replacing section of rear sub floor in 2007 28ft safari question

[jackvosney]

Hello again folks!

Okay so so am finally getting around to replacing the sub floor in our 2007 28ft safari. I am guessing the rot is due to the dreaded bumper sill area leak. The previous owner sold it too me knowing of the damage but had it covered by a tarp in the rear access hatch but i am partially to blame for not looking under it...none the less i do not think fondly of the person who sold me the AS.

okay to the questions. I really had no idea what i was getting into when i started taking things apart. I am skilled at carpentry and metal working, built my home etc, so i thought this will be apiece of cake.... wrong....

From what ive read you have to take take all the inner skins of off in bedroom area and i really do not wish to do this. I've potentially come up with a solution. The area i need access to will be covered by cabinetry. I see no reason why i cant cut out the section of skin in the attached photo to get access to the frame bolts and then replace with another sheet of aluminium slightly larger. I will never see this area, and i don't care if it doesn't match perfectly.

Am i missing something? could this be done with out affecting the shell integrity?

since im removing and replacing such a small section of the sub floor do i need to worry about the frame dropping when removeing the bolts? I have my balancing legs down would that be enough?

another question as well. are there any detailed write ups showing exactly where to caulk with photos the bumper/rear hatch problem area?

[TG Twinkie]

As you can probably see. The floor is sandwiched between the C channel and the cross member. The metal plate where the trunk lid is attached is also sandwiched.
I recently repaired the same area in my '74 Argosy. It had about 6" of damage across the back. I was able to make the repair from underneath. Only because of the minimal damage. And my vast number of tools I have on hand. The oscillating tool is a valuable tool to have on a project like this.
Once apart I could see how the water gets in. By removing the rub rail and banana wrap across the back and sides. There is good access to the area for caulking. Once the floor repair was completed I used Lexel caulk. I sqeezed the nipple of the caulking tube flat. Like a duck bill. Giving the ability to place the caulking into the sandwiched area. I made sure to get the caulking all the way under and in between the sandwiched area. Completely across the the back and around the corners where the sheet metal plate is tucked under.
Since I had that section of the belly pan off. I also caulked the bottom of the sheetmetal joint where it is against the cross member.
The water leaks thru the hinge and wicks its way along the bottom of the sheet metal. Where it soaks into the plywood. I also caulked under the sheet metal piece where it lays on top of the frame on each side.
I had no problem with the frame dropping.
You can notch the new flooring where the bolts are located. Therefore the frame is still attached to the C channel at those points. You can install new bolts across the back since the C channel is exposed.
To this day I don't understand why A$ has not addressed and solved this problem.
Good luck.

[HiHoAgRV]

That whole corner piece should come right out without cutting. Just drill out the rivets (I can't tell from the photo if they are gone) and it should slide from behind the other panels.

[rugjenkins]

I agree with HiHoAgRv. All the rivets look like they are drilled out. The panel should slide out. It's not hard to remove the inner skins and it's just as easy to rivet back in.

[MickeyC]

I had the same issue. After removing the center wall panel I just removed the rivets on the inside area that allowed me pull the side panels out far enough to get to the bolts behind that wall. It worked pretty well. You may have to have someone hold the panels out while you tighten the bolts and be careful not to crease the panels. I also removed the plate that the rear bumper cover hinges on and sealed the floor underneath with sheet metal. I am in the process of making a new hing bracket that will leave 1 inch space that will allow the water to pass by and fall to the ground. Hopefully that cures the issue. That is a poor design from the start.
Good Luck

[harryk]

No need to take off any skins. When you get all the old stuff out, (and you need a oscillating tool with several blades)you can see the bolts and then you can Vee the new plywood to go around the old bolts. Just finished the rear floor all the way across on our new to us 2005 31 Classic. Isn't it a coincidence that the PO hid the damage to mine also. And he was a former WBCCI President ! My fault for trusting !

[jackvosney]

Thank you all for your replies! i ended up getting all the plywood out without removing the skins using an oscillating tool and a dremel with a rototzip bit. I can now see how the water flows in, i even sprayed water on the rear hatch and bumper and watched it flow into the cabin on top of the bumper plate sheet metal in 10 or so different spots, terrible design!!! I am curious as to other designs to stop the water from ever making its way in aside from caulking. I would like a permanent fix to this.

So far I've seen wrapping the bottom of the ply with sheet metal. wouldn't the water continue all the way the the next piece of plywood?

Does anyone have a picture or sketch of their custom made flanges or fixes?

Also has anyone used pressure treated plywood? seems like a good solution and if off gassing is an issue i would imagine painting the top side of the ply with a strong primer would alleviate that issue. Thoughts?

[jackvosney]

Originally Posted by harryk

No need to take off any skins. When you get all the old stuff out, (and you need a oscillating tool with several blades)you can see the bolts and then you can Vee the new plywood to go around the old bolts. Just finished the rear floor all the way across on our new to us 2005 31 Classic. Isn't it a coincidence that the PO hid the damage to mine also. And he was a former WBCCI President ! My fault for trusting !

Ouch that hurts even more knowing he was involved in AS club culture!

[montanablue]

I am working on my 1997 Safari now. I did not remove the lower skins but after cleaning out the c channel, have notch out the plywood where bolts are located. I cut the whole rear plywood into two sections. Left section is installed. I then went ahead and relocated the electrical cable coming into camper from back bumper which threads through frame by installing a Smart plug on side of camper. I also am relocating and installing a water inlet on the side under Smart plug as well. Once that is done I will install second piece of plywood flooring. I will tell you that you have to pound the plywood into channel. It will drop in.

[Bill M.]

The chemicals in pressure treated plywood will corrode the aluminum and steel in the Airstream quite quickly.

The way to prevent future failure is to fix the leaks and keep the floor dry.