VHB or Threaded Fasteners Mount Solar Panels?

[Fair_Enough]

Originally Posted by billrector

Do not use alcohol or a solution containing alcohol if you plan to cover the mount with Sikaflex. See note from Sikaflex:

“Alcohol containing or alcohol releasing products will impair the polyurethane from curing. ... The optimum application temperature for Sikaflex[emoji768] (polyurethanes and silane terminated polymers) and the substrates is between 15 °C and 25 °C. Do not apply these products at temperatures below 5 °C and above 40 °C.”

Sikaflex cautions using certain solvents on "absorbent substrates". The smooth painted aluminum roof panels of an Airstream (in my case) isn't absorbent and thus the solvent is completely flashed / evaporated before proceeding. Always go by manufacturer's recommendations.
FE

[mythbuster88]

Thread summary so far:

1) Plastic razor blades work well for removing old Sikaflex and the like without damaging the aluminum.

2) Then clean with isopropyl.

3) Let dry then 4941 VHB two sided tape.

4) Silkaflex 221 to coat and seal.

Looking up 4941 VHB double sided tape, turns out there are different sizes and thicknesses so the 4941 advocates here should specify so the OP knows what to do to educate the dealer. If I were the OP I would buy the stuff and take it to the dealer and watch them do it.

[billrector]

Originally Posted by Fair_Enough

Sikaflex cautions using certain solvents on "absorbent substrates". The smooth painted aluminum roof panels of an Airstream (in my case) isn't absorbent and thus the solvent is completely flashed / evaporated before proceeding. Always go by manufacturer's recommendations.

FE

What I quoted was the manufacturer’s recommendation.

[GoBlueBird]

Proper prep is essential.

1) Clean with isopropal alcohol (rubbing alcohol)
2) Use 3M™ Adhesion Promoter 111 ( available at 3M distributors)
3) Apply VHB tape

[bandboss]

Just saw a program on TV that showed an ambulance manufacturer using 3M adhesive tape to hold on the wall panels, inside and out. If it can hold up to the daily abuse those vehicles take, I think it’ll stick down your solar panels, without piercing the skin.

[stevejones]

Originally Posted by carl2591

first it looks like the mount got ripped out not by wind but by something else....

Yeah, the dealer to get you to pay for the extra work

Just like some roofers “inspect” your roof by pounding holes in your sheething looking for “weak spots” so you need to replace it and of course pay them to do so.

Steve

[Bobber79]

I used 3M VHB tape to mount 3 solar panels in addition to the one factory-installed panel. After about a year, the most forward panel peeled away while driving on the interstate at about 70 mph. It flew off & took the connection box on the factory panel with it. Fortunately the cable connectors failed, protecting the two aft panels.

I'm not sure why the forward panel VHB tape gave way. The aft panels are still very firmly attached.

[billrector]

Originally Posted by Bobber79

I used 3M VHB tape to mount 3 solar panels in addition to the one factory-installed panel. After about a year, the most forward panel peeled away while driving on the interstate at about 70 mph. It flew off & took the connection box on the factory panel with it. Fortunately the cable connectors failed, protecting the two aft panels.

I'm not sure why the forward panel VHB tape gave way. The aft panels are still very firmly attached.

Did you have the VHB tape covered with a sealer like Sikaflex?

[Lag323]

VHB and lap sealant. Clean with denatured alcohol. Allow VHB to cure for 72 hours.

[gator.bigfoot]

I used acetone to clean along with the VHB tape and sikaflex. No issue to date. Panels have endured heat and extreme cold.

Here is 3Ms instructions on cleaning https://www.3m.com/3M/en_US/vhb-tapes-us/

[ts8501]

Does anyone know how the AS factory mounts the factory installed Zamp’s? Do they also use 3M VHB 4941 and Sikaflex 221? I really like this idea of no additional holes in the roof. I plan to install an additional 90w panel to go with the factory installed 180w.

[Jeff7176]

I know the factory used screws to mount ours. When we added 4 additional panels we also moved the factory panels to get them further from the AC unit’s shadow.

