Strength of Roof and Solar Install question

[Newbiecampers]

Hi all,

Have been getting the bug to install a solar system on the roof of our Coachmen Chevy based Class C. Was looking to do 300-400 watts (3 or 4 panels).

I researched that the roof board is only 1/8 inch thick laminated luan....and aluminum supports every 4 feet.

That seems way too thin to me to adequately hold the mounting bracket screws secure enough to survive 60-70 mph freeway speeds and resultant wind. I cringe at the thought of even walking on it now knowing it is only 1/8 inch thick.

Any thoughts or real-world experiences with that thin of a roof along with a solar panel set-up?

[2oldman]

PSW wrote:
.. I installed was a Renogy flexible panel from Amazon. They no longer carry flexible Renogy panels but have other brands.

I was shopping today on Amazon and they do have Renogy. I have a rigid panel failure and was thinking of installing a flexible panel with tape right on top of the failed one. I have heat concerns and really don't want an iron taped to my roof.

[Newbiecampers]

Thanks for the info PSW.

Upon discovering how thin the roof was I started to glance at those flexible panels. Haven't done much studying up on them yet. Good to hear it is working for you. I'll keep the 3M tape in mind as well.

[PSW]

I first installed a panel on our Phoenix Cruiser using the normal Z brackets, covering them with Dicor after mounting. Then, on the second panel, I used the 3M VHB tape SailingOn mentioned a few posts above. It is truly incredible stuff. The two panels have been up there three years now with no problems. I do check the integrity of the roof and everything on it in detail twice a year and I take a gander from the ladder before departing each campground just to make sure all appears casually well and make sure no debris has landed on the roof from trees.

Some folks really talk negatively about them, but the second panel I installed was a Renogy flexible panel from Amazon. They no longer carry flexible Renogy panels but have other brands. These panels are really light and I mounted it direct to the roof with the 3M tape and used Dicor around the edges.

NOW, my real concern was heating and the fact that the roof might get hot from the panel mounted directly to it, but it has proven to be a false worry. All I can say it worked great for me. The roof on a Phoenix Cruiser is well designed and sturdy so I can walk around up there with confidence, but I do use all fours to distribute my weight.

Others may have used the flexible panels and it would be interesting to hear their comments/concerns, successes.

Here is an example of a panel and it weighs just four pounds.
https://www.amazon.com/Winnewsun-Flexible-SunPower-Lightweight-Panels/dp/B076CBNK9X/ref=sr_1_2?ie=UTF8&qid=1526053851&sr=8-2&keywords=flexible+solar+panels+100+watt

Paul

[Newbiecampers]

It is the typical TPO/rubber type roof. Not fiberglass.

Knowing how these things are built, with our luck, it would rip the roof membrane right off the wood... Ha Ha

I came accross a "drill free" mount while searching. Something to add to the consideration list.

I'm going to check the roof for an area that feels (or knocks) like it perhaps has some more support as Harvey51 talked about. May see if taking down a ceiling tile inside isn't too much surgery to try and get a look from underneath. Perhaps a dewy morning will reveal the location of the roof support beams like it does on my car.

[SailingOn]

What is your roof surface?
I attached the two 100 watt panels on the roof of my Winnebago View with 3M VHB tape; no roof penetrations. Each bracket (4 to a panel) has a contact area of about 6 sq inches.
12000 miles later including Alaska and back they remain solid.

[Newbiecampers]

Healeyman wrote:
I don't mean to single you out as MANY people clean/wash their roof, but I do question the wisdom of doing that.
.....We don't wash our cars with a scrub brush.

Ok, perhaps "scrubbing" was too harsh a word. I was on my roof rinsing the dust and dirt off to help eliminate dirt streaking down the side of the RV. I was also using a sponge to clean areas of footprints from the dealer "techs" that installed our roof vent and also some areas of caked-on bird poop. There was no scrub brush involved. I was also cleaning the plethora of bugs off of the front of the air conditioning unit, as well as the front of the vent covers.

Anyway......back to the solar.

[Healeyman]

Newbiecampers wrote:
I went up on the roof to wash it. As I was on my hands and knees scrubbing...

Newbie,

I don't mean to single you out as MANY people clean/wash their roof, but I do question the wisdom of doing that.

We spent last weekend at a RV park near Austin, TX. While we were out running errands, a big Super C pulled in beside us. By the time we got back, he was pretty well hooked up and had a rug and chairs out and fancy matching color tire covers on the front and rear wheels.

As we pulled in, he was up of the RV roof with a push broom and was sweeping all of the roof "dirt" over the side.

I have a weather station up on a 15 foot pole over the RV and later he came over to ask me about it. At the end of THAT conversation, I asked him why he had covers over his tires and wheels.

He told me that the covers protect the tires from the sun's UV rays and that UV will cause the rubber tires to age and crack.

I asked him what protects his rubber roof from the sun now that he has swept off all of whatever was up there blocking the sun.

He shrugged, turned, and walked off.

Seems to me that nearly all roofs are made from rubber, plastic film, or fiberglass. We probably all know that the worst thing we can do to those materials is to expose them to the sun. The sun will degrade and destroy those materials. Have you ever seen a tire that has been laying in a field for a while. The sun side is all cracked and aged and the side that is face down in the dirt looks brand new.

I may be wrong, but I don't and won't clean my roof. And scrubbing or sweeping creates micro-scratches that will age the surface even more. We don't wash our cars with a scrub brush.

To each his own.

Tim

[Newbiecampers]

Lwiddis wrote:
Your roof does seem thin but don’t over estimate the wind forces on solar panels. Passing over and under reduces the force significantly. However, I’d screw to the aluminum supports and install 300 watts but wire for four. I wouldn’t walk on your roof at all.

