mounting my solar panels

Thanks everyone for the input. I have checked with Gulfstream, and was told that my roof is 3/8" plywood covered with rubber membrane. Yes, these are 2-100 watt panels. I have decided to go ahead and use well nuts 3/8" x 1". these are supposed to work for material from 5/16" to 5/8". My kit includes their Z-brackets, so that is what I will use.

I have read to put Dicor sealant around the hole before inserting well nut, as well as Dicor over the bolt head when done.

Panels are arriving later this week. Hoping for the best.

"200w kit" he bought "panels" for most likely means two 100 watt panels if my detective skills are on today. These are small'ish compared to the big 350's. A 100 watt panel does not need an abundance of screws. 4 will likely be enough. 8 is plenty and more than 8 per panel is over-kill. You do not need to mount them a foot high as the other pic, that will just really cause wind issues. Mine are less than 1/2 inch off the roof, more than 1/4, but it just needs enough to let air move, and 1/4 inch will do that.
I bought aluminum angle iron from hardware store, cut it to fit the short sides of the panels, used self-tapping screws to hold it to the panels and mounted the brackets to the roof. 4 screws for one 100 watt panel and 4 screws to hold it to the roof (mins was actually a metal roof so used double sided tape, two 4 inch strips per bracket was plenty.

"200W" kit doesn't tell much. 2*100W panels will be less of a concern as each one is small and attached with (at least) 4 brackets with (at least) 2 screws per bracket.

Single 200W panel is heavy and bulky, more wind resistance. However, I installed 2*245W on my travel trailer. I used 4 aluminum brackets per panel, each bracket is 6" long with 3* #10 screws per bracket.

Roof is 3/4 plywood under the rubber-ish coat. You need Dicor sealant https://www.amazon.com/gp/product/B004A2YKWI/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 , put it under the bracket, lubricate each screw with Dicor before running it in, and cover the screw heads with Dicor. I made brackets myself out of 1/4" aluminum angle, the shop cut it in 6" pieces. Brackets are attached to the panels with 1/4 bolts and rivet nuts into the sides of the frame.

You could also use 2-piece brackets (aka Z-brackets), like on the photos in the previous post, to attach to the existing holes in the frame and avoid rivet nuts. With 2*100W panels you should be alright with 2 screws in the roof per bracket, but space them at least 2.5" away. All bolts, nuts and screws have to be stainless.

To locate the roof rafters I emailed the factory and asked for a roof drawing that shows the rafters. This was not very accurate, so I additionally used a strong magnet to locate the nails - those are usually along the centerline of the rafter. 9 times out of 10 I hit the rafter. (With Z-brackets in the existing holes you might not hit the rafters though).

Don't pre-drill holes in the roof. It's a cr-appy particle board, not a real plywood.

Darklock wrote:
I have ordered some solar panels to put on my TT. I bought the 200 watt kit from Renogy. I doubt that I will be able to determine where the structural members are, so there is the very real possibility that if I just use screws they will only be into the plywood decking. In any other applications, I would trust this, but not for going down the highway at 60mph. Therefore, I am thinking of using expanding well nuts. Good plan? Or does the collective here feel that the screws should be enough?
Also, what is best sealant to insure no leaks? No clue what the roof surface is. TT is a Gulfstream Conquest.
Bil

I just went thorough this. I did not buy Renogy Panels but I did buy Renogy mounting brackets. The brackets come with mounting screws four per bracket. The first screw I put in did not bite. The screw is a number 10 or less. Fine threads. As soon as that happened I went down to the hardware store and got some round head number 12 x 1 stainless screws that have a course thread for biting into wood. These worked great no pilot hole just screw them in with impact driver being careful not to over torque. As soon as the driver ratcheted and screw head was flush that was it.

Prior to screwing down the brackets I cleaned with a little acetone I put a small strip of Eternabond between the roof membrane and the Renogy bracket. Eternabond will self seal around the screws as they pass through.

I used Dicor self leveling sealant to seal the screw heads and around the brackets. I was very generous with the Dicor. Which may have caused a little ripple affect with the roof membrane as it began to dry which I discovered the next day. I contacted Dicor about this by email which they did not respond too but I did find written information from Dicor that said the following.

