necessity of a roof

[roccit_53 at scirocco.cs.uoguelph.ca (C Boyko)]

OKay, not to look really simple and stupid here, but discussion so far has
been concerned with rigidity around the idea of keeping decent tire contact
patches, right? What about the horrible thought of a rollover, isn't that
at least part of what drives convertible designs into a roll bar? As in,
keeping the old noggin from going above roofline level/keeping the sides
from folding in? I can say from experience that the lower bracing on a
Cabby works well to resist a side impact too. I'm sure that a regular
Rabbit would have died in the "Goolie" T bone accident my daughter had with
the Cabby. And thankfully she was unharmed too, again, not so sure she'd
have done so well in a normal Bunny, even with a roof.
Cathy

On 1:55 pm 07/03/06 "Brian Haygood" <haygood@myway.com> wrote:
>
> I'm going to respectfully disagree with Al here.  If each side of the
> car were perfectly rigid, you would still get some twisting of the body
> because the sides would rotate relative to each other.  The thing that
> prevents this is the floor pan and the roof.  On the roof side, if you
> had no roof panel whatsoever, then you would be concentrating your
> resistance to twisting at the corners where the side rails meet the
> front and rear roof fails.  With no roof panel to help out, the stress
> at these spot welded intersections would be significantly higher.  How
> high would it be?  I don't know, but I wouldn't want to find out on my
> own car.
>
>
>
> Don't underestimate the structural rigidity provided by a thin sheet.
>  Consider that stressed skin construction is common in aircraft, often
> using sheets of aluminum that are considerably more thin than our roof
> panels.  They use spars underneath that would fail without the skin to
> keep the spars from twisting apart at their joints.
>
>
>
> So what I'm basically saying is that
>
>
>
> 1)the stress would be significantly increased if you just take out
> the roof, or a majority thereof, and do nothing else.
>
>
>
> 2) Our cars have all the torsional rigidity of a rubber band to begin
> with
>
>
>
> 3) By the time you have the headliner out and are up there cutting
> stuff away, it doesn't take much to put in some small braces between
> the front and side rails and the rear and side rails.  In fact, I would
> use the sheetmetal cut from the roof to make some boxes I could either
> weld or epoxy in at the corners.  I can explain that better if you are
> interested, but it would be dirt simple to do.
>
>
>
> Brian
>
>
>
>
>
>  --- On Mon 07/03, Allyn < amalventano1@tds.net > wrote:
>
> From: Allyn [mailto: amalventano1@tds.net]
>
> To: foxxinabox@wideopenwest.com, scirocco-l@scirocco.org
>
> Date: Mon, 3 Jul 2006 07:38:14 -0400
>
> Subject: RE: necessity of a roof
>
>
>
> So long as the side rails remain, removal of the center sheet of
> steel should have a negligible effect.  It is the tying of the A,<br>B,
> and C pillars that give the extra rigidity, and the side rails have
significantly more rigidity than the thin roof body panel<br>itself.<br>
> HTH<br>Al<br><br><br>>    i know that there are convertible sciroccos an
> d cabriolets <br>> with extra body support rolling around out there with
>  for the <br>> lack of a steel roof. <br>> but, what i'm wondering, woul
> d extra support be necessary if <br>> the frame of the roof is there and
>  not the middle section? in <br>> essence, to convert the roof into one 
> big sunroof? <br>> harebrained, i know. i just see these ads for new car
> s with a <br>> vertical sunroof rather than a horizontal one and wonderi
> ng <br>> if the middle man couldn't just be skipped. now, on with normal
>  life.<br><br><br>_______________________________________________<br>Sci
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