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roof top air
- Thread starter cbull
- Start date
marvin4239
New member
Bob Austin in Thataway has documented the install of one in his Cat in his photo album. Also Wefing has installed some in 22's.
Go to my "Thatway" photo album. There is also a fairly long blog on doing this, which you can probably find by searching--I'll see if I can find it.
Basically you need to build a support frame on the inside, so that the crown of the top is maintained and then make a flat platform on the top so that the foam gasket will seal properly. If you don't do this, there is a risk that the top will sag under the weight and then leak. I don' know if the center section of your 22 is cored or not. If it isn't then you definately need the frame, since in the 25's the weight of the Air conditioner will cause significant sag. If it is cored then you need to remove the core for about 1/4" around the 14 x 14" opening you cut, and then fill this with epoxy and filler to be sure that there is no water intrusion.
The 13,500 BTU unit will make the 22 into a freezer! I have a 8300 BTU unit on a Tom Cat and it is enough in Florida. But there are times when you might need more. I have a 13,500 unit ducted in a 30 foot Class A RV--and it is adequate.
Another problem with the 13,500 BTU units is that you will need more than a Honda 2000 to run them. Depends on the unit, but the start up load is more than the 2000 can handle.
If you have any problems or questions, please feel free to ask. I took some of the photos of the step cutting with a router of the inner frame off of the album.
But I traced out the curve of the top, made a templete and then traced that on the 3/4" oak I used for the inner frame--I then made step cuts with a router and used a belt sander to do the final curve cutting to make a perfect fit to the inner cabin top. The frame was held in place with epoxy and mishmash, so I didn't have to penetrate the core any more than necessary.
We use a 5,000 BTU window unit in our 25 and found it sufficient for traveling across Texas and Arizona this last fall.
Basically you need to build a support frame on the inside, so that the crown of the top is maintained and then make a flat platform on the top so that the foam gasket will seal properly. If you don't do this, there is a risk that the top will sag under the weight and then leak. I don' know if the center section of your 22 is cored or not. If it isn't then you definately need the frame, since in the 25's the weight of the Air conditioner will cause significant sag. If it is cored then you need to remove the core for about 1/4" around the 14 x 14" opening you cut, and then fill this with epoxy and filler to be sure that there is no water intrusion.
The 13,500 BTU unit will make the 22 into a freezer! I have a 8300 BTU unit on a Tom Cat and it is enough in Florida. But there are times when you might need more. I have a 13,500 unit ducted in a 30 foot Class A RV--and it is adequate.
Another problem with the 13,500 BTU units is that you will need more than a Honda 2000 to run them. Depends on the unit, but the start up load is more than the 2000 can handle.
If you have any problems or questions, please feel free to ask. I took some of the photos of the step cutting with a router of the inner frame off of the album.
But I traced out the curve of the top, made a templete and then traced that on the 3/4" oak I used for the inner frame--I then made step cuts with a router and used a belt sander to do the final curve cutting to make a perfect fit to the inner cabin top. The frame was held in place with epoxy and mishmash, so I didn't have to penetrate the core any more than necessary.
We use a 5,000 BTU window unit in our 25 and found it sufficient for traveling across Texas and Arizona this last fall.
The photos are #11-16 in the "Thataway" Album
The following is the post I did on the AC cutout:
"Update on the air conditioning hatch project. The 14 x 14" hole was cut with a Rotozip (I had used one years ago on wall board--a bit of a learning curve to make these long straight cuts,) but it is better than a jig saw. From the template, which I transfered to the edge of the 1 x 3, I determined I had to remove about 3/16 on each end of the athwartships 1 x 3 and taper it on up to no removeal in the center. I used a router starting with 3/16 cut on the outer inch, then brought the bit up 1/64 for a couple of passes accross the board, as I moved in toward the center. After about 5 cuts on each side of the two boards, we had a rough outline of the curve. A chizzel cut any wood between the router cuts and then a belt sander smoothed it to a fair curve to match the template. The fore and aft boards also had to be cut down about 3/16 on the outside, a bit less on the inside---I used a power plane for this, and cut on an angle to give the proper profile. This was laid out on the floor to be checked. Then the athwartships curved pieces were covered on the upper side with mish mash (small fibers, with colloidal silica and epoxy). The boards were allowed to set overnight clamped in place on the cabin ceiling and the next AM the fore and aft boards were epoxied in palce. There was enough epoxy "glue" to ooze out on all sides. The fiberglass in the boat for 3" around the cutout on the inside, was ground down to remove the gel coat. After the wooden boards were placed, a two inch flange which will be flat, was build on the top of the cabin. Duct tape defined the edge, 2" wide glass tape was the base--one layer all of the way across, athwartships, and then built layers from 5" to 2" were layered alternate with fore and aft pieces. This rim was faired with high density filler in epoxy. It took about 4 total "final" fairing builds to get this surface absolutely flat and equal fore and aft and athwartships.
