FiberCorr?

[chartle]

AlumaCorr looks interesting.

Read this:

AlumaCorr panels are ideal for exterior applications with a life expectancy of approximately 10 years.

Disclaimer: I am not associated with Nudo in any way and am not pushing any of their products.

AlumaCorr is made for use in road signs that are exposed to the elements year round. Unless you are using your teardrop year round and/or leaving it exposed to the elements in the winter I'd expect it to last 2-3 times longer than that.

In my case a 20-30 year life expectancy for an ultralight teardrop is a good tradeoff, especially if it's designed to be not too much work to install new exterior panels to re-clad it then. Also, at my age (60) I'll probably be dead in 20-30 years...

One issue about life expectancy, they only test it by exposing it to the weather that would be expected 5 feet off the side of the road or hung on the out side of a building.

They don't test it out building a TD then driving it down the road, hitting it with rocks and making something structural like a box.

I have some alumicor at work (part of my job is to make signs) and the aluminum is very thin and would probably be punctured by small rock hit. So make sure it has a thick enough skin.

[jonw]

(snip)
...The corrugations would run horizontally. A few 1"x1" vertical aluminum tube stiffeners would be bonded to the interior of the walls with foam sign tape, poor man's VHB

This is pretty close to my thinking, but for vertical wall framing I'm thinking of using 3/4 or 1in square aluminimum tubing or wood 1x1-1/4 (actual: 3/4x1in) ripped boards (probably poplar). The weight per linear foot for both of these are comparable but the aluminum costs about 3x as much as the poplar. For the roof/ceiling I'd stick with the traditional 1x2 wood strut.

I was planning on going with traditional wood frame and panel construction for the cabinets as these would also provide vertical support, reducing the number of vertical wall slats needed. Using AlumaCorr for this would certainly reduce the weight but I'd be concerned that it would increase the cost and build complexity, and how well it would it hold up over time as cabinet and kitchen surfaces.

[jonw]

They don't test it out building a TD that driving it down the road, hitting it with rocks and making something structural like a box.

I have some alumicor at work (part of my job is to make signs) and the aluminum is very thin and would probably be punctured by small rock hit. So make sure it has a thick enough skin.

Excellent point chartle. Might need to reinforce the bottom front with an additional aluminum skin or a tongue box.

[chartle]

They don't test it out building a TD that driving it down the road, hitting it with rocks and making something structural like a box.

I have some alumicor at work (part of my job is to make signs) and the aluminum is very thin and would probably be punctured by small rock hit. So make sure it has a thick enough skin.

Excellent point chartle. Might need to reinforce the bottom front with an additional aluminum skin or a tongue box.

On the material I have, the skin is much thinner than the really thin flashing at Home Depot.

I have looked into these materials and some is thicker. Still not sure its thick enough. Also the substrate makes a difference.

[jonw]

In my case I'm looking to use the AlumaCorr for the flat side walls but still use sheet aluminum for the front-roof-rear panels, so the aluminim would take the brunt of road debris.

I don't know how easy it would be to bend AlumaCorr or not, to be able to bend it around a profile. I guess we'll see...

[Trackstriper]

Aluma-Corr stiffness/strength.

OK...this is just for what it's worth. I ran some tests about three years ago to check out the panel stiffness of 10mm Aluma-Corr vs. plywood. Yes, the guys at Home Depot might have thought I was a little off....but they didn't bother me. The Aluma-Corr was tested at home, using a piece of 1x1 steel tubing as the straightedge. The A-Corr was 48"x48". The panel was supported with painted 2x whatevers that I had handy.

At Depot, I used 2x4's to support the plywood and a straight piece of 1x2 maple for the straightedge. All plywood was your garden variety, perhaps B-C grade....what they had in the pre-cut 48"x48" rack.

Fun and games blocking up and aiming the camera, setting the timer and getting myself into position. Test dummy weighed 165# wet. I stood in the center of the panel with my toes against the straightedge.


