2020 Montana 3120 roof truss spacing

[jwandkw]

I have a 2020 Montana 3120 RL and I am looking for a drawing to show the truss spacing in the roof for attaching my solar panels. Can anyone help with that? Thank you.

[R.S.O'Donnell]

I screwed all 12 of my Renogy 100w panels directly to the plywood using their Z brackets. Drilled a very small pilot hole and used 1/4” stainless #3 Phillips head screws. Been coast to coast at least a half a dozen times with zero issues. Put down a puddle of Dicor, install the screws just until they’re snug, and then cover the entire flange and screw heads with Dicor.

[Mikendebbie]

There are no drawings for Montanas (same applies for most makes of fifth wheels and travel trailers). I would get a stud finder and mark the joists.

You may be able to glean some info by watching some of the various Montana factory tour videos on YouTube, but you should pay attention to the date of the video because roof joist material has changed over the years. The screen shot below is from a YouTube by Home with the Hoopers from May 2019. Looks like they were using wood trusses.

[Daryles]

I used a stud finder to locate the rafters and marked them with painters Frog tape. I used 1" x 1/4" stainless steel screws to mount the panel brackets.

Rail mounting
If I was doing mine all over again I would use aluminum unistrut rails.
With rails you can be sure every screw you use to mount the rail goes into a rafter stud.
Use a stud finder and painters tape to mark the studs. If you use the mounting brackets that come with the panels, you can only be sure one side of the panel has mounting brackets mounted to a rafter stud (the leading edge). The other (trailing) brackets will have to be fastened where they lay.
Also with rails, you can move/replace/upgrade the panels without drilling new holes.
When you are ready to mount the rails, clean the roof with alcohol then put down a 2x2" piece of Eternabond tape where you plan to drill the holes for the rail screws. Next, set your rails and drill the pilot holes for the screws. Put Dicor self leveling sealant in the screw holes and between the rails and the Eternabond tape. Put a spacer (or thick washer) between the rail and the Eternabond tape to allow water to drain away under the rail off the roof. Install the screw through the rail and put some more Dicor over the screw head.
I would also recommend Renogy tilting panel mounts so you can clean under them easily.

[Foldbak]

I just located my panels where I wanted them and screwed them to the Luan. Not worried about hitting the trusses as per my service department. Don't over tighten and use lap sealant. So far so good.

[bamakeifer]

We rebuilt the roof on our 2013 303RK a couple years ago related to a height misjudgment on my behalf (costly error). The factory trusses were a plastic composite, we replaced them wooden trusses recommended by an RV tech @ Camping World. The factory trusses were on 24 inch centers so that is what I repaired our roof with.

[firestation12]

Originally Posted by Daryles

I used a stud finder to locate the rafters and marked them with painters Frog tape. I used 1" x 1/4" stainless steel screws to mount the panel brackets.

Rail mounting
If I was doing mine all over again I would use aluminum unistrut rails.
With rails you can be sure every screw you use to mount the rail goes into a rafter stud.
Use a stud finder and painters tape to mark the studs. If you use the mounting brackets that come with the panels, you can only be sure one side of the panel has mounting brackets mounted to a rafter stud (the leading edge). The other (trailing) brackets will have to be fastened where they lay.
Also with rails, you can move/replace/upgrade the panels without drilling new holes.
When you are ready to mount the rails, clean the roof with alcohol then put down a 2x2" piece of Eternabond tape where you plan to drill the holes for the rail screws. Next, set your rails and drill the pilot holes for the screws. Put Dicor self leveling sealant in the screw holes and between the rails and the Eternabond tape. Put a spacer (or thick washer) between the rail and the Eternabond tape to allow water to drain away under the rail off the roof. Install the screw through the rail and put some more Dicor over the screw head.
I would also recommend Renogy tilting panel mounts so you can clean under them easily.

I’m a fan of Darles solution of using 2 parallel runs aluminum super strut. It your roof has a rounded crown rather than being flat, you’ll find the brackets supplied with the panels will not elevate sufficiently above the crown.

[ToolMan]

With the amount of heat created by the panels, more space between them and the roof material the better. This is one reason I decided to keep my modest 3 panel solar set up portable.