ACM panel - your thoughts?

[aggie79]

For the past two years, I've been drawing sketches of a larger vintage-style trailer for my next build. I am now trying to finalize my design and would appreciate your thoughts on a material and construction techinique I may use.

I am thinking of using aluminum composite material in my sidewall construction. These panels are "sandwich construction" with 0.012 aluminum sheets front and back with a solid polyethylene core. The panels I'm looking to use are 3 mm thick. ACM panels are used in the sign industry and as an exterior finish building material. A 4'x8' panel weighs about the same as the same size sheet as 0.040 aluminum. The reason for use of the ACM panels is that they are much more rigid than sheet aluminum and I could eliminate the plywood backing on the framing.

The ACM panels would be the exterior skin of the trailer. They would be attached to either plywood or stick-built framing using a sealant adhesive similar to 3m 4200/5200. The sealant would need to be paintable. In addition to the sealant, I am wanting a riveted look and so the panels will also be mechanically fastened. I have thought about doing the same method as I used on my teardrop for that look. (On my teardrop, the roof aluminum sheets were overlaped by 2-3". On this build, the panels would be butt jointed to one another.) On it, I used stainless steel, washer head, square drive screws. The pilot holes in the wood framing matched the screw thread; however, the holes in the aluminum were drilled oversize (but smaller than the washer head). Each hole was filled with sealant before the screws were installled. The intent of using adhesive and oversize holes is to to allow for some panel movement due to differential expansion to the wood/plywood framing.

I don't have a good picture of it, but in the picture below, on the seam on my hatch, you can see the riveted look described above.



Thank you for reading this. Your thoughts are appreciated.

Sincerely,
Tom

[RandyG]

Sounds really cool . Those panel are rigid but .012 is really thin, almost like foil. How many scratches does your current trailer have now? A scratch an that could be a gouge on the thinner skin. Even so, I think it would make a nice building material, and delam is still a threat but not as bad as ply.

[Larry C]

Tom,
Sounds like a good plan. However, the butt seams may be the hard part. Are you relying on the sealant for seam expansion/contraction? Are there any trim pieces available for this product, such as an H channel for butt seams?

Larry

[aggie79]

Sounds really cool . Those panel are rigid but .012 is really thin, almost like foil. How many scratches does your current trailer have now? A scratch an that could be a gouge on the thinner skin. Even so, I think it would make a nice building material, and delam is still a threat but not as bad as ply.

That's a good point. I really haven't had many scratches on our teardrop. Part of this is due to the aluminum being anodized and part of it is due to the teardrop being "treated with kid gloves".

I had only intended the ACM panels for the sidewalls. The front wall would be .040 aluminum over plywood. There would probably be an aluminum lower front rock guard too. The curved roof and angled rear wall would most likely be epoxy and glass over plywood. (Have I given away my design in this description?)

There are ACM panels available in .020 aluminum skins for not much greater weight. I may consider this route.

Thank you,
Randy

[aggie79]

Tom,
Sounds like a good plan. However, the butt seams may be the hard part. Are you relying on the sealant for seam expansion/contraction? Are there any trim pieces available for this product, such as an H channel for butt seams?

Larry

Larry,

Again, good points to consider!

My intent for the adhesive/sealant is primarily structural to adhere the panel to the framing. Secondarily, it would provide for some expansion/contraction movement for the panels. There is H-channel available, but it would not go with the aesthetic I'm going after. I really like the look of a double row of rivets where two panels butt together.

Part of my consideration of the ACM panel is that I plan for a few fixed windows on the sides. The thickness of the ACM panel would allow me to using flexible rubber window channel and glass panes for these "non-square" windows.

From my other post, since I am considering a more traditional plywood "backer" on the front, I may do that for the sides as well. Then I could use standard aluminum sheeting. The challenge would then be how to do the fixed windows.

Take care,
Tom

[desertmoose]

I wonder what the insulation value of such a thin panel is. 3mm is only around 1/8 inch.

Might get a bit warm/ cold inside if the outside temps vary?

Pretty cool idea though. Keep us posted.

[KCStudly]

You could lap the panels using a row of 'rivets' to fasten, then put a dummy row on the other side of the seam to give the look of a double row.

I personally don't like the idea of putting any more holes than necessary, but your method seems pretty diligent and effective.

