VHB Purpose, Price, and Alternatives?

[CarlCruzin]

That link lets you ask the 3m technical engineer directly. If I had the time, I'd write up both the Z Bracket and Unistrut Panel Mounting details and ask them to validate it.

Personally, I'd always want to use mechanical fasteners. I can just hear the attorney asking me if I really expected those panels to stick on some foam tape. No data sheet is going to get you sympathy in that case.

With all due respect, that is like asking a screw engineer if his screw will work for this application. My father is an engineer and I know when you ask an engineer a question, you get 10-20 questions back (and about as many conditions) before you get your answer. There are too many variables to get a definitive answer. Even if you asked a mechanical fastener engineer the best method to accomplish the task, they would likely tell you to tear out the ceiling inside the RV, install large amounts of bracing, run extensive tests, etc. Like most DIY projects, we don't have the time, $$$$, or resources to get an engineer's approval or run through their recommended process that a corporate entity requires before accepting liability...

So most of the time we are left with relying on our own research, reasonable logic, and a little luck. I will likely use some mechanical fasteners also because I agree that it adds peace of mind.

Regarding the lawyer bit, this is what their website says:

• Fast and easy-to-use permanent bonding method provides high strength and long-term durability
• Virtually invisible fastening keeps surfaces smooth
• Can replace mechanical fasteners (rivets, welding, screws) or liquid adhesives
• Gray, 0.062 in (1.6 mm), multi-purpose adhesive and conformable acrylic foam core for good performance in a variety of applications
• Eliminate drilling, grinding, refinishing, screwing, welding and clean-up
• Creates a permanent seal against water, moisture and more
• Pressure sensitive adhesive bonds on contact to provide immediate handling strength
• Allows the use of thinner, lighter weight and dissimilar materials

So I would say in that theoretical scenario: "Yes. According to the manufacturer, it is a suitable method"

 

[Browneye]

I don’t know.

Boggles my mind. Then they seal around it ‘to be sure.’

Do outfits install solar on roofs with vhb?
Nananana no.

People are afraid to drill holes and/or have manufactured item dependency. I think vhb is dangerous myself.

I have installed solar panels, racks, antenna brackets, lighting, planer mast bases, transducers, tie-downs, RV vents (not replacements), skylights, aircon…. No misplaced holes, no leaks, and no vhb.

3M 5200 or polyurethane caulking is permanent, stronger bond than vhb, and waterproof. Leveling lap sealant isn’t exactly the most structural thing but it is a good sealant. But everything gets bolted; boats, cars, trailers, RVs.

FUD. Sorry man, yer way off base here.
Yes, vhb is used commercially.
It flat works.

 

[Browneye]

I am considering using VHB tape for an upcoming project, but am finding that it is quite expensive! For 2" wide it is about $5/ft and I'm going to use potentially 80'.
(adhering unistrut to the fiberglass roof of my rv for solar panel mounting)
I'm not trying to spend that much on tape, so that brings me to my next question. Why is everybody using VHB? Is it just for the convenience and minimal mess?

I'm considering switching to a construction adhesive, which I could probably do the project with a few tubes for a lot less. Is there any reason why I should consider sticking with the VHB?

Cuz It works.

 

[Browneye]

3m is a trusted institution. If vhb is good enough for high rise building glass you can trust it to stick. PERIOD.

 

[curiouscarbon]

vhb with proper force and loading calculations is used to affix windows to towers, or so i heard.

if VHB tape was being squeezed into something, i would feel confident about the shear force resistance, still being cautious about tension forces.

VHB + metal fastener i Prefer.

VHB alone, please do calcs

i've tested 1 inch x 1 inch strip of VHB, it is Inconvenient to remove. with heat and sustained forces, still feel confident a metal fastener would fail second. heat of sun weakens VHB by percentage points. it does not weaken bolts by much. either metal bolt or metal line, these great last line of defense. anchor with metal please!

it is about a COMPLETE ASSURANCE that innocent people on the road around me are safe.

even after experiencing VHB strength first hand I wish for all on the road to be Alive

 

[curiouscarbon]

3m is a trusted institution. If vhb is good enough for high rise building glass you can trust it to stick. PERIOD.

with proper load wind force calcs, i totally agree!

not sure if everyone does the "right" calculations. all due respect!

vhb + metal fastener for exterior mounted PV panels seems reasonable to me. all due respect to 3m!

 

[12VoltInstalls]

Yes, vhb is used commercially.

I’m well aware. Worked on many trailers constructed with it.

IT IS NOT USED COMMERCIALLY FOR LOADBEARING APPLICATIONS is what I was referring to.

Sorry man, yer way off base here.

Am I?

 

[Browneye]

Start here…

https://www.ellsworth.com/globalassets/literature-library/manufacturer/3m/3m-technical-bulletin-vhb-tape-durability.pdf

“One of the oldest and most visible applications for the VHBTM Foam Tapes is on ambulance bodies. The aluminum panels comprising the body of an ambulance can be bonded onto the frame with VHBTM Tape. These applications require durability in harsh conditions on rugged vehicles that are in service for many years.”

