Is there a trick to removing the paddle wheel in a Raymarine log

tudorsailor

tudorsailor

Well-Known Member
Joined
12 Jun 2005
Messages
2,756
Location
London
zebahdy.blogspot.co.uk
The speed log constantly underreads. I have tried recalibrating

I wonder if the wheel is not spinning as freely as it might. I would like to clean the housing and the pin. There is a pin that goes through from one side to the other. It is simply by an interference fit, meaning I can knock it out?
I see that there is a kit with a replacement wheel. I am not so sure replacing it will help so I would like to try cleaning first!

Thanks

Tudordsailor
 
tudorsailor said:
The speed log constantly underreads. I have tried recalibrating

I wonder if the wheel is not spinning as freely as it might. I would like to clean the housing and the pin. There is a pin that goes through from one side to the other. It is simply by an interference fit, meaning I can knock it out?
I see that there is a kit with a replacement wheel. I am not so sure replacing it will help so I would like to try cleaning first!

Thanks

Tudordsailor
Click to expand...
raymarine have a very good q&a page if you search + i phoned yesterday for advice, all freely given & most helpful
 
prv said:
Mine is. I have a piece of stainless wire the same diameter (or very slightly smaller) to push it through with.

Pete
Click to expand...

+1

Like the OPs mine under reads, ST60. However, I have cleaned mine quite a few times, +10 years old, cleaned the housing and checked for smoothness. I even lubricated the pin very slightly which might not have been a good idea. I am not sure but IIRC when I blew on the impeller it spun very, very freely. Now I think it may be slightly stiffer, more a perception than anything obvious.
 
Push out the stainless axle with a suitable size drift. Only little force required. Make sure you remember the orientation (cups point with opening forward on the bottom if you didn't - arrow on the housing indicates forward direction).

Calibration is either by manually adjusting the factor, or if you're certain there is no current running (e.g. boat is in locked in basin), you can calibrate it to SOG.

After calibrating, it should read more or less correctly for a while. Fouling will affect it, as can air bubbles and also if it is fitted in a bad location where it doesn't have a clear flow of water or isn't deep enough.
 
Which log is it?

They used to do a kit for an ST50/ST60 which was a new paddlewheel and a few other bits and bobs, and was knocked out quite easily. May well be worth it if it is not performing as it should.
 
As far as I recall, its easy to tap out the spindle and remove the impeller. I use a small electrical Phillips screwdriver. As you probably know, the transducer can easily be removed from the housing even when afloat as there's a flap valve which limits water ingress. I found my ST60 impeller didn't need cleaning more than once a year but in some areas it may do.
I have found that NASA impellers don't respond to cleaning and need a replacement service kit annually. (Fortunately they are cheap)
 
From the Owners Guide for the Airmar Tridata transducer (which i think the ST60 uses).

Operation & Maintenance
Anti-fouling Paint
Surfaces exposed to salt water must be coated with anti-fouling paint. Use water-based anti-fouling paint only. Never use ketone- based paint since ketones can attack many plastics possibly damaging the transducer. Reapply paint every 6 months or at the beginning of each boating season.
B744V/VL—Paint the following surfaces (see Figure 4).
• Exposedareasofthehousingincludingthetransducer’sface
• Boreofthehousingup30mm(1-1/4")
• OutsidewallofthepaddlewheelinsertbelowthelowerO-ring
• Paddlewheelcavity
• Paddlewheel
• BlankingplugbelowthelowerO-ringincludingtheexposedend

Cleaning the Sensor
Aquatic growth can accumulate rapidly on the sensor’s surface, reducing its performance within weeks. Clean the surface with mild household detergent and a Scotch-Brite® scour pad.
B744V/VL—If fouling on the insert is severe, push out the paddlewheel shaft using a spare shaft or a 4-D finish nail with a flattened point. Then lightly wet sand the paddlewheel with fine grade wet/dry paper.'​

I've no idea what a 4-D finish nail is, but the point (geddit?) is it can be pushed out with an appropriate drift, and it doesn't mention it only coming out in one direction (perhaps other models of transducers used by Raymarine are different?).

IIRC the service kit for the Airmar transducer includes a replacement spindle, and suggests using the new spindle as a drift.
 
There is also a Delrin shoe / water guide screwed to the hull which helps the paddle wheel read reliably. This can come off (or be taken off and lost by the yard when applying Coppercoat - grr). Since I lost this bit the log seems to read less and be more variable. Note to self - get another.
 
The ST60 can only be calibrated accurately at one speed - so try to calibrate it somewhere a few knots below hull speed. But above and below that speed, accuracy is not good.

The newer instruments can be calibrated at multiple points on the speed curve, so the reading is much more accurate at low and high speeds.
 
Don't get me wrong, I think NASA stuff is very good value for money but I just never managed to clean and polish the impeller/shaft to a high enough standard to restore performance. I only used WD-40 though and didn't try metal polish. Perhaps I'm being unfair and should shut up!
LittleSister said:
That's not my experience. I've used them on and off for years, and don't recall ever having a service kit.
Click to expand...
 
I haven't needed to dismantle my ST60 impeller in twenty years and it still works pretty well. I find that cleaning it when wet is OK for the major gunk and creepy-crawlies but is less effective for the bearing. I presume that the space fills with slime and spinning the rotor doesn't move it. More effective is to do it when bone dry, as at the start of the season, when spinning the rotor and jiggling it sideways appears to restore the performance.
 
johnalison said:
I haven't found it necessary and only use some silicone grease. A/F won't stop friction between the rotor and spindle, but maybe it depends on the brand of log.
Click to expand...

The interface between rotor and spindle is water-lubricated, it doesn't need any grease - indeed that might slow it down. Antifouling the rotor and the housing in which it rotates helps stop stuff growing in it or on it, and makes cleaning it much less frequent.
 
pvb said:
The interface between rotor and spindle is water-lubricated, it doesn't need any grease - indeed that might slow it down. Antifouling the rotor and the housing in which it rotates helps stop stuff growing in it or on it, and makes cleaning it much less frequent.
Click to expand...
Perhaps I didn't make myself clear. I didn't mean to suggest that I greased the joint itself, even if this were possible. Just a smear over the parts you would antifoul. If nothing else, it is easy enough to redo during the season.
 
Ric said:
The ST60 can only be calibrated accurately at one speed - so try to calibrate it somewhere a few knots below hull speed. But above and below that speed, accuracy is not good.

The newer instruments can be calibrated at multiple points on the speed curve, so the reading is much more accurate at low and high speeds.
Click to expand...

My experience exactly. Heel, water speed and which tack all induce large errors into log reading before you start to worry about paddle wheel fouling.
 
You must log in or register to reply here.

Share this page

Top