My thoughts while making this:
- compound curves are hard to get right (I got the "roof" of the tail eventually, but not the sides right).
- I need to round the transition from roof to sides; right now it's a sharp angle (unlike the car's shape ahead of it).
- The side-of-hatch to side-of-tail transition is messy. I really need to start the boat-tail sides at the forward edge of the hatch sides. Also, you can't tell in the photos, but the right side is tapered further than the left side (at first I was focussed entirely on roof taper, and didn't taper the right side as much as it looks like I could have).
- I tried to project the existing tapering lines of the bodywork into the tail without any big changes, but I could possibly be a little more aggressive. Only tuft-testing would say for sure (looking for clean flow, right to the back of the tail)
- Ryland: I had the same thought about getting a junk hatch. I know where there's a '95 sitting in a farmer's field about 20 minutes away.
- Materials? If this is worth making a "good" copy, I was thinking: fibreglass over high density foam (messy, complicated, time consuming, little experience with the materials); junk hatch with attached sheet metal, faired & painted (also time-consuming, but I'm more familiar with the materials & methods); lightweight plastic or aluminum frame covered with sheet plastic/sheet metal... Plexiglass? Might be hard to form into compound curves (the stuff I've used in the past was fairly brittle. Also, how to join the top & sides in a rounded transition?)
- Not sure about dimples or VGs though. Since I'm an amateur, I'm just trying to stick to the basics: reducing the size of the trailing wake by tapering the shape as much as possible without causing flow separation. Also, I recall reading that dimples don't work for automotive scale/shapes.
- a finished version which I leave permanently on the car could serve as an attachment point for an extended version for highway use.
