Actually, the surface of the roll bar and the windshield frame was considered set and we only suspected delicate detail optimizations in the front and rear area of the outer body in order to achieve the desired "better than 0.25" for the cd value, the so-called drag coefficient of the TWIKE 5. Admittedly, with its relatively short length of 3.15 m, the vehicle body is more in line with the short city vehicles, which usually have a cd of around 0.35. Also, a 1.54 m wide body cannot be pulled together at such a short vehicle length like, for example, a VW XL1 at the rear. But this one also has a cd of 0.19 and in our first simulation calculation for the TWIKE 5 there is clearly a 3 behind the decimal point. And that is a no-go.
In order not to rework too much of the development work created and thus possibly trigger more extensive and far-reaching packaging loops, it is now necessary to redesign and optimize the surface until we have reached 0.25 or a better cd. This also has an effect on the roll bar, which should have been derived from the exhibit shown at the Geneva Motor Show. Shape and size will change minimally in the foreseeable future, which will probably hardly be noticeable to the eye, but would exclude the present body for purposeful preliminary tests.
Overall, we ourselves are dissatisfied, especially with the resulting delay of 8 weeks for all work. In order to avoid further delays, external development partners were commissioned, whose control initially means more time, but which will pay off in higher development speed and quality in succession. A next blog entry reports about the contribution of the development partners and the progress of the cd-value.
Update from 15/11/2019
After a first revision of the bodywork surface, a newer calculation has already achieved a cd - value of less than 0.27.
We are now quite sure to reduce the value noticeably in further loops.