Enclosed/heated underbelly questions.

[C.LeeNick]

For those of you who have travel trailers with factory installed enclosed and heated underbellies, I'm wondering:

How well was it sealed up when you got the trailer? The dealership just installed one on my trailer that was SUPPOSED to have been installed at the factory, and I'm not sure it's "done right".

They used black coroplast, and it seems to be one big piece. (Trailer is about 23 feet) They put plenty of big self-tapping screws around the perimeter, and used big washers. That all seems fine. But there's not much holding it up in the middle. There's a pretty big sag over the axles.

Secondly, in several places around the perimeter, the edges just aren't tight against the frame. Particularly along the front. The gaps aren't huge, maybe enough to stick a business card through, but doesn't it seem water could get in there while on the road during a rainstorm and pool up underneath?

How well are your factory underbellies sealed up around the perimeter?

Thanks!

-Cary

 

[tjkarch60]

My Hideout 21FQWE didn't come with an underbelly, just some insulation under the floor.
So I added my own insulation and coroplast! I know it isn't heated, but it rarely gets below freezing and never below zero. (4 miles from the Pacific Ocean in SW Washington).
I did mine in sections so I could attach the coroplast to the crossmembers and ease of removal if I have to.
I used Gorilla tape to seal the edges where I thought any water could get in. That would be my recommendation for waterproofing.

If you want to try and get rid of the sagging, use a 2x4 or 2x6 to hold up the coroplast and use a jack to hold the lumber up to remove the sag. You might be able to find a crossmember and put in some screws and washers. I got mine at Home Depot. Just be sure it's a crossmember and not a tank! LOL

 

[bsmith0404]

That’s pretty much standard. If you want a better seal, get small strips of metal and attach them with the bolts to give support between them.

 

[Steveo57]

Yep that sounds like what mine looks like. I went around and sealed up all the gaps and holes with expanding foam.

 

[BamaRam]

Mine was sagging in front of the axle. I pushed up on it and the sharp end of sheet metal screws poked through. I threaded some sheet metal nuts with washers on to the screws and it doesn’t sag now.

I think the screws hold the fresh water tank to the frame.

 

[Notanlines]

"maybe enough to stick a business card through" No RV on the market has better coroplast installation than this. The sag is another matter, best handled
as described above.

 

[ctbruce5]

Describing the underbelly as "covered", rather than "sealed" would be more accurate.

 

[C.LeeNick]

A little update: After a weekend camping and a pretty thorough looking over, I see a few gaps along the front driver's side corner that might be up around a 1/4 inch. I'm not worried about heat getting out, the furnace seems to have plenty of "ooomph" to handle it...I noticed no difference in furnace performance indoors. I'm mostly concerned with water getting in. The service tech told me they wrapped the tanks with R-12 fiberglass, and if that stuff gets wet, it could be a problem.

I think I have a solution for the gaps, though. I'm going to use some steel or aluminum angle along the front and rear and "pinch" the coroplast between it and the frame. I'm thinking it should make for an effective seal. Along the sides, the fit seems pretty tight.

 

[cenders]

Same as the rest

My Fuzion FZ310, 36' is the same as described here. One solid length of coroplast, screwed around the edges to the frame. A few occasional screws in the middle, but sagging all over the place. At the edges, between the screws, my has significant gaps that I'm sure weren't there in the beginning. Formed due to expansion/contraction? Not sure. I ended up sealing those with expanding foam.

Like other comments, this is intended to be a "cover" not a "seal". It allows them to run all of your electrical, heating and plumbing between the frame rails instead of inside the trailer. Much easier to build.

My main concern (and experience) was with mice getting into the trailer, so the expanding foam got it closed up. Most recently, the foam around the fresh water drain fell out and we had 6 mice in behind our cabinets.

Water getting in from the road is not really an issue. However, water getting in and mixing with the road dust (depends on where you drive) will eventually turn to a hard cement... I've had my trailer 5 years, a buddy who had his for 9 took it off last summer and ended up removing hundreds of pounds of "cement" that had formed with the water/dust combination.

I'd like to pull mine off and replace all of the heating runs with insulated pipe instead but that'd be a big big job. I've seen people cut openings, use gorilla tape, etc, but it doesn't last.

 

[JRTJH]

My Fuzion FZ310, 36' is the same as described here. ...
I'd like to pull mine off and replace all of the heating runs with insulated pipe instead but that'd be a big big job. I've seen people cut openings, use gorilla tape, etc, but it doesn't last.

If you use your trailer in temps that are below freezing, you might want to reconsider replacing the un-insulated ducting in the "basement". The heat loss (actually radiant heat loss) is a "designed in feature" and the factory uses the "thin aluminum film ducting" that "meanders through the basement" intentionally. The heat ducting is "designed to lose heat" as it turns and meanders through the space. That "lost heat" is what keeps the holding tanks and fresh water tank from freezing. If you "clean up the long ducting runs using insulated ducting" you'll defeat a significant part of your "artic package" or "polar package" and may find that your pipes freeze at much warmer temps than before you modified the trailer..... YMMV, but think about it before you go ripping out a "design feature" without knowing why it's built that way......

