AC install in mc9

[mike802]

Hi guys:  Any of you following my build videos may remember I am at the point in my bedroom where I have to install the AC before finishing the ceiling.  I know how some of you just love the look of those "roof warts" LOL, I can understand that with the classic styling of the older coaches, but I dont feel they look that bad on the mc9, just my opinion.  Anyway I was considering mounting a heavy plate about 3/16" over the escape hatch opening, cutting my 14.25" x 14.25" opening in that and mounting the AC to the plate.  Of course the plate will have to be securely mounted to the bus roof.  I haven't looked yet, but I imagine I will have to remove rivets, add some type of sealer between the roof and the plate and attach.  My question is, should I worry about dissimulator metals creating oxidation?  And what type of metal is the mc9 roof made from?  Anyone having already made this modification, I would love to hear from you concerning your experience, what you did and what you would do differently, if anything.

Thanks.

[Oonrahnjay]

   Mike, are you talking about a 3/16" steel plate as your baseplate?   I've never done roof airs (they'd never fit in my bus so what I think of how they look is irrelevant) but other people seem to use simple wood framing.  All that steel sounds like overkill.  And dissimilar metal corrosion would be a concern but it's easily overcome in practice (some people have used tape for some places, others have used caulk or sealer type stuff, sometimes even the right paint will be enough); it's a concern but not usually an issue.

[mike802]

Yes the steel plate is intended to be the base plate.  The mc9 escape opening is to big for the AC, 3/16" is probably over kill, but I think would be much faster to fabricate than building a wooden frame, and I would not have to worry about moisture causing rot.  If I could use the same type of metal, that would cure the corrosion between different metals.

[thomasinnv]

I think you're still going to need to fabricate some type of frame around the opening for the ac to properly attach the ceiling to underneath, and some of the inside covers not only attach to the ac unit itself, but also to the framed opening.

Your roof hatch will be held in place by several rivets that you will need to drill out. The roof is aluminum. On my 8 there is only one roof hatch in the rear, your 9 should have 2, one up front and one in the rear. I kept my only roof hatch for easy roof access. I just step up onto the bed and pull myself up through the hatch. If your rear windows do not open you will want to consider keeping that rear hatch for a fire escape.

[TomC]

I used 1x2 fir stripping to create a wood frame around the roof opening.  Now 18 years and 30,000 miles later, no problems.  Remember-the roof airs only weigh at most 120lbs. 

I would use the Penguins since they have a 3spd fan and low is truly quiet.  Good Luck, TomC

[jmblake]

Mike,
When I did mine the worst part was removing the ss ring that goes around the hatch it is between the roof and the framing of the hatch, it was a pain in the a**! I then framed in with wood and riveted a new piece of aluminum on top. My ac had a plate that went on the ceiling and then 4 long bolts went up through and screwed into the bottom of the ac to hold it on. Mine were ducted but I would think they would all be the same. Keep up the good work. Jason

[bevans6]

I would do what Jason did.  Remove all of the hatch including the surround, rivet on a roof panel of 12 gauge aluminium (80 thou, more or less) with solid blind rivets and make a frame for the AC unit out of hardwood.  3/16" steel is just total overkill, and will be harder to seal, and will create corrosion issues.  Would be my last choice.

Brian

[mike802]

Sounds like a plan, thanks guys.  I am pretty sure I have some similar weight aluminum I can use. I will be installing more maple strips this weekend, should be able to get one side completed.  Making all the tongue and grove paneling is very time consuming.  I would have liked a penguin AC unit, but I have 2 Duo-therms model 57915.531 they are the ducted models, I think a non ducted unit would have worked better in the bedroom, but I got a real good deal on them, yea I know "famous last words". I have a friend who picked up two 18 foot travel trailers, they were only 4 years old and used lightly.  The State of Vermont had them for students at a fish hatchery, but they were damaged in a flood.  I got two AC units, two furnaces a 50 amp power distribution center with pig tail, three large windows, stove and range hood, two hot water heaters and miscellaneous lights, receptacles, etc all for a couple hundred bucks.  The flood covered everything at floor level with a layer of dirt and silt, but it looks like everything is still usable.  Of course I will check everything out before going through the trouble of installing, but for the price I think it was worth the chance.  I don't think I will be using everything, the hot water heaters are only 5 gallon and I would like something larger.  I also got the holding tanks, but they are only about 35 gallon and again, would like something larger.  My son thinks he might have use for what I don't use in his mc5.

[luvrbus]

I did mine a little different I framed my roof tops on our mci 8 with square tubing used one solid piece of aluminum rivet to the tubing and skin then I cut the 14x14 square out wasted a little material I know 

Tearing into the roof on a few old RV's I wasn't going with wood framing

[TomC]

If your skin is aluminum, then galvanic corrosion is a real concern.  My bus has steel roof ribs, then a 1/16" mylar insulator then the roof aluminum skin using riveted.  My bus is a '77.  The system works well as there is only a couple of small spots that the paint is bubbling a bit-but not concerned. 

The steel you want to use is thick enough that the aluminum skin will corrode if not insulated against each other.  Good Luck, TomC