“Given a product lifetime estimate for cyclic loading, the data can be extrapolated to estimate the maximum tolerable design stress. For Acrylic Foam Tapes, this is typically about 20 psi for one million cycles of full reversal loading. VHBTM Tapes tend to perform well in these types of tests because of their inherent viscoelasticity. The acrylic foam and adhesive absorb energy and relax stresses internally, thus helping protect the adhesive bond on the substrate.”

Used commercially for sign mounting in lieu of mechanical fasteners.

20 psi loading for a million cycles. My panels have 180 sq inches of adhesive mounting - 3600 pounds of lifting strength. PLUS mechanical fastening.

 

[12VoltInstalls]

PLUS mechanical fastening.

I’m not disputing anything in the documents you linked. VHB is a great product for so many applications.

None of the documents refer to structural use in tension which is the what mounting of solar panels to a roof is.

Having repaired a few new utility trailers constructed with VHB shells I’ve seen that it can fail. Repaired with polyurethane adhesive and/or screws. I think I pop-riveted one. No matter; rescue bodies, trailers: none of them are structural applications.

Mechanical fastening is required where structural attachment is important.

 

[Browneye]

I am considering using VHB tape for an upcoming project, but am finding that it is quite expensive! For 2" wide it is about $5/ft and I'm going to use potentially 80'.
(adhering unistrut to the fiberglass roof of my rv for solar panel mounting)
I'm not trying to spend that much on tape, so that brings me to my next question. Why is everybody using VHB? Is it just for the convenience and minimal mess?

I'm considering switching to a construction adhesive, which I could probably do the project with a few tubes for a lot less. Is there any reason why I should consider sticking with the VHB?

Here's a re-packer/seller on ebay - you should be able to get your 80' for about $75:

**35 Feet**Genuine 3M VHB #5952 Double-Sided Mounting Acrylic Foam Tape Adhesive | eBay

Genuine 3M VHB 5952 Double Sides Foam (Dark Grey) Adhesive Tape. 3M™ VHB™Tapes all-acrylic construction provides strength and durability in highly demanding applications. Leather / Suede / Velvet. Carbon Fiber.

www.ebay.com

And yes, you want to use tape, not construction adhesive. The latter is too difficult to control the glue joint. The tape is super easy - stick, peel, mount.

The main thing is that you get your mounting area squeaky clean. I used a gray scotchbrite pad and acetone, then a microfiber towel and isopropyl. When you rub your finger across the area it should literally squeak. Make sure you're putting it where you want it, cuz once it makes contact it's on there. I thought I would reposition one over less than a quarter inch, no way - it's not coming back up without a fight.

There are perhaps a couple of higher-strength item numbers but they're stupid-expensive. If you want a good description of all the styles and thicknesses, go here - full rolls only though: https://www.uline.com/Grp_240/3M-VH...o4L-DM97lnfUpZeU65YaAveBEALw_wcB&gclsrc=aw.ds

The 5952 is very popular for this application as it's a reasonable cost, easy to get, and plenty strong.
And yes, once your mounts are attached it is recommended to seal all edges to keep everything out - moisture, dust, UV, etc. etc. I used Sikaflex 221 - the stuff is sick.

To ensure a good contact bond I ran in three #12 self-tapper screws per strut. The fiberglass roof is very thin, over a thin luan. The bite was pretty good and the struts are down for good.

Eternabond tape sealed the strut slots - had to buy 2" tape and cut it down. Put it in the freezer for an hour or two.
Surely someone will complain about this stuff too. LOL

You can get non-slotted strut, and you can get aluminum. Not cheap, and not easy. If you insist then Zoro is a good source, ships readily. Figure about two to three times the cost. I don't know about you, but I'm already hauling 20K lbs and towing a car - a couple of extra pounds for steel struts makes zero difference. I'm still gonna get 8mpg no matter what. ?

 

[CarlCruzin]

Here's a re-packer/seller on ebay - you should be able to get your 80' for about $75:

**35 Feet**Genuine 3M VHB #5952 Double-Sided Mounting Acrylic Foam Tape Adhesive | eBay

Genuine 3M VHB 5952 Double Sides Foam (Dark Grey) Adhesive Tape. 3M™ VHB™Tapes all-acrylic construction provides strength and durability in highly demanding applications. Leather / Suede / Velvet. Carbon Fiber.

www.ebay.com

And yes, you want to use tape, not construction adhesive. The latter is too difficult to control the glue joint. The tape is super easy - stick, peel, mount.

The main thing is that you get your mounting area squeaky clean. I used a gray scotchbrite pad and acetone, then a microfiber towel and isopropyl. When you rub your finger across the area it should literally squeak. Make sure you're putting it where you want it, cuz once it makes contact it's on there. I thought I would reposition one over less than a quarter inch, no way - it's not coming back up without a fight.

