3M VHB Tape

Hdlaut · 08-18-2023, 07:08 PM

I have seen a number of posts referencing 3M VHB Tape for mounting solar panels to the roof. I have mounting brackets that should work well.

The only question I have is: there's a number of different types of the VHB. which one is the best for my use case?

Thanks in advance.

Best regards,
Don

Wavery · 08-26-2023, 08:30 AM

Quote:

Originally Posted by Hdlaut

I have seen a number of posts referencing 3M VHB Tape for mounting solar panels to the roof. I have mounting brackets that should work well.

The only question I have is: there's a number of different types of the VHB. which one is the best for my use case?

Thanks in advance.

Best regards,
Don

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

Hdlaut · 08-26-2023, 08:58 AM

Wavery, Thanks very much!

Wavery · 08-26-2023, 09:26 AM

Be sure to wash and rinse the surface of the roof AND the mating surface of your brackets. Then wipe the surfaces down with rubbing alcohol and let dry.

When you put the brackets in place, put pressure against them for 20-30 seconds to release the banding agent. then let it cure for 24 hours before putting pressure on them.

If you ever want to remove the brackets, get yourself some 4" razor scraper blades. Hold one end of the blade with a vise grip and slice the tape from the side. Slice one direction only. It will take several careful passes to get all the way through. If you're careful it won't even scratch the roof. When the bracket is removed, take your thumb and rub across the tape residue and it will come off completely.

https://www.amazon.com/Replacement-S...5&sr=8-49&th=1

When I mount my brackets, I screw all of the brackets to the side of the solar panel, ready to mount. I then place the panel on the roof, exactly where I want it. Then I mark the perimeter of each bracket with a pencil. Then, I remove the brackets from the panel and "Tape" them in place, one at a time. This way you can apply enough pressure on the individual brackets.

Once the tape has cured, set you panel on the brackets and put the screws back in. Here's a pic of my panel in place. You can see the type brackets that I use and how I attached mine to my panels.

I get the brackets with those rabbit ears and drill holes for self-drilling screws.

**rickst29** · 08-26-2023, 10:42 AM

For the case of mounting glass panels on Z-bar brackets, you will want to have full 1" width along the lower part of the bracket. They're only about 4 inches long, and the total surface area would be reduced (badly) by using less width.

For the case of mounting 'flexible' panel, I have used 1" width in the past, but now prefer width of either .6 inches or .75 inches. Any of those widths is "adequate", but the 1" width goes past the the edge of most flex panels and underneath the cells. The greater width is harder to cut, and removing a panel creates some risk of damaging the panel assembly when the tape stretches to far inwards.

For all cases of mounting with good contact, I slightly prefer a thin tape (0.40 thickness or less), rather than the thick ones with more foam in between. 'RP36' and '4950' fit the bill. Only for the case of a Z-bar foot not reaching down to the roof shell surface (due to the shells being bent, rather than flat) would I use thicker pieces.

In the past, fearing inadequate adhesion, I have used large amounts of VHB along my flex panel edges - up to 40% of the total edge length in the most extreme case. I'm moving and adding a couple of panels in the next two days., and intend to use much less as follows:

Just 8 pieces slightly less than 4" long each (total about 30 inches). One piece angled at 45 degrees in each corner, additional peices centered on each "long edge", and slightly shorter pieces centered along the each "short edge". Avoiding grommet holes, of course.

I have found subsequent removal of VHB tape to be pretty easy for the "gray foam versions in a hot garage, and absolutely beastly for the case of a su[per-thin "white foam" version. But that white foam tape might not have been a normal consumer product.

Hdlaut · 08-26-2023, 07:23 PM

Thanks to you both! These are the brackets I am planning to use.

https://www.amazon.com/gp/aw/d/B09XB...?ie=UTF8&psc=1

I used them before on a boat. Do you have any thoughts on them? BTW, I plan to mount a 335W Panasonic panel.

Hdlaut · 08-28-2023, 02:56 PM

Hmmmm. I currently have a 100W (I guess) factory panel where I want to put the new one. I guess I will have to remove it and test fit to see if they work unmodified.

**rickst29** · 08-28-2023, 03:14 PM

and can be mounted with only 4 Z-bars. It also weight far less, your bigger panel could create a lifting issue.

Are you looking the front shell or the rear shell? For the case of the rear shell, the remaining "depth" when closed is very important and varies according to the model of TM you have.

Hdlaut · 08-28-2023, 06:19 PM

Quote:

Originally Posted by rickst29

and can be mounted with only 4 Z-bars. It also weight far less, your bigger panel could create a lifting issue.

Are you looking the front shell or the rear shell? For the case of the rear shell, the remaining "depth" when closed is very important and varies according to the model of TM you have.

Oh. Rats. Something else I didn't consider. It would be installed on the rear shell of a 2006 3023.

**jagizzi** · 08-29-2023, 08:14 AM

I installed a 400W panel on the rear of our 2005 2720 using Z-brackets. I had to add additional aluminum spacers to allow clearance for the crown in the roof. The spacers were simply aluminum square extrusions.

The panel weighs 40#. I could still open and close the shell but elected to change out the torsion bars to the next larger size as they were fully adjusted to the max, and it was difficult to open. I am pretty sure that it would have gotten more difficult over time, hence the change out.

FWIW, and I differ from some on this, I firmly believe in backing up critical connections with a mechanical fastener. Failures happen, and I don't want my VHB tape attached panel to go sailing while I am traveling. The extrusions are through bolted to the roof with fender washers inside. The holes are sealed, at the roof, with 3M UV4000 and then the extrusions are also bedded in the stuff. There is no sealant in the screw hole itself nor inside at the ceiling. If there is a leak, and I don't expect it, I want to know it; and I will as it will drip on the bed ;-)

This setup has exceeded my expectations from a performance standpoint. I have gotten more than 30A into the batteries on many occasions and when the sun is available am always able to make up night time usage of my CPAP and the fridge.