Raymarine ST60 Log issues

G

gav101

New Member
Joined
10 Feb 2005
Messages
4
Visit site
Hi,

I have a Raymarine st60 Tridata instrument with speed log fttid to my Jeanneau SunFast 26. The speed intrument is the standard impeller type. I seem to obtain different speed readings dependant on my tack. On starboard the reading appears okay, but on port the reading appears to slow down by about 1 to 2 knots. The impellor has recently been changed but this has made no difference. The fitting is in front of the keel, slightly to the starboard line of the centreline of the boat. There is nothing in front of the fitting that could cause a disturbance. I am farily sure that the real boat speed does not change when I tack.
 
How do you know that the reading is 1 - 2 knts out? Could it not be that the boat is slower on one tack than the other.
 
Have you confirmed with GPS that the speed difference isn't real?

If the speed is the same on both tacks, there are two likely possibilities:

As the paddlewheel is to one side of the centre line there may be a disturbance to the water flow on one tack. If that is the case I would expect that the starboard tack reading would be low as the water flow has to cross the centre line before hitting the paddle whereas on port the water is hitting the paddle without first having been disturbed.

The other possibility is that the paddle wheel is not mounted exactly fore & aft. Look for a slight offset towards the port side.
 
Suggest that the speed difference is caused by one of two possibilities (or even both)

Log is not precisely aligned - some require the log to be pointed towards the bow, rather than parrallel.

wind direction is misaligned so that you are pinching on one tack, and sailing freeer on the other.
 
I have not confirmed the speed with GPS but I do race the boat and have not noticed that I am either pinching or sailing slower whilst on port tack. I normally sail to telltales on the jib rather than use the wind indicator.
 
Log reads speed through water not over ground, so tide immaterial in this problem.

Sounds to me like it might be a question of impeller alignment or depth/water density

Some keen boats I've sailed have had two impellers, P & S, with a tilt switch that changes between them depending on which one is downhill.
 
In that case suggest you get another boat to run alongside and confirm whether the problem is the log or not. Suspect the angle may be slightly wrong - if you had somebody else onboard, you could tweak the angle of the log whilst maintaining course and see if that makes any difference. if not, and if another boat shows that your log is accurate, suggest you check that mast is absolutely straight from side to side, and absolutely vertical, and that tension in the stays is equal.
 
[ QUOTE ]
ours frequently flips from Knots to Kph and sometimes miles per hour .especially when using auto pilot haven't found a cure

[/ QUOTE ]

This is a common problem it seems. Mine does it too, also autopilot related. I've never found a cure either.

My autopilot occasionally goes into standby mode as well when it feels like it. It probably just gets tired.

Raymarine software is not all it should be in my opinion.
 
A voltage drop to it, even a brief one such as from a loose connection, may drop the autopilot into standby.

Have come across the same problem with a Raymarine system - tracked it down to a slightly loose connection at the DC board distribution terminal strip for the conductors to the pilot computer.

John
 
You must log in or register to reply here.

Share this page

Top