2004 Holiday Rambler Neptune/Monaco Cayman roof construction

[marsingbob]

    I am in the process of adding solar panels to the roof  of a 2004 Neptune and trying to understand the roof structure better.  Based on the brochure of the 2005 and 2003 models (no 2004 brochure seems to be available) it is based on aluminum "C" channels.  After looking at our roof and checking flexing, they appear to be on 18" centers.  From the feel of the roof, the channels seem to be under the aluminum roof and probably a sheet of lauan.  Our plan is to screw the support for the solar panels into the "C" channels.  However--the schematic drawing in the brochure shows a "C" channel with large lightening holes in the wide cord, which will make it difficult to find the right spot if the holes exist and if they are oriented toward the top of the coach/roof.  However this seems to be for walls and the roof is described as having "double I-beam construction."

   I suspect the Monaco Cayman is the same.  The brochures for it do not show a frame layout or any information on the metal roof structure except it is "a double I' beam".  If the roof structure is a double I beam, we should be able to drill into it.  (The brochure shows a layer of tapered bead form insulation above the metal frame, and that is probably true of the Neptune as well.)

   Obviously the brochures are only a very imprecise impression of the actual construction.  Can anyone help me with additional information on the roof?  If you tried to drill into the "C" channels were you successful?  

[waterskier_1]

I tried to figure this out when I was mounting solar panels on my old Dynasty.  I have not seen (they may still exist somewhere) detailed manufacturing drawings with dimensions for the coach.  I'm not sure if you have an aluminum or fiberglass roof.  If aluminum, I'm not sure what coatings may have been applied.  

What I ended up doing on the fiberglass roof on my Dynasty, and again on my Executive is to use 3M VHB (Very High Bond) tape.  I chose the 5952 series for the installation temperatures and adhesion qualities.  The fiberglass roof does have a plywood or lauan under the fiberglass, but it is not always "adhered" to the Steel (Aluminum in the lower level coaches) superstructure.  I knew that the mounting holes in my panels were very unlikely to match up to the spacing.  I decided not to run a full rail to which one would mount the panels.  I made my own mounting brackets, which were basically 2" Aluminum Angle, (like an L-Bracket) one for the panel and one for the roof.  I drilled the holes offset so I could keep the panel slightly higher and allow for raising (tilting) the panels.  On the Dynasty (my first project) I used the VHB Double-sided tape and also a short 1/4" x 3/4" screw to mount the brackets to the roof.  I originally was skeptical of the tape alone.  I have removed the screws and check the integrity of the adhesive (unscientifically) and I believe that the fiberglass would tear/rip or otherwise give before the adhesive.  So, on my Exec, I only used the VHB tape.  This tape is used in the structural manufacture of products, like those aluminum trailers where they don't want rows of rivets.  I have had the panels on my Exec for over 5 years, and believe the panels are still on my Dynasty (sold to buy the Exec) for over 12 years.  I just just that method to my my Starlink Roof Mount last week.  

Not a direct answer to your original question, but maybe an acceptable solution to why you asked it.

  -Rick N.

[marsingbob]

Thanks waterskier, that's helpful.  I am going back and forth on tape.  I am currently thinking I will use Unistrut rails, and tape them, with screws at each end as well.  The screws may not mean much, but perhaps they would provide a little more peace of mind!  I am too old to get on the roof to inspect it from time to time so it may be a few weeks between inspections.

My coach has a metal roof and I do not know how it is secured to the metal structure.

[marsingbob]

A follow up on our installation.  We found the roof trusses on 18" centers.  I suspect the truss must be fairly wide because we hit all 12 holes on the first try.  From drilling the truss web seemed like 1/8" aluminum, maybe heavier.  The truss where we drilled is about 3" below the surface of the roof.