Kernwig's Solar Build

[TahoeJoe]

Originally Posted by dstreight

I have used 3M VHB tape for a variety of applications over the past dozen or so years. Getting the proper VHB type matched for the two surfaces to be bonded is key along with proper surface prep as mentioned above.

Here's a link to the recommended surface prep procedure for VHB tape from 3M: https://www.3m.com/3M/en_US/vhb-tape...ep1surfaceprep

Also be aware, just like many adhesives, full cure & full strength of the VHB tape bond takes about 72-hours depending upon ambient temperature and humidity level.

I have successfully removed VHB tape from two bonded surfaces, well after the 72-hour cure period, using a length of piano wire wrapped around two wood dowels to guillotine the tape from one of the bonded surfaces. Coincidentally, I had to do that today apart of a removable exterior table top project I've been working on for the 15A.

I didn't even realize there were so many different 3M VHB tapes available! OK I've got some research to do today to find the best one.

I've also used a similar removal procedure, in my case for the "badging" on my trucks (those plastic emblems on the sides and backs of the trucks), I used a heat gun and fishing line, and then to remove the remaining residue I used a 3M Adhesive Eraser Wheel attached to my drill. That experience did show me how strong that tape is!

[MyronL]

3M VHB tape -worthy of trust? I added s/s 1/4/20 bolts at the corners, just in case.
Seen this test? ( sorry about the stupid ad I have no control over)
https://youtu.be/X8tyU-2wqqo

[Centex]

Originally Posted by MyronL

3M VHB tape -worthy of trust?

I suspect it is, WHEN...

• The bonded planes are absolutely parallel to each other (e.g. not a flat on even the slightest curve)
• The bonded surfaces are properly prepared
• Water is prevented from contacting the VHB edge
• There is never any significant force trying to separate the surfaces which tends to lift / pry / leverage one edge of the tape

Lacking confidence I can ensure all of those conditions are satisfied throughout the life of the connection, I like...

Originally Posted by MyronL

... I added s/s 1/4/20 bolts at the corners, just in case.

YMMV

[TahoeJoe]

Now I'm falling down the rabbit hole of VHB tape research, trying to select which one is best...realizing that it's possible that I'm splitting hairs and any of these would work. Anyways, it seems as though a leading favorite among many posters here is 4950, which is also the same kind that AM Solar uses. I've also seen some swear by 5952 as being better. But then I reached out to 3M, and after a lengthy caveat about how they don't recommend any VHB tape for non-industrial applications like this, and how careful I need to be, etc (I assume they need to say this for liability purposes) they recommended...4941. Said it would have the best "strength balance".

They also recommended using 3M Primer 94 to make sure they stick better.

[TahoeJoe]

Originally Posted by TahoeJoe

They also recommended using 3M Primer 94 to make sure they stick better.

After the initial suggestion of Primer 94, they told me that this product is actually better, it's an improved version, it's called "VHB Tape Universal Primer UV":
https://www.3m.com/3M/en_US/p/d/b40062444/

[kernwig]

Originally Posted by TahoeJoe

they recommended...4941. Said it would have the best "strength balance".

They also recommended using 3M Primer 94 to make sure they stick better.

I went through the 3M website's VHB tape selector on their web site and it suggested two: 5952 and I think the other was 4950.

If you are talking AM Solar's means of just a couple inches per corner on a hard panel mount, I too would be concerned about the best "strength balance" and primer. For a strip across the entire leading edge of a flex panel, supplemented with Eternabond all around, I expect any VHB tape will do the trick!

My rear panel is holding great still, but perhaps I'll peal up the lead edge and put VHB under it as well. (Replacing with new Eternabond over it, of course.)

[TahoeJoe]

Originally Posted by kernwig

I went through the 3M website's VHB tape selector on their web site and it suggested two: 5952 and I think the other was 4950.

If you are talking AM Solar's means of just a couple inches per corner on a hard panel mount, I too would be concerned about the best "strength balance" and primer. For a strip across the entire leading edge of a flex panel, supplemented with Eternabond all around, I expect any VHB tape will do the trick!

My rear panel is holding great still, but perhaps I'll peal up the lead edge and put VHB under it as well. (Replacing with new Eternabond over it, of course.)

I did that selector too, and got 4941 and 5952, and those are the 2 I'm looking at. Check out this handy dandy sheet comparing them:
https://multimedia.3m.com/mws/media/...nglish-pdf.pdf

[MyronL]

When talking about taping down flexible panels I think the lesson learned is about the stresses involved. The panels will not long survive intense heat, and that roof gets really hot. If you stick with taping the perimeter and don't run tape in spaced strips at intervals centered across the underside, the thing is eventually going to buckle up and fly away. You got to protect the center. Taping the perimeter alone sets up the perfect storm.

Attaching a panel to the front of the trailer roof will multiply these issues by about a hundred thousand. (My humble stress assessment.) Has no one seen reports of VHB tape sticking to the gel coat but the gel coat pulling off the fiberglass shell?