"Lap sealants formulated for RV roofs, on the other hand, are made to bite into the EPDM or TPO roof material (Dicor lap sealant also works with metal and fiberglass) and hold fast. In the case of a common EPDM roof, lap sealants like Dicor's self-leveling and non-sag, non self-leveling sealants contain an oil-based solvent that reacts with the oil-based elements in the roofing material. At first, this reaction will actually cause the roofing material to swell a bit — you might even get a slight rippling effect. But don't worry! This is only temporary while the reacting oils evaporate, which brings the roof back to its normal state and, most importantly, essentially fusing the sealant and roofing material together".

It's been 3 weeks or so since I installed my panels and the rippling affect has improved but not perfect. Waiting for some nice hot days.

Yes, drilling 16 screws per panel x five panels is 80 holes but do a good job and forget about it.

Darklock wrote:
I have ordered some solar panels to put on my TT. I bought the 200 watt kit from Renogy. I doubt that I will be able to determine where the structural members are, so there is the very real possibility that if I just use screws they will only be into the plywood decking. In any other applications, I would trust this, but not for going down the highway at 60mph. Therefore, I am thinking of using expanding well nuts. Good plan? Or does the collective here feel that the screws should be enough?
Also, what is best sealant to insure no leaks? No clue what the roof surface is. TT is a Gulfstream Conquest.
Bil

I'm a well-nut fan. Though I have to say there is a fair amount data indicating the wind blows over the top of the panels and doesn't try and get under them as peel them off. I traveled across the US with panels that were just screwed into the 3/8" plywood as installed by the dealer. When I re-did my solar I removed the panels and used well-nuts to be sure.

Housted wrote:
I have 8 solar panels on my 5er. All are held on with Z brackets and coarse ss screws. The screws are driven through a blob of dicor and then the screw head is covered with dicor. No holes were drilled for the screws so they hold very well. Been like that for years.
BTW if you use double side tape you are depending on the glue holding the rubber roof on. If you use the tape on the frame of the panel you can maybe get enough to hold, but you then have no air circulation under the panels, so they may overheat in the summer sun.

Housted

same here on my 3 larger 200W panels. And for the effect of wind. There are two components of the force exerted on an object by the wind. (1) speed, and (2) surface area after accounting for the drag coefficient.

In the case of solar panels the surface area exposed to the wind is minimal. Airflow over and under the panel may create some lift or downforce. But in the end there really isn't much force on the panels especially considering the airflow is not laminar.

Now if the roof is a smooth fiberglass roof, then 3M VHB tape properly applied. (that means also using the proper cleaning and proper adhesive promoter and proper application) is likely to work well also. But IMHO NEVER on a rubber roof.

SO, by saying "ply-wood" we assume you have a rubber roof?
Your only option is to screw the mounts into the roof them, you cannot glue or tape the mounts in as this would only adhere to the rubber membrane and not the wood.
Not a big deal, use the sealant as others suggest.
You WILL NOT get 60mph winds across the top of your roof!
You WILL NOT have panels getting hit by highway speed winds!
There is just too much turbulence across a roof, air will churn, roll and wip in all directions. You could almost just lay the panels on the roof and drive and they would not blow off (for a while), but do not try this...
Keep the panels off the roof just enough (1/2 inch) that air can circulate under them as the panels need to be keep cool by circulating air under them.
I used aluminum L-bracket on the front and rear edges (front facing going down the road), this keeps air from entering under the panel and lifting it off, keeps rain water from flowing under, not that it matters...
Mount the brackets however is best for that spot on your roof though.
Make sure the AC unit or vent covers will not be casting a shadow too often, mount them away from structures when possible.
IF you can run the panels in series you can use smaller gauge wire and less wire.
Mount then at the front so the rear roof of the trailer has less junk on it, this way the air leaving the end of the trailer is as smooth as possible, which will be better handling.

I used #10 stainless steel sheet metal screws.
Drill a small pilot hole (1/4 the width if the screw), put Dicor on top of pilot hole, snug up the screw (don't over tighten), cover the screw with more Dicor.

Darklock wrote:
Or does the collective here feel that the screws should be enough?

Screws work well for me. And lots of Dicor. Still on my roof after 15 years.

You'll know when you put the first one in if it's strong enough.

I have 8 solar panels on my 5er. All are held on with Z brackets and coarse ss screws. The screws are driven through a blob of dicor and then the screw head is covered with dicor. No holes were drilled for the screws so they hold very well. Been like that for years.
BTW if you use double side tape you are depending on the glue holding the rubber roof on. If you use the tape on the frame of the panel you can maybe get enough to hold, but you then have no air circulation under the panels, so they may overheat in the summer sun.

Housted