Body Stiffening Issue

[pawp]

I suppose this could go in the body or handling sections.

I am considering removing the bulkhead between the trunk and passenger area on my 1980 convertible project. This will facilitate a pass through compartment arrangement for luggage etc. My plan is to surround the cutout with 1" square tubing 1/8" wall around the opening.  It will tie into the lower inner fender well on the sides, continue vertically up to the top of the panel just under the sheet metal where it will join a horizontal piece be tied into the upper wheel well area on each sides. The rectangle structure will also tie to the left over sheet metal and provide a frame for the passage door.  Do you think this arrangement will strengthen or weaken the existing structure?

[Bill Young]

I doubt if you'd notice any difference in structure, especially with the addition of the tubing section you describe. That bulkhead does offer some torsional stiffness, but not much since the upper portion of the body isn't tied to the front of the car at all. The GTs had nothing there at all and the roof didn't have any sort of diagonal brace to prevent torisonal twist.

[tr8todd]

My B had that panel cut out before I bought the car, and no other metal was there to replace it.  I put a welded in roll hoop and seem welded the floors and rockers during the sheet metal resto.  It is very stiff now, so I can't imagine that panel is more than a crush panel for side impacts.  You can see right thru to the trunk in this photo.  This car was originally a showroom stock race car in the 70s.  You can still see where the bolt in cage feet were mounted next to the battery boxes.  The bolt holes are still there.

[eyeosteverino]

I agree with B.Y.  Might be easier to to just roll the edges.  My  Midget was built with a pass thru and it's handy.

[roverman]

Anybody ? Post on measuring torsional strength, in real world ? We have some "brainy types", how bout ? Thanks, roverman.

[302GT]

There is an extensive discussion on measuring torsional body rigidity in a Mustang forum that might supply some ideas. The link is:
 http://www.stangnet.com/mustang-forums/723029-torsional-rigidity-test-67-coupe.html

[DiDueColpi]

Hey Richard;
Just my two bits worth, but I believe that bulkhead was a north american requirement to separate the fuel tank area from the passenger compartment. It really doesn't do much for rigidity. However I think anything that you can do to improve torsional stiffness and side impact protection is a good thing. So I would brace it up and add at least a 3 point roll bar.
On my race cars we have a cheap and easy way of gaging improvements to the body strength.
We set the car up on jack stands at the four extreme corners, weigh down the passenger compartment ( bags of sand work well) and level the chassis. I use an old laser level that has magnets glued to the bottom  and a target made from some leftover lexan and magnets. Sight the laser and target over the area to be checked, such as L front fender to R rear fender. Then just jack up each corner an inch or two and record the deflection on your target. You will be surprised at the amount of movement.
The measurements won't really mean anything but they will give you a way to judge any improvements.
Cheers
Fred