mounting 8 solar panels, roof questions on '99 Win. Adventurer

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lesd

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Jan 19, 2010
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33
Hello everyone,
On Sat I will be take possession of my first RV, a 1999 Winnebago Adventurer.
I want to install some solar on it, and will take eight 90 Watt panels off my home system to go on the roof of the motorhome. I would like to know more about the roof so I can mount them with as little issues as possible ( for example, not drilling in the wrong place and not causing and leaks ).
Each panel is about 42" by 21" .
My MH has a fiberglass roof, but I really don't know what else is between the outside gel coat and the headliner inside, and how thick the insides of the roof are.
Can anyone who has some advise on this roof and mounting things to it chime in ?
I don't want to ruin my 'new to me' MH !
-Thanks
-Les
 
That's a lot of solar panels - not sure if you will find enough room for all of them. There is already a lot of stuff up there.

I don't have specific info for a 99 Winnie but we have a lot of Winnie owners here and somebody can probably help. Winnie customer service is also a good source.

In general, the roof will be a skin over thin plywood, which in turn lies on simple, thin, rafters, with a depth of 2-4" to the interior. It is filled with insulation. Some wiring and ducting run through it, so some caution is advised.  You aren't going to be able to very selective in location with that many panels, so basically you are going to be screwing  to the skin and plywood sheathing. Use a good caulk or bedding compound for the brackets and screws. 

Despite what seems to be minimal construction, we seldom hear of problems with leaks around solar panels or anything else that is screwed to the roof. I've mounted carrying brackets for a folding boat and various other things by simply screwing to the roof sheath and caulking, with never a problem. Satellite domes are mounted the same way and rarely leak if caulked well.
 
Thanks for the info. So I would think that some kind of 'hollow wall' expanding nut type of fastener would be most appropriate then? I think I will try to bolt down some aluminum rails and then attach the panels to the rails with some risers to let the air get under the panels for cooling.
Maybe if I call Winnebago that can send me a drawing of where any ribs are, or anything else to be concerned with. At least there are no fuel lines up there ! ( don't ask why that would enter my mind ;)
 
Yeah, you could use a hollow wall anchor of suitable depth or perhaps a blind (rivet) nut. I've had excellent results with coarse thread screws, though.

Using brackets is a good idea, since it allows you to do a permanent mount of the bracket and leave it alone. One you get it fastened to the roof, you don't ever want to have to disturb the mounting screws/bolts and associated caulk. A flat footed bracket also gives you a larger surface to caulk around, keeping the water away from the actual hole in the roof.
 
lesd said:
Hello everyone,
On Sat I will be take possession of my first RV, a 1999 Winnebago Adventurer.
I want to install some solar on it, and will take eight 90 Watt panels off my home system to go on the roof of the motorhome. I would like to know more about the roof so I can mount them with as little issues as possible ( for example, not drilling in the wrong place and not causing and leaks ).
Each panel is about 42" by 21" .
My MH has a fiberglass roof, but I really don't know what else is between the outside gel coat and the headliner inside, and how thick the insides of the roof are.
Can anyone who has some advise on this roof and mounting things to it chime in ?
I don't want to ruin my 'new to me' MH !
-Thanks
-Les
Click to expand...

I'm getting ready to put up 6-8 panels myself. On a fiberglass roof you can use 3M VHB tape to secure the panels to the roof. In know some prominent RV solar panel builders/installers that do this. the 3M VHB is amazing stuff. Some trailer makers use this instead of welding. There are a variety of grades, thicknesses and so on. The tape I'm using is ultra thin, the tape with a foam carrier is NOT the one to use. This stuff is about a thin as paper.

The trick is to insure the fiberglass roof is ultra clean. It can't have any dirt or smeary stuff on it at all. There is a recommended cleaning procedure you can get from the company.

Here is a link for some info: http://solutions.3m.com/wps/portal/3M/en_US/VHB/Tapes/

I have used 3m VHB to make bonds between aluminum and a variety of plastics and also aluminum to aluminum. If applied properly the bond is as strong as you need and not subject to vibration, a common problem with other fastening methods.

No drilling. If you search around you'll find the professional installers and RV system builders that use VHB for their installations.

One word of caution. When you bond something with VHB, it is pretty much permanent. While you can get the bond apart, simply pulling on it will mean ripping off your roof before the panel mounts come off.
 
Disadvantage of glue. I see many Rvs with solar panels tilted up at an optimal angle to the sun. They even leave them tilted while they go to the dump station at Quartzsite.
 
I would like to tilt also. Would the different thermal expansion coefficients of the aluminum side rails of the panels and the glass roof tend to work itself loose , over the 42" of panel length ? It may, but on the other hand the panels themselves are glass plates, really. Hmmm.    That double side taped might be better for small panels, I would think.
 
Yes Winnebago will send you a pdf file with drawings showing the location of the aluminum ribs in the roof. As I recall they also show the wiring channels routed in the foam core but I am not certain of that.

As RVRoamer said the roof is a sandwich of thin fiberglass (maybe 1/16 inch thick), luan (maybe1/8 inch thick), foam (about 4 inches thick), luan again and then the interior roof covering - vinyl or very thin carpet like material - whatever they used that year.

