Mast Trimming Help !

[bob perry]

PLEASE!

[HappySeagull]

sorry.If my verbosic peeves are choking your email inbox,you can go to UserCP and click "Unsuscribe".But first,you must copy the CHS'WestCoast Tide and Current tables out longhand or no sailing for you!

[cal40john]

Originally Posted by bewitched

Juan,

Assumuing every thing else is equal (mast in straight, foils not asymetric or misaligned, weight distributed evenly in the boat, waves the same on each tack etc, etc), this is your problem.

The sail trim shouldn't necessarily be the same on each tack just because the true wind remains constant. You must trim to apparent wind and this may vary from tack to tack if there is current present.

I hope I can explain how apparent wind may change - picture is probably best. Take the example of the port tacking boat in the picture below.

The True Wind Speed (TWS) is 10 kts. TWS is the wind speed the boat would feel if it was anchored. So it could be called 'Wind Speed over Ground", but it isn't.

The boat sails through the water at 6kts, but the water itself is moving because there is current (relative to the ground). So the current could be called "Current over the Ground", but it isn't.

The current effects how fast the boat moves relative to ground (and so relative to the wind as TWS is also referenced to the ground). This could be called "Speed over the Ground". Hey, it is - SOG!!

So, your Apparent Wind Speed (AWS) is the sum of the TWS plus the effect of the SOG and it's true angle to the wind (TWA). for SOG=5kts and TWA=45 degrees, this is 2.5kts.

So the AWS for the Port tacking boat is 10+2.5 = 12.5kts.

Now take a look at the starboard tacking boat in the second picture. Its SOG is not being slowed by the current, but increased. Therefore it's AWS has been increased.

So, if you have the perfect trim on one tack and then use the same trim on the other, you may indeed feel a difference in the helm as you will be either over, or under trimmed.


Which is all a very long winded way of saying - If there's too much weather helm, and the boat is set up OK, then it's the trim that's the problem.

Of course the trimmers will say it's the helm that is pointing too low ; )

The flaw with your diagram is that you are constraining your tack angles to the true wind. How you are getting AWS is wrong. Also I'm not sure if you're approximating SOG or if that's somehow wrong as well.

You are right that the AWS is going to be different if you look at your GPS and carefully steer to make a track over the bottom at 45 degrees to the true wind. The port tack diagram shows that you have to steer 13.6 degrees below the 45 degree track and your speed over ground is 4.4 knots to achieve the 45 degree track angle. AWS is the vector sum of all the winds, the true wind, the wind created by the current moving the boat and the wind created by the boat sailing. The wind vectors created by the current and sailing the boat are equal and opposite of the vector of the motions. The AWS is 13.5 knots, and the AWA is 45 degrees on your port tack example.

The starboard tack diagram shows you steer 13.6 degrees above the 45 degree track travelling at 7.2 knots over the bottom to achieve the track. The AWS is 15.9 knots and the AWA is 14 degrees. Note that you are sailing at an impossibly high AWA for most boats, so your attempt to sail at 45 degrees off of the true wind would fail. So yes you have different wind speeds and you are sailing at different angles to the wind, you will see different weather helm and most likely different speeds through the water.

OK, who the heck steers their boat 45 degrees off of where they think the true wind is on each tack? The only way you can determine true wind and actual current is by either GPS giving you SOG, and track over bottom, or by two fixes to get the same information. Without references to the earth (GPS, fixes) all the rest of your instruments are relative to your boat.

Stop the boat in the water. The wind speed and direction you feel on the boat is the sum of the true wind and current. The orange lines on the true wind and current add up to the green on the right. So you sitting on your boat out of sight of land with no GPS will see 10.2 knots of wind out of 349 degrees, (assuming true wind is out of the north in this example, an 11 degree shift.) Without a land based reference you have no knowledge of the 2 knot current or that the wind is 10 knots out of the north. Now start the boat moving at 6 knots on a course of 59 degrees (14 degrees lower than the 45 dgree track you wanted) and you form the third orange arrow pointing in the opposite direction of your motion. The wind that you saw with the boat not moving (relative to the water) plus the wind created by the boat sailing gives you the left green vector, the AWS and AWA. Again without a land based measurement you don't know about the 2 knot current or that your actual track over bottom is 45 degrees with a SOG of 4.4 knots.
　
What you want to do is have the same apparent wind speed and angle on each tack. The boat should have the same speed through the water under those conditions. In this example you would be tacking through 140 degrees. Note now on starboard tack you're now travelling at 7.9 knots over the bottom with a track of 277 degrees.
　

