Plan for mounting solar panels

[ependydad]

I have a 2022 Precept 36C motorhome with a fiberglass roof that I’m going to be installing solar panels onto it. I contacted Jayco and they said the roof was 3/4” plywood. I’m going to be building a rack out of 2” x 1/8” thick angle aluminum.


Here’s what the rack idea will mimic:

I’ll be gluing it down with a bead of 3M 5200 as well as using 3/4” felt tipped roofing screws every 6” to secure it. and the covering every screw in Dicor self-leveling lap sealant.

Thoughts? Opinions? Witty commentary?

 

[Yellowstone Randy]

Looks like a good idea... may keep some of the heat off of your roof?

 

[ependydad]

Looks like a good idea... may keep some of the heat off of your roof?

That’s what I’ve heard. The shading seems to decrease the roof temperature even if you’d really think the panels would increase it.

 

[Grumpy]

I contacted Jayco and they said the roof was 3/4” plywood.
Thoughts? Opinions? Witty commentary?

I think they meant 3/8" not 3/4".. I would double check that info, they have never used 3'4" on any roof. Even the spec says it is their vacuum bonded roof which is 3/8".

 

[ependydad]

I think they meant 3/8" not 3/4".. I would double check that info, they have never used 3'4" on any roof. Even the spec says it is their vacuum bonded roof which is 3/8".

Sadly, I have to add this to the list of incorrect things Jayco has told me. I’m going to pull a vent down and will verify the roof thickness but I expect you’re very correct.

I’ve also asked them for schematic/drawings/materials for the roof. I’ve had very hit or miss luck getting responses, unfortunately.

 

[Jerry713]

I have a 2022 Precept 36C motorhome with a fiberglass roof that I’m going to be installing solar panels onto it. I contacted Jayco and they said the roof was 3/4” plywood. I’m going to be building a rack out of 2” x 1/8” thick angle aluminum.


Here’s what the rack idea will mimic:

I’ll be gluing it down with a bead of 3M 5200 as well as using 3/4” felt tipped roofing screws every 6” to secure it. and the covering every screw in Dicor self-leveling lap sealant.

Thoughts? Opinions? Witty commentary?

Should help with the heat for sure.

On the 3M if you think you would ever want to remove the aluminum framing you might consider going with 4000UV instead of 5200. 5200 is permanent and you'll have to tear your roof off to remove the aluminum framing. 4000 still provides a waterproof seal but it is not as permanent.

Also what are felt tipped roofing screws?

 

[ependydad]

Should help with the heat for sure.

On the 3M if you think you would ever want to remove the aluminum framing you might consider going with 4000UV instead of 5200. 5200 is permanent and you'll have to tear your roof off to remove the aluminum framing. 4000 still provides a waterproof seal but it is not as permanent.

Also what are felt tipped roofing screws?

Good call on the 4000UV vs. the 5200. I don't think I'd have a reason to remove the angle aluminum especially given the # of holes that will be put down to hold it all together.

As for the screws, I wrote that wrong- screws with a felt/neoprene washer. Something like these:
https://www.lowes.com/pd/Pro-Twist-...-Self-Drilling-Roofing-Screws-1-lb/1000365281

 

[Jerry713]

Good call on the 4000UV vs. the 5200. I don't think I'd have a reason to remove the angle aluminum especially given the # of holes that will be put down to hold it all together.

As for the screws, I wrote that wrong- screws with a felt/neoprene washer. Something like these:
https://www.lowes.com/pd/Pro-Twist-...-Self-Drilling-Roofing-Screws-1-lb/1000365281

Gotcha thought there was a new type of screw on the market lol.

 

[Jagiven]

Good call on the 4000UV vs. the 5200. I don't think I'd have a reason to remove the angle aluminum especially given the # of holes that will be put down to hold it all together.

As for the screws, I wrote that wrong- screws with a felt/neoprene washer. Something like these:
https://www.lowes.com/pd/Pro-Twist-...-Self-Drilling-Roofing-Screws-1-lb/1000365281

Glad you corrected the screws. I was going to make a suggestion to replace the felt nails to screws.

Personally, I would make a mockup of the installation plan. I might recommend a dab of adhesive (4000UV or 5200) under the AL angle, and around the pentation for the screw head. Just to reduce the chance of water pentation. I also might consider adding a small piece of Eternabond over the screw head and your caulking. No such thing as to much waterproofing on a rolling earthquake.

Last thing I might consider is using C-Channel over angle iron. It would not be hard to make the cells able to tip to maximize solar gain when parked.

Good Luck, please post an update with lots of photos

 

[ependydad]

Gotcha thought there was a new type of screw on the market lol.