 

[Gearhead]

I used perforated angle steel (has slots and holes) across the frame side to side to help with the sagging. You should be able to get it at a good hardware store, or Lowes, Home Depot, etc. I think I used 1.250" X 1.250" angle, maybe 1.5". I connected it into the frame with the same size self drilling self tapping stainless steel screws that the factory used. Got them at Fastenal. If you screw into the same general area the factory used you should be good. I used a 1/4" cordless DeWalt nut driver. Grind the corners off the angle so you won't cut your head open the next time you roll under it. Paint it flat black and git on down the road.

 

[tmason-KEY]

Having to open the underneath more than once I found a product called Eterna Bond to be very good at sealing the cuts ant staying in place.

 

[66joej]

Having to open the underneath more than once I found a product called Eterna Bond to be very good at sealing the cuts ant staying in place.

I found the new heavy thicker Gorilla tape works good. Much cheaper and can be removed without damaging the coroplast. JMO

 

[GlennB724]

Last year on my second trip in my new (at the time) Alpine 3401RL, after a day of BOUNCING down the road crossing Nebraska, (iirc Interstate 80???), we pulled into the campground and wife discovered that the underbelly cover had pulled off for about 3/4 of its length, and it was sagging down with half of the fiberglass batting hanging out, (the other half was added to the environment somewhere). After having a mobile repair service guy come out, he re-attached it along the edges and added some wood furring strips across the bottom side to side, (metal angle iron was not available nearby). It held on like that for the rest of the trip until I got home and could put the trailer in for warranty repair. (I have no idea if the missing insulation was replaced.) It's on the long list of "someday I'll have to check on that" items. As mentioned already, it was pulled very tightly across one of the water tanks, and I think the bounce of the weight of the water while driving down the horrible road just ended up tearing the plastic from the screws attaching it.

 

[Ranger 3/75]

I have a 2019 cougar 33sab and if gets below 25 all my water lines freeze. That's with the furnace on 74 degrees. Last night it got down to 22 and the bathroom was froze again

 

[Steveo57]

I have a 2019 cougar 33sab and if gets below 25 all my water lines freeze. That's with the furnace on 74 degrees. Last night it got down to 22 and the bathroom was froze again

Have you crawled underneath and checked the coroplast underbelly the make sure it's sealed up tight. I wouldn't expect one night with temps like that to cause any problems especially since you had the heat running.

 

[chuckster57]

Having to open the underneath more than once I found a product called Eterna Bond to be very good at sealing the cuts ant staying in place.

Eternabond is primarily used on the roof membrane. Gorilla tape is good but the adhesive will fail years before it will using scrim tape. Scrim tape is designed for coroplast.

https://www.rvupgradestore.com/Surf...d2ed3f&gdfms=CA2311EBADC34504944FACA1583AEE5B

Picture for description only.

 

[ajk170-KEY]

Chuckster57- That's a great tip about the Scrim Tape for people like me that's not real savvy on this stuff but can do a lot of this stuff on my own. I thought the eterna bond was a good idea until I saw your suggestion!

 

[JRTJH]

Every year at the beginning of the winter season we get questions about the "arctic package" and "heated basement problems". Then they seem to be "forgotten" until it gets really cold and people start having frozen pipes. They need to do something to "fix the issue of frozen plumbing" but honestly, mid winter in sub zero temperature is not the time to "FIX" it, rather it's the time to get it working again. Adding heat to the basement, turning up the thermostat inside (to share the heat "down below") and trying to prevent "cold air from blowing under the trailer" are some of the most effective "stop gap" measures.

The time to "FIX" the problem is next spring/summer, when you're not thinking about frozen pipes but the conditions are much nicer for "human intervention"... While it's warm and comfortable is the time to pull the coroplast, move plumbing runs away from the steel frame rails (where they're guaranteed to freeze) and to pull everything out of the closets/cabinets on outer walls inside the trailer and reroute the plumbing so it doesn't "touch the outside wall" by using small bits of rigid foam board between the wall and the pipe. Back under the trailer, if you look at the frame rails that make up the sides of "your heated basement" you'll see that they are not insulated, filled with holes ranging from 1" to 4" in diameter. That's like opening all the windows on your RV and wondering why the furnace can't warm things up inside.... All of those holes can't be closed, some are part of the slide mechanisms and must be open, but there are ways to seal much of the basement that is "for the most part, open to the elements all winter".....

As for frozen pipes in 20F weather, that's more or less a given way of life with today's "arctic package protection". If you can make it through until spring, don't forget about it until next winter. While the weather is nice, spend a couple of days under your trailer, improving next winter's "survivability"....