There are perhaps a couple of higher-strength item numbers but they're stupid-expensive. If you want a good description of all the styles and thicknesses, go here - full rolls only though: https://www.uline.com/Grp_240/3M-VHB-Tape?pricode=WA8985&AdKeyword=uline vhb tape&AdMatchtype=e&gclid=Cj0KCQiArt6PBhCoARIsAMF5waiemoggPdFk21eMObTUOElggflG6FOFXgFEo4L-DM97lnfUpZeU65YaAveBEALw_wcB&gclsrc=aw.ds

The 5952 is very popular for this application as it's a reasonable cost, easy to get, and plenty strong.
And yes, once your mounts are attached it is recommended to seal all edges to keep everything out - moisture, dust, UV, etc. etc. I used Sikaflex 221 - the stuff is sick.

To ensure a good contact bond I ran in three #12 self-tapper screws per strut. The fiberglass roof is very thin, over a thin luan. The bite was pretty good and the struts are down for good.

Eternabond tape sealed the strut slots - had to buy 2" tape and cut it down. Put it in the freezer for an hour or two.
Surely someone will complain about this stuff too. LOL

You can get non-slotted strut, and you can get aluminum. Not cheap, and not easy. If you insist then Zoro is a good source, ships readily. Figure about two to three times the cost. I don't know about you, but I'm already hauling 20K lbs and towing a car - a couple of extra pounds for steel struts makes zero difference. I'm still gonna get 8mpg no matter what. ?

Wow, Great price! Thanks for the link and details!

 

[Browneye]

This a commercial RV solar installer that has been using VHB tape mounts for a couple of decades, and "we've never lost a panel".
Tons of how-to DIY info here as well:

Mounts - AM Solar | Solar Panels for RVs | RV Solar

amsolar.com

I believe they use the white or clear 4900-series. The majority of VHB tapes use pretty much the same adhesive - the type of foam, color, and thickness varies. There's quite a variety of items, can be a bit confusing. We end up pouring over all this data and then just come back to the same one everybody else uses. ?

What I DO NOT subscribe to are the standard 'z-mounts' just glued on - I don't think that is enough surface area, and why I chose full length struts for my panel mounts.

 

[TEV]

The main reason I was considering running the whole length is for more adhesive contact area.

But, isn't the Unistrut slotted? And so , the contact area reduced?

 

[Browneye]

Some VHB strength testing....
If you want more content on the how's and why's of this product just search YT. 3M has a number of vids themselves, and there's quite a bit of technical content on application techniques and such as well

But, isn't the Unistrut slotted? And so , the contact area reduced?

Most of it is. I used half of the area for strength calcs due to the slotting. Elsewhere I found bonding strength at 18psi. So my struts are 60" long by 1-1/2" wide, times two, so 180 square inches @18psi at 50% is 1620lbs of lifting strength. I will submit to you that a panel cannot nor will not create lifting power anywhere near that.

In the resources wiki there's a wind loading technical brief that calculates solar panels on a tilted roof, 6" off the roof, in 90mph winds, to generate up to 250lbs of lift. My panels are 1-1/2" off the deck, open on all sides for air escape and venting, to prevent lift. Some add an air-dam on the leading edge to stop air from entering underneath - I didn't like the way that looked and didn't think it would add anything so did not do that.

 

[Browneye]

 

[curiouscarbon]

awesome references,

taking notes..

long strut, not small Z Foot

clean surface with scotchbrite, acetone, “squeaking clean”

apply VHB to strut

apply strut to surface

apply metal fasteners

apply edge protection sealing

 

[Browneye]

Here's another vid on strength testing the various brands and offerings, including 3M 5952 VHB. It is the clear winner on metal to metal.
I would not use VHB for attaching wood members as they did in the early part of the video. The metal test with a smooth surface is most telling.

 

[A.Justice]

Securing panels to the roof of a trailer, with ANY type of tape (or adhesive), that'll be doing 70+ miles an hour goes straight in the "fu*k nope" category.

Here's what I'm picturing:

Little Jimmy just got his driver's license. It's Tuesday and he's taking his 7-year-old triplet sisters to ballet practice. Kidz bop's blaring on the radio, everybody's having fun. Jimmy figures he'll get behind this big RV and go nice and slow, just to be safe. One of the triplets yells to Jimmy, "I have to go to the bathroom" and as Jimmy responds, unknown to him, a work truck has lost a large metal nut, and it bounced up and shattered one of the solar panels on the roof of the RV. Wind is now able to get underneath of the panel, that had been taped on, and 60 mph speeds into 25 mile an hour headwinds blow the panel off the roof with more force than a shotgun. A fragmented piece of aluminum strut now heads for little Jimmies windshield.

Jimmy and his sisters didn't stand a chance. The RV drivers insurance doesn't cover it, because the adjuster decides that securing solar panels to your roof with TAPE wasn't the best idea, and the RV driver was responsible for securing their loads. Now the parents are suing for $4 million a child.

All because somebody didn't want to add a few extra screws to their solar panels.

 

[curiouscarbon]

metal fastener and VHB seems safe to me, but VHB alone i would not want to be on same road.

lots of surface area helps

this video had a fun overview of how to apply, and some impromptu tests

 

[12VoltInstalls]

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