Building a frame for a new AC unit

[Gkiesel]

Hello all. Can somebody point me to a thread concerning building a framed 14x14 opening for a new ac unit? I replaced the old armstrong a few years back with a dometic brisk air II. At that time I framed out the opening, but frankly, I don't think I did it properly. Specifically, I contoured the top of the wood to conform to the curvature of the outside roof. The result being that I don't think the ac unit seals properly when tightened down. It leaks like a sieve. Not when running, when parked or driving.

Any advice on the proper way to frame the opening would be appreciated.
Thanks, George

[GMFL]

I’m not sure there is a need to “frame” anything. The factory 14x14 opening already has the support needed for the AC unit. Anything you add to that may just be creating a problem. Photos might help me understand what you are trying to do.

[TheGreatleys]

Originally Posted by Gkiesel

Hello all. Can somebody point me to a thread concerning building a framed 14x14 opening for a new ac unit? I replaced the old armstrong a few years back with a dometic brisk air II. At that time I framed out the opening, but frankly, I don't think I did it properly. Specifically, I contoured the top of the wood to conform to the curvature of the outside roof. The result being that I don't think the ac unit seals properly when tightened down. It leaks like a sieve. Not when running, when parked or driving.

Any advice on the proper way to frame the opening would be appreciated.
Thanks, George

Those AC gaskets do need to be tightened down to a pretty specific spot, so I can see how trying to install one against a curved surface wouldn't seal properly.

When I replaced my AC, I built my frame out of aluminum square tube to flatten out and brace the opening, pop riveted and glued in place with TremPro. The pop rivets are underneath and toward the inside of the AC seal, so leaking there shouldn't be an issue. There's photos on the blog linked in my signature, but it's not really much to look at.

I did have to remove and shim a couple of rivets into a nearby rib to give me enough play to form the skin into a flat square. I've seen more extensive modifications on this forum to make a flat surface, so maybe my method is the lazy way, but it worked great, and has been sealed nicely for a couple of years now.

It was frankly far more work to install buck rivets in all the screw holes from the old Armstrong unit.

I'd suggest removing your AC, removing the curved bracing and replacing it with something flat, then replacing your AC using a brand new gasket. You might need to remove a couple of rivets if you're too close to a rib, but once your bracing is in place, you can shim them as necessary and reinstall rivets in their place.

[rmkrum]

Some A/C installations use two gaskets stacked to get a good seal. If there is only one gasket in there that may be the root cause of the leaks...

[57Vintage]

I agree with the Greatleys. I created a frame of square aluminum tubing. It will create the flat surface for the seal. To match the thickness I used 1.5". Since you're close to ribs the distortion isn't really visible.

[TheGreatleys]

Originally Posted by 57Vintage

I agree with the Greatleys. I created a frame of square aluminum tubing. It will create the flat surface for the seal. To match the thickness I used 1.5". Since you're close to ribs the distortion isn't really visible.

Attachment 334453 Attachment 334454

I was going to dig up my blog link, but yours looks better than mine, so let's just go with your photos. Nice job!

[Crackerman]

What I like to do as well, is use a rib as the rear "frame" of the a/c opening.
Use 2 pieces of 1.5" square tube, extrusion or channel, extend forward to the next rib, and buck rivet it all together, then fill the front portion of the framed opening in with another piece of material.
Also riveting the exterior skin to the structure, as well the interior increases the strength in the area markedly.

[Hein]

We produce AC adapter plates for vans and I made one for our Airstream when I replaced the roof top AC with a new Dometic Penguin. They are CNC'd to fit the curvature of the roof and provide flat surface for the AC seal. Another benefit is that it raises the foam seal interface above any pooling water on the roof. It also stabilizes and reinforces the roof metal.

We also made one for the new Maxair Deluxe vent I installed. The old vent had forced the roof flat and caused low spots that would pool water ahead and behind the vent.

Below is a photo of the AC adapter and shim (to keep the AC level) prior to final sealing of the adapter and installing the AC. With the flat surface there is less chance of the seal not being adequately compressed at the edges.



Sealed and ready for the AC.


More detail information and photos of the vent fan and AC installation can be found in our 94 Excella refurbish thread: http://www.airforums.com/forums/f44/...la-183717.html

All the best,
Hein

[Foiled Again]

Originally Posted by Hein

We produce AC adapter plates for vans and I made one for our Airstream when I replaced the roof top AC with a new Dometic Penguin. They are CNC'd to fit the curvature of the roof and provide flat surface for the AC seal. Another benefit is that it raises the foam seal interface above any pooling water on the roof. It also stabilizes and reinforces the roof metal.

