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Old 12-07-2022, 07:28 AM   #1
1977 31' Sovereign
1987 29' Airstream 290
Norman , Oklahoma
Join Date: Sep 2012
Posts: 104
Images: 14
Hoisting out the old and lowering in the new

All, I am fortunate to have a 30' X 40' heated shop with 15 foot rafters up at the roof line. Being 65 and working alone I will need to use imagination and cunning because the brute force and upper body strength has gone with the years! I've determined that the 1977 Armstrong A/C needs to go. It blows air, but that air is not conditioned. Just blows and blows! I've got a plan to use an inexpensive electric vertical hoist purchased at the local Harbor Freight tool store. Cost was $79.00 and it will lift 440 pounds vertically. I can see no lift eyebolts on the old unit so I procured two lifting cradle straps to wrap around the A/C body. This plan should be a straight forward solution to getting the old one out. I'll lift it about ten inches, pull the Airstream out of the shop, then lower the old unit to the ground. My issue isn't getting the old one out. The real issue is what do I replace it with? I've read 35 different views on what to get and what not to get. Now I'm just confused. I'd like to have the new unit mount just forward of the old Armstrong in the 14" X 14" vent cavity since 'most' new AC's are 14 X 14. I think that would be easier than reinforcing the crater left from the OEM A/C (???) Your thoughts on this are appreciated. Also, thoughts and real life experiences on which 15,000 BTU A/C would be best (easiest) to install in the new 14" X 14" opening. Also, an old Buddy of mine said it would be better to get the patch on the Armstrong crater TIG welded verses Riveting a patch plate. Is there any truth in that and does it really matter since no weight will be placed there in the future? I've attached some Pics of my near future project. Any thoughts are appreciated very much.
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Old 12-07-2022, 08:02 AM   #2
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2004 22' International CCD
Beaumont , California
Join Date: Jan 2021
Posts: 323

I’ve used one of those hoists for years… last week I hoisted an 1100- pound Cummins engine with it, the line doubled and hook on the end of the line affixed to the beam rather than the hoist body.

I would disagree with TIG- welding a patch, first because you could start a fire in the ceiling, next because it’ll be really hard to control warping, and c) because there’s nothing wrong with riveting when done correctly (as evidenced by almost no one complaining about leaks or riveting).

Just do it the way you planned; use the hole, and rivet a patch.

Just my two pennies

- Ken
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Old 12-07-2022, 08:47 AM   #3
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1977 23' Safari
Niagara on the Lake , Ontario
Join Date: Aug 2011
Posts: 966
Images: 3
Definitely rivet your patch, that metal is very thin even for tig, and if riveta were good enough to build the trailer out of they are good enough to patch with.
1977 Safari Land Yacht
2005 Toyota Tundra SR5
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Old 12-08-2022, 08:42 AM   #4
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1976 25' Tradewind
Currently Looking...
Flushing , Michigan
Join Date: Feb 2009
Posts: 168
I removed my old Armstrong A/C unit from the roof of my ‘76 Trade Wind a few years ago by myself. Once I had it completely unfastened, I placed a piece of plywood on the roof, lifted it out of its opening/cavity onto the plywood and then slid it onto a nearby platform and dropped it to the ground/lawn—hey, it was junk anyway in my view. I then duct taped an aluminum patch onto/over the opening and left it to the guys at my Airstream dealer to then finish the install of the new unit, which they did into the same opening. Good luck with your project!
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Old 12-08-2022, 04:01 PM   #5
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1960 26' Overlander
Tipton , Iowa
Join Date: Jan 2007
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Just a thought...have you considered taking it to a HVAC person? These old Armstrong units were made to be rebuilt! It sounds a whole lot easier than what you are proposing.
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Old 12-08-2022, 06:12 PM   #6
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Ridgecrest , CA
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Originally Posted by ericjan2 View Post old Buddy of mine said it would be better to get the patch on the Armstrong crater TIG welded verses Riveting a patch plate. Is there any truth in that and does it really matter since no weight will be placed there in the future? ...
Definitely rivet a patch vs TIG. 2024 aluminum is generally considered "unweldable" using an arc process and when it is welded is susceptible to stress corrosion cracking.
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Old 12-08-2022, 10:19 PM   #7
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2018 25' International
Slidell , Louisiana
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I second cloudless sky's concern about corrosion and stress cracking, so avoid welding on the skin.
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Old 12-08-2022, 11:12 PM   #8
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1994 25' Excella
Waukesha , Wisconsin
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The trailer was built originally and survived to this day with panels being riveted in place, not welded. I agree with the others that a properly riveted and sealed aluminum patch would be the way to go.

Welding a patch introduces too many new potential problems for my liking.
1994 Excella 25 Follow the build on Gertie!
1999 Suburban LS 2500 w/7.4L V8
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Old 12-09-2022, 06:28 PM   #9
1977 31' Sovereign
1987 29' Airstream 290
Norman , Oklahoma
Join Date: Sep 2012
Posts: 104
Images: 14
Quick question. On the patch, how far apart should the rivets be spaced and which sealant should be used? Thanks for all of your comments above. Eric
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Old 12-09-2022, 08:02 PM   #10
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1976 31' Excella 500
Crewe , Virginia
Join Date: Sep 2016
Posts: 133
Images: 9
Just my two cents worth.......I would seriously consider finding an HVAC person come take a look at your unit before taking it off and replacing it. I have a 76 Excella 500 with the original Armstrong unit on the roof. Ours did not have the cover on the outside, just the galvanized shrouds. It worked, but would freeze up. I had someone come and take a look at it and it only needed to have some freon added to it. It was around 8oz worth and cost me $40. It freezes us out. They take commercial components and the parts are available with just a little cross reference work. I will keep ours as long as it works.
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Old 12-10-2022, 12:21 AM   #11
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1977 31' Excella 500
West Sacramento , California
Join Date: Feb 2008
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Hoisting out the old and lowering in the new

Adding a couple more pennies-I hated to replace the Armstrong on my 77 but I came to the realization that HVAC technicians were unwilling to want to get on the roof to service a unit that is older than they are. When the unit breaks down, on the road and in the heat, the chances of finding someone locally willing to diagnose it and repair it are slim. For these reasons I replaced it with a modern unit that can be replaced easily anywhere.
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Old 12-14-2022, 01:15 PM   #12
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1971 27' Overlander
Fremont , New Hampshire
Join Date: Sep 2016
Posts: 21
Gravity works fine

I replaced the A/C on 1972 Overlander. Unhooked the wires and attaching bolts/screws, moved the A/C unit to a moving pad on the adjacent roof and
pushed the pad and A/C over the side. Sloped roof and gravity worked just fine to have it return to earth.

The replacement dometic A/C fit the opening in the roof, but the roof opening lacked adequate support between the exterior skin and the interior skin on two sides. I constructed supporting ribs for the unsupported sides out of 3/4 inch plywood and installed them to the existing aluminum struts. Rather easy.

When the adequate roof supports where in place, the dometic A/C was installed per dometic instructions and wired up.

I owned the trailer for three years after the install and towed it about 15,000 miles and everything work as envisioned. The dometic unit was actually half the weight (+/-) as the factory original unit so weight or supporting structure was not an issue.

The only drawback of this installation was that the replacement A/C condosate drain vented open to the roof and flowed over the roof to the ground. The factory unit condosate flowed through a drain line to vent under the belly pan.
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