Pour in polyurethane foam.

[javajoe79]

Looking into this as insulation and some added strength inside the aluminum square tube frame of my camper. http://www.shopmaninc.com/foam.html.

Anyone have any experience with this stuff?

 

[Victorian]

Haven't used that stuff but looks like a potential big mess ;-)

 

[IdaSHO]

I used Froth Pack to do it.

Yes, a bit messy, but seemed to do the job!

My square tube subframe after filling.

 

[chet6.7]

How much strength does it add?
Thanks.

 

[Huffy]

It will add virtually no strength to the aluminum tube and not much insulation value either as the heat will still conduct through the aluminum just as if the tube had air in it. BTW this stuff is crazy messy to work with and it sticks like nothing you have ever seen. Get it on your fingers and you will still be peeling it off two weeks later.

 

[IdaSHO]

I didnt use if for insulating or strength purposes.

I did it to reduce condensation / moisture build up within the tube.

My camper is a true 4-season camper, and is used as such.

 

[javajoe79]

I used Froth Pack to do it.

Yes, a bit messy, but seemed to do the job!

My square tube subframe after filling.

Nice! How much did you spend to use that setup and what density is it?

It will add virtually no strength to the aluminum tube and not much insulation value either as the heat will still conduct through the aluminum just as if the tube had air in it. BTW this stuff is crazy messy to work with and it sticks like nothing you have ever seen. Get it on your fingers and you will still be peeling it off two weeks later.

Hard to imagine it adding virtually no strength. Their hardest foam is really hard stuff.

*Physical Properties:
Parallel Compressive Strength: 580 psi
Tensile Strength: 450 psi
Shear Strength: 230 psi
Flexural Strength: 750 psi

Also it will surely insulate better then just air and have the added benefit of sound deadening. My plan is to skin the structure of my camper inside and out with foam panel insulation between the skin and fill the tubes with this stuff. Any suggestion on a better way to insulate a structure like this?

 

[Ducky's Dad]

Re the insulation value of foamed metal tubing: heat is like water and will follow the path of least resistance. That metal is the path of least resistance and heat will flow out of the camper through the metal, regardless of what is inside the metal. To insulate the tubing, you need to cover the tubing, probably with foam panels. The best insulation value in foam panels is probably still polyisocyanurate. Get the stuff with foil facing and face the foil in to reflect heat. Different brands of foam panels have different R-values, so do a little research to see what's available in your area.

 

[Yuman Desert Rat]

This might sound silly, but does it cut down on noise and resonance? Probably but nothing noticeable?

 

[Ducky's Dad]

does it cut down on noise and resonance?

Not a camper or truck application, but I use the foam a lot in residential remodeling for just those reasons. Anytime you can keep a panel from vibrating, it should make things quieter. Won't really cut down much on noise from outside the vehicle because it actually can provide a better mechanical path for noise transmission from outside to inside. Best solution to reducing noise transmission is to either create physical separation (decoupling) or to add mass (like the sound deadener sheets used by the car audio guys). Adding mass adds weight, so it's a tradeoff.

 

[javajoe79]

That's not all true though. That's like saying the the air in the tube wouldn't carry any heat out. It still carries some.

 

[Ducky's Dad]

That's not all true though. That's like saying the the air in the tube wouldn't carry any heat out. It still carries some.

It's all true. Dead air is a great insulator, and if all the tubing joints are sealed, you have dead air. Not a perfect insulator but pretty good. The vast majority of the heat will be lost through the metal. If there are openings in the tubing that allow for convection currents, then the air will carry heat out with it. Remember that all insulation foam does is to encapsulate the air so that it can't flow and carry heat with it. Foam is just dead air in a plastic shell.

 

[Huffy]

I was not trying to shoot down the idea. Someone asked if the foam would help insulate, as shown inside the tube it will do very little to nothing to improve the insulation of the tube. Foam is as noted, dead air. There was also a question of adding strength to the tube, again it will do very little. The strength (stiffness) of the tube is dependent on its diameter. Filling it with steel would not appreciably increase its stiffness. It would make it less prone to collapse when bent. Bottom line, a hollow aluminum tube and a solid aluminum tube of the same external dimensions are very similar in stiffness. To insulate well you will have to cover the entire surface. Then you have something.

 

[Sabre]

Yeah, the square tubing is a box beam; filling it with anything at all won't add any bending strength. The web plates of the beam are created by the sides of the tubing; these, along with the flexural strength of the top & bottom plates, determine bending strength.

Nor will the foam have any insulating properties at all in this application, as there's no thermal break created by the foam. Of course, it's great when used in a sandwich construction.

If the OP's primary purpose is to eliminate condensation inside the tubing, it's certainly going to do that (but not because of its insulating properties). It's simply excluding air from the inner surface of the steel.

 

[javajoe79]

So if dead air insulates as good as foam, why fill a wall with insulation? I understand that most of the heat will travel through the tube itself to the outside or vice versa but how does the foam not help some? Why are coolers filled with the same foam in question? Also the outer surface of the tube will be coated in something like Acryl R SM5430 with aluminum sheet riveted to it. That leaves the rivets as the only direct, metal to metal path.

The strength (stiffness) of the tube is dependent on its diameter. Filling it with steel would not appreciably increase its stiffness. It would make it less prone to collapse when bent. Bottom line, a hollow aluminum tube and a solid aluminum tube of the same external dimensions are very similar in stiffness.

I work with tubing on a daily basis and when bending tubing with a thinner wall but same diameter as another tube, it is physically easier to do so by sheer manual force and when using my hydraulic tubing bender you can hear it laboring less and see it bending faster. I can guarantee that if I filled a piece of tubing with this foam and installed a pressure gauge on my bender, it would show the difference. Good example, I can bend 1.75" x .120 wall DOM with my bender but I can't bend 1.75" solid rod. Can't even begin to bend it.