Bonding aluminum brackets to fiberglass roof

[K1ngN0thing]

I've mounted some aluminum angle to my roof to keep my panel in place, but I'm not confident in the long-term adhesion and would like to make doubly sure it doesn't land me in a lawsuit down the road. Not looking to drill any more holes than I need to, so that leaves me with epoxy or some adhesive. What's best for bonding these two materials?

 

[K1ngN0thing]

Forgot to mention I'm keeping it in place with 3M VHB tape.

 

[highdesertranger]

if you prepped the surfaces according to their directions I would say you are good to go. I have tried to remove something bonded with that stuff, let me tell you it ain't going nowhere. highdesertranger

 

[K1ngN0thing]

I did a quick wipe with an alcohol/water solution but didn't use any primer. It feels strong but it's a risk I'd rather not take.

 

[highdesertranger]

well did the instruction call for primer. if they did pull it off and follow directions. I know that stuff will hold if properly installed. highdesertranger

 

[DannyB1954]

You can get fiberglass tape at most auto stores. They often sell it to repair mufflers. I have seen it at Home Depot as well.  I would put a layer or two over the bottom of the bracket using the epoxy as the resin. Extend the tape a couple, three inches on each side, and be sure to slap some paint on it as Epoxy is not very UV resistant.

 

[akrvbob]

How much surface is taped to the roof? If you have 6 feet on both side of the panel that is a lot. If you only have a 6 inches on each corner that may not be enough.
Bob

 

[K1ngN0thing]

3 feet x 1 inch on the long sides, 1 foot x 1 inch on the shorts. I'm sure it'll hold for the time being, but I'm worried about it eventually starting to weaken years from now. Adhesive around the edges would provide additional holding strength and serve as a visual to weakening tape if cracks start forming.

 

[TMG51]

I've mounted some aluminum angle to my roof to keep my panel in place, but I'm not confident in the long-term adhesion and would like to make doubly sure it doesn't land me in a lawsuit down the road. Not looking to drill any more holes than I need to, so that leaves me with epoxy or some adhesive. What's best for bonding these two materials?

Many use that doublestick foam tape with aluminum angle and find it to be sufficient. While I admit that stuff is surprisingly strong in some applications, I wasn't willing to bet my panels on that.

What I did instead was fit cleats. I used PVC trimboard ('Azek') because it doesn't rot and won't need painting. I glued the strips of 1x4 plastic board in place using E-6000 (very good solvent based adhesive), weighed them down to dry, then caulked around the perimeter with acrylic caulk to ensure no water would get under to work at the adhesive. Then drilled and mounted my brackets into the cleats, taking care not to puncture the fiberglass, and also sealing the screw holes with more caulk.

Pictures here.

https://vanlivingforum.com/Thread-TMG-s-Van-Thread-Picture-heavy?pid=138049#pid138049

 

[K1ngN0thing]

Many use that doublestick foam tape with aluminum angle and find it to be sufficient. While I admit that stuff is surprisingly strong in some applications, I wasn't willing to bet my panels on that.

What I did instead was fit cleats. I used PVC trimboard ('Azek') because it doesn't rot and won't need painting. I glued the strips of 1x4 plastic board in place using E-6000 (very good solvent based adhesive), weighed them down to dry, then caulked around the perimeter with acrylic caulk to ensure no water would get under to work at the adhesive. Then drilled and mounted my brackets into the cleats, taking care not to puncture the fiberglass, and also sealing the screw holes with more caulk.

Pictures here.

https://vanlivingforum.com/Thread-TMG-s-Van-Thread-Picture-heavy?pid=138049#pid138049

Looks like a solid adhesive. Do you think the bond will be strong enough if it's just around the edges of the brackets and not directly between the aluminum and roof?

 

[TMG51]

Looks like a solid adhesive. Do you think the bond will be strong enough if it's just around the edges of the brackets and not directly between the aluminum and roof?

No. That's never the way to glue something. Get a good, tight bond across the surfaces you're mating.

But then, there's also some interpretation of the phrase "strong enough" at hand. The tape is probably "strong enough," for a while at least... I wanted to be sure mine would be a permanent adhesion.

 

[Willy]

I've used Black Knight clear roof patch with great success. Trying to remove something glued onto a fibreglass roof with this stuff often leads to the surface being torn up.. tuff stuff indeed. ..Willy.

 

[K1ngN0thing]

What can I put around the edges to augment the already-in-place vhb tape?

 

[highdesertranger]

I guess like Bob said it depends on how much tape you used and how heavy the panel is. also what type of tape, 3M has several different ones. all the info is on their web site here's some http://multimedia.3m.com/mws/media/...hure.pdf?&fn=3M VHB-Tape-RP BrochureRed Liner . I have used the outdoor tape rated at 5lbs/inch and you will have a hard time with a crowbar trying to remove it. with the dimensions you gave you will have close to 500lbs of holding grip. that would be sufficient if install properly. just follow the instruction for your surfaces all the info you need is on their web site. highdesertranger

 

[66788]

No. That's never the way to glue something. Get a good, tight bond across the surfaces you're mating.

But then, there's also some interpretation of the phrase "strong enough" at hand. The tape is probably "strong enough," for a while at least... I wanted to be sure mine would be a permanent adhesion.

Nothing beats a strong mechanical connection.   I drilled 23 holes in my fiberglass high top and used 1/4-20 stainless steel fasteners sealed with DOW silicone, with Dicor sealing the outer edges of the exposed aluminum angle mounts.  On the bottom side of the high top are aluminum flat brackets that act as large area washers, preventing stress near the holes.

These fasteners will not fail, ever.   They also will not leak.

Why mess with glues and tape?  You won't find those items securing anything substantial on the outside of an aircraft.

 

[K1ngN0thing]

Got 3 feet of vhb 4910 running vertically on the long sides, and a foot horizontally on the shorts. I don't think it's going anywhere. If I ever feel the need to make it more secure, I can always add another 3+foot length of aluminum angle on each side, on the same bolts.

 

[DannyB1954]

Adhesives can be quite strong. Ever try to pull a windshield out of a car without using something to cut it out?
The tube of adhesive to do that job costs $25.00.