Horizon, thanks for stopping in and adding your comments. They are much appreciated.
As stated earlier, adequate (?) headroom will be made by making the top horizontal from the top of the rollbar forward ~18 inches, then drop down to the top of the windshield, not a straight line as shown in the the buck photos. My currrent plan is to follow the roof line from the roll bar forward as shown from my earlier topic in the Exterior forum, but not the full top though, just a sunroof with similar side wraps:
Are you thinking I need more headroom further forward than shown? I'm listening. I still have time to rethink that part....
1st, let me restate, the the pink foam you see is just being used as part of the buck. It allowed me to slit and form the continuously changing radius curve. The final roof layup will (fingers crossed) release from the buck and have no foam. The foam is a use once and throwaway material. I may use the foam to form stiffening ribs that will be fiberglassed over but not as structural members itself. Your suggestion of ply being used as rib forms is well taken. I had planned on using oak in the front and rear and still plan on it. Using the ply on the sides makes sense.
That melamine faced masonite is great stuff and I have used it in the past for making flat fiberglass sections. However, it will not form anything close to resembling a curve, let alone a complex curve. For a slightly tighter single curve, some thin plastic shower wall sheets "might" work a bit better.
And yes, thin ply with some glued on edges or doublers will work very good for a flat surface like a dash. I have built similar constructions for indoor use using cheap luan ply. I wouldn't use that in an weather-exposed car though. Jack uses Fir or Birch (I believe?) ply for his bonnet reinforcements in his Lalo body.
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Chuck.
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