A foamie, but you wouldn't know it

[Jack Olsen]

I've done some searching, but I'm probably not familiar enough with teardrops in general and less so with foamies.

Is there an example (or two) of foamies that would visually look just like the familiar plywood and aluminum skin teardrops? I know that as a light-lean-and-economical construction technique, it usually makes sense to cover the foam with canvas and glue and paint. But if the goal was to make a foamie that looked like this -



- has someone done it?

I know foam is often used to insulate and lighten wood-framed teardrops. But have people gone with foam-structured tears that get skinned with aluminum on the outside and wood on the inside?

[Fred Trout]

I can not recall seeing any examples of what you want.

Either way you would end up with a foamie with a good deal of wood or a standard stick built with a lot of foam simply because the aluminum skin typically requires a solid framework to attach it's retaining points. I haven't tried it but my understanding is that gluing aluminum directly to foam would cause "oilcanning" problems but I read good things about using one of the 3M tapes rather than rivets, so something might be possible. Bleeding edge for sure, but it would not hurt too much to test it out.

http://multimedia.3m.com/mws/media/4013 ... 20High.pdf

You might check the kayak & canoe forums - they try some pretty wild & crazy stuff and have some success too.

[KCStudly]

Jack, my build uses thin ply inner skins and I plan to cover with canvas. (See my build link below... if you dare. )

Atahoekid did a similar hybrid construction with epoxy/glass outer. Though neither are traditional teardrop shapes with rounded front and tapered rear, the construction techniques are easily transferable.

Fred is correct about needing a hard edge to attach aluminum skins and trim, but maybe it could be done using the plastic screw in drywall anchors; although that would be tedious and sketchy. There is a thrifty advantage in using the canvas instead of aluminum in that you can eliminate the coast and effort needed to install the trim, plus you can do a radius edge instead of a sharp corner. Again, not as traditional, but an option.

I think there is at least one example where a traditional or skeletonized ply build has been insulated and the aluminum put over the wall and roof foam without an extra layer of ply, but the frame work was still used for attachment points.

OT: Your BBII car build has me looking at 914's again. Spent the morning going thru CFR's Tangerine website, and last night looking over Renegades LS/Speedster 6 spd conversions then ebay to see what the market looks like for rolling stock. Probably just a pipe dream for me, but... just know that your stuff is truly inspirational!

[Jack Olsen]

There are a few different reasons not to do it, I guess. For one thing, a 4x8 of 2" foam weighs only 8.3 pounds (according to my Googling), while a cover of .040 Aluminum skin would add 18.2 more pounds -- basically for looks. And adhering the aluminum to foam would probably (as Fred points out) have problems with the thermal expansion rates of the two materials. Canvas is going to be a lot more cooperative, and affordable, and cost-effective.

But if you're like me and you like the look of the old aluminum-skinned teardrops, it gets you thinking.

An aluminum frame wouldn't be the end of the world. I keep promising myself I'll learn to TIG weld aluminum. But one possibility would be to forego the aluminum sheet and sandwich the foam between two sheets of FRP. Filon is a UV protected FRP product used for the exterior of RVs. In a perfect world, you could adhere Filon to both sides of inch-thick foam for a sandwiched/composite effect. But again, thermal expansion rates might make that turn out ugly. But Filon could be covered with the material they use now to wrap vehicles, which is available in the matte silver finish I've got stuck in my head since I saw the Atma Travelear here.



The more-expensive route would be to use an Aluminum Composite Panel like Dibond. It's like foam-core board, but sandwiched between two thin sheets of aluminum. A 4x8 sheet is 24.9 pounds, which is pretty heavy -- except for the fact that it's already got the aluminum skin adhered as a structure-strengthening component. It's only 1/8" thick, but is rigid and flat and strong.

Foam is better from a dollars point of view. Foam is better from an insulation point of view.

But the two approaches would be comparable from a weight point of view. I could line the 'living quarters' part of the teardrop with 1/2" insulation and Filon panels on the interior. My walls would be 3/4" thick for the door and windows that way.

Compared, by weight:

.040 Aluminum, 2" Insulation, Filon interior
18.2+8.32+5.89=32.41 lb

Alupanel, 1/2" insulation, Filon interior
24.9+2.08+5.89=32.87 lb

Filon exterior, 1" Insulation, Filon interior (with matte silver wrap)
5.89+4.16+5.89=15.94 lb


And to put it all in one place, the more traditional approach:

Aluminum, 1/2" plywood, Filon interior
18.2+40.6+5.89=64.7 lb

Or the traditional foam approach:
Foam, glue & canvas
8.32+1=9.32 lb

Very hard to beat foam and fabric, when you look at it that way. Just that it doesn't give me the look of the trailer I've had in my head.

