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Old 12-12-2019, 11:52 AM   #1
Bus Crazy
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e-roof patch that will be AC: cut hole now or later?

Getting prepared to skin over at least one rooftop emergency hatch hole, which I plan on cutting out later to accommodate a rooftop AC (14" opening). It seems to me I have two options; cut the hole now, which would seem to be easier before being mounted, or cut it later once installed. If the former, I'd have to 'stub out' a covering of some sort, as I don't have an AC yet & can't be having a big hole in my roof.

What would you do? And if the second option is your choice, what would you use as a temp cover?


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Old 12-12-2019, 02:11 PM   #2
Bus Nut
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I would cut later.

The a/c hole is 14" square, but it doesn't have to be super-precise. You can cut a fine hole with any number of metal-cutting tools when the time comes.

Cutting now then trying to seal the hole to keep water out sounds difficult and unnecessary.

I replaced my emergency hatches with boat hatches. However, the boat hatches were slightly smaller, so I got 16 gauge sheet metal and riveted it over the opening, with a hole cut for my new hatches. I later added two AC units by cutting holes in the roof elsewhere.
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Old 12-12-2019, 02:18 PM   #3
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Originally Posted by TheHubbardBus View Post
cut the hole now, which would seem to be easier before being mounted,

before what is mounted? the AC or roof-hole-patch?

I would cover the hole with sheet metal now with 3M Urethane seam sealer and 4-8 screws, then remove the patch, cut open the hole to the size the new AC unit, then install the AC.

I never like cutting into my vehicles, and would put it off until the project is 100% go forward. Mice may chew up your already purchased AC unit while it is in storage waiting. A new better unit that is smaller, cheaper, more efficient, and cools with more BTU capacity than the one in the store you have your eye on may become available.

Who knows what tomorrow may bring? (no I didn't make that up, but it's a good saying)
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Old 12-12-2019, 04:51 PM   #4
Bus Nut
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Location: Johnson City TN
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Year: 2004
Coachwork: IC/AMTRANS RE
Engine: T444E 7.3 w/ MD3060
Rated Cap: 36000lbs / 78pass / 39'
Def put off cutting until your ready to install the ACs.
I installed mine over the emergency hatches. I'm about to pull them down and put the old covers back on and insulate them for the winter. Come spring I'm going the mini split route, I was used 2 15k BTU units from a 1984 class A motor home, they both worked like champs the 2 seasons I used them but they are old and the outside covers broke so I just wanted a temp solution and it worked well, they just BARELY covered the hatches though by something like 2 inches.
Like Biscuit said, the hole for an RV roof air unit is 14" square and doesn't have to be perfect but not much smaller. Careful lugging them up there, I sat mine on my E350 then brought it as close to the bus as I could then got on the van and lifted them to the bus, no helper and I really should have but ah that's the way things go with me, almost always a one man army LOL.

But yeah just wait till you get them to go about cutting, IF and IF you were to change your mind or find a good deal on a mini split or anything to take you away from putting roof units in you will hate that you cut on the bus....
If you would like to check out my website that has all sort of information especially for the T444E/7.3PSD engines check out I've got helpful downloads and articles as well as a link to my YT for other how to videos mainly on the F series trucks.
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Old 12-12-2019, 05:38 PM   #5
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I removed both hatches and replaced them with tinted Lexan panels. The rear one got a 14" cut for the MaxxAir fan. There was a passive vent fore on the roof, it was cut out and the 14" piece of Lexan was put over that hole. So I have a 24" and 14" skylight and a Maxx fan surrrounded by 5" of light coming through. Cutting the hole on the roof after it's installed is a decent work area.
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Old 12-12-2019, 07:40 PM   #6
Bus Crazy
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Biscuits, Mountain, Patrick, Marc... THANK YOU! Great advice & you answered questions I hadn't even thought to ask yet.

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Old 12-12-2019, 11:54 PM   #7
Bus Crazy
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If you’re going to do it, don’t you want the infrastructure in place? Wire, bracing, (do they need condensate drains?) before you do the finish work? You can button it up like
You aren’t doing it provided you know exactly where to cut later.
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