[C320-list] Speed log problems

[Warren Updike]

Graeme, why do you need it?  Racing maybe?  I gave up on mine: a pain to
insert and remove, and would readily be clogged with critters.  Now, I rely
solely on SOG from GPS.  Yes, I don't get true wind; but, then I've never
had it (different story.)  If you really want/need true wind, for about $100
you can get a device that will use SOG and output STW on Sea Talk and forget
the headache with the transducer.  If interested, let me know and I'll dig
up the product info.

Warren & Pattie Updike
1994 C320 #62 "Warr De Mar"

-----Original Message-----
From: Graeme Clark [mailto:cg at skyflyer.co.uk] 
Sent: Thursday, July 04, 2013 5:37 AM
To: c320-list at lists.catalina320.com
Subject: [C320-list] Speed log problems

Our original fitted instrumentation (#303, 1996) was ray marine ST50+
Tridata and two years ago we fitted a replacement Ray transducer
paddlewheel. This is located directly beneath the two smaller drawers in the
forepeak cabin, pretty much on the centreline, with the depth transducer
next to it.

I am having a real problem calibrating the instrument. earlier in the year
we set a calibration factor of around 0.80 and now it has had to be change
to 2.00 to get anywhere near a sensible reading.

I regularly withdraw the transducer and clean it for any fouling and other
marine life and even pushed out the axle pin, to enable a really thorough
cleaning and gave everything a squirt of silicone spray lubricant before
reassembly, but still the calibration changes

I can only come up with two theories: (1) the instrument or transducer is
faulty or (2) other fouling and marine growth on the hull in front of the
transducer is affecting the water flow over the paddle wheel as the season
progresses.

I'd be grateful for any other suggestions and also for an efficient way to
trouble shoot without simply replacing every single item piece by piece!  I
guess a haul out and scrub would initially show whether the hull fouling was
a factor, but (where I am) that is the bets part of $500. A new transducer
is about the same and a replacement  instrument (ST60+ is nearest available
type that is compatible) would be $3-400 I think. If I end up doing all
three that is and expensive trouble shooting exercise!

Graeme
(Simia, #303, Falmouth, England)