[Larry C]

Tom,
Sounds like a good plan. However, the butt seams may be the hard part. Are you relying on the sealant for seam expansion/contraction? Are there any trim pieces available for this product, such as an H channel for butt seams?

Larry

Larry,

Again, good points to consider!

My intent for the adhesive/sealant is primarily structural to adhere the panel to the framing. Secondarily, it would provide for some expansion/contraction movement for the panels. There is H-channel available, but it would not go with the aesthetic I'm going after. I really like the look of a double row of rivets where two panels butt together.

Part of my consideration of the ACM panel is that I plan for a few fixed windows on the sides. The thickness of the ACM panel would allow me to using flexible rubber window channel and glass panes for these "non-square" windows.

From my other post, since I am considering a more traditional plywood "backer" on the front, I may do that for the sides as well. Then I could use standard aluminum sheeting. The challenge would then be how to do the fixed windows.

Take care,
Tom

Tom,
I get the picture better now, but the butt seam with rivets on both panels may cause the edges of the thin aluminum skin to lift right at the seam from the rivets being tightened?. Maybe a 1.5 mm deep rabbet joint routed from each 3 mm panel would create a lap joint with a better seal and the same "look" with maybe a tighter smoother joint.

Are your fixed windows similar to an automotive type fixed window where the gasket fits the glass on the inside gasket groove, and has to fit the thin skin on the outside gasket groove?

Larry

[aggie79]

I wonder what the insulation value of such a thin panel is. 3mm is only around 1/8 inch.

Might get a bit warm/ cold inside if the outside temps vary?

Pretty cool idea though. Keep us posted.

DM,

You're correct. The panel by itself wouldn't provide much insulation. And in Texas, we get hit with high as well as low temperature extremes.

By its nature the ACM panel has a "built-in" thermal brake compared to aluminum sheeting. In addition, I had planned on insulating the framing which will be at least 3/4" thick, but most likely thicker. The interior would be sheathed in either t&g cedar or birch plywood.

Take care,
Tom

[aggie79]

Tom,
I get the picture better now, but the butt seam with rivets on both panels may cause the edges of the thin aluminum skin to lift right at the seam from the rivets being tightened?. Maybe a 1.5 mm deep rabbet joint routed from each 3 mm panel would create a lap joint with a better seal and the same "look" with maybe a tighter smoother joint.

Another fantastic idea Larry! Keep them coming. Sign shops use CNC routers to cut the material. It apparently machines pretty easily. I could fill the lap with sealant. Instead of true rivets, I would use screws like I did on my teardrop.

Are your fixed windows similar to an automotive type fixed window where the gasket fits the glass on the inside gasket groove, and has to fit the thin skin on the outside gasket groove?

Larry

Yes, that's what I had in mind. I've used it before and it works pretty good.

Take care,
Tom

[RandyG]

If you go for the riveted joint, I would put a strip of .040 - .063 under the skin with 2 rows on each skin. When it comes time, I would be willing to drive there and lend you a hand for a few hours. I'm just over here in Shreveport and my wife loves going to the major city to shop. I could even bring a rivet gun, bucking bar, and the rivets. The offer is there.

[aggie79]

Thank you Randy. If I decide to build this, I may give you a call. If you helped out, the expert level for the metalworking would go from barely novice to expert.

[RandyG]

Expert... maybe . I'm still learning.

[alaska teardrop]

Tom,

Sounds worth exploring. Could you post a link to the ACM panels that you're considering? Have you had your hands on a piece or can you get a sample to experiment with?

Thank you, Fred

[Bogo]

Just use VHB Tape or auto body adhesive to hold the panel in place. A butt joint can be made by running a 2" to 4" wide strip of aluminum on the back side, and VHB taping both panels to it. When using VHB tape or auto body adhesives, surface preparation is vital. Usually it is clean with XYZ chemical, possibly treat with another, then make the bond. When using VHB tape, you use a roller to press the panel to the VHB tape. Frames can be made of anything the VHB tape is compatible with. Look around, and you likely can find a supplier that will sell larger panels. I've seen them 5'x10', 5'x12', and 6'x12'. They are also available from many of the makers in sizes up to 40 something feet long. Basically large enough to do a whole RV or trailer side. Mose manufacturers will also custom CNC cut them for you. You tell them the shape, and they cut it out. I'm not sure they would do a one off, but I know they will do batches.