Fiberglass floors (was: Re: mail Digest for 8 Dec 2004 in hour 0:00 (fiberglass floors))

[Matt Haas <mhaas@xxxxxxx>]

Frank,

Okay, so cutting out the entire front floor was taking things a little far 
but...

What was gone on my car was the "foot well" area. It was better than 80% 
gone on both sides (more like 90% gone on the driver's side) and I can tell 
you first hand that the car flexed a lot. It flexed so much, in fact, that 
you couldn't open or close the front doors if the car was jacked up. Just 
replacing the drivers side made a tremendous difference in the way the car 
rode and drove. I really wasn't kidding about have to use a floor jack to 
put the frame sill in the proper place when I fixed the floors in the car 
(BTW, this is a reference to an article I recently wrote for AIM). just 
from the "foot well" area being gone, it allowed the frame sill (and the 
floor pan it was attached to) to sag. The part of the pan under the seat 
was in good shape but the thing is that the foot well helps support that 
part of the floor (it's that whole unitized construction thing -- body 
strength is gotten from all of the components working together -- none of 
the are strong by themselves) and without the support from that thin piece 
of metal, it just sagged.

The problem with using fiberglass to fix the floors is that the car's flex 
quite a bit. Even when they were brand spanking new, they flexed quite a 
bit (especially compared to today's cars). Fiberglass just can't take the 
flexing which is why Corvettes don't have fiberglass floors anymore and use 
a massive steel frame. You can bend steel quite a bit before it will crack 
to the point of failure but fiberglass isn't so forgiving. I'm not going to 
argue that fiberglass is weak compared to steel (it isn't when done 
properly) but it's just the wrong material for this application.

Also, the method you mentioned below does nothing to even attempt to 
stabilize the frame sills. Those have to be attached to something with some 
strength and rusty sheet metal ain't strong.

Matt

At 09:24 AM 12/8/2004 +0000, you wrote:
> Okay, I should be more precise -- I really just meant the floor pans or 
> foot wells, the most commonly rusted pieces, not the ENTIRE floor! I 
> didn't think the post would have referred to the entire floor either, so I 
> didn't elaborate much. The bracing under the floor is strategically 
> located for strength and stiffness of the entire structure. I didn't mean 
> that you could cut the entire floor out and replace with fiberglass, but 
> fiberglass is a good repair for rusted floors. There should be over 50% of 
> the metal still there. That will serve as a reinforcement for the 
> fiberglass. Other than that, clean it real good (no need to cut it out, 
> even if it looks like swiss cheese after cleaning), prime, paint (to seal 
> away moisture and air), then 'glass over on top and seal the bottom with a 
> good undercoating. There will never be any rust and it will be as strong 
> or stronger than the original floor. As far as tensile strength goes the 
> fiberglass should be as strong or stronger than st!
>  eel. It doesn't have as much compression strength or stiffness. That's 
> why there is usually reinforcement built into boat and such. Take a look 
> at a concrete bridge. Darn concrete is strong!! Now take a look at a 
> bridge being built. Never knew there was so much steel bar in there did 
> you!! To make the entire floor from fiberglass would require some steel 
> reinforcement, but it should be safe to replace most of the large flat 
> unbraced areas with fiberglass. Yes, I guess I'm back pedaling a bit 
> here!! Should have been more detailed the first time.. (spitting foot out 
> now!!)
>
> One of Datson's tricks was to add about 1/4" of fiberglass mat and resin 
> to a perfectly good steel floor to stiffen the entire floor structure of a 
> car for road racing. Adds a little weight, but apparently stiffened enough 
> to be worth it.
>
> --
> Frank Swygert
> Publisher, "American Independent
> Magazine" (AIM)
> For all AMC enthusiasts
> http//:farna.home.att.net/AIM.html
> (free download available!)
>
>
>  -------------- Original message ----------------------
>
> > Date: Tue, 07 Dec 2004 20:52:17 -0500
> > To: mail@xxxxxxxxxxxx
> > From: Matt Haas <mhaas@xxxxxxx>
> > Subject: Re: mail Digest for 6 Dec 2004 in hour 0:00
> >
> > <snip>
> > >The fiberglass remark is unwarranted though. You obviously don't
> > >understand the strength of fiberglass! There are entire boat hulls made
> > >from it with minimal wood bracing embedded inside, why wouldn't it serve
> > >as a floor? Car floors aren't really a structural member. Sure they help
> > <snip>
> >
> > As someone who drove a car with no front floors to speak of, all I can say
> > to this is bull hooey and I invite you to chop them out and see how well
> > the car does. Of course, I'm not sure how you'd drive it since the seats
> > mount to the floor but I'd bet you'll be pretty unhappy when the car caves
> > in on itself after you hit your first hard bump (the frame sills attach to
> > the floor also). The simple fact is that on any car, the floor is just as
> > important to the structure as the roof or the sides. In fact, anything 
> that
> > isn't bolted on is a structural part of the car (on my 1996 Ram, even the
> > windshield is a structural part). Do some parts contribute more than 
> other?
> > Sure, but the floors contribute a bunch more than you think.
> >
> > And yes, entire boats are made of fiberglass but you don't see large flat
> > sections of fiberglass that don't have reinforcements. Corvettes? The 
> early
> > ones crack badly due to body flex (and older cars flex a lot more than
> > newer ones) and had full perimeter frames. The newer ones have a huge 
> steel
> > frame under them and the body is mostly for looks and aerodynamics. Take a
> > look at http://www.mattsoldcars.com/gallery/PowerTour2003/page6.shtml 
> for a
> > picture of a previous generation (C5) Corvette frame looks like.
> >
> >
> > mhaas@xxxxxxx
> > Cincinnati, OH
> > http://www.mattsoldcars.com
> > 1966 Rambler Rebel
>
> > 1968 Rambler American sedan

mhaas@xxxxxxx
Cincinnati, OH
http://www.mattsoldcars.com
1966 Rambler Rebel
1968 Rambler American sedan
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