Stowe Type Log

This is an update on my "walker" type log. http://www.thingiverse.com/thing:740651.
I was fortunate to be able to borrow a Stowe trailing log and so this is a more accurate copy. The main difference is that the fins are now straight. The curved fins on the previous version may have made the calibration speed dependent. A real Stowe log is (I think) 8600 turns per nautical mile, and has only one magnet.
This version has two to make it nearer the Raymarine / Airmar number of pulses per nautical mile.
The centre screw is a 60mm M5, and the sensor is the same as in my previous version. The magnets are 3mm dia by 10mm long and much less fiddly than the previous version, but be sure to test that the magnets are the right way around before pushing them home.
Make sure you seal the connections.. I used hot melt glue.