I agree, but no one suggested removing the entire roof skin. Only a
section for standing in the main floor area is trimmed out, and not
anywhere near all the way to the gutters. Cut 1/3 of the center of the
shoebox lid out and not all the way to the edge and see the minimal
impact on rigidity.

Mark

Mike wrote:
>   In a 'unibody' (also referred to as 'monocoque') design structure, any
> skin section is a structurally-stressed component of the entire
> structure.  A Vanagon is considered unibody, even though it does
> have frame strengthening members underneath.
> Those roof support arches are more for rollover protection than
> torsional rigidity of the body.   The roof skin, however, is an
> engineered, diagonal bracing that contributes greatly to torsional
> rigidity of the entire body, in addition to providing added metal
> structure to add crash or rollover protection.
>   Take a shoe box, remove the lid and grab the ends and attempt to twist
> it; it will easily deform.
>   Now, put the lid on and repeat; you'll have a hard time deforming the
> box from it's basic shape.
>   And, now, for the final proof of the body weakness created by a
> large, unreinforced sunroof opening; cut a good -sized 'sunroof' into
> your shoebox lid and repeat your twist test.  What happens?  My bet is
> that a great amount of overall rigidity is lost due the 'missing' area.
> You've cut the center out of your 'diagonal bracing!
>   VW made up for it by adding 'doublers' inside the factory sunroof, not
> just a couple of cross ribs.  The probably also added outboard, lower
> frame cover plates (I know they did on the earlier buses).  Side impact
> crash protection, must also be taken into consideration in this
> modification.  (Smack the side of the shoebox to demonstrate this aspect.)
>
> Mike B.
>
>
>
>
>     As long as you don't cut the 2 main roof arches, one at the front edge
>     of the slider door and one at the rear edge, the roof area between is
>     just roof skin and not of much importance structurally, IMHO.