Tank supports

Freshwater System, Grey and Black Tanks, LP Gas
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KYAvion
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Tank supports

Post by KYAvion »

I saw a post on FB where an Avion owner lost his freshwater tank--it appeared to fall on the road through the belly pan. It appears the only support was a plywood sheet. Is that the case for all years? There's no sheet metal straps or pan holding the tanks in place?
KYAvion
1984 Avion 30R
Sawmiller
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Joined: Fri Jun 16, 2017 4:45 pm

Re: Tank supports

Post by Sawmiller »

My 68 had 2 pieces of aluminum angle riveted to the frame. These ran under the tank with foam board on top.
Sawmiller
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Re: Tank supports

Post by Sawmiller »

Misread the post. That was for my black tank. My fresh water tank sits on the floor in the front of the unit. No way to fall out.
Rostam
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Re: Tank supports

Post by Rostam »

I need to inspect my fresh water tank at some point. Since I do not know the condition of the support beams, I travel with empty water tank for now.

I plan to cut the belly pan right under the fresh water tank to make access to fresh water tank easier. I will then re-rivet the square aluminium sheet to the rest of the belly pan. It seems the previous owner of my trailer did a similar thing for waste tanks. When I crawled under, I noticed that I can remove a portion of belly pan to get access to waste tanks. Ideally, this would have been a feature coming from the factory, say a sliding door that can be locked and gives you easy access to water tanks.
1978 Avion 26-H
2021 Toyota Tundra SR5
RISK
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Joined: Wed Aug 02, 2017 10:50 am
Location: Sunset Valley, TX

Re: Tank supports

Post by RISK »

I have just peeled the onion that is the belly pan in search of a grey water leak. Dr. Gradeless said I should have the ply wood shelf supporting my tanks, though when I pulled the underwear off my girl, I found the grey water tank held up by two pieces of angle iron. This both delighted and disturbed me. Delighted because I didn't have to replace any rotting wood. I'm tired of rotting wood, I also own an Airstream. It disturbed me because this tank is huge. That's a lot of weight hanging in there. I swear that once I fixed the leak (at the outlet, nothing big to report) and added maybe 10 or 15 gallons to test, the tank started to bulge from the weight and probably heat (Texas).
My take away here is:
- Don't try to fix anything, you'll just be haunted by how things are under there and you'll lay awake at night thinking about driving down the road while 30 gallons of fetid water come pouring out of your trailer on the state trooper who just happens to be behind you
- you'll realize what rabbit holes any vintage travel trailer can be.
- Or you'll endeavor to improve upon the design and make it better. Like I did when I was renovating an Airstream and the best fix I had for it was to get an Avion and actually go camping.

I will finish that Airstream. I'll sell it for way more than I could get for the avion. I'll keep the avion.

Ian
1978 26M
1964 SilverStreak Sabre
1977 Airstream Sovereign (in a million pieces)
silverloaf
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Re: Tank supports

Post by silverloaf »

I'm glad this subject is being broached. We bought a 1988 30-W 5 weeks ago. I now rests on 8 wood piers and jack stands in my driveway.

I have removed the brakes, axles and suspension for re-build. I started removing pieces of belly pan due to its condition.

This unit has a full bathroom across the rear. The holding tanks are behind and adjacent to the wheel housing on the left side. I uncovered severe sub-frame damage on each side of the gray/black dump valves. A cross-trailer steel floor support is also missing a flange due to water exposure. I had to remove a lower body panel to see everything.

It appears someone had replaced the black water tank. 3 aluminum channels support the tank. The channels are anchored to the left/right sub-frames by small sheet metal screws. The channels are just barely secured to the rusted-out sub-frame, suggesting the metal rotted out before the tank was replaced. The elbow for the gray water tank has a hole in it from rubbing against a jagged hole cut in a cross member.

I'm forced to remove the gray and black water tanks to reconstruct the steel framing. Mine has a plywood beneath the gray and fresh water tanks. It must come out as well.

But I'm confounded by how the dump valves were originally routed through the sub-frame while still preserving structural integrity. The dump valve outlet does not line up with the access hole in the compartment door.

This area has seen a lot of moisture intrusion. Has anybody experienced this issue on their unit? Can you explain (maybe a picture) of what this transition is supposed to look like?

Thanks in advance.

Bob
" Faith can move mountains, but don't be surprised if God hands you a shovel.”


Silverloaf (Bob)
Dawsonville, GA
1988 30P
silverloaf
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Re: Tank supports

Post by silverloaf »

My comments have to do with creating a drainage plane for unwanted water that can affect tank supports.

I now have the fresh and black water tanks out. The fresh tank was supported by a sheet of plywood; the black tank by 3 aluminum channels. The plywood and aluminum channels are in good shape. But the sub-frame that anchors the channels for the black tank on the left side is rotted out.

One thing I have observed is the top of both tanks have sagged in the middle; there is no internal support. Another thing is that the tanks appear to get their support structure from their outside walls. The middle adds little value; more like a bladder.

I got a bath while removing the black tank. I was drenched in 2-3 gallons of water. Fortunately it was clear.