This photo is typical of the test rig, the white Aluma-Corr had a protective blue film on the surface. The 2x supports just happened to also be painted white...hard to see edges:




Next is 10mm A-Corr in the strong direction, working with the corrugations...think corrugated cardboard:




This is the A-Corr in the weak direction:



Next, 3/4" 6-ply plywood, strong direction:




Same 3/4" ply, weak direction:




1/2" 4-ply plywood, strong direction:




1/2" plywood, weak direction, in which case I'm supported by the concrete floor:





The Aluma-Corr was a little less stiff than the 3/4" plywood and more so than the 1/2". A good, equal comparison would be quality 1/2" cabinet grade plywood with many plys. Remember, this product weighs about the same as true 1/4" plywood, is pre-finished, won't rust, won't rot. No, I don't sell this stuff.

Hope this helps a little.

[chartle]

In my case I'm looking to use the AlumaCorr for the flat side walls but still use sheet aluminum for the front-roof-rear panels, so the aluminim would take the brunt of road debris.

I don't know how easy it would be to bend AlumaCorr or not, to be able to bend it around a profile. I guess we'll see...

You can bend Corrplast be cutting the back with a special tool that kind of makes relief cuts. It really weakens it.

Here is the tool and technique.

http://pages.videotron.com/plastkut/

Not sure if this applies to AlumaCorr.

[jonw]

Thanks Trackstriper for your research/comparison. Looks like AlumaCorr would be fine for use in vertical walls...

[GPW]

Might be Nice on the roof too

[Trackstriper]

Aluma-Corr, or equivalent product, would take some tinkering with to come up with to come up with construction methods. It won't bend unless the joint is routed on the backside, and then you would need to support the inside skins to keep some strength. It won't curve as in the shape of a traditional teardrop roof. But something like a "weekender" could be done completely in the product.

For a traditional TD, the sides could be made with A-Corr, with vertical stiffeners at maybe some points....probably at the door jambs and the galley walls would be enough. Add interior formers, gluing blocks, whatever you want to call it.... around the inside edges of the curves just like you'd do with a 1/2" plywood panel. Then a sheet of .040"...maybe lighter...aluminum could be fastened and glued to the former to make the roof. Some might say that's not enough thickness but my cargo trailer has .030 side skins all the way around, rather typical of cargo trailers, and should take a small stone impact reasonably well. Put a little diamond plate on the lower front side. With .040 available in 60" widths you could build a 5x8 or 5x10 TD using single piece walls and a single piece roof. The .040 might be a little stiff to bend at the typical TD nose radius. Probably the lower portion below the galley would need to be .030".

You could use wood to make the stiffeners as folks are more used to the material. Glue it to the A-Corr with PL polyurethane in the caulking tube. This should work OK with wood...not so good with metal to metal as the moisture doesn't get into the joint very well, at least it didn't for me....sort of never set up. Metal to metal does better with a two-component glue rather than moisture cure.

As to cost for aluminum tubing, I've been able to scrounge surplus 1"x1" aluminum fence pickets from time to time at metal salvage prices. The are typically powdercoated black but that has an advantage in that they can be lightly sanded and you're not having to get glue adhesion on raw aluminum which can be tricky. Same with the pre-painted A-Corr or aluminum sheets. The manufacturer has done the hard work to properly prep the metal, the paint's not likely to flake off.

[jonw]

Got my AlumaCorr sample today (that was fast...).

It's the 5mm (.200in) thickness. I originally thought I'd need the 10mm stuff but it looks like 5mm will work well in place of 1/4in plywood for exterior frame-covered walls. My sample is 3in x 3in and it's very stiff. It looks like it will also be great for lightweight pop-up roofs (which I'm also hoping to use it for).

My thinking on the edges is similar to Trackstripers, but I'd probably screw into a wood frame or pop rivet into an aluminum tube frame in addition to any glue/caulk. The screws or pop rivets could be hidden by covering them with edge moulding.

At this point I'm thinking of using wood instead of aluminum for frame material. I'm going to experiment using countersunk wood screws that would sit nearly flush with the AlumaCorr surface.