There are substantial aluminum extrusions along the entire length of the edge of the roof where the walls are connected. Perhaps  cross pieces could be made that would go edge to edge and provide a good anchor for the panels.
 
So if the outer skin and the luan is only 3/16 thick, I should be wary of the strength  of the fasteners because they might pull out too easy. Perhaps gluing or double side taping down some long aluminum rails would be the best way, and then attach the brackets to these to distribute the load. That 3M tape looks good for that, the version that has more foam thickness to allow for roof imperfections, etc.
 
An update to my post about 3m VHB tape. If you are concerned about the ability of VHB to hold the panels securely or are concerned about the thickness of your roof, you can attach pads to the solar panel feet and then use the VHB to mount the panels. In that way you have more surface area and the weight is spread out over a large area and you get more tape contact.

When buying the tape, you'll get a better price if you go to an industrial supply house rather than a Home Depot. The industrial supply houses sell the tape in large rolls for much less than you'll pay for small packages in other stores. They will also usually carry a variety of the tapes.

The most important part of using VHB tapes is to use a tape that has the least amount of foam carrier as possible because the foam is the weakest part of the link. If you can, use the foamless type because the bond is stronger, there is no foam to degrade or come apart and the less the panels can move around from vibration, the stronger the bond remains.
 
How does VHB tape compare to Eternabond double sided tape ?
I have heard such great things about the eternabond, but I'm not sure about the double sided version.
I have some VHB tape, but it is so thin that I am worried that it will let go when the roof flexes during driving a bumby road, and the 42" solar panel does not flex 'with it' ....
Thin tape also means no room for 'give'.

I have four mounting pads for each panel, each is 3" by 6" aluminum area  to contact/glue to  the roof.

-Les
 
OK, well, I did a little test, and the Eternabond does seem to stick a bit better, but it looks like it will remain viscous
rather than hold it's position. In a hot summer climate, it may start to drift and slide . I don't know if after a while it will 'set' for lack of better words.
 
Eternabond? Why mess with anything less than VHB @ 150lb/sq. in.  I have 4ea. 100W panels on the roof, all attached with VHB. Do what Crackodawn says and they will never come off. Once mine were attached and set (a week or so) I went back and sealed the bond to the roof with Dicor to keep the elements off of the VHB.

FWIW, I asked AM Solar if they had ever had issues with panels coming off, they said only once, and they were convinced it was bad prep. If you look around on the web you will find amazing stories about VHB tape. I think mine are attached with #4950

- Here's Mine
- VHB Cut Sheet
- HERE is a guy on eBay that sells small quantities.
 
OK, I have about 70 yards of 4646, which is about 1/2 the thickness of the version you used. According to the 3M data sheet, it can tolerate up to 3 times the tape thickness in shear displacement, so I'll just triple up the thickness to allow for some extra sheer. My MH will be covering some rough roads, and I want to consider the roof flex to be safe.
 
lesd said:
OK, I have about 70 yards of 4646, which is about 1/2 the thickness of the version you used. According to the 3M data sheet, it can tolerate up to 3 times the tape thickness in shear displacement, so I'll just triple up the thickness to allow for some extra sheer. My MH will be covering some rough roads, and I want to consider the roof flex to be safe.
Click to expand...
A word of caution about this!! I doubled up 2 layers of VHB to re-stick a panel on the car that I didn't think would really grab well with one strip. Well.... I just came in from the garage to report that the VHB is bonded to both surfaces like it's been welded, BUT the 2 layers of VHB have separated from each other! And this is with very little pull, maybe, possibly 1lb or so. Don't do it or someone will be wearing your panel.
 
That's odd. You would think that the tape would stick to itself better than anything else.
Was it adhesive to adhesive, or was it adhesive to foam ?
 
crackodawn said:
One word of caution. When you bond something with VHB, it is pretty much permanent. While you can get the bond apart, simply pulling on it will mean ripping off your roof before the panel mounts come off.
Click to expand...

Do you mean that if you wanted to remove the panels, you "could" get them off w/o damaging the roof?

Also, RV roofs are seldom perfectly flat, and bow for drainage. It would seem to me that the curvature would lend itself to screws vs. tape.

Anyway, I doubt that taping would ever work for me.  I have two 80W panels that I have had on my last 3 RVs. Each time they were fastened with screws dipped in caulk -- then the head covered with caulk. That's also the only way I have ever seen solar installers install panels. I have also had a number of Internet and/or TV satellite antennas on my roofs and they were installed the same way -- and removed when I purchased another rig.

When removed, I simply re-caulked the screws and put them back in the holes. I would "never" consider a MH my last MH - and have always moved items such as my solar panels, inverter, charger, and so forth to the newer rig. Would never want to consider the installs of such items as "pretty much permenant".  :)
 
I'm not a chemical adhesives engineer, ,but if I were I would probably say something like these adhesives are built to stick to (x), not a like substance. My fix is going to be to slide a small metal plate in-between the 2 strips and it'll be fine. I could probably even use aluminum foil.

As to the roof curvature issue, that's true. But since all AM Solar panels are on single bolt tilt mounts, they find their own flat surface. When I mount my panels, I loosen the feet ever so slightly, position the panel, make sure all feet are flat on the roof, tighten the tilt knobs, pull the backing off the tape and stick em' down.
 
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