[C320-list] Calibrating/Aligning Raymarine ST50 Windvane

[Warren Updike]

If you have a mechanical wind vane on your mast top, that is what I use as a guide in aligning the instrument (until this big-ass osprey sat on and broke it.) Simply steer into the wind until the vane is dead-on the bow, then in "Cal" mode, use the rocker to move the needle left or right until it aligns with the vane. Without the wind vane, steer into the wind using a ribbon or some light material tied to a shroud or stay until wind is on the nose, then adjust the instrument. It doesn't need to be 100% unless you are racing, in which case you need a faster boat anyway.

Warren and Pattie Updike
1994 C320 "Warr de Mar" #62
Middle River, MD (Chesapeake Bay)


-----Original Message-----
From: Dave Hupe [mailto:hoopdtwo at yahoo.com] 
Sent: Thursday, July 26, 2018 5:23 PM
To: c320-list at lists.catalina320.com
Subject: [C320-list] Calibrating/Aligning Raymarine ST50 Windvane

I recently had my masthead wind instruments unit rebuilt (by Dan Gerhardt in Durango, CO), mainly because my wind anemometer cups did not spin at all last year when I bought the boat.  I elected to also have the wind direction part rebuilt while the unit was off the boat.  
I just reinstalled the masthead unit.  The anemometer cups stop in light wind and/or are not spinning as freely/fast as I think they should (especially comparing them to the same setup on the 320 in the slip next to mine).  I'm hoping the cups will spin more freely after they have a chance to continue to spin in the wind (new bearings loosen up?) .  
The wind direction part is working (it did before, but hung up occasionally), but now my wind instrument panel shows the wind is about 180 degrees off (when the wind is blowing at the bow, the indicator suggests it is instead blowing toward the stern).
I looked a my manual and it says for calibration to first "linearise" the direction transducer by powering up the unit and driving the boat in 2 complete circles. Then it talks about pushing down the left-hand instrument panel CAL button for 2 seconds until "CO" is displayed, then pushing the rocker button (is this the right button?) as many times as needed to move the pointer to the correct wind angle.  
I understand steering the boat in circles, but the second part of the procedure confuses me (when and what is the correct wind angle?).  The only way this seems straightforward to me is to physically have someone on the mast hold the windvane still as if it were blowing directly at the bow, then push the CAL button to appropriately correct the pointer.  However, this doesn't seem like what the manual directions indicate you need to do. 
Has anyone been through this with old instruments on an early (1994, etc.) 320?  Can you explain this better for me?
Dave Hupe
1994 Cat 320 "Mayan Sun" (#32)
Holland, MI