Spraying Foam into Frame...opinions?

[Flinkly]

since i'm finishing my frame and want to do things right the first time, what do you guys think about spraying foam into the chassis rails? I started thinking about it after i read that ratco has the option on their frames. wish they sold gt6 frames.

is there any improvements in sound/vibrations or rust prevention? what are the downsides, possible increased rusting? i would have it done professionally, not just from cans at home depot, but would it ever be worth the trouble?

 

[Eric]

There has been chat on both Miata.net and rx7club.com about this and a magazine (Sport Compact Car if memory serves)did a test. In these cases it was filling the sills and pillars with foam to stiffen the unibodies. It made a difference for them, but you needed to get the right sort of foam. There was also some concern about the foam helping to trap moisture and promoting rust.

I'll see if I can dig up some links for you.

 

[tdskip]

I think prevailing wisdom is NOT to use foam as it can attract / hold moisture.

Check out this thread;

https://www.britishcarforum.com/bcforum/u...true#Post245160

 

[Don Elliott]

Don't do it. My 1992 Buick had foam in the upper parts of the "A" posts around the windscreen right down to the floor. This is where the doors were hinged. They all rusted out. They don't do it any more because of that. It's better if some air can get into the frame and dry them out. If you have foam in there and the frame gets wet, the water will be trapped between the foam and the inner steel walls of the frame and they will surely rust.

In the last 17 summers, I have driven my restored TR3A over 94,000 miles. About 3,000 miles were driven in the wet. How much will you be driving your TR in the wet over the next 20 or 30 years ? Do you really need protection if you never plan to drive it in the wet ?

Don Elliott, Original Owner, 1958 TR3A

 

[Flinkly]

ok, so the possible downside (rust) far outweighs the possible upside (vibration damping). gotcha. woulda cost money anyways and i'm always looking to save.

 

[Tinster]

FINALLY!!! A topic on which Tinster is
truly an expert. Sprayed urethane foam,
or PUF as it's known in the construction
industry.

Polyurethane and polyisocyanurate are the two
most common sprayed foams. Both are closed-cell
molecular structure with minimal interstitial
voids. Thus they are excellent insulators against
heat loss/gain. They are a two component, rising
foam that expands many times it's liquid volume.

The two part chemical reaction is hygroscopic
which means it readily accepts moisture into the
molecule during the curing process. This equates
to the need for extreme low humidity controll or
the foam curing creates millions of small voids
that can accept and hold water -to the degree you
can squeeze water out like a sponge.

I've seen the tops of commercial buildings collapse
where PUF was sprayed over the 20 gage steel decking.
The PUF soaked up so much water the steel rotted in
a matter of a few years..

Want to rust rot your car fast? PUF it!!

tinster

 

[GB1]

I have used waxoyl with good reults, but it will oooze out for quite a while.

Patrick

 

[Eric]

Found the article - the foam part is near the bottom of the page:

https://www.sportcompactcarweb.com/projectcars/0006scc_project_nissan_300zx_part_5/

 

[GB1]

I hate to say, but I am with the Tinster on this one.

https://www.marinefoam.com/liquid-sprayin-foam.html

 

[Monkeywrench]

The only cars I would do this to is an unibody chassis. Also all the times I've seen it used, it is used in self contained boxed sections with no way for water to get in from the outside (unless the outer metal rusts from the outside). Also the hole used to pour this in is usually sealed off. On a full framed chassis car, I'm not realy sure where you can put the foam. The best way to stiffen up a frame is either box certain frame rails, full out cage that ties the front to the back (competition), and/or a few stragecially located boxes/rails.

 

[AweMan]

Another thing to consider aside from the foam cellular structure collecting and holding moisture causing a rapid rusting of the structure of which it is in contact. Is, if you ever have to weld on any structure containing foam, this foam gives off very nasty highly toxic fumes. I myself wouldn`t recomend using it.

 

[Tinster]

Yupper, Kerry is correct.

1. polyurethane burns like a bitch and is self sustaining.

2. polyisocyanurate burns under flame and gives off cyanide gas.

Closed-cell occurs under laboratory or factory
conditions. In the real world, both absorb water
and will rust our cars (or buildings)quickly.

Can anyone spot the rust in this urethane covered
20 gage steel deck? It doesen't hold water, eh?

d

 

[LastDeadLast]

Dale,

I'm curious though... don't they use structural foam in cars today? Or is it all about the application of said foam.

Thanks for the info!

 

[tomshobby]

So, with foam my frame would rust really fast, the foam can burn, if it burns the fumes are toxic. It could be in my garage when it burns and the fumes could get in the house.

My frame is 30 years old and not rusted, bent, or broken. Besides that it does a fine job of holding my car together and my car handles much better than my driving requires.

Hmmmmmmm, tough decision! /bcforum/images/%%GRAEMLIN_URL%%/smile.gif

 

[Tinster]

Yes, the vast majority of problems associated with
both types of foam relate directly to ambient humidity
and installation technique.

Structural foam is a far more sophisticated product
than anything we can purchase off the shelf as consumers.
It's installation parameters are tightly controlled.

Pay $10 for a can of spray foam at Home Despot and
you'll quickly see it is junk.

I'd stick with wax to stop rust.
Weld some tiny c-channels to the frame if you
want to stiffen it.

Heck, I'd be greatful if I could look inside my
car and not see the garage floor below.

d

 

[trrdster2000]

Tinster, thanks for the information, and as you said we hit your expertiese and I hope it will save someone from destorying their frame.

Wayne

 

[Guest]

Curious, Ratco's website specifically talks about their version of filling the frame with foam and they basically guarantee the frame for life. Maybe there are some automotive-style foams that fill the bill and don't cause rust.

 

[swift6]

Or their frames are boxed or tubes and sealed after the foam is put in. Still, after Dales info it would seem that most of those foams would pick up moisture while they are being sprayed. Pull it right out of the air. Which would concern me when it is applied in a humid state.

 

[DNK]

Maybe someone should contact them and ask them to explain their process.

Isn't someone from here friends or something with them??

 

[Darwin]

Someone here at BCF, I think it was Tony, related a story of filling the frame with fiberglass batting soaked in resin. Probably would help with stiffness and noise control but it seems like a lot of work. Don't know how it would be for promoting/ inhibiting moisture. Maybe if Tony sees this he can comment.