We got a question from Bjørn Johansen about his Coxmate HC impeller

 
 I have a problem with sudden changes in the response of the impeller.  In one case I observed a change of about 6 % compared with GPS (no wind, and very little current). Is this a known problem?

And so we consulted the manufacturer, Peter Hodson and this is his reply.

I have actually seen this happen on my scull – so I believe you! It is very strange, and the only explanation I could come up with was there is some transitional change in flow around impeller. I suspect it might be related to the alignment of impeller, but I have never been able to make it happen.

I have since bought a new scull and impeller is mounted nearer to the bow and I have never seen problem again. I was talking to a cox of an eight and he observed similar effect with an NK impeller on an eight when the impeller was mounted ~12 metres from bow.

I don't have a certain fix for problem, but I strongly suspect it is relate to position or alignment. My suggestion is to move impeller further forward – Mine is mounted under seat. If my theory is right, it may only require a small shift to keep it out of the transitional zone.

Apologies not to be more helpful, and please forward any details which might help understand causes better.

Other articles about Coxmate HC

• Video Tutorials to set up HC display
• Using Coxmate HC on an NK wiring loom 
• HC Display specification options
  
• Calibrate HC using GPS – hire one
• HC brochure
• Coxmate FAQ