It's a long time since the last posting, so here is an update:
To find out, how the numerous 3d-sketches will look in reality, I've scrapped the old ugly rear box of the steel tandem and build a new tail with a more sophisticated shape and enclosed rear wheel wells.
To reduce the increase in weight, the drivers seats are now an integral part of the tail box.
With this much more massive body, the weight is just 4kg/8pounds higher than before.
For a racing velomobile this would be a catastrophe, but for a cargo-tandem like this it's acceptable.
I have used 4mm birch plywood, except the sides, which are pine (left over from an abandoned project)
structurally integrated bench
internal partition with wheel wells
top panel is on
A look in the trunk, childs backrest not in place
My first test drivers
the attached retro rear lights
Although it looks really wide, it's just 119cm/3 ft, 10inches in width.
The entire box is attached to the frame via 4 bolts and can be easily removed if maintenance or repair is necessary.
There is not enough space to make any repair on the wheels or even to adjust the derailleur or brakes, as long they are inside the wells, so easy removing is essential.
We have driven 100km since the modification and are very happy with the new tail.
It provides a lot of space behind the backseat (ca. 100 litres/ 4 cu.ft.), our childs are much more protected from the airstream than before, it's rock solid and looks way better, so the pluses outweights the few drawbacks in our opinion.
Next building projects are a front hood and a light soft top to make it a fully faired retro pedal car.
I had made a paper model two years ago, which I had given a pointy nose, instead of the more blunt front of the CAD designs:
Pic from previous post for comparison
Which looks better in Your opinion ???