Double Roofed CT?

[Optimistic Paranoid]

As I continue to plan the ultimate cargo trailer conversion for when I retire in a year or two, a question has arisen in my mind concerning the roof.

I am looking hard at the possibility of mounting solar panels on the roof. The problem is, then you can no longer park under cool shade trees, but must sit out, exposed, under the hot sun.

A little while ago, I ran into a reference to the fact that, in the old, pre-airconditioning days, Land Rover used to offer an optional Tropical Roof. This appears to have been white canvas, stretched on a frame and mounted above the regular roof so as to create an air space of an inch or two. It was said that this option would keep a Land Rover 10 to 15 degrees cooler under the hot, tropical sun.

This has led me to consider putting two-by spacers across the CT roof, over every steel rib, and putting a light, 1/8 to 1/4 inch plywood roof over it. There would then be a 2" air space between the new roof and the original one. The solar panels would of course mount above the plywood roof, which I think I would paint with boat paint, or maybe some of that rubberized roof paint.

The upside is that it SHOULD keep the trailer cooler when parked out in the sun, and an added advantage is that the trailer should be quieter - and easier to sleep in - during rain storms.

The downside is that there will be added expense, and also it will add some weight to the project.

I was wondering if anybody here has tried this? Or any other comments on it's feasability? Or lack of same? Also, I guess this would require a trailer with a flat roof, as opposed to one with the rounded roofs. Any comments about the innate desirabilty of one style over the other, if any?

Thanks
Regards
Joh

[vreihen]

Can't the solar panels be used as a secondary roof?????

[Blotto Bros]

While camping I watched a guy pull in with what looked like a contractors trailer and convert it on site.

He had a ladder rack on the roof that bolted to the top support rail on the sides of the trailer. He had installed snaps along the sides and just snapped a canvas over the top of the whole ladder rack to create an instant "SAFARI ROOF". He also stated that it reduced interior temps by 10 degrees or more.

You could use this idea AND simply make your canvas the same length as your trailer but twice as wide and have an instant awning as well.

[8ball_99]

I'm really not sure it would be worth the trouble. Also IMHO you would be MUCH better off just getting an extra tall ceiling in the trailer and adding the air gap there. That way the roof stays water proof. Or you could just add more insulation there then normal. You also don't want a 100% flat roof like your talking about cause it would hold water. Even the flat room trailers have a slight crown in the center for water run off. I have 4 different layers of insulation in my roof. I also have painted the roof flat white with paint made for metal roofs. Inside of my trailer in direct sun is no hotter then outside air temp. Atleast not enough to notice.. Of course that is with two roof vents open and one of them has a fantastic fan. Doesn't matter how you insulate it if you don't have any ventilation it will heat up sooner or later inside..

[8ball_99]

BTW I understand shading the trailer would work better then extra insulation. I just don't think a second fixed roof would be worth it.

[Optimistic Paranoid]

Can't the solar panels be used as a secondary roof?????

A 7X16 trailer is 112 square feet of roof. 3 60X20 inch panels will only shade about 25 square feet.

Regards
John

[Optimistic Paranoid]

While camping I watched a guy pull in with what looked like a contractors trailer and convert it on site.

He had a ladder rack on the roof that bolted to the top support rail on the sides of the trailer. He had installed snaps along the sides and just snapped a canvas over the top of the whole ladder rack to create an instant "SAFARI ROOF". He also stated that it reduced interior temps by 10 degrees or more.

You could use this idea AND simply make your canvas the same length as your trailer but twice as wide and have an instant awning as well.

Intriguing idea, but how would I mount the solar panels so they stay ABOVE the canvas?

I thank you for confirming that a second roof actually works for keeping the trailer cooler.

[BC Cargo]

I added a white sheet of plywood to my black fiberglass hard top of my Jeep (like the Land Rover)and it did make a big difference. Where you could not touch the exposed black roof in the sun, you could in the shade of the plywood. I was able to attach a luggage box up there and carry a second spare wheel. I was also able to stand on it and take great pictures and video. Well worth the $50 to make it. I used special plywood that is used in making Hwy signs. It has a paper like coating on each side and because of its many plys is very strong for the thickness. To support it off the roof I used big suction cups like on the very old style roof racks. However I drilled through the cup completely and bolted it with a fender washer on the underside of the Jeep roof. This sealed good to the curve of the roof.
I think it would be a great idea to mount the solar to but is only required to go under the solar by the amount needed to mount it. So your roof is either covered by solar or ply but not both. This would also allow for more hot air to escape in the cracks made by the solar mounting hardware.
Also, even a "flat roof" is not truly flat. Most manufacture try to put a little rise in it so water does not pool.

[Optimistic Paranoid]

I'm really not sure it would be worth the trouble. Also IMHO you would be MUCH better off just getting an extra tall ceiling in the trailer and adding the air gap there. That way the roof stays water proof. Or you could just add more insulation there then normal. You also don't want a 100% flat roof like your talking about cause it would hold water. Even the flat room trailers have a slight crown in the center for water run off. I have 4 different layers of insulation in my roof. I also have painted the roof flat white with paint made for metal roofs. Inside of my trailer in direct sun is no hotter then outside air temp. Atleast not enough to notice.. Of course that is with two roof vents open and one of them has a fantastic fan. Doesn't matter how you insulate it if you don't have any ventilation it will heat up sooner or later inside..

