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Old 11-25-2017, 11:20 AM   #1
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1977 Argosy 28
Austin , Texas
Join Date: Jul 2015
Posts: 4
A/C replacement - info on reinforcing the roof?

I have pulled the original A/C unit off my 1975 Airstream Argosy 28ft. As discussed elsewhere, the old A/C was screwed onto the roof around the perimeter of the unit, whereas my new Dometic Brisk Air 13500 btu creates a seal by sandwiching the inner and out pieces of the unit with 4 long bolts.

Any advice on reinforcing the roof to support this new unit and create the appropriate seal???

I'm sure folks have run into this dilemma before, but I cant find any details beyond simply discussing the need to reinforce.

If anyone as advice or photos, please it would help a bunch!

Thank you!

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Old 11-25-2017, 03:05 PM   #2
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1974 27' Overlander
Baltimore , Maryland
Join Date: Mar 2016
Posts: 760
Square aluminum tube framing the underside of the opening worked well for me. 1-1/2" should match the thickness of the roof, and if you attach it with pop rivets from the top just at the edge of the opening, the pop rivets should be well under the AC seal, so leaking through the rivets shouldn't be an issue.

You could also make a frame with wood, but aluminum seemed like the material to use.

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Old 11-25-2017, 03:26 PM   #3
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1991 34' Excella
Princeton , New Jersey
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You may want to reinforce the rails that come with the Breeze and are used to hold the unit down. They are very cheap and will bend with any torque on the hold down screws. I used the rails form my old unit inside the newer ones. You could get a channel from th Big Box Store and use that.
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles

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Old 11-26-2017, 07:36 PM   #4
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1976 29' Ambassador
Fitchburg , Wisconsin
Join Date: Oct 2007
Posts: 166
I used wood for my frame. The corners were connected with pocket screws. I also put some thin weather stripping on the top and bottom of the frame. I attached the frame to the rib at the rear of the opening to help stabilize the AC. Finally I replaced the plastic pan under the old unit and used the pans as described very well by Lewster. This also includes using a double gasket around the main ole and a small support foam piece to support the end of the AC. This made the unit much quieter since the foam helped “decouple” the AC from the metal roof.
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Old 05-26-2018, 05:05 PM   #5
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1978 31' Sovereign
Somerset , Ohio
Join Date: Aug 2016
Posts: 3
Hi, I am curious what you did in the end? I am replacing the ac in a 78 sovereign and am also curious how to reinforce the roof. I assume you have to connect the wood frame to the rib but unsure of best way to do that on all sides as there’s not much room to fit a board on the one side. Any advice would be appreciated! Thanks, Ryan
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Old 05-26-2018, 07:19 PM   #6
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1974 31' Sovereign
1979 23' Safari
Wayland , New York
Join Date: Jan 2012
Posts: 1,632
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I had a similar issue on my 79. The original AC had a flat metal pan bottom. There was one rib for support at the front of the AC but there was no more support until well past the back of the rear of the AC. The weight of the AC pushed the roof flat at the rear and the metal AC pan wore cracks/holes in the roof, patched those. To fix the no rear support I made 2 supports from aluminum flat bar material. One part of the support I cut to fit the curve of the roof then welded the other parts together to form an arch. Notched the support for wire run clearance. Then I put a bead of polyurethane on top to cushion between the skin and support and attached the arch on the ends to the longitudinal supports in the ceiling. this was easier with the interior skins removed.
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Old 05-26-2018, 07:24 PM   #7
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1974 31' Sovereign
1979 23' Safari
Wayland , New York
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The wood supports just get made to fit around the outside of the 14" opening. This gives the bolts that tighten the AC down something solid to squeeze the gasket down against. Doesn't need to be anything fancy. Just a square box of wood. You can cut the arches and taper the sides to get a nice fit on top and flat across the bottom. It'll be a little taller in the middle due to the arch and meet flush at the ends. Sorry I don't have pictures of this. Some holes that you can seal with caulk for the wires to run through.
If you have rib support at both ends of the AC you can skip the metal ones discussed previously and just create the wood framed box out of 1X(3/4") material.
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Old 05-27-2018, 12:08 AM   #8
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1958 26' Overlander
Battle Ground , Washington
Join Date: Jun 2013
Posts: 143
Images: 21
I did the same as Greatleys. Used 1-1/2" square aluminum tubing. Rivets through the roof skin and a couple self tapping screws through a rib into the tubing. Drilled a hole through the tubing to run wires, deburr edges and added a short piece of tubing to protect wires.

I have a coleman mach 8 that bolts from the underside and compresses to the framework.

Harold & Rebecca
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