Tank supports

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

Post by KYAvion » Tue Jun 20, 2017 8:23 pm

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
Posts: 43
Joined: Fri Jun 16, 2017 3:45 pm

Re: Tank supports

Post by Sawmiller » Wed Jun 21, 2017 6:52 am

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

Sawmiller
Posts: 43
Joined: Fri Jun 16, 2017 3:45 pm

Re: Tank supports

Post by Sawmiller » Wed Jun 21, 2017 6:54 am

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
Posts: 131
Joined: Tue Oct 04, 2016 9:54 pm

Re: Tank supports

Post by Rostam » Wed Jun 21, 2017 1:25 pm

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 (Rear twin beds, center bath, front dinette)
2012 Mercedes Benz GL 350 Bluetec, 3.0L V6 Turbo Diesel, 3.45 Axle Ratio

RISK
Posts: 68
Joined: Wed Aug 02, 2017 9:50 am
Location: Sunset Valley, TX

Re: Tank supports

Post by RISK » Thu Aug 10, 2017 11:29 pm

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

silverloaf
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Joined: Wed Aug 23, 2017 8:01 pm

Re: Tank supports

Post by silverloaf » Thu Aug 24, 2017 12:15 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.

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

silverloaf
Posts: 98
Joined: Wed Aug 23, 2017 8:01 pm

Re: Tank supports

Post by silverloaf » Fri Sep 01, 2017 10:09 am

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

ericlarson
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Joined: Mon Oct 23, 2017 5:59 pm

Re: Tank supports

Post by ericlarson » 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.

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