You’ll love solar. My batteries are almost always full by 1 pm.

Nope, will never walk on it again. I even stopped doing it before I found out the "thickness."

The solar definietly fits my preferred stye of camping (boondocking, no full hookups, etc.).

We purchased a renogy 100w suitcase type of solar panel that has their latest waterproof controller. Amazon looked like they were getting rid of them as the price of $202 was far lower than anybody else, and they no longer have it available via amazon. Wish I would have been watching the renogy 200W suitcase (which is also gone) to see what kind of deal they had on it. After doing further research, I'm not sure 100W is going to meet our needs with two batteries to feed.

Was all gung-ho to do a larger roof install, but I'm not so sure now with that roof. I've been researching the heck out of doing a solar setup, but I should have saved my time and researched the roof first...:S Maybe I'll just add another 100w panel to the suitcase when using it...not sure. We are still in the return window for it. I haven't even opened it yet to inspect.

The types of setups that Healeyman and valhalla360 mentioned (to avoid the roof) sound like a good idea, but I'm not sure how involved I want to get with fabricating/welding etc..

EDIT: Looks like the long dimension of the renogy 100w panel is 47.3 inches. If the roof supports are indeed 4 ft apart, it would be close for screwing both mounting brackets into a support. Looks like the mounting brackets add roughly 1.5 inches, and I'm not sure how wide the roof supports are.

What to do, what to do.....:h

[Newbiecampers]

Thanks for the replies to date everyone.

Harvey51 wrote:
It seems to me if you walked on the roof it has to be stronger than 1/8 inch luan with supports 4 feet apart.

valhalla360 wrote:
I'll give you 1000-1 odds it's more than 1/8 inch with 4' support spacing.

Believe me, I wish (hope) that were true. I got the info from Coachmen. I also asked a dealer and they thought the same. And finding out that it is only 1/8 inch verifies an observation I had the first time I went up on the roof.

After returning from our first trip, I went up on the roof to wash it. As I was on my hands and knees scrubbing, I would come accross small areas that had, for lack of a better word, variations in it. Especially near the area where the dealer installed a vent cover, or in the areas I walked to get towards the front. I figured I was just paranoid, and that they were just variations in the TPO material being glued down. But to be on the safe side, I never walked on it again. Only crawled on hands and knees to spread the weight.

Finding out it is only 1/8 inch thick luan leads me to the belief that my initial paranoia was correct, and that those small areas of variations are very slight "dips" created by walking on it. And I am not by any means a weighty person. So now, not only will I only crawl on hands, knees, and rear-end (moving like an inch worm), I think I will bring a board up there to sit on to distribute weight even more.

[valhalla360]

I'll give you 1000-1 odds it's more than 1/8 inch with 4' support spacing.

Personally, I would steer clear of the roof entirely. I would mount a simple folding bracket on the rear wall that allows you to tilt them up when parked but quickly drop them for travel. That avoids penetrations thru the roof and considerations of wind resistance. It also allows for better airflow under the panel (they put out less power when overheated). When parked, they wouldn't block any windows. As long as the deployed position is close to the roof line, shading shouldn't be an issue.

The only possible downside is if you have a viable rear window that works with your rear view mirror, you might lose that...but the majority of RV's (include class C's) don't.

[Harvey51]

It seems to me if you walked on the roof it has to be stronger than 1/8 inch luan with supports 4 feet apart.

Our MH has a metal roof, less than 1/8 inch I think. I did go up on it when we first got it and I think I broke one of the supports. The metal drooped so a puddle formed when wet. I fixed it by opening the ceiling and putting a piece of wood on top of the too low support oriented front to back and extending from 1 crosspiece forward of the bad one back to the one behind it.. After that when I went on the roof I put a couple of 2x6 planks across the width of the roof and scooted out on a sheet of plywood on the planks.

I meant to work inside the ceiling and run metal joists on each side of that crosspiece but never got around to it.

When installing our one solar panel, I discovered that the rear portion of the roof was stronger built with heavy plywood over the wood crosspiece supports. I ran two of the panel frame screws into that and another two into another cross piece support forward of the plywood. The four good sized screws are adequate - no sign of movement or looseness. I don’t go over 60 mph and go at 55 if traffic permits. I can accommodate another panel the same way but don’t need it - 100 watts is perfectly adequate for our small MH and two of us.

[Healeyman]

Newbiecampers wrote:
Any thoughts or real-world experiences with that thin of a roof along with a solar panel set-up?

I have a Chevy based Coachmen Freelander and helped a friend who also has a Freelander mount solar panels on his rig.

Using 1" X 1" angle iron, we welded up a framework in which the side-to-side rails overhung the width of the RV and turned down. After power coating white, the rails were bolted through the sidewalls into the studs.

All of the framework and solar panels are rearward of the awning.

The electrical wiring was run down the outside backwall (by the ladder) in a wire moulding and forward under the RV. The wiring was then brought up into the RV through the floor.

The frame was 1" above the roof (NO weight on the roof) and there were NO roof penetrations, so no leaks.

The electrical panel was mounted in the storage area under the bed near the water tank.

4 years later, it still works well. For occasional cleaning, he climbs the ladder with a Swiffer in hand.

If doing it again, we would design the framework so that it would tilt to track the sun.

Tim

[scrubjaysnest]

No problem with ours, I used a sealing adhesive for the screws and Dicor over that.

[2oldman]

That's what I have and 4 brackets with 2 lag screws each work fine. Whether you can walk on it is largely a function of your weight.