[KCStudly]

Meant to add that you might want to consider Alaska Teardrop's construction methods. He does a light weight build using steel tube frame and aluminum outer skins. You certainly have the skills and shop for this type of build, converted to a teardrop shape.
Here's one of his builds: http://www.tnttt.com/viewtopic.php?f=27&t=51991

[halfdome, Danny]

I'm not a foamie fan & especially since someone on this board had one blow over while traveling.
Their just too light for my liking.
Somewhere on the internet I read where the tow vehicle should withstand a 35 mph side wind directed at the trailer.
It said a semi and you on a two lane road passing by each other is about that.
The tow vehicle should be able to correct the trailer in that situation.
Since you'd be towing with your Porsche I'd do some research before you build too light.
A few years ago I drove my step sons 1984 Porsche from Portland OR to the Seattle area which was a real gas, but I wouldn't tow a teardrop with it, it's just too small.
I saw a teardrop at the IRG last year that the guy built it entirely from import plywood which is just under 1/4".
Kind of scary to me, but to each his own.
I'd rather build traditional and tow with a vehicle that can handle the load.
Our life and property is worth the extra expense, besides it's tried & true building practices.
It's just my opinion and others may or may not agree.
Danny

[KCStudly]

Can the Dibond do a radius?

Is the desire for a lightweight build based on what you expect to be towing with, or is it just sort of engrained in your racing psyche?

Even the traditional method can be built light enough to tow with pretty much anything, especially in the 4x8 size.

There is a unique build going on right now where Robot used a silver paint (Slipstream build thread). With a little more prep work and a solid base coat (because some of the silver paints can tend to weather poorly) it might suit your needs.

Any reason why you couldn't have a painted foamie wrapped in matte silver vinyl?

Penguino was a tall narrow build that tipped up on its front corner in a 50 mph crosswind in the dessert. Limited damage could have been easily repaired.

Kind of made me laugh a bit thinking about anything that could tip the wide arse on BB2. But there is a valid point to consider all aspects of a design, including the intended end use and regions/conditions that may be encountered.

[Fred Trout]

Another possible way to do it is to assemble the foamie in the traditional manner but add steel flashing on all panel corners & edges (see ghcoe's #1 thread). Then you could drill and rivet as usual (works fine) for aluminum or use the 3M tapes to the steel for your rigid strong mounting point. Corrosion might be an issue needing resolution with some sort of coating over the flashing & rivets. I am going to guess that aluminum flashing is available as well.

Easier and lighter than a full welded frame and the flashing technique is a more or less proven foamie technique, although it must be treated carefully so no bends or distortions of its straight edge will occur. We use Gripper paint and / or Great Stuff to glue it to the foam edge but plenty of other options are available. EPS compatible contact cement might be easier and more consistent. I ended up with the occasional 2-4 inch bow that did not adhere to the foam. A squirt of caulk, spreading it around with a thin shim, and some clamping/weight resolved those easily enough.



EDIT:
I would not be too worried about building too light as long as you use a more or less traditional heavy trailer & keep the center of gravity low with wide stance tires. You did not plan to build a standy, did you, so it's a non-issue unless you make your trailer out of tissue paper.

As they say in Kelly's Heros
Oddball: Why don't you knock it off with them negative waves? Why don't you dig how beautiful it is out here? Why don't you say something righteous and hopeful for a change?

Moriarty: Crap!

[tony.latham]

Aluminum skin would add 18.2 more pounds -- basically for looks.

My 'drop is out in the sun right now (It'll be out there all summer long), and the UV rays are bouncing off it like little rubber micro balls. I don't know a another finish that will stand up to the sun like that.

But sticking it to a straight foamie with all that expansion/contraction? Dunno. I'm a wood-foam sandwiched wall guy. Here's my rig on sixty-miles of teeth chattering washboard road:



No problemo.

Tony

[Jack Olsen]

Thanks, guys.

Since you'd be towing with your Porsche I'd do some research before you build too light.
A few years ago I drove my step sons 1984 Porsche from Portland OR to the Seattle area which was a real gas, but I wouldn't tow a teardrop with it, it's just too small.
I saw a teardrop at the IRG last year that the guy built it entirely from import plywood which is just under 1/4".
Kind of scary to me, but to each his own.
I'd rather build traditional and tow with a vehicle that can handle the load.
Our life and property is worth the extra expense, besides it's tried & true building practices.
It's just my opinion and others may or may not agree.
Danny

I appreciate it, Danny. Right now, I'm just in the thinking-out-loud stage. I'm not looking to build a so-light-it's-basically-a-parachute trailer -- if it worked out to 600 pounds dry, I'd be thrilled. My particular trailering situation will involve climbing from seal level to over 7,000 feet in a 45-minute drive, so my initial concerns are 1) not putting undue stress on my transmission during the uphill or the downhill, 2) simply having the power to get the thing up the hill, 3) not boiling brake fluid on the downhill, and 4) not getting pulled off the road when the route gets too twisty or too windy. If there are other important factors I need to think about, I'm here to learn.

