Help Understanding Roof Types for Mounting

bajajoaquin

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Sep 1, 2021
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My Jamboree Class C I’m working on to add solar has a crowned roof (about 4.5”) at the center with a flat section about 3” wide at each edge. After looking at various track systems with Yakima towers, I decided I’d be fiddling so much I might as well start from scratch and build crossbars that span the whole roof.

I’ve drawn up racks that will span the width of the roof from 16-ga 1” sq steel tube. Each foot will have a pad to spread the load. The panels will be mounted on aluminum T-section bar running longitudinally and allowing me to install multiple mounting brackets. (Comments welcome)

The main question is understanding the options for attaching the racks to the roof. I haven’t heard back from the manufacturer about the material and recommended adhesive and mounting strategy, but I was hoping that someone would have some general guidance.

The roof is some sort of rubberized coating. I understand that this is unsuitable for VHB tape, right? I’m figuring on Dicor, VHB and as few screws through the roof as possible.

Guidance and comments are greatly appreciated!
 

McCarthy

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If there is any aluminum sheeting / supports in the roof, I'd use Rivnuts and channel struts.
 

K8MEJ

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Pictures would help a lot. That said, my travel trailer has an TPO roof membrane (rubber like) with a wood deck below it and wood rafters. The roof is also crowned. I used 5/8" x 13/16" aluminum strut channel running lengthwise across the roof. I made sure to hit as many rafters as I could. Using SS lag screws, I attached the strut channel to the roof with about 3" of butyl tape between the channel and roof and then a glob of self-leveling sealant on top of the screw head. I chose to use aluminum tilt brackets but that's not necessary and fastened them to the strut channel using SS spring nuts and SS screws. It does make it easier to lift the panels up if I want to do wiring or some other maintenance under the panels. I have two sets of channels running down the sides of the roof.

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bajajoaquin

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That’s very interesting, thanks. You chose more holes but lower profile, it seems. Maybe I’ll reconsider my approach. Where did you get the strut channel and tilt brackets?

Here are some snaps I took of the roof a few days back when I was trying to visualize the space. They aren’t very good but what I currently have, sorry.
 

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K8MEJ

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I bought the strut channel from my local Grainger, but you could probably order the aluminum type from any electrical supply shop. The aluminum tilt brackets are sold by quite a few different solar panel dealers. The least expensive I found at the time was Eco-Worthy.
 

bajajoaquin

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That’s fantastic. I was trying to remember the name of the product and couldn’t remember “strut channel.” I found it at McMaster-Carr in several thicknesses. It looks like I can get low profile (13/16”) up to high profile (3-1/4”) which should allow me to make them nearly level without buying any extra parts.

One problem is that I have a TV antenna which was going to be under the panels with my rack system. I don’t use the TV so I don’t care about it. I might have to remove it if I use strut channel, though.

I might even use it for my rear surf racks rather than welding up something from scratch.

Here’s a rough drawing of my space. I’m planning on putting 4x100w panels in the 57” gap forward. Surf racks will be all the way aft behind the A/C unit. My biggest board is 120”, but I figure it can hang off the back 5-10” without hurting anything.
 

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K8MEJ

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There are a number of companies who make strut channel. Unistrut is one brand. McMaster-Carr is here in my state of Ohio. Surely you can find a local seller. Another product to look at is called 80/20. Just google 80/20.

If you don't use the TV, remove the antenna. You can always try a portable antenna if the need arises.

Are you certain 400W of PV is going to be enough? You should figure you're only really going to get 200-300 watts depending on the angle of the sun, time of year, etc.

Depending on the strength of the rear bumper, I'd be looking to put as many panels on the roof as will fit and then mount your boards vertically on the rear of the camper. If you can, turn them sideways to keep the wind load down.
 

jwelter99

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Pictures would help a lot. That said, my travel trailer has an TPO roof membrane (rubber like) with a wood deck below it and wood rafters. The roof is also crowned. I used 5/8" x 13/16" aluminum strut channel running lengthwise across the roof. I made sure to hit as many rafters as I could. Using SS lag screws, I attached the strut channel to the roof with about 3" of butyl tape between the channel and roof and then a glob of self-leveling sealant on top of the screw head. I chose to use aluminum tilt brackets but that's not necessary and fastened them to the strut channel using SS spring nuts and SS screws. It does make it easier to lift the panels up if I want to do wiring or some other maintenance under the panels. I have two sets of channels running down the sides of the roof.