Thanks for taking the trouble to respond. You're comments are interesting.

I'm thinking that the new roof would take the brunt of the water and keep the original roof fairly dry. As for run off, with a scissors jack at each of the four corners, I should be able to cant it just a hair and control which way the water runs off, at least while it is parked.

Regards
John

[8ball_99]

Thanks for taking the trouble to respond. You're comments are interesting.

I'm thinking that the new roof would take the brunt of the water and keep the original roof fairly dry. As for run off, with a scissors jack at each of the four corners, I should be able to cant it just a hair and control which way the water runs off, at least while it is parked.

Regards
John

My line of thinking was your planning on screwing or bolting wood 2x and painted plywood on top of a metal roof. So even if the plywood top blocks most of the weather your still adding many holes to your nice hole less metal roof. Also you don't want have to control water run off by setting the trailer up off level. The water should drain off the roof with the trailer level. I just don't think the extra holes and wind drag is worth a little extra insulation. Not when you can do about the same thing with insulation inside..

[BC_Explorer]

Up here where there a lot of trees, many campers simply rig a tarp over their trailers to keep some of the heat of the sun off the trailer roof. This is all I plan to do for my 6x10 trailer and there is a store here that sells very light (almost beige) tarps that will not absorb the heat like the darker blue and brown tarps.

Another idea I have is that I have one of those portable 8x10 canopies that fold up and store in a bag for carrying. I was looking at it the other day and it would not take much work to extend the collapsible legs to get the height I need to clear the exterior height of my trailer which is 7' 6". I figure if I extend the legs to 7' 10" then this would be enough to give a 4" air gap between the canopy top and the trailer roof.

Of course, neither of these will not work if you plan to have solar on the roof.

[Optimistic Paranoid]

My line of thinking was your planning on screwing or bolting wood 2x and painted plywood on top of a metal roof. So even if the plywood top blocks most of the weather your still adding many holes to your nice hole less metal roof. Also you don't want have to control water run off by setting the trailer up off level. The water should drain off the roof with the trailer level. I just don't think the extra holes and wind drag is worth a little extra insulation. Not when you can do about the same thing with insulation inside..

The thing is, I'm not contemplating doing this as a stand-alone project, but as part of adding solar power for boondocking. 3 solar panels will require putting a dozen holes in my metal roof, plus the junction box for the wiring ANYWAY.

An alternative approach would be to have the trailer built with about four ladder racks, spaced about 4 feet apart, and mount the solar panels on THEM.

The problem is, I'm not sure how well the factory attaches those things. Also, they look like they are designed to principally support weight pushing down. If there are large panels on them, how well will they resist any UPLIFT caused by the wind geting between the roof and the panels?

Anyway, still doing a lot of thinking, and appreciate your comments.

Regards
John

[Optimistic Paranoid]

To support it off the roof I used big suction cups like on the very old style roof racks. However I drilled through the cup completely and bolted it with a fender washer on the underside of the Jeep roof. This sealed good to the curve of the roof.
I think it would be a great idea to mount the solar to but is only required to go under the solar by the amount needed to mount it. So your roof is either covered by solar or ply but not both. This would also allow for more hot air to escape in the cracks made by the solar mounting hardware.

I've seen some of those old roof racks where the cups were badly cracked from age and exposure. How long did your system last, permanetly mounted like that? Thanks for the post.

Regards
John

[Shadow Catcher]

I have an 185W panel on the top of our tear and the plastic mounts give a couple of inches stand off above the roof. There is quite a bit of surface area to the mounts and they are attached using 3M VHB tape (no holes). I have only two holes in our roof, the Sirius radio antenna (made for fiberglass) and the Perko electrical connector (made for fiberglass).

[8ball_99]

The thing is, I'm not contemplating doing this as a stand-alone project, but as part of adding solar power for boondocking. 3 solar panels will require putting a dozen holes in my metal roof, plus the junction box for the wiring ANYWAY.

An alternative approach would be to have the trailer built with about four ladder racks, spaced about 4 feet apart, and mount the solar panels on THEM.

The problem is, I'm not sure how well the factory attaches those things. Also, they look like they are designed to principally support weight pushing down. If there are large panels on them, how well will they resist any UPLIFT caused by the wind geting between the roof and the panels?

Anyway, still doing a lot of thinking, and appreciate your comments.

Regards
John

You wouldn't have to make dozens of holes. You could use the 3m tape like over the top did. Or you could make a aluminum rack for the panels to mount to. Just secure the rack at four corners. You could also have the mounts on the side of the trailer for the rack that way you would need any holes in the roof. I wouldn't have the factory add a bunch ladder racks. If you really want to go that route I'd do it your self. Most of them have the base trailer figured out, But they aren't so swift with the extra's IME.