RV roof angle 6+" curve

[mmmmmdonuts]

I have 8 residential solar panels (39"x78")that I plan on mounting to my roof of the RV. It is a walking roof with aluminum trusses 16" on center and I was going to put down unistrut down first (lags in trusses and plywood) and mount 3 panels per 10 foot section using 6 z brackets per panel. My issue is I have 6+" curve the whole width of the roof.

My question is how do I handle the curve of the roof? My initial thought was to straddle the center of the roof for the solar to minimize unistrut and keep it uniform and maximize sun exposure.

Do I use angle brackets and small sections of unistrut before connecting them all together? Do I just bolt them at the angle on both sides of the roof essentially doubling the unistrut used and go length wise. Can I get away with a L bracket and a short piece of vertical strut before going length wise?

Just keep changing my mind on how to do this as efficiently, safely and effectively as possible.

 

[chrisski]

I recommend cutting the strut to lengths it won’t curve. This may be impossible.

Unfortunately for me and my fifth wheel, cutting a flat piece of metal was impossible with the curve roof. that meant cutting the mount at each of the four corners of the panel to bolt it in. This defeats the purpose of uni strut.

After I thought of putting shims at different points between the strut and the beams in the roof to avoid the curve. Since mine are installed, I never tested the idea.

 

[mmmmmdonuts]

I recommend cutting the strut to lengths it won’t curve. This may be impossible.

Unfortunately for me and my fifth wheel, cutting a flat piece of metal was impossible with the curve roof. that meant cutting the mount at each of the four corners of the panel to bolt it in. This defeats the purpose of uni strut.

After I thought of putting shims at different points between the strut and the beams in the roof to avoid the curve. Since mine are installed, I never tested the idea.

I was thinking to put the struts lengthwise (with the curve) as I knew I wasn't going to be able bend the struts. I was wondering if this would help Adjustable brackets

Was thinking like this but was not going to do cross channels if possible.

 

[chrisski]

I was wondering if this would help

I don't know.

My roof curves length and width wise, less so width where I used these, but still had to cut the bottoms to six inch lengths at each corner, just too much curve in the roof.

I don't tilt the panels because it takes at least 30 minutes to tilt six panels.

 

[HRTKD]

Here's a few pictures of how I put my strut down.

Post in thread '48 Volt System Toy Hauler Build'

Apr 19, 2025

I forgot to post pictures of the solar panel install.

I used CAD to figure out how I was going to deal with the arched roof and the obstructions. The panels I went with are Jinko JKM425N-54HL4-B (44.65" wide, 67.8" long and 1.38" frame), 425 watt. The options I had from my local supplier were limited. I should have held out for different panels (Qcells Q.Tron M-G2+, 430 watt because they weren't as wide) but they were backordered at least 30 days.

The stock of strut that I started with.


In post #5 I thought I was going...

• HRTKD

• 

I'm going to add at least two more panels (slightly smaller) and I will not be using strut.

 

[mmmmmdonuts]

Thank you this is extremely helpful. So you went with the curve of the roof to help with the install. Looks like this maybe how I want to do it and go from the sides then rather than right over the center hump.

 

[Aussieguy]

put the panels lengthway my 40 inch panels fit side by side with a walkway
uni-strut locate it so it runs the same way as the panels length and only attach to the sides of the panels (more difficult to layout)

mounting uni-strut length ways is more tricky as it can trap water , dirt and leaves but it is doable if you incorporate a washer or two on each mounting point between roof and uni-strut


TEST it using a piece of wood to see if your mounting preferences require modifications... bigger brackets etc
I didn't change the angle the roof made the panels tilt to ..... as the slope made keeping water and dirt OFF easier

 

[mmmmmdonuts]

put the panels lengthway my 40 inch panels fit side by side with a walkway
uni-strut locate it so it runs the same way as the panels length and only attach to the sides of the panels (more difficult to layout)

So are you leaving walking room between the panels or on the sides of the panel. Do you have a good picture of what you did?

 

[Aussieguy]

no walking room on the sides to install then later inspect on the sides I used a ladder
there is just enough room between panels at top of roof to do a drunk driving test walk ... one foot in front of the other

don't try walking between them if you got balance issues

works well... and have not had to do any work on them since install
just make sure you seal them real good

 

[MattMan119]

That’s what I did… put them down the sides and leave a walk way down the middle.. does not help you truss plan much sorry..

 

[mmmmmdonuts]

Thanks for the help and pictures. That's probably what I will end up doing. I was looking at beveled (angles) washers to level things out as well.

