Log transducer probs?

[Bryan1]

The log on my sailing boat only works when going backwards! I have checked the paddle wheel when the boat is out of the water and I get a reading both backwards and forwards. The paddle wheel when checked has always been free moving. The only explanation I can come up with is that some of the magnets are no longer working. Has anybody got an answer?

Regards Bryan

 

[JonJon]

has it ever worked forwards? Is there an obstruction on the hull in front of it?

 

[philip_stevens]

If you are getting a reading in one direction, it shows that the magnets are still there.

It may be that the transducer has to be fitted in a correct way. Is there an arrow or other mark on the top of the transducer inside the boat??

The transducer for my Navman log has to be fitted with the arrow pointing forward, as the paddles are made to "catch" the flow in one direction.

Check to see if yours has an arrow or other mark to show correct orientation.

 

[Bryan1]

Yes the log has worked fine and it is correctly positioned. Perhaps its the transducer that is at fault?

 

[tim3057]

So just turn it round then. Unless you sail backwards a lot. /forums/images/graemlins/smile.gif

 

[pampas]

Your impellor is fitted purely by chance in an area of a pocket of still water, when going stern the prop wash disturbs this hence the reading, had a similular problem on a Snapdragon, where the previouse owner had fitted the log in an easy to get at position. cure i am afraid to say is to move the los if possible, further down and forwd.

 

[philip_stevens]

As I said, if it works in one direction, it will (or should) work in the opposite direction. All there is, are either 2 or 4 magnets, one at the end of each paddle, and they operate (probably) a Hall Effect module inside the transducer unit. It just counts the clicks against time.

Look for an arrow mark (or "forward" legend) and/or check if the paddles have been fitted in in the correct orientation - to "catch" water flow.

 

[Bryan1]

Thanks for the above suggestions, will try again next weekend.

Regards Bryan .

 

[hightech]

Have a close look at the paddlewheel itself, sometimes they are shaped or angled. If so then the "scoop" effect shoud be forward. This can happen if the paddlewheel has been removed to clean or replace.

While you are there, double check the amount of play you have, both sideways and also twist, sometimes a badly worn bearing or pin can cause non rotation. If in doubt, buy a replacement paddlwheel kit.

Hightech

 

[dmayes]

As Pampas said, your impeller is probably in an eddy area or an area of dead water on your hull. You could try rotating the paddle wheel off centre to get a reading. I had one fitted on a Hardy Pilot that would read 20% slow when facing directly ahead and had to be turned off centre as it was in the disturbed water behing the keel. The real solution is to move it somewhere where it will be in a good laminar flow. Or just sail backwards.