How many brackets for RV roof mount?

[SomebodyInGNV]

Hello. I'm prepping to mount my Newpowa solar panels on the roof of my Rockwood Mini-Lite. The trailer has a 1/4" lauan plywood deck, but no trusses. The only thing I have to screw into is plywood and it's not CDX roof decking but at least it's not the thin stuff used on interiors.

My panels are 58 x 26. I intend to mount them lengthwise so the leading edge in the wind will be the narrow end. There are 8 mount positions pre-drilled on each panel.

The roof has a crown which I can compensate for by using standard z-brackets on the inboard side and curved-roof brackets on the outboard side. But the curved-roof brackets are twice the price (or more) than the standard brackets. (I could make my own but don't want to go to that effort.)

Questions:

1. Are 4 brackets per 58 x 26 panel enough? If I need 6 or 8 (Newpowa recommends 2 sets for each), is there any benefit to mounting two on the leading and trailing narrow sides, or should I use 4 on each side? That would be easiest since the holes are already drilled.

2. Does being level matter? Can I just use standard Z-brackets or should I use the curved roof brackets on the outboard side? The result would be each side being canted outward slightly.

3. The fasteners that come with the brackets are self-tapping screws appropriate for mounting on metal. Should I use 1" #8 or #10 pan-head wood screws instead? Are the rubber washers on the self-tapping screws important? If so, and if I use different wood screws, do I need to add rubber washers?

 

[snoobler]

1. 4 on each side using pre-drilled.

2. If I understand you correctly, no. I would expect you can bend the Z-brackets individually to be "flat" against the localized portion of the roof.

3. I would pre-drill and use wood screws. The rubber is likely a lame attempt at sealing. Adhesive/sealant under and over the bracket should suffice.

 

[SomebodyInGNV]

2. If I understand you correctly, no. I would expect you can bend the Z-brackets individually to be "flat" against the localized portion of the roof.

My thought was not to make the foot of the bracket flush on the roof, but to make the outboard side slightly higher off the roof to compensate for the curve. As I won't be able to control much about how the trailer is oriented in parking, I suspect that being level vs slightly off level doesn't really matter.

 

[Rocketman]

Here are my thoughts:
The last thing you want is to lose a panel - if you think 6 is fine - use that or 8 use that. Us strangers on the internet can't see your roof. I would think it would be a good idea to put one of front and one on back - then use 3 on each side.

Level does not matter - non-level water ( dirt in the rain) will drain to one side.

Sealing. Dicor is your friend - drill the holes for the bracket. Cover area that bracket will be - making sure that each hole has plenty of Dicor in it. Place bracket in position - lining up the holes - that you just covered with Dicor. Insert screws. Then add Dicor to top of screws and all around the bracket. Use Dicor like you own the company.

 

[SomebodyInGNV]

The predrilled bracket positions are not distributed evenly down the side. They're grouped in pairs at each end. I think I'll compromise and use 6 per panel, 4 being at the leading end and 2 at the trailing end. If I'm able to butt the panels together end-to-end, the value of extra brackets on the second panel is diminished.

As for sealing, I intend (and always had) to pre-drill the hole in the roof, lay down a 1" wide strip of Eternabond, set the panel in place, add a dab of self-leveling Dicor at the bracket holes before installing the screws, then cover the heads with more Dicor.

My thoughts about the rubber/plastic washers was not so much about sealing against water, but that they some provide vibration protection to reduce the risk of the screws pulling out.

 

[Whinny]

Take a look at this video...at 2:10ish you can see the roof layout. Yours may be similar.

You can take out speakers and vent moulding to take a look for roof trusses, try to pick up at least 1 of them for the front panel mount. If it's not built like that is there enough room on a Z bracket to have 2 screws?
If you can't pick up a truss use 8 per panel, if you can get a truss use 6 per panel.
I like eternabond doublestick under the Z, and more Dicor than if you owned the company....
I don't think out of level is a concern.

 

[SomebodyInGNV]

The only place Mini-Lites have aluminum trusses is under the AC vent location. Other than that, there are no other roof supports of any kind. It's all 1/4" lauan plywood laminated directly onto styrofoam, with an aluminum frame around the edges, On my trailer, the AC support is 2/3 of the way down the length of the trailer. My panels won't be anywhere near it.

A factory rep emailed me a diagram of my roof, including trusses and reinforcement strips. I confirmed the AC truss is 13' back from the leading edge and is of no use in this installation. I did learn front edge of the aluminum perimeter frame is at the joint with the fiberglass cap. I may be able to get one screw into it but have to determine if that would leave the front edge hanging out over the curved part of the cap. If so, that would be a lot of upward pressure on the panel from the wind.

Rockwood is now laminating metal strips into the roof of 2021+ model years for panel mount reinforcement, where roof panels are ordered as an option. The standard order is 1 panel. The factory will install 2, at most. The reinforcement strips are limited to the area where they're installing the panels. It would be nice if they'd offer reinforcement as an option, without being required to install an entire system. Their choice of systems and method of installation (location of SCC and routing and size of conductors) leaves a lot to be desired.

I also just got a response from Newpowa. They recommend a single set of standard Z brackets for RV roof installation. I'm still going to use a couple extras at the leading ends to reduce the risk of loss due to wind at 65 MPH.

All panels will be tied together with a stainless cable for safety. What I'll attach that to, I don't know. Maybe screw down a strap across a section of the front aluminum roof frame?