[HappySeagull]

mmm.I began to draw diagrams too but it's the waves that complicate it...and I adamantly disagree that you can't tell you're in a current.I mean,you rig the boat,leave the hrbr and man,it's choppy out here!More than "expected".
Ideally,I suppose you shouldn't be able to.But practically,not so.I wonder if this is because a wind driven chop has a proportion of the wave "sheltered" behind each crest while a current is driving the whole mass of water,troughs and all.
Compared to a currentless example,a current contrary to True wind builds up a short,steep chop-a bit similar to a swell hitting the beach.A current WITH the wind smooths and lengthens chop...a current at a angled-vector to true wind is further complicated.But whichever,I maintain that 2 knots of current,is pretty obvious,in the dark,without a gps,etc.

[cal40john]

Originally Posted by HappySeagull

mmm.I began to draw diagrams too but it's the waves that complicate it...and I adamantly disagree that you can't tell you're in a current.I mean,you rig the boat,leave the hrbr and man,it's choppy out here!More than "expected".
Ideally,I suppose you shouldn't be able to.But practically,not so.I wonder if this is because a wind driven chop has a proportion of the wave "sheltered" behind each crest while a current is driving the whole mass of water,troughs and all.
Compared to a currentless example,a current contrary to True wind builds up a short,steep chop-a bit similar to a swell hitting the beach.A current WITH the wind smooths and lengthens chop...a current at a angled-vector to true wind is further complicated.But whichever,I maintain that 2 knots of current,is pretty obvious,in the dark,without a gps,etc.

Ok, fine you can tell that there is some current and in some direction due to wave action, that has nothing to do with the original assertion that sailing in current gives you different helm on different tacks.

John

[boatman61]

Speaking as a 'Hacker'... I'd figure it was down to my trim if it only happened one way... so I'd tweak till I figured the right set up...
If it was structual.. twisted keel whatever it seems logical to me if it had weather helm one way she'd understeer the other if as I read apparent wind/current are equal on both tacks...

[HappySeagull]

Originally Posted by cal40john

Ok, fine you can tell that there is some current and in some direction due to wave action, that has nothing to do with the original assertion that sailing in current gives you different helm on different tacks.

John

well,it's not exactly my assertion that Juan's problem is the current.My assertion (above )relates to whether or not a current is detectable without the shore and satellites.It's a digression,but important.
Repeating myself,quickly,from earlier posts;sailing in waves where direction doesn't match the wind ,the waves and apparent wind are current generated and given apparent wind+waves are related to weather helm,tack versus tack,....then current is a reason.

It never was my first guess as to Juan's troubles and his short description.I said it's a possibility,albeit way down the list from a bent tiller or rudder or mast or badly-moulded hull.But-he asked if it was possible.

[HappySeagull]

Originally Posted by boatman61

Speaking as a 'Hacker'... I'd figure it was down to my trim if it only happened one way... so I'd tweak till I figured the right set up...
If it was structual.. twisted keel whatever it seems logical to me if it had weather helm one way she'd understeer the other if as I read apparent wind/current are equal on both tacks...

Hmm,he said"same wind,same trim". But not the direction relative to the current-wind could be from the shore...But yes,the boat sure comes to mind first-especially a brand new one new to him,too.I hope there's a warranty....

"No,No,Juan..the rudder stock LOOKS bent,but it's an illusion-see how shiny the hull is?and don't worry the mast sits a little to port-that's a feature of the Deluxe Package..it's fooling you is all-everyone in the River Parana knows that the tacks are different..."

[bewitched]

Happy seagull - absolutely you can tell if you are sailing in current, but I've never felt current on the rudder when sailing - apart from eddies, upcurrent on a shelf & the like, but in steady even tide / current - never.

CAL40John - Sorry, you lost me, but if it helps I assumed 6kts boat speed as a ball park for a 25ft boat on the wind. Beating at 45deg to the true wind again was a ballpark assumption - most boats will do something around this i.e. tack through 90deg).

[Pete7]

Originally Posted by tgzzzz

This is a tough read. Think I'll go back to easier threads like which is the best anchor, or cruising the Caribbe on a dollar a day.