Do you think it's possible to mount the panels length wise and just mount to the unistrut that way in 4 spots along the channel or better to add cross members as well?

 

[HRTKD]

I was looking at beveled (angles) washers to level things out as well.

I went down that rabbit hole, even made a prototype of my own that fit in the channel and provided about 8° angle. I looked at buying beveled washers too. In the end, I used a piece of 1/8 aluminum on one side of the channel but not the other. A hole drilled in it kept it aligned with the bolt in the strut channel and kept it from moving. Here's a picture of how I planned for it to work (and it did!).

Do you think it's possible to mount the panels length wise and just mount to the unistrut that way in 4 spots along the channel or better to add cross members as well?

If the strut is run parallel to the panels and the mounting brackets are on the short ends of the panels that would be OK for smaller panels. That gives you four points of contact. For larger panels you'll want more points of contact, which means the mounting brackets need to be on the long sides. I think the strut needs to run perpendicular to the panels if you're going to mount on the long sides. I haven't used residential strut mounting brackets but I think they are designed to work when they're used parallel to the strut. I could be wrong.

Strut usually runs well parallel to the length of the trailer because the roof is flat in that direction. Strut doesn't work well run perpendicular to the length of the trailer because the roof arches. That's why I used two layers of strut, to account for the arch.

If you don't have to work around roof obstacles and don't expect to change out the panels for a long time, strut is overkill. Using strut increases project time and cost. I had no idea how much more time it was going to take.

 

[mmmmmdonuts]

Part of the reason I was looking at strut honestly was to get a few inches of height to deal with a couple obstructions in a few areas. I could go with less panels if without strut and mounting directly to the roof but it maybe harder to hit all the studs in that case as well.

That's what I am really trying to balance. I think I can get 6 panels if I don't use strut and 8+ if I use it just due to obstructions but I will have to remeasure some things.

On my panels at home that were professionally installed they mount the panels horizontally with 4 mounting points say 1/4 to 1/3 of the way in from the edge of the panel.

My other slight concern is how much additional weight 2 layers of strut will be.

I have wondered about this too: Link and basically tee across at the studs

 

[HRTKD]

My other slight concern is how much additional weight 2 layers of strut will be.

Aluminum strut is available. Costly, but it's less weight than regular (steel) strut.

I have wondered about this too: Link and basically tee across at the studs

Angle aluminum would be simpler.

 

[mmmmmdonuts]

So I made some good progress on this. Hopefully will have it all done this weekend if it ever stops raining. I put two sections of strut up 10 ft a piece and spread approximately 40" apart roughly centered on the roof. I needed 3 washers to till the brackets I bought up to make it level and then attached L brackets to the mount. It allows me to go over most obstacles on the roof. Butyl tape and dicor with lag bolts into the studs at 32" roughly for spacing.

 

[MattMan119]

Looking good..

 

[mmmmmdonuts]

Got the rest of the panels up. Got 6 total, STP295 panels for a total of 1770W of solar. I did have 8 total and I probably could get two more up if I really wanted to but would need to hang off or go over the AC or at the really front of the RV. Opting not to do it right now due to weight considerations.

The spacing between the two ACs and back of the trailer is 152" and if I criss -crossed the panels in 2x2 squares I am at a 154". So I couldn't do it, so I settled with 3 in each section.

I like that I still have room to walk along the side fairly easily as well. In hind sight if I could of got the 45" wide panels that are a little shorter or the 4x8 panels it would of got me quite a bit more power and taken up pretty much the whole roof. I will also post some finishing pictures in my build thread located here.



Edit: And power is going. A little late in the day but have been pushing 1250W+ in the last hour before it became a bit overcast.

 

[High Desert Wanderer]

Simple, quick, easy, lightweight and cheap... I used 4x3x1/4" angle, and have the panels about 6" off the roof. Lag bolted into the plywood only since it's surprisingly stout. I used 3/8" lags, 5 per bracket with dicor, and they are solid as can be. Altogether probably weighs 20lbs or less...

I built an aluminum spoiler / wind deflector on the front panel to guide the air over it because it is right at the edge of the cap, and all is holding very well. Maybe adds 15 lbs...

4 365s max out my controller at 96 amps, and I've seen nearly 9kw in a day, but that all depends on how much power I use of course.

Looks like you have a more sophisticated grid tied system than the simple system I built. I figured if I was going to be in an RV park & pay for power, I might as well use it. This RV only has a 2-way transfer switch, so I simply ran a cord from the inverter outs to a 50a receptacle, and choose whether I plug the RV into shore power, or that. Either way, I always have power available with minimum complexity & investment.