How does the fastback attach at the rear? Is it intended as a permanent replacement or to be removable?
Looking great so far. Can't wait to see the finished product!
The fastback started out as an Autokonnexion hardtop. It attaches to the body of the car using all the OEM hardtop attachment points (windshield header, sides, frankenstein bolts) as well as two bolts which go through the trunk rails. The trunk is removeable and uses the OEM latch to hold it closed. I kept these mounting points.
I hope to get the top functionally completed fairly soon (within a few months).
Really? How extensively modified? I've always thought the autokonexion looked rather ugly and half assed.
One of the problems the Autokonnexion top has is that it's equipped with screw mounted Lexan windows. Although this is a lightweight solution, it isn't weatherproof, is unattractive, and in the case of the rear window, was incorrectly designed to use a flat mounted window. The Lexan, laid flat without any curvature to it, is unfortunately prone to sagging. Autokonnexion addressed this with a buttress support piece, but that's an awkward solution. I wanted my fastback to have a more natural, curving flow to it, so I made some extensive modifications to the fastback to take custom made one-off automotive safety glass that's been made for the application. The glass was ridiculously expensive and took nearly a year between ordering and delivery. There are some awkward lines that the original top had that were eliminated (they had lines that were inspired by S2000 fastback tops, but didn't work for the Miata). The top also had to have the window mounting channels recessed and strengthened for the glass. The result is that the rear window has a curvature to it that matches the rest of the lines of the car. The quarter windows (also tempered custom auto glass) have compound curves in them so that, they too, match the curves of the fastback.
I also have two trunklids for the fastback which are being modified to flow more cleanly with the car. Some cut lines will be filled in, the overall top curvature will be reworked to flow with the glass, and the rear trunklid lip is being reworked into a more subtle duckbill lip. One trunklid will be "clean" and meant for street use with the fastback. The other trunklid will be notched to allow mounting APR wing as part of setting up the car for "Track Mode" (Trapp lip, track wheels/rubber, fastback, rear wing, rocker extensions).
I'm still working on the top (I'm do my work solo in my free time), but I'm getting pretty close to the point where I can mount the glass to the top. There may be a delay, though, as I'm considering experimenting with latch mechanisms to allow for the rear quarter windows to be opened to allow airflow out of them...we'll see.