rivets or screws????

[brian_bp]

Some of the examples of riveted construction successes may not be so applicable. urbanironaz is asking about fastening the aluminum to steel, and several replies have addressed ways to handle the difference in materials; an Airstream, on the other hand, is generally a bunch of aluminum bits riveted to other aluminum bits.

[Trackstriper]

Been noodling through this question about fastening aluminum to steel tubing. I had a 6x12 cargo trailer several years ago with tape bonded skins over steel hat sections for the sidewalls. I was thinking that it was totally taped, but I just remembered that they ran aluminum trim molding at the bottom of the wall and at the top to trim out the roof sheeting joint. At any rate, the sides were pretty flat and smooth and I think the trailer had standard .032 aluminum rather that the optional .040 skins. The vertical lap splices between sheets were done only with tape. 3M has a brochure:

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

that describes some of the ways the bonding tapes work. Notably, the tape makes a lot of surface contact between the frame and skin and has the ability to lozenge (it is foam cored) to handle the different expansion rates of the metals. They also show two types of bonding, one with mechanical fasteners and one without. Draw your own conclusions.

3M gets a pretty penny for their products. I have been playing around with a bonding tape that is used in the sign industry that is a lot more affordable. This tape seems to be pretty good from what I've seen:

http://www.alumapanel.com/view_product.cfm?step=1&lines_ID=307&name=Alu%2D%20Tape%20Double%20Sided%20Foam%20Tape

I also found a short article about solid rivets and blind rivets. This article deals with rivet applications for homebuilt aircraft but it's worth reading. This guy knows his stuff:

http://exp-aircraft.com/library/heintz/riveted.html

Note the corrosion issues with dissimilar metals. Aircraft have to be done correctly and for the long haul...with a teardrop things can be much less perfect but why not do it right if it's just a little more effort.

Hope this stirs the pot a little.

J.B.

[urbanironaz]

thanks for the reading material and the effort to share it...a great asset for the do it your-selfer

[Bodyman]

...the VHB is a definte way to go...you might well want to check out some of the body panel adhesives used in the car/truck body repair business...nowadaze most body panels on vehicles are bonded with an adhesive(usually a 2part urethane)

If you want a really clean look panel adhesive may be the way to go. I would use the panel adhesive sparingly not on every surface of your tubing. That would be overkill and very costly. You would still need to use VHB on the spots not bonded. The metal needs to be sanded or ground shiny clean to bond properly.

3M Automix 8115 Around $50 for dual cartrage would maybe do both sides if you didn't get too nutty, but I wouldn't bet on it. You also need a 3M 08191 applicator gun $148.88 !!!!! Or Motor Guard makes one for around $80 if you can find.

[brian_bp]

By coincidence I was recently reading the annual technical reviews from Mitsubishi Motors. In the 2006 edition (No. 18), they reported on the use of aluminum roof panels in their otherwise steel cars (Development of Application Technology of Aluminum Roof), which is essentially the same situation as this aluminum-skinned but steel-framed teardrop. The 2006 example is the Outlander SUV, but the extreme performance Lancer Evolution was the first application at Mitsubishi.

They used a structural adhesive for both bonding and corrosion prevention, and fastened with self-piercing rivets. I doubt that the self-piercing rivets are practical for home use (or even factory application to this situation), but tape or adhesive, combined with rivets, does seem like a workable plan.

[Keith]

We've built five trailers that are five feet wide by ten feet long using steel frame construction with aluminum covering it. The first two trailer we build in 2001 and used .080 aluminum on the roof. It was the only five foot wide aluminum that we could get. The last three we built we used .063 aluminum. We had to attach it to the front of the trailer and then drill holed in the overlap in the back and use ratchet straps to tighten it down. The aluminum around the back we used a roller to roll the aluminum into shape.

Unfortunately my web site is down and I haven't had a chance to rebuild it. Here are the pictures of our builds.

We used 10-24 stainless screws on the first build. We drilled and hand tapped every hole. On the second build we used 1/4 - 20 stainless screws and used a tap in the drill to tap the holes. It went much faster.

We haven't had any issues with corrosion on the roofs but some in the back where moisture has stayed.


http://www.flickr.com/photos/five_wide_club/sets/72157603689987540/

http://www.flickr.com/photos/five_wide_club/sets/72157603689929590/

Keith