Adhesive for steel solar brackets to aluminum roofs

[Sentinelist]

I've seen a couple recommendations from long ago, but is there a de-facto standard product for this solution? I've got two 100w Renogy panels I'm planning to install in the next week and would rather not drill into the roof to mound the Z-brackets. Is it still recommended to throw some Dicor sealant on top of the contact part of the brackets as well? Thanks.

[vapman]

I just installed 400 watts of flexible solar using VHB tape. I haven't taken it out yet, but I'm sure it's good to go.



Here is the blog post I did.
http://blog.thevap.com/?p=2070

[Sentinelist]

Luckily my roof is flat, but it's a cool concept. Great looking boat!

[HMS_Beagle]

There are a couple of kinds of flexible solar panels. The amorphous silicon ones are really flexible, you can roll them up. These are about half as efficient, e.g., twice the area needed for the same power. The other kind are semi-flexible, usually laminated onto a sheet metal backing. The best of these use the same mono crystalline cells as rigid panels. You can only bend them a little, usually 3% arc is specified. They can be glued directly to a surface. They are 2 - 3x the price of rigid framed panels, and since they cannot get cooling air underneath will run hotter (which reduces output some). But you cannot beat the clean low profile installation, and they are usually walkable. Got a bunch on my boat:

[mlts22]

I've seen this problem addressed by people using flexible solar panels. Of course, those are more expensive per watt and give less energy than regular panels, but they just need taped and caulked down, due to no need for a rigid frame.

[Sentinelist]

Thanks for the continued help. I got a PM from a member here with the same camper as mine who said the roof on these are 2" thick. Seems about right with the roof, framing, insulation and ceiling panel. I picked up some 3M 5200 sealant at Home Depot this afternoon for $15 and will plan to carefully get to work on this Sunday!

[billtex]

Redsky wrote:
VHB tape is used even on aerospace applications. It does work well if the surface is properly cleaned with the recommended cleaner beforehand.

Screws only work if there is enough thickness for 3-4 threads to bite and hold. Most RV roofs do not have a very thick roof all the way across. If you don't trust VHB tape the best alternative is 1/2" rubber Well-Nuts. They take a 1/2 inch hole and then a 8-32 stainless screw is threaded into the Well-Nut to expand its diameter. Finish by applying sealant to the screw head so not water can penetrate.

I used stainless self taping screws on my solar panel rack but I had 4 feet on an edge that was screwed every 8 inches into the edges where there are two tubular aluminum framing sections. I had 20 plus screws holding the frame down to the roof.

Why don't you post some pictures detailing this work? We would love to see this...

[Redsky]

VHB tape is used even on aerospace applications. It does work well if the surface is properly cleaned with the recommended cleaner beforehand.

Screws only work if there is enough thickness for 3-4 threads to bite and hold. Most RV roofs do not have a very thick roof all the way across. If you don't trust VHB tape the best alternative is 1/2" rubber Well-Nuts. They take a 1/2 inch hole and then a 8-32 stainless screw is threaded into the Well-Nut to expand its diameter. Finish by applying sealant to the screw head so not water can penetrate.

I used stainless self taping screws on my solar panel rack but I had 4 feet on an edge that was screwed every 8 inches into the edges where there are two tubular aluminum framing sections. I had 20 plus screws holding the frame down to the roof.

[Sentinelist]

HMS Beagle wrote:
I just posted a thread on what I did to mount mine. On an aluminum roof I would probably convince myself to put a screw in each mount in addition to gluing them. Polyurethane will bond pretty well to the aluminum, but it is a thin sheet and might lift from the plywood underneath. I didn't have to worry about that with the fiberglass roof.

Thanks, I checked it out- looks good!

billtex wrote:
3M 5200 adhesive...

I appreciate it- this and a screw each will probably serve me well enough. Added to my Amazon cart. Hoping to tackle this next weekend...

[tony_lee]

Tape might be OK for flat roofs but most have enough of a crown on them that an adhesive bed is necessary

[billtex]

3M 5200 adhesive...

[HMS_Beagle]

I just posted a thread on what I did to mount mine. On an aluminum roof I would probably convince myself to put a screw in each mount in addition to gluing them. Polyurethane will bond pretty well to the aluminum, but it is a thin sheet and might lift from the plywood underneath. I didn't have to worry about that with the fiberglass roof.

[Mello_Mike]

YC 1 wrote:
You don't have to find a frame member. The wind load is low and the screws just add additional security. To prevent drilling into wires you can pre-drill very small pilot holes using several wraps of electrical tape on the shaft of the drill bit to make a depth stop. Then gently insert a small wire down the hole to test clearance. Be sure to use short screws when you fasten.

x2 Also use a short screw with wide threads for extra holding power.

[YC_1]

You don't have to find a frame member. The wind load is low and the screws just add additional security. To prevent drilling into wires you can pre-drill very small pilot holes using several wraps of electrical tape on the shaft of the drill bit to make a depth stop. Then gently insert a small wire down the hole to test clearance. Be sure to use short screws when you fasten.

[Sentinelist]

Thanks for that!