Sealing a large gap?

"VincentMalamute-Kim" (VincentMalamute-Kim)
08/03/2020 at 00:18 • Filed to: None

Good looking Class B RV.

AC on my friend’s Roadtrek went out. It had a large plastic rain shield/air diverter that kept the exhaust and intake air for the condenser from mixing. There was no room to work and I was afraid to cut up the shield to remove it. I told her to have the experts at the RV repair place to do the AC replacement.

She did that and with the first storm, rain soaked the interior. I could see looking through these louvers that they had torn up the plastic water/air shield and didn’t replace it. I told her I didn’t trust them to fabricate a new shield and I’d take care of it now that I knew they were bozos.

PITA getting the

outside cover off - they cross-threaded a screw and overtightened one. Had to use a hand impact driver.

They’d replaced the Dometic RV AC with a household Toshiba! You can see the accordion flaps here. Condenser intake and exhaust air mixes together along with intake air for the evaporator. And they pre-mangled the condenser fins.

And then inside:

Orange arrow on the right is the metal roof of the RV. Green arrow on the left is a 3/4" gap between the AC unit and the metal roof. This is completely open to the outside!!! Just above the orange arrow, you can see black sealant - so they sealed the sides but not the bottom. argh.

Yet another example of not letting “professionals” fix your stuff. I could’ve screwed this up much better than they did.

I suspect I’m going to have to redo the entire install.

Question: But how would Oppo seal that bottom gap? 3/4" is really too much gap for any kind of sealant to cross.

DISCUSSION (25)

Dead_Elvis, Inc. > VincentMalamute-Kim
08/03/2020 at 01:03

Kinja'd!!!

jminer > VincentMalamute-Kim
08/03/2020 at 01:12

Foam plus a fat bead of silicone.

That unit is also loud as hell, had one on my office but returned it as it was loud.

Rusty Vandura - www.tinyurl.com/keepoppo > VincentMalamute-Kim
08/03/2020 at 01:14

In my experience, anybody who claims to be an RV mechanic is probably named Clem and pick a few other stereotypes...

The foil tape is a good suggestion also, you might consider aluminum flashing and foil tape. You can buy the flashing and a roll at Home Depot and then cut a strip to fit. Also there are a couple of different kinds of RV specific sealant that don’t behave like ordinary caulk. It’s sort of flows and smooths out differently. It’s hard to explain, but it works better on RVs.

I had a supposed RV shop install a vent fan in my tent trailer and what a big mistake that was. They totally butchered it, it leaked the first time it rained, and I’ve been playing catch up ever since.

notsomethingstructural > VincentMalamute-Kim
08/03/2020 at 01:51

You could either get a foam backer rod and use the sealant against the backer rod (same way they make expansion joints in masonry) or use expanding foam in a can (same way they do window frames). You can also trim back and overlay the foam with something afterwards like Jb weld. Both would be acceptable. I would just spray foam it since the access is pretty minimal - the JB weld is overkill here unless there’s signs of corrosion or active leaks after the foam is in . Get a closed cell foam as it will be more water resilient. I think loctite makes a closed cell foam that’s guaranteed not to leak for 5 years.

sony1492 > VincentMalamute-Kim
08/03/2020 at 02:10

Kinja'd!!!

Flat aluminum bar from the hardware store and self tapping screws

Dogsatemypants > VincentMalamute-Kim
08/03/2020 at 09:17

Foil tape with durabon d strips or mat to insulate and protect from tearing.

This is what we'll show whenever you publish anything on Kinja: > notsomethingstructural
08/03/2020 at 10:36

I just came here to say “ Rod and Caulk"

notsomethingstructural > This is what we'll show whenever you publish anything on Kinja:
08/03/2020 at 10:49

heh rod. heh caulk.

VincentMalamute-Kim > notsomethingstructural
08/03/2020 at 21:02

Thanks. After thinking about it all day - I’m probably going to remove the AC to see how they sealed the sides. It looks good from the inside but that’s the unit sealed to the finished interior trim. I can’t see how they sealed the sides of the unit against the exterior fiberglas cap. If they even did. Given the workmanship, I’m having doubts.

Thanks to everyone’s ideas, if I do reinstall the unit, I’ll have access to install a PVC ledger along that bottom and have a small gap that I can caulk.

VincentMalamute-Kim > Rusty Vandura - www.tinyurl.com/keepoppo
08/03/2020 at 21:05

My one experience with RV mechanics confirms your stereotype. I bet you’re thinking of Dicor RV sealant. Self lapping. Also comes in non-self lapping. I used it during the vent fan install on my Transit. I did a fine job if I do say so myself! Compared to your RV shop. Difficulty in finding good people is s o irritating.

After t hinking about it all day - I’m probably going to remove the AC to see how they sealed the sides. It looks good from the inside but that’s the unit sealed to the finished interior trim. I can’t see how they sealed the sides of the unit against the exterior fiberglas cap. If they even did. Given the workmanship, I’m having doubts.

Thanks to everyone’s ideas, if I do reinstall the unit, I’ll have access to install a PVC ledger along that bottom and have a small gap that I can caulk.

VincentMalamute-Kim > sony1492
08/03/2020 at 21:07

After thinking about it all day - I’m probably going to remove the AC to see how they sealed the sides. It looks good from the inside but that’s the unit sealed to the finished interior trim. I can’t see how they sealed the sides of the unit against the exterior fiberglas cap. If they even did. Given the workmanship, I’m having doubts.

