Friday, November 11, 2011

Measuring lateral speed (leeway)

It is possible to measure directly the lateral speed through water of a sailboat making leeway, by using a pulse-to-pulse coherent Doppler profiler. This is the technique used by the Volvo Ocean Race Puma team. In their case, the transducers are installed under the bulb keel.

For a conventional sailboat, a different arrangement can be used.

In the project that I am considering, 2 transducers will be able to measure the component of the speed of the water parallel to the axis of the ultrasonic beam at a distance of 30 cm from the hull.

By knowing the installation and the heel angles, it is then possible to calculate the lateral speed of the boat.

A good introduction to the pulse-to-pulse coherent Doppler technique can be found in these documents:

“Pure coherent Doppler systems – how far can we push it?”  Lohrman and Nylund, 2008.

“Performance of a Single-Beam Pulse-to-Pulse Coherent Doppler Profiler”  Zedel, Hay, Cabrera and Lohrmann, 1996.


  1. Thanks for providing information on measuring lateral speed of sailboat.

  2. Leeway certainly is one of those navigational headaches that encroaches on effective yacht performance management

  3. Have you made any headway on the doppler flow measurement for lateral (and longitudinal) boat speed? This looked very promising and you seem to be one of the first except for some very high-end teams.

    1. I tried to develop my own RF amplifier, but being a Mechanical Engineer, I realized that I was missing the expertise and tools required. I then searched for existing alternatives and found this promising device:
      I got a quote of 475 US$, which is (at least for now) outside my limited development budget. I would really like to pursue this project, but this will require either some unexpected funding, or finding help from an electronics guru able to design and build some open-source custom RF electronics.

    2. I know what you mean. Would this help:
      Someone designed a low-cost US driver for under $100

    3. Thanks for the link. I read the paper, and it was indeed promising. I contacted the authors to get the PCB file, but without success (probably related to the fact that one of the author has been awarded a patent since the publication). I may have reproduced their prototype given the PCB file, but I don't want to redesign it from scratch.