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Bonding alum panels to a steel trailer

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  • Bonding alum panels to a steel trailer

    I am building a custom enclosed trailer for my race car. Everything above the 3x3 main channel is steel spaceframe construction of 3/4 and 5/8 tubing, all triangulated - the welder got a real workout with about 500 welds.

    It's time to panel the whole thing in aluminum. I want a smooth look, no screws or rivets to mess up the paint job its going to get. I am thinking about structural adhesive to bond the alum to the steel. I've read about the two-part super adhesives like Lord Fusor, but the price is prohibitive for the many hundreds of feet I have to bond. Anyone have experience with something a little less spendy? The marine industry loves 3M 5200 for bonding and sealing. I'm wondering if that might be strong enough to withstand the sheer and peel the panel will be subject to at 75 MPH, and the temps we get in Phoenix (110+). Or any other ideas for bonding?

    Also, I am trying to decide on panel thickness. Local suppliers have alum 3003 in .032, and 5052 in .025 & .032. I'm familiar with 5052 but not 3003. Any recommendations here?



  • #2
    3003 is really pliable, bends easy, great for forming . But would dent really easy.
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    • #3
      I would bet good money that youll have lots of buckling just from sitting in the sun. Id rather have the screws.
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      • #4
        The adhesive on 100% of the steel structure makes the alum a stressed member. Screws only make a connection where ever they are placed, essentially giving about 5% contact. The glued panels should buckle less than screwed panels - in theory.

        My current PACE trailer is screwed and it buckles all over the place. Anyway, it's an experiment on my part. If I wasn't trying to build a super-light trailer I'd probably go with some kind of thicker fiberglass panel and glue that.


        • #5
          Good stuff

          I'd go for the 5200, about a year ago a 80' racing sailboat came thru here, the owner said theres like 17 bolts in the whole boat. All most every thing is stuck together with 5200 even the chain plates.


          • #6
            The adhesive used on windshields is also used for structural panels in some app;ications. Just make sure they are properly positioned when applied.


            • #7
              3m vhb

              i used it for the panel on some hay racks i made for the top of horse trailers and one of them has been in use for 8 years and looks like new still. the horse trailer i have has all the paneling bonded with it too
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              • #8
                Don't use 5200 for trailer

                I use 5200 all the time for marine applications. It works great in a wet environment because it takes years to cure. It will skin over in about a day but will take over a week to be able to hold anything. I recently took apart a sign I built 10 years ago and used 5200 on some parts. The 5200 was still very sticky after you puncture the skin. On boats it works great because it remains flexible as the boat flexes in the water. Thats just my 2 cents.
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                • #9
                  IMO 5200 is for sealing and not bonding.
                  The Lords glue is truely awsum and requires less prep and equipment than competitors products.
                  I'm trying to imagine your project...what shape is the tubing? square?

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                  • #10
                    It's square tubing. Imagine a plane fuselage. Gives lots of strength in a light package.

                    All my car chassis are built that way, but the panels are screwed and sealed (but not bonded) since they have to be able to be removed at times for crash repair. I'm thinking the trailer won't need to be repaired, much, so a permanent bond should work well and allow the uses of lighter alum. I should have mentioned up front the goal is light weight. I am replacing my existing dual axle, full height 7,000 lb trailer. The new one is a single axle, low profile 3,500 lb, with a bit of aero taper up front for less wind resistance.


                    • #11
                      find some aluminum allthread and cut it to the lenght to go through the supports and weld it to the back side of the paneling put a hole in the support then you can just bolt it up


                      • #12
                        In my experience, aluminum monocoque chassis are generally glued AND hard riveted. However, this is formed aluminum that is glued and bonded to itself without any tube framing. Very strong and rigid. The modern monocoque of course is all composite materials.

                        Although I can appreciate your desire to go without fasteners, I would probably use 3M VHB followed by the proper rivets, or small screws for cheap insurance. That VHB is some strong stuff and would be less mess than epoxy. The downside to using the VHB, is that you had better have some help placing the panels down in the right spot, because once it's down... it's down - kind of like using contact cement. As you know, with epoxy you have some play to finesse the sheet into place before you hard fasten it. The downside to using adhesive of any kind (including VHB) is that replacing any panels will be a b!tch.

                        Good luck.
                        Show some pics when it's finished.
                        How about some race car pics?
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                        • #13
                          After re-reading, then re-thinking your trailer's frame construction, 3/4" or 5/8" tubing does not provide a lot of surface area for bonding, especially if two panels are sharing a width of tubing with no overlap. I don't know how close together your ribs are, but it seems as though it would be hard to get each panel to bond sufficiently to ALL of the tubing area without any Clecos, which means rivets/screws. To account for gaps, I would almost be inclined to use a good, flexible structural adhesive from a caulking gun followed by fasteners.
                          If this were a shed or something immobile, I'd definitely forgo the fasteners, but I wouldn't go there with a trailer and all the anticipated vibration, flexing, and windload.

                          Just my $ .02.
                          Last edited by chrisgay@sbcglo; 07-12-2008, 03:14 PM.
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                          • #14
                            Some screws or rivets for back up wouldnt hurt. You dont want a sheet coming loose at 70mph on the highway.
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                            • #15
                              If you do use winshield urethane, remember to get the primer for metals. Otherwise it will eventually seperate from the metal.