My thoughts too

Since the boat the OP is sailing is new, it just might be worth checking the mast is upright as suggested with a halyard moving it to various locations on each side to see they are equal. Borrow a rig tension gauge to check the standing rigging is equal and next time the boat is out of the water see if the tiller and rudder are alined. Our tiller is slightly off but since we use a wheel as well its not important. My thoughts are since its a new boat they may have rushed the installation of the mast.

Sailing on a river with 2.5 knots must be interesting if the wind drops. At least with a tide you know you can get home even if you have to wait 6 hours.

Pete

[savoir]

. . . . but . . . . but . . . . but what if the bar shuts in 5 hours ?

[HappySeagull]

Originally Posted by bewitched

Happy seagull - absolutely you can tell if you are sailing in current, but I've never felt current on the rudder when sailing - apart from eddies, upcurrent on a shelf & the like, but in steady even tide / current - never.

...etc.

Of course not!(barring powerful swirls etc that we've got here,in BC)
Of COURSE NOT!
I'm not saying current affects directly twisting the rudder independently of the boat!!!!!.

Look,A very simple example:I can sail through a tidal pass hereabouts WITHOUT any true wind.I tack backnforth in just the wind the CURRENT alone is causing.My boat actually has weather helm in this situation.She'll round up if I release the tiller.I REPEAT there is no wind caused by weather.It's a flat calm past the pass.Now,did the current cause weather helm?It caused apparent wind and that gave weather helm.See?
Now,as to DIFFERING weather helm,each tack,you'll have to reread....

PS:This is a simplified example...the actual case is wee bit more exciting.If someone is going to say"Why tack through the pass-why not just drift?"-well,simply,you must have CONTROL or you can lose the boat...

[bewitched]

Heh heh heh - I think this thread has got so confusing that were actually debating in agreement.

A current has an effect on AWS.
If the current is moving toward the wind, the AWS increases.
If the current moving away from the wind, the AWS decreases.

So if you don't trim for the AWS (which may be different on each tack) you may feel an increase (or decrease) in weather helm.

So yes the current has caused the difference, and I guess it's just semantics, but you don't trim for current, you trim to the apparent wind.

Which is what I was trying to say back in post 30 - but I don't think with much success

peace

[savoir]

Originally Posted by HappySeagull

Of course not!(barring powerful swirls etc that we've got here,in BC)
Of COURSE NOT!
I'm not saying current affects directly twisting the rudder independently of the boat!!!!!.

Look,A very simple example:I can sail through a tidal pass hereabouts WITHOUT any true wind.I tack backnforth in just the wind the CURRENT alone is causing.My boat actually has weather helm in this situation.She'll round up if I release the tiller.I REPEAT there is no wind caused by weather.It's a flat calm past the pass.Now,did the current cause weather helm?It caused apparent wind and that gave weather helm.See?
Now,as to DIFFERING weather helm,each tack,you'll have to reread....

PS:This is a simplified example...the actual case is wee bit more exciting.If someone is going to say"Why tack through the pass-why not just drift?"-well,simply,you must have CONTROL or you can lose the boat...

Not at all, unless you can locate a place with current on the stern pushing in different direction to current on the bow. I have never sailed in such a place. In the real world the current will push equally on all parts of the hull to which it has access.

You continue to confuse increased pointing due to current and weather helm. They are not the same. Increased pointing due to current is undetectable to anyone on the affected boat who does not have access to a fixed reference point.

[HappySeagull]

Originally Posted by bewitched

Heh heh heh - I think this thread has got so confusing that were actually debating in agreement.

A current has an effect on AWS.
If the current is moving toward the wind, the AWS increases.
If the current moving away from the wind, the AWS decreases.

So if you don't trim for the AWS (which may be different on each tack) you may feel an increase (or decrease) in weather helm.

So yes the current has caused the difference, and I guess it's just semantics, but you don't trim for current, you trim to the apparent wind.

Which is what I was trying to say back in post 30 - but I don't think with much success

peace

oh,sorry-but ya had me goin'there with yer previous, "Happy seagull - absolutely you can tell if you are sailing in current, but I've never felt current on the rudder when sailing - apart from eddies, upcurrent on a shelf & the like, but in steady even tide / current - never."
sorry,eh.