[Tater]

Screws and about 30 tubes of caulk.

[Lag323]

VHB has worked for me without issues. Clean per 3M recommendation. Once cures, skillaflex or Dicor lapseal. I did my own installation 4 years ago and I inspected it regularly. No issues. Tell the repair company to quit screwing around

[carl2591]

Lew, the guy that does some of the solar panels/systems installs for AM Solar in Oregon, ONLY uses VHB tape on the now HUNDREDS of installs with no issues..

there is not reason to use screws on the top of an airstream other than your desire to have a possible leak..

I installed 3 panels on my 2005 with vhb tape and they have over 2 yrs of full time RV travel from east coast to west and now back east with NO issues. they have seen 10-25 MPH head / side / and quarter side winds as well.

if you want to use screws go ahead.. but for me and hundreds of others, the use of VHB tape is better.. the correct product a 5640 i believe will have MORE strength than the two screws you are using..

[vanderwielen]

Just installed 4 panels using VHB tape and Sikaflex. It appeared the lone panel installed on my 2022 20FB did not have screws. You need 55F temp for proper adhesive of the VHB and 'should' have a few days of 70F for the sikaflex to cure, however, I applied it at 60F and have allowed a month at about 32F for complete curing. They are not coming off.

[ts8501]

Originally Posted by carl2591

If you want to use screws go ahead.. but for me and hundreds of others, the use of VHB tape is better.. the correct product a 5640 i believe will have MORE strength than the two screws you are using..

I’ve been seeing one uses VHB 4941, but you’re noting VHB 5640. Which of these?

[oldenavy]

So, I started putting on my 2 additional panels today (upgrading from 400 to 600w). I was recalling this thread and thought I'd apply a little engineering to it and estimate the wind force on the panels.

Drag force for any object moving through a fluid can be calculated from:
F = 1/2*C_d*rho*V^2*A

see: https://www.engineeringtoolbox.com/d...ent-d_627.html
and: https://www.omnicalculator.com/physics/drag-equation

where: C_d is the drag coefficient (assume = 1.98 to be conservative)
rho = density of air = ~ 1.2 kg/m^3
V = velocity = assume 70 mph = 31.3 m/s
A = projected frontal area of body (in my case = 20"x1.5"=30sq. in = 0.0194m^2
Put that all in the calculator and it comes out to 22.5 Newtons or about 5.06 lbf. of drag force on each panel (assuming unobstructed airflow into the panel). In reality, the panels are so close to the trailer's roof that they are probably partially in the boundary layer of air surrounding the trailer and likely do not see the full free-stream air velocity so the 70 mph value is also likely conservative.

The 3M datasheet for VHB tapes lists the 90-degree peel adhesion for 4941 as 22 lbf/in and the tensile strength as 70 lbf/in^2. I have about 4-1/2 sq. in of tape per leg and 4 legs per panel (total of 16-18 sq. in. of tape and 9 linear inches for the peel adhesion per panel).

Bottom line. I'm not too worried about the 3M tape holding as long as the Silkaflex weather seal isn't deterioriated. However, I'll still check them regularly.

[trumpetguy]

Originally Posted by carl2591

first it looks like the mount got ripped out not by wind but by something else.. not sure how old this installation is but I would make sure AM solar has access to the pictures as well.

clean up the area and remount the goot.. VHB tape and 221 on and around and king kong will have problems pulling that foot off..

My VHB mounted solar panels are five years old. What is the life expectancy of the VHB/Sikaflex mounting method.

[dznf0g]

Originally Posted by trumpetguy

My VHB mounted solar panels are five years old. What is the life expectancy of the VHB/Sikaflex mounting method.

At about 8 years, it was time for a new covering of polyurethane. After it was removed, I noted some crunching and crackling of the foam in the tape. Adhesion was still good, but it seemed the foam was degrading. I left all in place, but installed rivets in the feet and recoated with polyurethane. I wasn't going to trust another "term" with tape alone. If you are averse to rivets, I'd remove the feet completely and apply new vhb tape.