Bonding aluminium to galvanized frame

[Billy Onions]

I have a 1" x 1" x 14 swg SHS mild steel frame. I would like to attach 16swg aluminium sheets on the outside and am considering whether I could fix it without fasteners or rivets.

I know it's possible as there is a chemical bonding used in the areospace industry for the same purpose. I need to know if this is worth thinking about ie. is it affordable and if so what is the product name.



Lee

[Dewi]

Would Gorilla Epoxy not do it?

Cheers, Dewi

[Billy Onions]

Dewi

It might. I know people on here have lots of success aluminium to wood. The problem in the past with metal to metal is neither material is porous and I know there have been issues.

I was wondering if anyone had any experiences with aluminium to galvanized steel.

[Dewi]

Totally different scale of gluing obviously, but years ago I used to build sunbeds... we had a metal bracket that fitted to the inside of another metal bracket and we glued them together... roughed up the surface a bit first, and it held like the proverbial to a blanket... but as I say, scale. It was no more than 6 inches long and weighed less than a bag of sugar.

I like the option of aluminium skinning, but I hate the idea of rivets... I've had to wrap vinyl over rivets and its a pain in the butt. Plus, to my wifes amusement, I once managed to catch my stomach inbetween a rivet gun... still have the scar to prove it

Cheers, Dewi

[Nitetimes]

There is some kind of tape I believe made by 3M that is just for that. Might want to check their site. I understand it works pretty good. ie, ya can't get it back apart once it's together!

[Trackstriper]

Rich beat me to it while I was looking for the 3M page!

One of the inherent problems is the difference in the rate of thermal expansion between the aluminum and the steel. The aluminum will wrinkle with heat if glued or mechanically fastened whereas foam tapes will deform and allow for expansion. I owned one cargo trailer (sold it to my brother) with bonded aluminum skin over a steel framework and the trailer still looks good today eight years later. The correct thickness of the tape is important to allow for movement.

Check out: http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs66Ser3COrrrrQ-

[Dewi]

Might be able to help with that... I use VHB tape with signs that bonds aluminium faced board to brickwork, windows, walls... the whole kit and kaboodle. I can send you a sample of it... used to use it by the bucket load. Actually just used it to attach number plate to the donor for towing it back here.

Cheers, Dewi

[xrover]

I would recommend you put some barrier between the al and the steel to prevent corrosion and oxidation. I own landrovers which are al skins and their trouble spots are always at the contact with steel.
why not go with aluminum or ss rivets? aircraft style I have thought make less imposing physical look.

[Billy Onions]

Thanks guys.

The tape is obviously tried and tested successfully. Good point about the thermal properties.

Dewi, that would be great if you can sort us a piece out. I can always find something test it on.

[Trackstriper]

I have played with some of the sign grade bonding tape and the price is right. My sign supply guy says that the tape is made for sign usage and that 3M's VHB tape might be a better bet in the long run - especially considering temperatures - he was in the RV industry for some years. The price difference between generic sign tape and 3M would probably be substantial.

My experiments with the sign tape, however were quite encouraging. I set up two strips of 1/16" aluminum, bonded together with a a 1"x5" piece of foam tape, long-wise. I drilled some holes in the aluminum and hung a 50+ pound weight from the strips to test the shear capabilities, this stuff was rated for something like one or two pounds per square inch, so I seriously overloaded it. The bond held for about a week at room temperature and then the foam sheared, it was not an adhesive failure. The shock load factors for these tapes is quite high. Might be worth playing with.

Keep in mind that you would be using a lot of square inches.

[Billy Onions]

I would recommend you put some barrier between the al and the steel to prevent corrosion and oxidation. I own landrovers which are al skins and their trouble spots are always at the contact with steel.
why not go with aluminum or ss rivets? aircraft style I have thought make less imposing physical look.

I looked at the rivet option, and it is something that I will have to think about. The bulbtite rivets to get the airstream look require a secondary finishing action which involves the use of a shaving tool to get the solid head look.

I would probably have put a silicon or rubber between the 2 materials if going for the full rivet look. You are right about water lying between ally and steel, not nice.

I would still like to use rivets along the roof side of the trim, but was thinking maybe I would prefer smooth sides. It's food for thought at the moment

[Dewi]

if you can sort us a piece out. I can always find something test it on.

PM me your address, I'll get a sample sent off to you asap... if the stuff I have at the minute isn't up to scratch, I can put you in touch with the best suppliers for the other types of tape... use a variety of tapes... the best I've come across comes from Tapes Direct... I think it was £30 a roll.

If I'm down your way soon, I'll bring what I have and you can test out with some decent lengths as well... the stuff I have at the minute was the leftovers from a job at Epsom race course. Used it to hang banners from the pillars in there.

Cheers, Dewi

[Billy Onions]

[quote="Trackstriper"]I have played with some of the sign grade bonding tape and the price is right. My sign supply guy says that the tape is made for sign usage and that 3M's VHB tape might be a better bet in the long run - especially considering temperatures - he was in the RV industry for some years. The price difference between generic sign tape and 3M would probably be substantial.

My experiments with the sign tape, however were quite encouraging. I set up two strips of 1/16" aluminum, bonded together with a a 1"x5" piece of foam tape, long-wise. I drilled some holes in the aluminum and hung a 50+ pound weight from the strips to test the shear capabilities, this stuff was rated for something like one or two pounds per square inch, so I seriously overloaded it. The bond held for about a week at room temperature and then the foam sheared, it was not an adhesive failure. The shock load factors for these tapes is quite high. Might be worth playing with.

Keep in mind that you would be using a lot of square inches.[/quote]

Just reckoning that up now. Around 30 running metres 1170 inches. 96 square feet of 16 swg ally. At around 0.9 lb per sq. foot.

[Billy Onions]

if you can sort us a piece out. I can always find something test it on.

PM me your address, I'll get a sample sent off to you asap... if the stuff I have at the minute isn't up to scratch, I can put you in touch with the best suppliers for the other types of tape... use a variety of tapes... the best I've come across comes from Tapes Direct... I think it was £30 a roll.

If I'm down your way soon, I'll bring what I have and you can test out with some decent lengths as well... the stuff I have at the minute was the leftovers from a job at Epsom race course. Used it to hang banners from the pillars in there.

Cheers, Dewi

Cheers Dewi I will do. Thanks.

[Trackstriper]

96 square feet of 16 swg ally. At around 0.9 lb per sq. foot.

Maybe you could go thinner on the ally. Most of the small cargo trailers in the States typically run 0.030" aluminum, about half the thickness you are thinking, and it saves weight. Skins of 0.040" would be premium here. I put up a picture of my old trailer, which had bonded .030 skin and you'll notice very few wrinkles even though the panels were somewhat "trapped" by the aluminum trim at the top and bottom of the sidewalls which was screwed into place. Not the best photo but this was available. The vertical posts are on 16" centers, so if you have much more open space in your frame you might want to consider .040 or whatever the thickness standard is over there.