Foaming the chassis, good or bad?

[solma]

What do you thinks about foaming the chassis? Does it make a real difference in the stiffnes of the chassis?

[maj75]

If you saw the size of the space in the door sills, you would be amazed.

Do some research. There are different kinds of foam. To get any benefit you would have to use the proper automotive/marine structural foam and pour it into the sill area. It would add weight but it would definitely strengthen the area and make it quieter.

I thought about it when I had the interior out for sound deadener. The right foam is two part and can be a mess to do. I did not have the foam, the expertise or the time to do it right so I left it on the to do list later.

[7thgear]

people have done it (the hardned kind) but it's a messy job and would require you to take apart the inside of your car and have a clean working area. The compounds are typically quick acting and you have a short time window to pour them in.

in some cases you might need to drill holes through the floorboard to access the bottom rails.

but the benefit is minimal, i would only do this for a time attack car that does not require a rollcage/bar to get as much stiffening without the added weight

i would also guesstimate that a proper seam-weld job would give you better benefits.

[solma]

I do lapping days a few time per year but the mostly DD, I know its a big job, but more simple then welding as I am not a welder nor have experience in welding. I am just wandering how much it will help in the short and long run, as it serve 2 purpose, one is filling the void(meaning stiffning) and the other is gluing the seam, maybe not solid as welding but still, aluminium car chassis(aleast some) are glue.

[GTB/ZR-1]

I foam my wife's chassis regularly...

[7thgear]

Originally Posted by GTB/ZR-1

I foam my wife's chassis regularly...

is she that loose?

[GTB/ZR-1]

Originally Posted by 7thgear

is she that loose?

Her FX35's chassis--get your mind out of the gutter! lol

[7thgear]

yeah man, that's what i meant, cuz cars are female

[meeks]

hahahahaha lost it with the correct usage of memes!

to the op: did it to the old ef hatch, good results, however it was an old car that really did benefit from bracing the crap out of it. i dont know if we would benefit much if we did it our chassis considering it is new, so correct me if i am wrong.

[Miniata]

Done right, with the correct structural foam, it can be beneficial on many cars, but not done properly, it can trap moisture and lead to rust issues down the road.

[Wes]

Im not sure.. but you might be able to make it amphibious like on top gear lol

[orangeblue]

Originally Posted by 7thgear

people have done it (the hardned kind) but it's a messy job and would require you to take apart the inside of your car and have a clean working area. The compounds are typically quick acting and you have a short time window to pour them in.

in some cases you might need to drill holes through the floorboard to access the bottom rails.

but the benefit is minimal, i would only do this for a time attack car that does not require a rollcage/bar to get as much stiffening without the added weight

i would also guesstimate that a proper seam-weld job would give you better benefits.

seam welding requires as much if not more work, considering you have to strip any potentially flammable parts, grind/sand off paint and undercoat to get a weldable surface, weld, then repaint over the welds to prevent corrosion.

[Silverpike]

Originally Posted by solma

What do you thinks about foaming the chassis? Does it make a real difference in the stiffnes of the chassis?

I have spent a lot of time in the past investigating chassis foaming. My conclusions are as follows:

1. Foaming might make sense if you are building an all-out street car, or compete in a form of racing which prohibits chassis reinforcement. You could do it just because you can, but it's a large time investment.
2. Foaming the chassis right takes a great deal of time. The strategy needs to be carefully planned out ahead of time. Every car has different cavities which benefit from foaming, and they need to be mapped out and investigated.
3. The car needs to be fully stripped of the interior to pull this off. You will also need friends to help you. Any gaps in the cavity needs to be sealed off with duck tape, and foam has to be applied very quickly at certain intervals. If you screw up, you will never be able to fix it, because the foam dries in like 20 sec. If you forget to seal even one gap, the foam will come leaking out and drip on your garage or interior parts. Once the foam dries, it's not coming off no matter what.
4. The foams required for this are very very nasty things. The correct foam is quite dense when dry, and made of urethane. If you get any on your skin, it will not come off unless you remove the skin with it (no shit). You need to wear protective clothing from head to toe, and be careful not to get stuff on you. This stuff is expensive in quantity, and probably falls under hazmat guidelines for shipping.
5. Foaming a car means the chassis can never be repaired after a collision. If the frame is hit hard enough to bend during an impact, it can never be straightened again by shop equipment because the foam is so rigid.
6. Foaming parts of the frame also means you can't run wires down the frame cavities if you ever do electrical wiring in the future.

It can be done, but this job has a very high time and preparation investment given the benefits.

[solma]

Here a product, http://www.dowautomotive.com/capabil...y/betafoam.htm that seem to support the fact that you can reinforced the stiffness of the chassis with foam, aside that to be qualified as "structural foam" it need to be in the 20lbs per cubic foot density, meaning a lot of weight if the frame would be fully done.