View attachment 65674View attachment 65675View attachment 65676

Nice install!
 

jwelter99

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There are a number of companies who make strut channel. Unistrut is one brand. McMaster-Carr is here in my state of Ohio. Surely you can find a local seller. Another product to look at is called 80/20. Just google 80/20.

If you don't use the TV, remove the antenna. You can always try a portable antenna if the need arises.

Are you certain 400W of PV is going to be enough? You should figure you're only really going to get 200-300 watts depending on the angle of the sun, time of year, etc.

Depending on the strength of the rear bumper, I'd be looking to put as many panels on the roof as will fit and then mount your boards vertically on the rear of the camper. If you can, turn them sideways to keep the wind load down.

Check our Zorro online for strut channel - they have really good pricing and delivery is not so bad if you need several lengths at once.
 

bajajoaquin

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Sep 1, 2021
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My last camper had a 64-watt panel wired through a $20 controller and feeding a 12v 80ah FLA battery through the fridge wiring. Our family of four including two small children did fine with that for a week in Baja only running the generator fir about a half hour in the middle to use the hand held vacuum we have. The only additional draw on this camper is a larger fan for a larger furnace. 400w directly through an MPPT controller and 206ah LiFeSO4 is a huge upgrade already. I don’t remember my energy audit results off the top of my head, but I think 200w was a comfortable amount. We use the water pump and LED interior lights sparingly, and background draw for the LP fridge. Furnace is set to 60 degrees and rarely runs. No electronics, TV or such. Maybe an hour of CD player.

If I’m wrong, I can run two additional at least down the right side and since the farthest aft vent is tapered to the front, I can probably fit another one on the side of the surf rack. I’ve got more room to squeeze other panels too if I need.

Vertical board storage would be with fabrication time or a lot of money. Both are in short supply with the RV purchase, solar, tire, differential and other upgrades and a November 3 departure date.

I might even put boards on the aft bed for this trip if I run out of time.

Old setup:
 

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Bob The Builder

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Sep 25, 2021
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Pictures would help a lot. That said, my travel trailer has an TPO roof membrane (rubber like) with a wood deck below it and wood rafters. The roof is also crowned. I used 5/8" x 13/16" aluminum strut channel running lengthwise across the roof. I made sure to hit as many rafters as I could. Using SS lag screws, I attached the strut channel to the roof with about 3" of butyl tape between the channel and roof and then a glob of self-leveling sealant on top of the screw head. I chose to use aluminum tilt brackets but that's not necessary and fastened them to the strut channel using SS spring nuts and SS screws. It does make it easier to lift the panels up if I want to do wiring or some other maintenance under the panels. I have two sets of channels running down the sides of the roof.

View attachment 65674View attachment 65675View attachment 65676
Where did you get the clips to attach the panels to the struts? Looks awesome!
 

bajajoaquin

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I ended up not going with strut channel. It was going to require a lot more holes in my roof. I decided to fabricate a full-span rack from 1” 16-ga square steel tubing.

Having said that, I bought all the hardware from McMaster-Carr.
 

K8MEJ

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Location
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Where did you get the clips to attach the panels to the struts? Looks awesome!
I'm not exactly sure which part you mean. I used stainless steel spring washers in the strut channel itself. I used aluminum PV tilt brackets and used SS screws to attach one piece of the tilt bracket to the SS spring washer in the Unistrut and SS screws and lock nuts to hold the other piece of the tilt bracket to the PV panels. Then I mated the tilt brackets together and used the included plastic knob, screw, flange nut to clamp the two pieces of the tilt bracket together. If I actually want to tilt them then I will install the third piece of the brackets.

Brackets can be found here: Eco-Worthy and other places.

Did that answer your question?
 
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