For a demonstration of eddy currents, I used a cylindrical magnet slowly running down an aluminium U-profile.
In order to show the magnet's speed without the eddy current effect in a conductive rail, I needed the same profile made of non-conductive material.
Unfortunately, the maximum length my 3D-printer can produce is about 20 cm.
Therefore I designed these connectable U-profile-rails. Just slide the connectors (verbinder) over both L-shaped ends of two rails (schiene).
The "endkappe" can be used to terminate the outer ends of the completed long rail in order to prevent the magnet from leaving the rail.
(The foto shows the short test version!)
Have fun!