 

[SomebodyInGNV]

This is the roof diagram I was just provided. Yellow strips and the orange block are reinforcement points but they're on the top of the ceiling, not the bottom of the roof. They're where cabinets and partitions attach to the ceiling. The orange plate is where the microwave oven hangs.

I'll attach an anchor for the safety cables on the front frame. It will be a strip with several screws so I won't be dependent on a single screw to stop a flying panel.

 

[Bob B]

Another option I have seen people use is to fashion your own bracket and screw into the side where the roof meets the side wall ... kinda like where the awning would be attached .... then secure the other side of the panel the best you can.
It's also pretty easy to design some sort of deflector to the front of the panel to prevent up lift.

 

[SomebodyInGNV]

It's also pretty easy to design some sort of deflector to the front of the panel to prevent up lift.

I hadn't thought of that but yes, I imagine a sheet of aluminum screwed to the front edge of the panel and down to the roof in front of it would be easy and effective. A similar approach with a strap of aluminum would reinforce it.

 

[HRTKD]

You're lucky if you have 1/4". Most of the Luan in my trailer is 1/8". Either way, that's some flimsy material.

Is there any access to the roof from inside the trailer? My thought is if you could slide some 1"x2" pieces into place and then screw into those for the brackets that would give you a (more) solid anchor. Failing that, maybe use Toggle Bolts?

I used three Z brackets per side on my panels. Each bracket has at least one screw in a truss. My panels are bigger than yours. I went with 6 brackets because I do a lot of driving through Wyoming, which has some wicked winds.

 

[HRTKD]

I hadn't thought of that but yes, I imagine a sheet of aluminum screwed to the front edge of the panel and down to the roof in front of it would be easy and effective. A similar approach with a strap of aluminum would reinforce it.

The argument against that is that it could affect heat dissipation. Since the other three sides are clear, probably not much blockage.

 

[Hedges]

Is there any access to the roof from inside the trailer? My thought is if you could slide some 1"x2" pieces into place and then screw into those for the brackets that would give you a (more) solid anchor. Failing that, maybe use Toggle Bolts?

Bolts all the way through to the interior, and fan out to a large surface area?
I put a rack over the cab and hood of my pickup, using stove bolts and washers from the inside.

To be a bit more cosmetic, could use a hole saw like for recessed lighting, cut a 7" plug out of the ceiling, and install backing material. Replace the discs you cut.

If you can locate structural members, you could mount rails like are used one residential roof mount.

 

[SomebodyInGNV]

You're lucky if you have 1/4". Most of the Luan in my trailer is 1/8". Either way, that's some flimsy material.

Is there any access to the roof from inside the trailer? My thought is if you could slide some 1"x2" pieces into place and then screw into those for the brackets that would give you a (more) solid anchor. Failing that, maybe use Toggle Bolts?

I used three Z brackets per side on my panels. Each bracket has at least one screw in a truss. My panels are bigger than yours. I went with 6 brackets because I do a lot of driving through Wyoming, which has some wicked winds.

It's definitely 1/4". I was told that by a manufacturer's rep I correspond with occasionally and observed it personally when I took the interior shroud off a vent fan installation.

There's no access from the inside. It's solid. The roof plywood is glued to solid Styrofoam and that is glued to the 1/8" lauan ceiling. The composite sandwich structure is what gives it its strength. Channels in the Styrofoam form AC ducts which are also used for wiring.

I will use 2 screws into the roof on each bracket. I'll replace the self-tapping screws with wood screws, as advised here.

 

[HRTKD]

I can't find anything that says the roof cannot be walked on. But given that construction, I would be very reluctant to get up there.

 

[SomebodyInGNV]

Rockwood roofs are very strong. I and other owners walk on them all the time.

https://forestriverinc.com/rvs/travel-trailers/rockwood-mini-lite#lg=1&slide=14

 

[HRTKD]

Rockwood roofs are very strong. I and other owners walk on them all the time.

https://forestriverinc.com/rvs/travel-trailers/rockwood-mini-lite#lg=1&slide=14

How? A piece of foam insulation sandwiched between two pieces of thin plywood doesn't seem all that strong to me. I did look this up before my prior post. I thought for sure that I would find something that said it was not a walkable roof, but that was not the case at all. I was surprised, given your description of the roof.

 

[Hedges]

How? A piece of foam insulation sandwiched between two pieces of thin plywood doesn't seem all that strong to me. I did look this up before my prior post. I thought for sure that I would find something that said it was not a walkable roof, but that was not the case at all. I was surprised, given your description of the roof.

Bet you could stand on an interior door balanced between two saw horses.
1/8" plywood on each face and honeycomb of corrugated cardboard inside.

If the roof is curved, all the more so.

 

[HRTKD]

Bet you could stand on an interior door balanced between two saw horses.
1/8" plywood on each face and honeycomb of corrugated cardboard inside.

If the roof is curved, all the more so.

An interior door has a lot more structure to it.

I'm not saying it's impossible. Just that it doesn't seem to be an ideal roof and I wouldn't be on it very much. Heck, on my walkable roof, I still use plywood to spread my weight.

 

[grizzzman]

Here is a pic of my 2504S Rockwood mini lite. Right off the edge of the roof to wall there is a solid connecting point. About 3/4" inward from the side wall. This set up has many thousands of freeway miles as well as lots of dirt roads. I used polyurethane as sealant and glue and 5 screws per 5" home built mount.