stuctural foam in chassis?

gestalt1 · 08-04-2009, 07:03 PM

hi all, I ran across this stuff and researched it a little and am not sure it is worth it. It is a 2 part closed cell expanding foam that is put into enclosed chassis rails to add strength. i guess this stuff is used on infiniti's from the factory. other web boards have tried it with mixed results. i'm mostly interested if it will contribute to rust issues with condensation etc. i guess the face that it is closed cell helps but because it is non-reversable proceedure i would hate to cause a big problem by trying to add a little chassis strength. what do you guys think?

http://www.foampower.com/store/two_component/index.html

Zeke · 08-04-2009, 07:15 PM

The one continuous longitudinal contains your warm air for the heat and defrost. I don't think you want to shoot that one full. The sub forms, or frame horns most likely do their job just fine. Any chassis flex on a 911 is across the floor pan, a singe thickness structure, and between the shock towers, a vacant space.

gestalt1 · 08-07-2009, 08:08 AM

the swb 911 i believe has continuous steel tubes in the sills for the heat - no flex hose as in the lwb cars. i would not foam those, just around them. i would think that the foam would connect (structurally) the heat tube to the sill and inner rocker to greatly add strength. i'm also not going to have heat in my car so the tubes are not that important. i'm also starting from a bare tub so i don't have to worry about wires/hoses being permanently encapsulated in foam. i agree the floor of the 911 is a weak spot for twisting forces. that is where a cage really would help. my thought is tha the foam is cheap, easy to install and may have great structural strength as well as help with noise while adding very little weight.

Paulporsche · 08-07-2009, 08:26 AM

I don't know the answer, but I'm pretty sure VW experimented in the 70s w/ foam in the front fender cavities on the Scirocco to help prevent rust. On my 78, those were among the first areas to rust.

The foam used today may be more closed and absorb water less, and the steel may be better treated, but, while I like the concept, I would do a lot of reearch before using it.

DW SD · 08-07-2009, 09:25 AM

Interesting concept!

I read through the info about this product. It doesn't suggest structural applications in any way. Has its value in this application been proven? I would suspect some product exists that would be used in this way, but the marketing info doesn't suggest so?

In my view, marketing folks usually will give every possible use, even if barely appropriate, so that's why I wonder if this is the right product.

Doug

RWebb · RWebb's Garage

seems like a plastic foam would never add much

do not confuse this however with Al foams - former aerospace tech. that now can be had for use by us peons (well-heeled peons, anyway)

gestalt1 · 08-07-2009, 10:55 AM

i think you guys are right, the foam might seem rigid but in a 5-6 foot long chunk it may bend quite a bit. i would think that that is when you really want it to be sturdy. it could be that the bending forces of the chassis are greater than the compressive strength of the foam - making the foam useless. the rusting issue really bothers me also. air ventilation and drainage will keep enclosed areas dry, the foam would block that venting process. i heard about this from it's use in Infinities and the handi foam is recommended for bodyshops to use when repairing Infinities. a few sport compact folks have tried it but there really has not been a good test to see if it really does anything. the real problem is that its a one shot deal, once it is in the frame your stuck with it. if the sills start rusting you can't really fix it without major surgury. maybe seam welding is the best option.

RWebb · RWebb's Garage

probably worse then bending - I'd expect it to be very friable.

JFairman · 08-07-2009, 11:39 AM

PVC foam sandwich construction or nomex honeycomb sandwich using fiberglass, kevlar, and carbon fiber composites using only high solids epoxy resin is great for boats and some parts of race cars and aircraft.

Do not use it in a steel chassis car, polyester foam has no bonding strength and it slowly absorbs water.

You'll just make an unbelieveable mess and destroy your car doing that.

burgermeister · burgermeister's Garage

Foam is used to maintain the shape of the section during nonlinear (=crash) events (prevents buckling). Foam does not carry load, aluminum or otherwise. In a composite, foam keeps the outer sheets apart. The outer sheets carry the load, the foam just spaces them part.

So it won't do you any good in a 911....

si Banker · si Banker's Garage

What would be the effect on the reduction of road noise inside the car? Could the foam also retain moisture; or would it rust proof the inside of the cavity?