Let her breath or try for sealed up tight?

[simple sanctuary]

Dear Airstream family, needing more of your much appreciated advice.

I've made progress in my subfloor repair: finally have the rotted section, fiberglass, and debris out of the back and have ground out the bolts and screws in the C channel. (I've attached a few photos to show my progress).

There are a few areas where I can see clear to the outside (small openings between belly pan and banana wrap?). When I was at Out of Doors Mart buying supplies, one of the wise service folks remarked that it's important to have a way for any water that might find it's way into the belly pan be able to find it's way out. So, before I reinstall insulation and new plywood, I have a few questions…

1. Would you recommend sealing ALL the openings (or leaving for some ventilation)?

2. If so, what would you use to seal A) the cracks? B) the eroded hole in the back bumper which does not seem to pose any structural issues? (see pix)

3. And though I thought I would not replace the fiberglass insulation with same stuff, it seems like that might be the best option (at least the white less itchy stuff with the backing pulled off) for a few reasons: it has a better chance of drying if it gets wet than say bubble wrap resting in the belly pan, it's what's in the rest of the trailer (i'm only replacing one 4x8 sheet), and I'm doing this repair with the belly pan on. Any other recommendations I should consider here?

Thanks~
Kim

P.S. Don't be alarmed, I am going to apply a rust converter to the frame then paint. And I have a friend who is going to come help me with bolting in an angle iron in one corner before hoping for a smooth plywood installation this weekend

P.P.S. While I wish my trailer could be perfect in the seen and unseen parts, I don't have the time or financial resources to do a shell off full-on renovation. Gotta get her ready to move in full-time by June (while working my other jobs) so I'm aiming for safety and functionality without getting sucked down a never ending fix it list .

[Inland RV Center, In]

Originally Posted by simple sanctuary

Dear Airstream family, needing more of your much appreciated advice.

I've made progress in my subfloor repair: finally have the rotted section, fiberglass, and debris out of the back and have ground out the bolts and screws in the C channel. (I've attached a few photos to show my progress).

There are a few areas where I can see clear to the outside (small openings between belly pan and banana wrap?). When I was at Out of Doors Mart buying supplies, one of the wise service folks remarked that it's important to have a way for any water that might find it's way into the belly pan be able to find it's way out. So, before I reinstall insulation and new plywood, I have a few questions…

1. Would you recommend sealing ALL the openings (or leaving for some ventilation)?

2. If so, what would you use to seal A) the cracks? B) the eroded hole in the back bumper which does not seem to pose any structural issues? (see pix)

3. And though I thought I would not replace the fiberglass insulation with same stuff, it seems like that might be the best option (at least the white less itchy stuff with the backing pulled off) for a few reasons: it has a better chance of drying if it gets wet than say bubble wrap resting in the belly pan, it's what's in the rest of the trailer (i'm only replacing one 4x8 sheet), and I'm doing this repair with the belly pan on. Any other recommendations I should consider here?

Thanks~
Kim

P.S. Don't be alarmed, I am going to apply a rust converter to the frame then paint. And I have a friend who is going to come help me with bolting in an angle iron in one corner before hoping for a smooth plywood installation this weekend

P.P.S. While I wish my trailer could be perfect in the seen and unseen parts, I don't have the time or financial resources to do a shell off full-on renovation. Gotta get her ready to move in full-time by June (while working my other jobs) so I'm aiming for safety and functionality without getting sucked down a never ending fix it list .

The underbelly MUST breath, or else the steel will rust away.

Andy

[Belegedhel]

I'll second the above--don't worry about making the underbelly water/air tight. You do want to seal up any hole large enough for a rodent to crawl into, though, just to forestall the inevitable habitrail inside the wall.

[simple sanctuary]

thanks, ya'll. think i have a better handle on this now. and i'm actually going to use bubble wrap and staple in onto the underside of my subfloor before i lay it in (versus the fiberglass).
~kim

[J. Morgan]

Simply stated, keep the water out, and let air circulate to dry things when water gets in , and it will.

[dznf0g]

So, there have been a few post in the past relative to installing vents in the underbelly, but not much of a theoretical discussion of the pros and cons. I have been thinking of installing some stainless clamshell (marine) vents with screens in the belly skin. What say you all?

