Last night after a great deal of anger and frustration and reading through many different car forums I hit upon a solution to the windshield problem that will ultimately only required four additional holes drilled into the car.
I have always liked the Hallock Style of V windshield seen on hot rods. It makes a great alternative to a flat piece of glass stretching across the car. It was originally a boat windshield on Chris Crafts from the thirties and forties, and the early hot rodders adapted it for their use. As seen on BlackToBasics below:
While this windshield looks curved in this picture it is actually two pieces of flat laminated safety glass. Unfortunately windshield frames like that are both heavy cast bronze (the Hot Rod guys evidently do not care about weight) and expensive ($1700) and won’t fit. Luckily the Jalopy Journal forums had several technical articles about fabricating a windshield frame like that from scratch. The advantage it has over the single pane of flat glass is that there is some support in the middle of the span which will reduce the likelihood of cracking the glass.
So, onto fabricating a Hallock style windshield for a Lotus Seven Clone, while minimizing the changes to the car and the expense.
I decided to stick with the supplied windshield stanchions and fabricate a center brace then use standard automotive glass adhesive methods to attach the glass. This will preserve the “frameless” look I had with the polycarbonate windshield.
Since the glass is flat, and is very unforgiving to twisting it is important that the sweep angle of the center brace match the sweep angle of the side stanchions. This sweep angle is set by the existing stanchions. I measured the stanchions and found the sweep to be 60 degrees. I fabricated the center bracket out of two piece of 0.065 aluminum sheet riveted together. I formed the bends using a 6″ press brake in my vice. As it turns out you can make very nice long bends with this short little brake if you carefully position the brake and make several passes.
With the center brace fabricated and mounted it was time to make a pattern for the window glass. A simple way to match the contour of the scuttle is to use index cards to approximate it. I clamped a carpenters square to the driver’s side stanchion then used painters tape and index cards taped to the square. The carpenters square keeps the card along a straight line as the is what the glass will be.
Once I was happy with the fit of index cards I transferred the card to a sheet of melamine to make the initial cuts on the window pattern.
The real mark of success is seeing that the one pattern works for both sides simply by flipping it over.
Another mark of success is that the melamine meets the center brace and the stanchions to within 1/16 of an inch all along the bond zone, which seems to be well within the gap filling capabilities of urethane adhesives used to hold down windshields.
The next step is to get the glass cut and purchase the adhesive. I think I will try to buy some scrap glass to practice with the adhesive before I commit to the car.