No, I'm just dumb. :lolhitsign:

Glad you corrected the screws. I was going to make a suggestion to replace the felt nails to screws.

Personally, I would make a mockup of the installation plan. I might recommend a dab of adhesive (4000UV or 5200) under the AL angle, and around the pentation for the screw head. Just to reduce the chance of water pentation. I also might consider adding a small piece of Eternabond over the screw head and your caulking. No such thing as to much waterproofing on a rolling earthquake.

Last thing I might consider is using C-Channel over angle iron. It would not be hard to make the cells able to tip to maximize solar gain when parked.

Good Luck, please post an update with lots of photos

I'm thinking I'll drill for the screw, back it out, fill the hole with sealant, and re-run it in. Back when I did some kayak building, it was similar to the "drill-fill-drill" approach just without using or waiting for the epoxy to cure.

I've had a few recommendations for unistrut (like your c-channel recommendation). I think there's merit in that and will consider it.

 

[Jerry713]

After looking at the photo again that design may have them but if not I would plan on adding some angle bracing (from the outside towards the center of your roof). Forward and backward bracing wouldn't hurt but I can how the aluminum angle will help with that some.

Should be a fun project.

 

[ependydad]

After looking at the photo again that design may have them but if not I would plan on adding some angle bracing (from the outside towards the center of your roof). Forward and backward bracing wouldn't hurt but I can how the aluminum angle will help with that some.

Should be a fun project.

Yeah, I plan on a base mount, uprights, and then angles from corner to corner between quite a few of the attachment points to give it some rigidity.

Here's a more detailed picture of that install:

 

[Jagiven]

I'm thinking I'll drill for the screw, back it out, fill the hole with sealant, and re-run it in. Back when I did some kayak building, it was similar to the "drill-fill-drill" approach just without using or waiting for the epoxy to cure.

I've had a few recommendations for unistrut (like your c-channel recommendation). I think there's merit in that and will consider it.

I like Unistrut but it is heavy stuff. The only holes are on opposing side of the open face, and the edges are rolled. I would think it would take a lot of time and more effort to modify to fit your needs. But accessibility to Unistrut might be much easier. Just something else to consider.

 

[billcf7]

I like Unistrut but it is heavy stuff. The only holes are on opposing side of the open face, and the edges are rolled. I would think it would take a lot of time and more effort to modify to fit your needs. But accessibility to Unistrut might be much easier. Just something else to consider.

They make aluminum unistrut, expensive though. Thats what I was looking into.

Check this solar install

 

[Onyrlef]

They make aluminum unistrut, expensive though. Thats what I was looking into

Grainger has it, but as you say it's higher'n a cat's back. About $10.00 per ft. vs. Galv. 12 ga. @ $3.50 per ft. The galv. was half that pre pandemic. The non perforated channel strut would likely be better for what you're doing. The perforated is designed for hanging from threaded rod in attics.

 

[ependydad]

Grainger has it, but as you say it's higher'n a cat's back. About $10.00 per ft. vs. Galv. 12 ga. @ $3.50 per ft. The galv. was half that pre pandemic. The non perforated channel strut would likely be better for what you're doing. The perforated is designed for hanging from threaded rod in attics.

Yowza. Yeah, that is a budget breaker. I am figuring I'll need 3 x 28' sections of it for my panel layout:

 

[Jagiven]

Yowza. Yeah, that is a budget breaker. I am figuring I'll need 3 x 28' sections of it for my panel layout:

That's a lot of solar. What's your battery bank like?

Check out this massive solar setup

 

[ependydad]

That's a lot of solar. What's your battery bank like?

It's a DIY lithium pack. I'm running 608 ah @ 48v. It powers a pair of dual Quattro inverters.

• Full Solar Design
  
• BMS Setup
  
• Battery/Inverter System Design

 

[ependydad]

Rack Design - Cross Member supports

I'm building my parts/order details for the rack for solar panels. The rooftop air conditioners are a whopping 14" tall or so which means my uprights need to be at least 15" tall in order to clear the air conditioners. Note, this still leaves me with an overall RV height right about 13' (assuming the 12' 10" specs are correct).

I plan on having diagonal supports between the uprights to add rigidity and minimize movement. But what I can't decide is if I can get away with little 2" angles or if I need to go fully corner to corner.

Edit to add: do I also need them on both sides of the panels? Or just 1 side per panel is sufficient?

Thoughts?

Hopefully this picture uploads with a decent enough quality to see the 2 options. If not, you might need to click on it to see it in its full glory:

 

[01tundra-JAY]

I don't have a fiberglass roof, but since roof access for maintenance isn't going to be as easy once the panels are installed, I'd consider investing in some Eternabond tape and sealing everything up prior to installing the solar.