We also made one for the new Maxair Deluxe vent I installed. The old vent had forced the roof flat and caused low spots that would pool water ahead and behind the vent.

Below is a photo of the AC adapter and shim (to keep the AC level) prior to final sealing of the adapter and installing the AC. With the flat surface there is less chance of the seal not being adequately compressed at the edges.



Sealed and ready for the AC.


More detail information and photos of the vent fan and AC installation can be found in our 94 Excella refurbish thread: http://www.airforums.com/forums/f44/...la-183717.html

All the best,
Hein

Thanks for this most useful and informative post. I wish your adapter plates were standard as I have a dishing issue on my 25 ft widebody. Please PM me with price and availability. Airstream doesn't even do the squash two seals trick, which seems to be a.classic jury rig to me.

I totally get the OP's problem, because the Armstrong units peobably went out with the 13 segment roof curve.

TRIVIA: A few years back Airstream had ad banners showing "the evolution of the curve" which changed the roof profile as the number.of end segments went from 13 to 7 to 5. Back in the vintage era, the Argosy Minuet added an even narrower body and its own unique curve.

At present there are still 3 different curves, the 8.5 foot wide body (25 ft and up) standard 8 foot wide units (16 ft to 24 ft) and Sport/Euro units that are 7.5 wide. (16 ft to ??) I can spot the difference easily by looking at the center end segment.

PAULA

[harryk]

So Hein, can you make me one for my 31 Classic ? I am contemplating having to replace my ac and the roof looks flat near the ac and I guess the ac caused that & it looks like the water will pool...

[Hein]

Originally Posted by harryk

So Hein, can you make me one for my 31 Classic ? I am contemplating having to replace my ac and the roof looks flat near the ac and I guess the ac caused that & it looks like the water will pool...

We would be honored to produce one for you. For the Airstreams we need to determine the chord height over 24" as close as possible where the AC is located. To do this, lay a 24" long straight edge across the center of the roof and shim it so the gap at both ends is the same. Then give me the height of the gap to the nearest 1/16th. Its actually better and more accurate to measure it to the nearest millimeter using a stainless pocket rule. (Every engineer should have one in their nerd pouch)

In most cases, we are assuming a constant radius. Please also send a photo to my phone (# below) so I can see if there is a flat spot in the middle. If so then measure the width of the flat spot and give me that dimension as well.

Due to some deformation of the roof of our Airstream in the area of the vent I had to transition from one curvature to another over the length of the adapter. If that is the case then you need to provide me with the chord height at the leading edge and trailing edge. This can also be the case for the AC.

For AC adapters, it is possible that the roof in the location of the shim/support that holds up the rear of the AC is yet a different curvature. If so then provide me with the chord height in that location as well.

We have a lot experience making these for all kinds of vans with raised roofs, pop tops and other wacky profiles so usually can get it right on the first try. If not we just tweak it a bit and run a new adapter. Then ship that to you at no extra charge. Then you return the other adapter that didn't fit perfectly.

This product is patent pending.

All the best,
Hein
541 490 5098

[AlinCal]

How are you dealing with the condensation cups? Can these be built like airstream used to with a tray system that gets drain piped to the between skins hose down to wheel well?

[Hein]

Originally Posted by AlinCal

How are you dealing with the condensation cups? Can these be built like airstream used to with a tray system that gets drain piped to the between skins hose down to wheel well?

Thank you for asking.

Take a look at our refurb thread (link below) for details on that. I had to cut them down to fit but could machine a recess into the top of the plate to accommodate the cups. To be honest, those took me a bit by surprise but I was able to make it work.

All the best,
Hein

[Gkiesel]

Wow. Thanks for the replies. I was away for a few days and my post took on a life of it's own.

[Gkiesel]

Thanks for all your responses. We made a solid frame from 1 1/2 in aluminum c channel that I had when i redid the old gouchos. Much stronger now and attached to the fore and aft ribs much like 57 vIntage.

Question now about how much to tighten down when using the drain cups. Install instructions without cups says 40-50 inch pounds. Instuctions that came with drain kit only says that the 3/4 inch measurement does not apply because of the double gaskets.

What is the correct way to tighten this down?, and do you guys go back after 6 months to retorque the unit?
Thanks, george

[cinerose]

Hein,

Can you make one for my 1981 13’ Scamp. I need reinforcement before installing a rooftop AC. How much? Where are you located and do you do rooftop AC installs or can you recommend a place in the Los Angeles Area that does AC installs. I want to put it over the escape hatch hole (13” x 20”). Thanks!

Rosemary Phillips
818-288-7526
rc_phillips@me.com