly has become a problem.
Had an issue with the underbelly last month from water leaking in and soaking the insulation and also a leak around the fresh water tank. I paided $700 to fix the leak and seal up around the edges for water intrusion from outside when running in the rain.The dealer sealed up with silicon and spray foam and I used 2 tubes of silicon and a can of foam myself and thought it was sealed.
Two weeks ago I noticed a bag in the underbelly and cut it and sure enough , water.
I made a couple cuts to drain what I could while parked and then taped them up with the heavy duty black tape. I had to pull about 300 miles today and better than half in the rain. Of coarse when I got setup I had a look underneath and water was running out the end where the tape was.
Ive talked with the dealer and they will take it all down again and dry it out , remove the fiberglass insulation and replace that with the plastic foam type and reseal everything.
What am I missing here?
I don’t want to have to do this all the time , how does one make sure it’s water tight.
This is my 5th RV and I never had anything like this on the others.
I will call Heartland but as it’s out of warrantee don’t think they will help, maybe some advise to fix.
Tired of wet feet!!
BD

I had water intrusion driving in the rain, so it was obvious the force of the spray around the area of the wheels was the problem. What I did was purchase 2” wide flat aluminum, 1/8” plate. I had to measure and cut to fit around spring shackles. I then used self tapping screws into the frame and applied lots of sealant between plate and corroplast. After four years I never had any more problem.
PS, I did this also on front of belly.

MT, you wouldn’t have any pics of your repair?
BD

Honestly if you drive in a driving rain, there isnt any fool proof method to seal the under belly. I have had the same rain ingress issue on my landmark. In my tiny mind...the coroplast is a cover not a seal.


So if you go and fill the holes with foam, and tape the heck out it. Water will still get in and now it wont ever dry out. I have several 1/4 inch holes drilled in the coroplast, in the lowest areas...to act as a permanent drain.

bigdob24 said:

MT, you wouldn’t have any pics of your repair?
BD

Click to expand...

Wish I did. It was too long ago, and I no longer have the trailer; but it did work for me. Corroplast won’t leak, except around edges or seams. Pressing/wedging the corroplast between the aluminum plate and frame eliminated the route for the water to enter.

Here's what I did:

Removed and replaced all the wet insulation, put rigid foam board between the fiberglass and the coroplast, then before closing it all up, I bought 1/2 inch plastic conduit and put that between the foam board and the coroplast, every 3 feet. This created a air gap, so if water did get in, it didn't get anything wet.

Also bought some metal 1/2 conduit, flattened the ends and drilled a hole at each end. Then put this conduit across the width of the camper to help hold the coroplast up, using the same screws to hold the conduit in place.

No more sagging, so far......

Also bought some Gorilla weather proof tape and put it everywhere it looked like there was a hole.

They seemed to use a torch to cut part of the hydraulic jack mount away for the propane supply pipe to go straight, and all the slag blew onto the coroplast, so there was lots and lots of little holes around the jack. Gorilla water proof tape works great. It looks like Eternabond tape, but its black.

Thanks for the ideas
Will have to do something to fix this
BD