Another attaching idea would be to drill a hole in the outside surface large enough for a flat screw head to sit inside the substrate and screw through the back AlumaCorr surface into the frame. This would fully countersink the screw head if that is desired (and it gets covered with moulding or something else).

I used .040 aluminum on my current TD and had no trouble bending it around the profile. .032 aluminum is lighter but only by about 3 1/2 lbs per 4x8 sheet, so for the minimal weight savings I'd probably stick with the thicker and stronger (against dents) .040.

[chartle]

I don't thing you should counter sink anything. A lot of its strength comes from having two skins like a torsion box.

[Trackstriper]

Jon, if you're looking at the 5mm Aluma-Corr you might also look at the 3mm PolyMetal. It's a little bit heavier, essentially a similar panel with a solid rather than corrugated core. It will bend to a reasonably large radius curve. Here's a thread a couple of years back from someone who used this product. He is still active on the forum I believe. He could be a great source of info.

http://tnttt.com/viewto ... al&start=0

The stiffness comes from spacing the aluminum skins farther apart. 5mm A-Corr is stiff, but not nearly as much as 10mm. If you like the thinner panel you probably aren't giving up that much stiffness going from 5mm corrugated to 3mm solid core. The PolyMetal will drill, countersink, whatever, like a wood panel. The corrugated would be trickier to work with, that's why I'd use the inherent strength of the 10mm although tougher to work with. Maybe higher tech fastenings and gluing.

With 5mm corrugated you could possibly use bugle head screws and locally collapse the core, letting the screw head deform the skin and countersink itself. The core is not very thick and it just might work. With 10mm you'd have a mess....the head would likely pull through the skin if you were to tighten enough to get some structural strength with the fastener. Thinking the 5mm might be cool though.

But, if you will be making a wall frame anyway, look at the Polymetal, or equivalent product. In the Atlanta area the 3mm Polymetal is about 2/3 the cost of the 5mm A-Corr. You don't have open corrugations to worry about contending with if using PolyMetal. I could send you a sample if you wish...I have a remnant piece on hand. PM me if you want to experiment with a sample...maybe 8"x10".

Bruce

[jonw]

(snip)
With 5mm corrugated you could possibly use bugle head screws and locally collapse the core, letting the screw head deform the skin and countersink itself. The core is not very thick and it just might work. With 10mm you'd have a mess....the head would likely pull through the skin if you were to tighten enough to get some structural strength with the fastener. Thinking the 5mm might be cool though.
Bruce

That's what I'm thinking. I'll try some tests on the sample I have and post a picture of the results.

Thanks for the heads up on the Polymetal. I'll look into it...

[jonw]

Here are pictures of a test using screws of different sizes and types, screwing a sample of AlumaCorr to a piece of pine.

All screws were drilled using a Harbor Freight 18v drill that has a maximum clutch setting of 17.

From right to left:

1) a Spax 3/4in #8 self threading wood screw drilled through the AlumaCorr without any pilot hole, and with the drill clutch set to #5. Notice the crushed surface.

2) a round head 3/4in #6 screw, with a pilot hole drilled first, and the drill clutch set to #5 (same as above). Note it does not compress the AlumaCorr at all. I suspect much of this is the difference in force between the #6 and #8 screws...

3) a Spax 3/4in #6 self threading wood screw, no pre-drilled pilot hole, and with the drill clutch set to #3. Better than 1) but still some surface deforming and internal rib crushing.

4) same Spax screw as 3) but with a pilot hole drilled only on the top surface whose diameter is about halfway between the thickness of the screw shank and the screw head. This was a rough attempt at countersinking. IIRC the drill clutch was also at #3. Note minimal deformation.





It still needs some experimentation, but in trying to get screws as flush as possible without compromising holding power I think 4) with a slightly larger hole with the same or lighter clutch setting would yield the best compromise.

It also means that if we use AlumaCorr with screws we need to do some test drilling with the screws and the wood we'll be using to determine the correct countersunk hole size and drill clutch setting.

As with everything else, YMMV.