Foaming filler?

[pats16v at columbus.rr.com (Erik Patterson)]

This may help, taken from a very un-VW magazine.

http://www.sportcompactcarweb.com/projectcars/0006scc_proj300zx/


Foam-Filling the Chassis
In any high-performance car, it is impossible to make the chassis too stiff. 
The stiffer the chassis, the higher its natural frequency, making the energy 
imparted to it by bumps less likely to excite the body's structure. A 
stiffer chassis enables the use of stiffer springs and shocks without 
hurting the ride. This is because a stiff, non-flexing chassis transfers 
more force into the suspension where it can be dissipated by the springs and 
shocks instead of transferring the force to the occupants. A stiff chassis 
is also more responsive to roll rate tuning for balancing understeer and 
oversteer. This is one of the reasons why automotive engineers are 
continually investigating ways to stiffen chassis without adding weight.

In a final bit of reengineering to stiffen the body, we injected the chassis 
with catalyzed rigid structural polyurethane foam. Structural foam, in the 2 
lb per cubic foot density that we used, can stiffen chassis members up to 40 
percent.

Higher densities of foam can increase stiffness by up to 300 percent. Since 
we cannot retool custom parts to redo the Z's body, we figured that this 
would be an excellent, low-cost way of greatly increasing chassis stiffness. 
Injecting foam is not a new technique for chassis stiffening. The Infiniti 
Q45 uses this sort of foam in some of its chassis members to increase 
stiffness, as do a few other premium cars. In fact, the foam we chose is the 
foam recommended to repair damaged Q45s.

To get the correct foam for our project, we contacted Art Goldman, 
Foamseal's automotive product manager and author of an SAE (Society of 
Automotive Engineers) paper on the use of structural foam for the stiffening 
of automotive unibody structures. We used Foamseal's two-component foam kit, 
p/n 11-22 to fill the main members of the chassis. Like we mentioned 
earlier, Foamseal is the supplier that I-CAR, a national certification group 
for quality auto repair, recommends for the repair of damaged, foam-filled 
chassis. The Foamseal kit uses a two-part catalyzed polyurethane foam, which 
quickly cures into rigid, waterproof, closed-cell foam. To prep the car, we 
carefully masked off all painted areas anywhere where the foam could drip. 
As this sort of foam is a thermosetting catalyzed plastic, we realized it 
could be icky if it spilled on paint or any part of the car's interior. This 
foam is nasty stuff. It is impervious to all known solvents and cleaners.

Rubber gloves must be worn. Get some of it on your hands and it will stay 
there for more than 3 weeks--don't ask how we know. Do not get this stuff on 
your paint. Wear old clothes; we ruined ours while learning how to handle 
the product. We injected the foam into the rocker panels and frame rails of 
Project Z through existing bolt and drain holes. When injected, the foam 
reacts like shaving cream and quickly expands to fill the empty space. You 
can judge how much foam to add by watching its expansion progress through 
some of the holes. Once injected, the foam expands and begins to cure in 
about a minute so you need to work fast and plan how you inject the foam 
before you start.

The life of the foam kit is limited to a few hours once the seal is broken. 
We filled all of the Z's unibody frame members using five foam kits. When 
foaming a chassis, you must remember the wires and other lines that pass 
through the chassis must be relocated or they will be entombed forever.

We were amazed at how this simple procedure improved the performance of the 
car. The chassis now almost feels like it has a roll cage. A sloped driveway 
can be driven up sideways with nary a creak. Even though the Z already has a 
pretty tight chassis, it feels more solid. The ride has improved and road 
noise has been reduced noticeably. We bet that the car will be even more 
responsive to chassis tuning measures in the future. If you are a slalom 
racer, a road racer, have a lowered car or even just want a smoother ride; 
foaming is a worthy, easy-to-do modification. Foamseal has foams in 
densities as high as 10 lbs per square foot if you desire to make things 
even stiffer.

Do not--I repeat--do not attempt to use cheap, hardware-store canned foam. 
This is not the same thing, and if injected into your chassis, will form a 
gummy mass that won't dry. Foamseal foam is a professional grade foam, which 
although it is a little unforgiving to cleanup mistakes, has superior 
mechanical properties and catalytic curing so it will dry even in an 
enclosed space.



HTH



Erik

----- Original Message ----- 
From: <julie@menloparkrandd.com>
To: "Org, Scirocco" <scirocco-l@scirocco.org>
Sent: Sunday, March 19, 2006 11:57 AM
Subject: Foaming filler?


>I asked this before and got no awnser.
> 1) What can be used to seal and replace the monkee s**t that coats the 
> inside of the fenders?
> 2) Can standard sealing foam (canned) be used to fill in the spaces like 
> the A pillar (instead of the foam block)?
>
> Julie
>
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