I used a "long board"--24" long, with sandpaper glued on one face. This is pulled back and forth to make the surface flat and fair. Finally the deck core, and the oak was encapsulated in epoxy. Instead of gel coat, I elected to smooth the side surface of the top flange with marine tex--and will blend gel coat into its as it goes up the side.. (This will not be seen with the AC or a hatch in place. I have made the lips before, when putting a hatch on a curved deck, but the oak backing blocks really stiffens up the deck and I feel is essential for the airconditioner (94lbs). It was asked exactly what fan I would be using when I was not using an air conditioner: Maxx Air RV Roof fan. This uses a three speed fan, with thermostat if you wish, with exhaust or pull in air on 12 volts. I have used it in hurricane conditions on my RV's--so it will be a good substitute for the Air conditioner in Nothern Climates.
Why do the airconditioner first? We live in N. Florida--and want it comfortable while I do the electronic and other work on the inside.
Photos are being posted currently. If C Dory were to make molds for the lip and the backing blocks, this process could be done in a couple of hours.
I have E mailed to Jeff what I was going to do, and the reasons for the stiffening (so that water doesn't pool under the flange of the AC and get into the boat)."
The following is the post I did on the AC cutout:
"Update on the air conditioning hatch project. The 14 x 14" hole was cut with a Rotozip (I had used one years ago on wall board--a bit of a learning curve to make these long straight cuts,) but it is better than a jig saw. From the template, which I transfered to the edge of the 1 x 3, I determined I had to remove about 3/16 on each end of the athwartships 1 x 3 and taper it on up to no removeal in the center. I used a router starting with 3/16 cut on the outer inch, then brought the bit up 1/64 for a couple of passes accross the board, as I moved in toward the center. After about 5 cuts on each side of the two boards, we had a rough outline of the curve. A chizzel cut any wood between the router cuts and then a belt sander smoothed it to a fair curve to match the template. The fore and aft boards also had to be cut down about 3/16 on the outside, a bit less on the inside---I used a power plane for this, and cut on an angle to give the proper profile. This was laid out on the floor to be checked. Then the athwartships curved pieces were covered on the upper side with mish mash (small fibers, with colloidal silica and epoxy). The boards were allowed to set overnight clamped in place on the cabin ceiling and the next AM the fore and aft boards were epoxied in palce. There was enough epoxy "glue" to ooze out on all sides. The fiberglass in the boat for 3" around the cutout on the inside, was ground down to remove the gel coat. After the wooden boards were placed, a two inch flange which will be flat, was build on the top of the cabin. Duct tape defined the edge, 2" wide glass tape was the base--one layer all of the way across, athwartships, and then built layers from 5" to 2" were layered alternate with fore and aft pieces. This rim was faired with high density filler in epoxy. It took about 4 total "final" fairing builds to get this surface absolutely flat and equal fore and aft and athwartships.
I used a "long board"--24" long, with sandpaper glued on one face. This is pulled back and forth to make the surface flat and fair. Finally the deck core, and the oak was encapsulated in epoxy. Instead of gel coat, I elected to smooth the side surface of the top flange with marine tex--and will blend gel coat into its as it goes up the side.. (This will not be seen with the AC or a hatch in place. I have made the lips before, when putting a hatch on a curved deck, but the oak backing blocks really stiffens up the deck and I feel is essential for the airconditioner (94lbs). It was asked exactly what fan I would be using when I was not using an air conditioner: Maxx Air RV Roof fan. This uses a three speed fan, with thermostat if you wish, with exhaust or pull in air on 12 volts. I have used it in hurricane conditions on my RV's--so it will be a good substitute for the Air conditioner in Nothern Climates.
Why do the airconditioner first? We live in N. Florida--and want it comfortable while I do the electronic and other work on the inside.
Photos are being posted currently. If C Dory were to make molds for the lip and the backing blocks, this process could be done in a couple of hours.
I have E mailed to Jeff what I was going to do, and the reasons for the stiffening (so that water doesn't pool under the flange of the AC and get into the boat)."
Some folks have been able to run 13,500 BTU AC units. On the other hand one of the dealers has had problems getting a Coleman Polar Cub 9200 BTU unit to run on a 2000. (The 9200 has replaced the 8300, and uses another amp running--there seem to be a few 8300 units still out there).
Yesterday I was at the fuel station (filling up fuel cans in advance of Gustov) and there was a 23.5 Trophy which had one of the Coleman 8300 units on his cabin (Pilot house version)--and he claimed that at above 15 knots that there was a problem with his shroud and the fan. This seems strange to me, since the RV air conditioner is designed to run while the RV is traveling down the road at 65 miles an hour. I don't have that problem on the Tom Cat.
Keep in touch and let us know how the 13,500 does on the Honda--you might try a second soft start relay/capaciter.
Yesterday I was at the fuel station (filling up fuel cans in advance of Gustov) and there was a 23.5 Trophy which had one of the Coleman 8300 units on his cabin (Pilot house version)--and he claimed that at above 15 knots that there was a problem with his shroud and the fan. This seems strange to me, since the RV air conditioner is designed to run while the RV is traveling down the road at 65 miles an hour. I don't have that problem on the Tom Cat.
Keep in touch and let us know how the 13,500 does on the Honda--you might try a second soft start relay/capaciter.