Good idea. I f I do reinstall the unit, I’ll have access to install a variant of your idea using PVC ledger board along that bottom and have a small gap that I can caulk.

VincentMalamute-Kim > jminer
08/03/2020 at 21:09

L uckily it’s not my RV. If I don’t mention that to her, she’ll never notice the sound level of that AC unit.

After thinking about it all day - I’m probably going to remove the AC to see how they sealed the sides. It looks good from the inside but that’s the unit sealed to the finished interior trim. I can’t see how they sealed the sides of the unit against the exterior fiberglas cap. If they even did. Given the workmanship, I’m having doubts.

If I do reinstall the unit, I’ll have access to install a using PVC ledger board along that bottom and have only a small gap that I can caulk.

If I don’t reinstall the entire thing, I’ll probably do the foam/caulk.

VincentMalamute-Kim > Dogsatemypants
08/03/2020 at 21:10

Durabond? Google only shows drywall tape? I do have super sticky RV coal tar looking tape, forget what it’s called. I bet that’s what you’re referring to.

VincentMalamute-Kim > Dead_Elvis, Inc.
08/03/2020 at 21:11

Thanks for the idea. I’ m thinking most adhesives on tapes won’t last long enough. I don’t know about foil tapes though.

After thinking about it all day - I’m probably going to remove the AC to see how they sealed the sides. It looks good from the inside but that’s the unit sealed to the finished interior trim. I can’t see how they sealed the sides of the unit against the exterior fiberglas cap. If they even did. Given the workmanship, I’m having doubts.

If I do reinstall the unit, I’ll have access to install a using PVC ledger board along that bottom and have only a small gap that I can caulk.

If I don’t reinstall the entire thing, I’ll probably do the foam/caulk.

Rusty Vandura - www.tinyurl.com/keepoppo > VincentMalamute-Kim
08/03/2020 at 21:16

Dicor: yup.

I’d probably strip all of the household plastic window a cc ordio n flap garbage and make my own flashing. Also, did the Dometic unit vent and flow air the same way as this window unit does? I’d be taking a hard look at airflow and what I could do to make it more copacetic.

Dead_Elvis, Inc. > VincentMalamute-Kim
08/03/2020 at 21:33

I don’t know if I’ve used that particular brand, but I’ve used this type of tape to temporarily repair a cracked air filter housing. Ul timately never bothered to repair it properly, since the adhesive seemed to be perfectly tolerant of underhood temps after a couple weeks . A year later, it still hadn’t peeled, bubbled, or shifted at all. It was a much more aggressive adhesive than what you find on duct tape, more like Gorilla tape.

You’ve only got one chance to put it place, though - it’s not coming off in one piece for repositioning, IME. If you can bridge the gap with it, it should stay in place as long as you need. ( But if you’re going to go to the effort of pulling the unit out, I’d probably take your approach.)

notsomethingstructural > VincentMalamute-Kim
08/03/2020 at 21:46

In my humble opinion, when I encounter questionable workmanship especially on water issues, trying to fix a small issue frequently turns into fixing a big issue. For example, if you can’t properly flash around the opening because all the other waterproofing wasn’t installed correctly. Sometimes it’s better to improve something that’s working than it is trying to do the work correctly and breaking it. Plus There’s times people tried to do it right and it just wouldn’t work.

VincentMalamute-Kim > Rusty Vandura - www.tinyurl.com/keepoppo
08/03/2020 at 21:57

I can’t remember how the Dometic air flow was. It doesn’t matter now since the unit is different and they tossed all previous air management shielding.

I think what I come up with will be similar to what was there before.

And another good reason to reinstall the unit - get rid of the accordion flaps and see what they did behind them.

VincentMalamute-Kim > notsomethingstructural
08/03/2020 at 21:59

True on all your points. I’m thinking (hoping? ) that if I do redo it myself, I’ll do the entire job correctly. That is what usually happens on my projects. Not always. But usually.

VincentMalamute-Kim > Dead_Elvis, Inc.
08/03/2020 at 22:01

That’s nice to hear about the foil tape. I do have some hacked together water shields in my Transit’s engine bay that could be better sealed with the foil tape then .

yeah, I’m leaning to pulling the AC unit and redoing everything given their workmanship. Stay tuned.

Rusty Vandura - www.tinyurl.com/keepoppo > VincentMalamute-Kim
08/03/2020 at 22:11

Was that work done recently? Maybe you should go in and tear somebody a new rectum. Or surgically install one with a reciprocating saw.

VincentMalamute-Kim > Rusty Vandura - www.tinyurl.com/keepoppo
08/03/2020 at 22:18

It was done l ast summer. It’d be a leap for me to make a scene - I’m too non-confrontational.

Rusty Vandura - www.tinyurl.com/keepoppo > VincentMalamute-Kim
08/03/2020 at 22:47

No, you never struck me as a scene kind of guy

Dogsatemypants > VincentMalamute-Kim
08/04/2020 at 14:54

Meant eternabond. Got the names mixed up

VincentMalamute-Kim > Dogsatemypants
08/04/2020 at 15:16

ah. I actually have some but didn’t think to use it.