Some of this is counter-intuitive, at least to me. I've got three cars, and my first thought was that my best candidate for towing would be my Jeep CJ-7. But then when I thought about it, I realized my sedan had 1) more power (230hp vs 110hp), 2) better brakes (modern disk vs 1980s drum) and 3, better lateral stability (without the Rancho lift kit making things precarious). Aside from that, I don't know if the 911 will ever make sense to put a hitch on. But it's something I'm considering. It's got decent power, great braking capacity and a very low center of gravity. Its achilles heel is no doubt its overall weight (2400 lbs), but in terms of a trailer pushing it sideways, it's better equipped than most to remain stable under lateral loads. It can sustain 1.4 lateral G's in corners, which is better than any tow vehicle, ever, pretty much. That's not the whole story, when it comes to towing. But it's something.

And to be clear: I'm not saying it's a good idea to tow with a car that light. But I'm at the researching stage, still. In my mind, the jury is still out on whether it will ever make sense.

Meant to add that you might want to consider Alaska Teardrop's construction methods. He does a light weight build using steel tube frame and aluminum outer skins. You certainly have the skills and shop for this type of build, converted to a teardrop shape.
Here's one of his builds: http://www.tnttt.com/viewtopic.php?f=27&t=51991

Thanks. I've looked at his pages and am very impressed. I'm curious as to whether any framing (outside of sandwiching the joints with aluminum L-stock) is essential for strength in a monocoque approach to the trailer I've got in mind. I'm not saying it isn't -- not at all -- and an aluminum or steel square-tube frame is certainly something I could put together. And even though I weld, I've already ruled out aluminum for the tongue and trailer part of the chassis. But for the less-essential parts, I'm looking at aluminum with structural adhesives, mechanical fasteners (like Alaska Teardrop) and TIG welding. I'm still very much listening and learning.

Can the Dibond do a radius?

Is the desire for a lightweight build based on what you expect to be towing with, or is it just sort of engrained in your racing psyche?

Even the traditional method can be built light enough to tow with pretty much anything, especially in the 4x8 size.

There is a unique build going on right now where Robot used a silver paint (Slipstream build thread). With a little more prep work and a solid base coat (because some of the silver paints can tend to weather poorly) it might suit your needs.

Any reason why you couldn't have a painted foamie wrapped in matte silver vinyl?

Penguino was a tall narrow build that tipped up on its front corner in a 50 mph crosswind in the dessert. Limited damage could have been easily repaired.

Kind of made me laugh a bit thinking about anything that could tip the wide arse on BB2. But there is a valid point to consider all aspects of a design, including the intended end use and regions/conditions that may be encountered.

In some ways, I'm sure I'm under the influence of racing in this process. Getting things down to race weight while maintaining reasonable safety is not the same thing when you're building a trailer. There's a real penalty to overbuilding in racing. That's not so much the case with a trailer. And a failure is one thing on the track, where everyone understands there are heightened risks -- but much less forgivable when you're driving in front of some ordinary family out on their annual vacation.

I don't think I'd be able to get vehicle wrap to reliably adhere to a sanded and painted canvas/foam structure. But I could be wrong about that. I think I could definitely get it to work with FRP panels, and the wrap might address the lower-cost panels' shortcomings when it comes to UV protection. But I've ordered some aluminum composite samples and I'm going to do some tests to see how they would work.

And yes, aluminum composite panels can be square-bent with a brake or radiuses with rollers. They hold the curves you put into them permanently, and that radius can go anywhere from teardrop-size down to the diameter of a pencil:



Here are some panels curved more reasonably, for the front of a framed trailer.

[KCStudly]

Cool. I'm looking forward to following along. You are taking the right approach, IMO, doing your research up front and planning it out before you make any rash decisions.

[GPW]

Jack , first and foremost , Do NOT listen to posters who have only a very little knowledge of the subject ... enough to come to totally WRONG conclusions ... We have FaceBook for that ... The particular blow over incident happened to a trailer that was Unusually Tall and Narrow ... and was in a LOT higher winds than 35mph .. The circumstances dictated the Failure and it was a Human error , not the Foam That caused the problem . We have already discussed this endlessly ... Those who refuse to read it will Never learn , and continue to make erroneous assumptions ... From Day One , we Foamie’s have been dogged with Naysayers, and you know what ? They were All WRONG !!!

BUILD what YOU want to !!! Only then will you be Happy !!!

(technically) There is an RV tech locally we’ve conversed with , and his intent was gluing Aluminum skins to 2” foam , thin ply on the inside and manufacturing campers from that ... If he’s an RV tech professionally , I assume what he’s talking about makes good sense... so according to him it “could" be done ... There has to be an easy to deal with the edges .... Best check the AL trailer guys ...They’ve done all that ...

Re: Oilcanning ... After studying this problem on many local local cargo trailers ( and they are Everywhere here) , it was concluded those trailers skinned during the Hottest months of the year , did much Better , showing little if any bucking of the skin ... The Physics reason is during the Hot times , the metal is fully expanded , during the cold months , the metal contracts and tightens up further... If the metal is applied in it’s Cold contracted state , when it gets warmer and expands its sure to buckle if held down at fixed points (rivets, screws) We’ve seen 50%-50% oilcanned trailers on the streets .. Just saying’