A knot faster on port tack?

[peasea]

I have checked the lee shrouds and they seem to have equal amounts of slack on either tack. Any other ideas please? The log rotator is on the centreline of the hull.

<hr width=100% size=1>PC

 

[Jim44]

Does it matter??

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[boatless]

1 Is the mast upright? Check with a steel tape from the main halyard or topping lift pulled bar tight to the mast crane, measure to either side, a stanchion or chainplate.

2 Is the boat trimmed level? Look at it from behind.

3 Can you be certain that the log transducer is absolutely aligned with the longitudinal centreline?

If yes, yes, yes, then you may have an assymetric hull, which does happen. But (3) is the most likely cause.

Lastly, wind shear can cause this. The higher the datum, the more the wind points towards low pressure, so on one tack you have a shear which suits the twist of a sail, and on the other tack the opposite is true.

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[jonlaw]

Would an offset prop make a difference ?


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[Peppermint]

What about speed over the ground by GPS. Does that vary by a knot tack to tack.

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[extravert]

Is your means of measuring wind direction centralised? Are you sailing equally close to the wind on both tacks? This one caught me out once.

<hr width=100% size=1>One day, I want to be a real sailor. In the mean time I'll just keep tri-ing.

 

[dickh]

Is your keel vertical - on my boat it's about 2/3º off centre!! and I have noticed the same thing - I point higher on one tack than the other - but cannot remember which...

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Romeo]

How are you measuring speed? Is there a log impellor on your starboard sice by any chance?

I sail better on the starboard tack, which I put down to the bowsprite being offset to starboard.

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[squidge]

A knot is a lot ! What boat have you got?
Assymetric hull The builder should be shot !
Your hobbie is "saling" not that it matters a jott.
I hope that you find the missing knot for your yacht.
/forums/images/icons/smile.gif

Insanity is just a state of mind

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[snowleopard]

have you tried measuring SOG from the GPS to check whether it is a true speed difference or a log error?

i would suspect that the different flow over the paddlewheel depending on the direction of your leeway is affecting the log in different ways. it's easy to have the axis of the paddlewheel off-line by a few degrees.

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[Aardee]

I used to sail on a Beneteau 390 which definitely preferred port tack. When the owner came to sell it we found the keel was decidedly off-centre!!

<hr width=100% size=1>"I am a bear of very little brain and long words bother me" - A A Milne.

 

[howardclark]

How about weed on the hull - I had a similar problem - she'd been one way around on a trot for several months - more growth on one side than the other, really told when she heeled

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[mirabriani]

When I sailed a friend's Limbo I found the same.The owner blamed my helming. Later I found the mast was not true. It had a curve and was not centred.
Briani

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[A_7]

If you have a furling headsail and it is is partly furled it will be because of the airflow round the forestay.

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[mirabriani]

In addition to all of the above. If during sailing in, say, a river, one tack is almost in line with the current and the other tack is substantially across the current. Then surely this will result in one tack being faster than the other?
Is my thinking correct?
Briani

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[boatless]

Mirabriani, quite right as far as ground speed is concerned, water speed remains unaffected though.

<hr width=100% size=1>my opinion is complete rubbish, probably.

 

[VicS]

There are two possible reasons. I am surprised that nobody has so far metioned either.

Firstly in the nothern hemisphere when the wind gusts it tends to back slightly so when you are on a port tack the wind in the gusts is a little more free and the boat speed increases. On the starboard tack the boat becomes slightly too close to the wind and the speed drops.

Secondly if the helmsman is right handed he will be steering the boat with his right hand and his overall helming ability will be just that little bit better than it is when using his left hand while on a starboard tack.

<hr width=100% size=1><font color=purple>Ne te confundant illegitimi.</font color=purple>

 

[alahol2]

If one tack in the current is up (or down) wind and the other is across the wind then the apparent wind speed will be different on different tacks. I frequently notice this in the Solent. Obviously, the lighter the wind, the bigger the effect.

<hr width=100% size=1>I really would rather be sailing...