This leads me to the conclusion that these depressions act as a reservoir. They capture water from leaks like plumbing, rain, wheel splash, body, roof, etc. In quantity, it will overflow, slosh and saturate their surroundings. Add the belly pan and a wet cavity resembles a humidor.

I suspect this scenario took out the plywood on the FB post and the floor & and sub-frame on ours.

This creates a conundrum for me. There is no realistic way to inspect or drain these craters with the tanks in place. I must ensure every plumbing joint from tank to "sink/toilet/shower" to roof must be water-tight. This includes the roof.

Here's a few things I'm considering before re-installing the tanks.
1. Encapsulate the tank cavities with a waterproof membrane (self-sticking water and ice shield comes to mind). This includes the floor and steel framing. Force any potential water to drain down.
2. Convert the plywood holding the fresh water tank to a removable, structural metal ladder-frame. Install foam panels within the ladder.
3. Provide a means for water to drain out through the belly pan.
4. Install air vents in the belly pan.

I may not be able to totally prevent moisture intrusion. But I can at least manage collateral damage.

Make Avion Great Again!!

Bob
" Faith can move mountains, but don't be surprised if God hands you a shovel.”


Silverloaf (Bob)
Dawsonville, GA
1988 30P
ericlarson
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Joined: Mon Oct 23, 2017 6:59 pm

Re: Tank supports

Post by ericlarson »

I am interested in how you went forward and what your decisions resulted in. In my limited uncovering of the belly of my Avion I see that the cross members (T type steel reinforcements from side to sidethat support the "chip board" plywood) are rusted a lot. I don't feel good about not re-enforcing or even replacing these. Please share the path you took and the results you have.
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KYAvion
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Re: Tank supports

Post by KYAvion »

silverloaf wrote: Thu Aug 24, 2017 1:15 pm I'm glad this subject is being broached. We bought a 1988 30-W 5 weeks ago. I now rests on 8 wood piers and jack stands in my driveway.
How's this project coming along? Hope you took a lot of pics to document your work.
KYAvion
1984 Avion 30R
silverloaf
Posts: 763
Joined: Wed Aug 23, 2017 9:01 pm

Re: Tank supports

Post by silverloaf »

ericlarson wrote: Fri Jan 12, 2018 1:00 am I am interested in how you went forward and what your decisions resulted in. In my limited uncovering of the belly of my Avion I see that the cross members (T type steel reinforcements from side to sidethat support the "chip board" plywood) are rusted a lot. I don't feel good about not re-enforcing or even replacing these. Please share the path you took and the results you have.
First, let me clarify that ours is a 30-P, not a 30-W as previously noted.

I took a lot of pictures of the underside during the restoration process. Unfortunately, many were close range in tight quarters. It is difficult to keep the surroundings in proper perspective.

You are talking about the fresh water tank. The cross-members you refer to are likely Z-channel; the top flange goes in one direction and the lower in the other. The member is roughly 9" in height. These cross-members are welded to the main frames that extends along the outside of the trailer. 3/4" angle iron is then welded to the channels and frame to secure the plywood which hold the tank in position.

The cross-members encapsulating my tank were rusty as well. It was mainly heavy surface rust that I knocked down with a wire brush and wheel. I then applied a liberal coat of rusty metal primer.
https://www.homedepot.com/p/Rust-Oleum- ... /100112883

If portions of your channel or angle iron are rotted though or missing, I recommend you cut out the bad stuff with an angle grinder and graft in some new. I had to do this in the back of the trailer.

After further consideration, I decided not to fabricate some fancy metal ladder support in place of its wood counterpart. I would have been limited to 3/4" angle iron. I didn't have a quick way to calculate the number of cross pieces to mimic the load capacity of the OEM plywood.

I did replace the OEM material with 3/4" AC plywood because the edges were soft after 29 years. I selected plywood made with exterior glue ( most are these days). I used the old plywood as a template for the new, including the fastener holes. I rolled on 2 coats of high quality oil-based exterior primer.

I wasn't aware that some Avion trailers used chip board (or OSB) for the tank support. Although plywood and OSB have competitive span and load rating characteristics, they behave quite differently when wet. The edges of OSB are particularly vulnerable to swelling. I would be concerned the fasteners securing the board to the cross-members might pull through the edge. Here's an article that might interest you on the subject.
http://www.greenbuildingadvisor.com/sit ... FHB169.pdf

By the way, I replaced the hoses and fittings for the tank. I used the following thread joint sealant:
https://www.homedepot.com/p/RectorSeal- ... lu+sealant.

Lastly, I cut a rectangular access hole in the plywood and belly pan directly below the service hole in the floor. This enables me to inspect all the tank connections for leakage and repair them on top or underneath. I made a simple aluminum cover plate that is secured to the belly pan.

Let me know if this is what you are looking for or need more info. I also replaced steel and the rear floor above the black tank if you need some help there.

Bob
" Faith can move mountains, but don't be surprised if God hands you a shovel.”


Silverloaf (Bob)
Dawsonville, GA
1988 30P
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