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RE: [T3] The safety FAQ

<x-charset windows-1252>Phillip Bradfield asked:

>>What is your basis for the structural integrity lost when a full length rag
>>top is installed? 

Sorry for chiming in a bit late, but I was on vacation and away from the data for my reply.  So here goes.....

There are actually two types (roll-over and overall torsional rigidity) of structural integrity that Keith is referring to.  Both are compromised by the addition of the ragtop, one more than the other and in different ways.

The roll-over integrity is compromised by having a soft fabric covering or nothing at all between you and the road, stumps, trees, rocks etc in the event of a rollover.  It is true that much of the resistance to roof collapse comes from the pillars of the car, the roof panel helps to transfer the load more evenly between the pillars and helps to stabilize them from buckling.  These effects are certainly reduced by having the ragtop in the roof panel.

The overall torsional rigidity is where the structural integrity is really compromised by cutting a large hole for a ragtop sunroof in the steel roof panel.  For comparison......

1987 Honda Accord 		6,100
1987 Honda Accord w/o glass	4,800     21% reduction!
1990 Toyota Cressida		7,360
1990 Toyota Cressida w/o glass	4,634     37% reduction!

These reductions are accounting for BOTH the front and rear glass on these cars, but you are essentially cutting an additional windshield opening in the roof panel which by my estimation would reduce the overall torsional stiffness by 10-20%.  I call that significant.

John Jaranson (that pesky Ford engineer)
'71 FI Auto Fasty (Jane)
'66 Square (???)
About Half a Late Square (Organ Donor)

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