Like these:

http://www.defender.com/product3.jsp...90140&id=46679

[Minno]

We used those vents to ventilate the sealed space for our AGM batteries. They are quite small, but install easily.
We used no insulation under our floor, and did not seal the belly pan completely. We did seal cracks big enough for mice to get in. Our floor is floating cork, which is quite warm in cool weather.


Kay

[cameront120]

Fibreglass insulation retains water and stays wet unless the water can go somewhere and air gets in there to dry it out. The fact that fibreglass insulation does retain water contributes to it's losing insulating value and becoming next to useless. I would replace the pink stuff with a rock wool insulation such as that made by Roxul. This type of insulation is hydrophobic. That is, water is repelled and not absorbed by the insulation. It won't deteriorate like fibreglass and retains its insulating qualities better. It's a bit more expensive, but is worth it.

[simple sanctuary]

thanks all! more insulation and ventilation questions...

i bought a roll of bubble foil thinking i would staple to the underside of the subfloor (except for a few inches along the edge which slides into the c channel) before laying on the chassis. then a friend pointed out that i already have the benefit of reflection in the belly pan and therefore the bubble wrap might not be so valuable, especially if it might hold moisture close to the plywood (planning to use AC plywood and paint the edge plus 6 inches in, top and bottom).

he asked about resting styrofoam rafter vents down in the chambers of the belly pan and then placing 3 1/2 inch fiberglass insulation on top of that (so that it's not sitting in the belly pan holding water when any does get in). has anybody tried the styrofoam rafter vents (like used in attics?) to keep insulation out of the bottom of the bellypan?

guess that i could do the same but use the rock wool instead of fiberglass over the styrofoam vents. cameron, do you know if the "rock" wool is same as "stone" wool by roxul? and how were you suggesting inserting? attached to bottom of plywood or resting in the chambers in-between the frames? thanks for the tip…didn't know about this stuff.

kay, did you use a vapor barrier between your floating cork floor and subfloor?

[SeeMore]

You may find this thread of interest for pink foam board insulation:

http://www.airforums.com/forums/f46/...ml#post1428559

[cameront120]

Originally Posted by simple sanctuary

cameron, do you know if the "rock" wool is same as "stone" wool by roxul? and how were you suggesting inserting? attached to bottom of plywood or resting in the chambers in-between the frames? thanks for the tip…didn't know about this stuff.

kay, did you use a vapor barrier between your floating cork floor and subfloor?

Yes, rock wool and stone wool are the same. The insulation is made out of spun molten rock. You could place it between the metal floor cross-members and hold it in place with long fasteners designed for fastening the insulation to exterior walls (they have a large plastic washer to prevent the insulation from passing over the head of the fastener). This method would be good if you used Roxul Comfortboard insulation, which is more rigid. If you were to use the regular Roxul batts, you could hold it in place with strapping fastened to the underside of the metal frame.

With respect to Vapour Barrier, your plywood subfloor will act as a VB, so no need to add one.

[TinTin]

Originally Posted by dznf0g

So, there have been a few post in the past relative to installing vents in the underbelly, but not much of a theoretical discussion of the pros and cons. I have been thinking of installing some stainless clamshell (marine) vents with screens in the belly skin. What say you all?

Like these:

Sea-Dog Clamshell Midget Ventilator

I like the idea! Would sheet metal screws be appropriate for attaching the vents to the belly pan, or is there a better alternative?

[dznf0g]

Originally Posted by TinTin

I like the idea! Would sheet metal screws be appropriate for attaching the vents to the belly pan, or is there a better alternative?

I will probably rivet them in place. I found some round 1" screened plugs. The clamshells will go over them.

[TinTin]

Rich, how many vents were you thinking of for your 30 footer?

[dznf0g]

I decided on 6. 2 behind the tanks and 4 up front.

[TinTin]

I believe that I'll install six of these as well. I found a local source for the sea-dog midget clamshell vents.

I'll try and find some screened covers for the holes locally as well. I may go a little smaller than one inch holes, perhaps 3/4".

Thanks for the idea, Rich!