From: Jim Bailey [jim@928intl.com]
Sent: Thursday, April 11, 2002 7:15 PM
To: 928
Subject: [928] Re: Less weight...fiberglass roof panels! (long you 'll
be sorry anyone asked)

To better understand the roof question requires an anatomy lesson. the outer
roof skin is a single panel of rather thin steel. I just removed this from
the widebody 1980 by carefully drilling at each spot weld being careful not
to drill down through the two layers of reinforcement panels which are
welded to the roof skin (just deep enough to free the top skin) . With the
skin removed you now see the two layers of roof reinforcement which support
the windshield and make up the continuation of the A pillar /top of door
opening / B pillar . This structure also is the mounting for the rear hatch
hinges . This makes a "roll cage" of folded sheet metal comprising a box
section (about 3 inches by 2 inches) all around the outer edges , front ,
rear of the roof . The "flying buttress" of the section above the rear 1/4
windows is the down tube needed to complete a proper roll cage again layers
of folded welded sheet metal . The sunroof cars have an additional inner
steel drip panel welded to the roof reinforcement (it collects the water
which always leaks in around the sunroof trim (seals? ) drains out of 4
holes one in each corner. With all this as background , the roof skin (no
sunroof) by itself does not weigh very much 17.5 lbs, the question then
becomes how much of the Unibody structure should be compromised by drilling
additional lightning holes( makes a cheese grater for hands which are
flailing about in an "Oh $hit" )  or cutting away material which if you do
very much means the windshield frame ( A pillar )may as well be cut/
replaced as it now attaches to nothing structural , same for B pillar and
the rear buttress . Obviously the drip panel (sunroof car) motor, cables,
can be removed for some weight savings plus the sliding panel is two layers
and pretty heavy ( 14.5 lbs ); more important to many of us you get more
headroom for a helmet . For safety you should have some air gap between your
helmet and the roof to avoid compressing your spine if you get upside down .
Brendan you asked about Mark Anderson's car , he uses all factory body
panels no fiberglass . The light weight is from starting with a completely
bare chassis then building from the ground up questioning and weighing
everything before it becomes part of the car . Details like a smaller
alternator , special light starter , only half the fender bolts . Building a
lightweight car with the car assembled is much like  " building a ship in a
bottle " one compromise leads to another , then another . Theoretically the
1980 widebody may end up being pretty light as it is a 2 valve and has glass
front cover, fenders , carbon fiber hood , glass rear GTS 1/4s , little
mirrors , cutout rear floor panels taillight housing rear bulkhead ,
(Aluminum panels), fuel cell , cut out rear seat wells . No stock wiring or
relay board , no dry sump or accusump , no electric fans but it will have a
pretty strong (heavy) cage with "Nascar" door bars . My Daughter / son in
law have a desire to drive an "open road " event so I really need to pay
attention to the safety issues . I can live with doing injury to myself but
somehow have a higher standard when I think of others getting hurt by any
compromises .
The 60 feet of tubing is on the floor next to the car just needs some bends
to fit the car (that will be another week of "vacation" soon) .The only way
to get any significant weight savings beyond removing the inner drip pan and
motor cables involves seriously affecting the strength of the unibody (all
the convertibles have issues with body flex and required additional "frame"
reinforcements ). I personally prefer having a bit of tin over my head that
will stretch and bend rather than break into jagged bits of broken
fiberglass and even with a strong cage added I like to keep the integrity of
the original very strong unibody to resist chassis flex . The 89 GT which
Ron has here , another "racer" at 928 international ,is a theft recovery
race seats no interior , no heater /ac , no front inner bumper , no drip pan
sunroof inner door liners etc. etc. does have the rear bumper aluminum and
big brakes rotors ...weighs just about 3,000 lbs wet is just marginally a
"street car " . My old Brown very brown 1980 weighs 3300 with a/c no sunroof
small brakes .(less now with no a/c compressor , no power seats, no rear
seat backs and 15 inch wheels) I will try to weigh it again tomorrow as soon
as I unload the extra set of wheels , aluminum , tools helmet etc.  Short
summation of the above , the roof skin for a no sunroof is 17.5 lbs just the
sliding sunroof panel alone weighs 14.5 lbs. you probably can save 40 lbs
without getting into the structure using a tin roof maybe 10 lbs more with
glass . I do not have a cutoff roof at this time to weigh the assembly but
should have one off the GTS in a day or so . Shoer metals on Kramer blvd
about 3 blocks from me has a scale and for $3 will weigh your car .
Jim Bailey

Jim@928intl.com