Bellypan Questions for the Experts - Need Advice

[dbj216]

Greetings All, I am replacing my bellypan and really appreciate all the solutions and knowledge offered in this forum. Quite helpful. I need a little help from the experts please. 1. I plan to use .025 roll aluminum 48" wide, snipped in sheets to the correct trailer width. I plan on joining the aluminum sheets together with rivets every 1" or so to make a continuous sheet from the tank cover to the rear bumper. What is the best way to make a bellypan seam while it is on my work table? 2) Anyone ever install vents in their bellypan? Critter proof ones of course. My insulation was quite wet, and yes rust is a problem. I'd like to vent the belly pan so it will stay dry. 3) I think I get quite a bit of rain water in my bellypan area from the rear bumper. I noticed the skins are not attached or sealed to the rear bumper. Seems to me rain water collects on the sewer hose storage compartment lid, and then runs under the bumper and into the "basement" (floor to bellypan).

I will need your help while I complete this belly pan replacement project. Thank you in advance.

David

[n2batr]

David, I found the belly pan as some of the more difficult work on my restoration because of the angles and curve of the metal. But it is a bellypan so perfection is not needed. Mine is a 1950's trailer so the degree of difficulty may not be the same. Not sure how to answer your first question. You could simply rivet the overlap of the sheets together. It does not need to be sealed/ watertight and in fact needs to not be water tight so it can drain. Expect that some water will get into your bellypan and needs to drain. Having said that I would work to seal the water entry site you mention at your bumper. No point in allowing water to enter if preventable. I used a combination of polyisocyanate insulation covered with reflectix. It came out very clean and neat. I did install aluminum vents at low points in the belly mostly in the front and rear. These were round 4" small louvered vents I got from Ace. I added screen to the inside to keep out critters. I thought this was a good way to assure drainage and ventilation. Ed

[overlander63]

To put in the belly pan, you can run it as long as the sheet of aluminum, and overlap the seams by about 3/4". A rivet every inch is probably overkill, more like every 2-2.5" would be acceptable. I'm not sure I'd put any sealer on the belly pan, you would want any water that gets in there to be able to get out. Overlap from the rear, that is, put the piece of belly pan from the front under the one to the rear, so it won't act like a water scoop when driving in the rain.

[LI Pets]

Don't think you need vents, what are you planning on doing about reinsulating?

I overlapped mine about an inch, 4" on center rivets.

3 years all look fine

See Promax

[dbj216]

Thank you for your advice. I plan on insulating the floor bottom with foam insulation. The frame channels are 5 inch channels, so 4" of foam would give 1" of air space between the foam and bellypan. I figure I'll use home improvement store stuff that people use insulating the basements. I won't be using the fiberglass batting that was origionally there. It was wet, and holds moisture.

David

[LI Pets]

That's ok if you never go on the road, but if that's not the case, it will turn in powder from the movement and vibration.

You may want to do some more research.

[DanB]

Originally Posted by LI Pets

That's ok if you never go on the road, but if that's not the case, it will turn in powder from the movement and vibration.

You may want to do some more research.

This is a real question.....

Really? (re: "it will turn in powder from the movement and vibration")

Do we really know this and has it been tested or photographed? Or is this an Airstream urban legend?

What is refrigerated semitrailers insulated with? Seems there has to be something out there that would work.

I would think if 4" think panels were adhered to the underside of the plywood, the only "movement" would occur from the steel frames rubbing against the sides. And then, the "rubbing" would stop as soon as a gap was created.

Am I correct that the factory doesn't use batts in the belly?

[toastie]

Originally Posted by DanB

This is a real question.....

Really? (re: "it will turn in powder from the movement and vibration")

Do we really know this and has it been tested or photographed? Or is this an Airstream urban legend?


Am I correct that the factory doesn't use batts in the belly?

DanB

Good point on the foam. I will not use batts on my 1955 restoration, perfer the air space.

toastie

[n2batr]

David, I don't think rigid foam/ polyisocyanate sheets are a problem under the floor and between the frame rails/crossbeams. Most of the question/discussion regarding foam involves spray-in foam in the walls which some claim will break apart over time due to constant movement. Some think it is a problem ,some don't but I think the under floor use of foam sheets should be fine. If it does get wet I don't believe it will hold the water as long as fiberglass in the belly and next to your steel frame. Thats my opinion. Ed

[LI Pets]

I recall seeing the problem reported here.

IN any event I don't believe any insulation should go in there.

I put Promax on top of the floor then a pergo type floor, it works in the winter as my feet will testify

Whole belly pan area is empty and stays dry.

[dbj216]

Taking the rear belly pan off was the easy part. Clean and seal frame members, foam insulate, and then install a new bellypan. The .025 Aluminum is on order, big head rivets on order, and I have an idea for holding the new belly pan in place while I drill and rivet.

Here are a few pictures I thought you would be interested in. You can see from the pics that my rear most frame cross member is rusted through. Standing water and wet insulation likely caused this. I figure the water gets in there through the rear sewer hose storage compartment, and the rear "bumper wraps" on each side of the trailer. There is no factory sealing system in these areas. My thinking is to provide a belly pan drain and air vent in this area so the water can get out and dry up.

Nothing like laying on the ground under an old Airstream with Minnesota mosquitoes festing on my face!

[Silverwanabe]

1986 model AS old?
It's still new to me....

[Ken J]

Couple of thoughts from my belly experience - .032 is easier to work with - its not as flimsey - I did not put any insulation back in - to me its just a big sponge and I've not missed it - I don't plan to be camping much below 32 degrees - mine is on, but I'm still trying to decide on the vent thing, thought about just putting in some pin holes to let water out - my belly is not sealed, so should be plenty of air flow without additional venting

Ken J.

[LI Pets]

Originally Posted by dbj216

Taking the rear belly pan off was the easy part. Clean and seal frame members, foam insulate, and then install a new bellypan. The .025 Aluminum is on order, big head rivets on order, and I have an idea for holding the new belly pan in place while I drill and rivet.

Here are a few pictures I thought you would be interested in. You can see from the pics that my rear most frame cross member is rusted through. Standing water and wet insulation likely caused this. I figure the water gets in there through the rear sewer hose storage compartment, and the rear "bumper wraps" on each side of the trailer. There is no factory sealing system in these areas. My thinking is to provide a belly pan drain and air vent in this area so the water can get out and dry up.

Nothing like laying on the ground under an old Airstream with Minnesota mosquitoes festing on my face!

just paint it with por-15