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Better on one tack than the other upwind


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We are finding the boat a full knot quicker on port than we are on starboard and for sure we have a fairer shape to the main on port with quite the bubble in the luff of the main on Port. 

We tuned the mast using the North Guide and a Loos Gauge when we stepped the mast and I plan to go back to review it now in pursuit of a solution. Looking at the sail it occurred to me that a hook in the middle of the mast might cause this but sighting up the mast one is not obvious. 

Where would you Folks look first for a solution? We are comfortably hitting our polar target on the weaker tack though perhaps not able to point as high as we might like, especially at higher wind speeds where we are managing the traveller to keep the heel in range and the rudder engaged. 

Dan

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Ok, the mast is symmetric - now how about the jib sheeting angles? (Bubble in the luff…) 

BTW, there was a full threat about exactly that just a few weeks ago. Try the search. 

 

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I had read that thread with interest and perhaps I should have added my question to it, but I have excluded virtually all of the elements of it by ignoring the instruments other than speed and steering to the telltales with frequent looks to my windex which is as centred as I can make it. I had also read a fairly long set of responses on a J/99 having similar problems. 

I had focussed on the main and mast as the issue but will try to spend some time on the jib sheeting angles to make sure the jib settings match and the shape looks good. 

Thanks for the feedback, 

 

Dan 

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29 minutes ago, danstanford said:

I had read that thread with interest and perhaps I should have added my question to it, but I have excluded virtually all of the elements of it by ignoring the instruments other than speed and steering to the telltales with frequent looks to my windex which is as centred as I can make it. I had also read a fairly long set of responses on a J/99 having similar problems. 

I had focussed on the main and mast as the issue but will try to spend some time on the jib sheeting angles to make sure the jib settings match and the shape looks good. 

Thanks for the feedback, 

 

Dan 

Measure the jib sheet track to see it if is symmetrical.... for that matter, measure everything, chainplates too, to see if it is actually the same on both sides.

Something is out of whack

FB- Doug

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Check to see if your partners are in the center of the boat.  This can absolutely give you the shits.  You didn't say, but I'm assuming the masthead is in the center?

 

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27 minutes ago, Steam Flyer said:

Measure the jib sheet track to see it if is symmetrical.... for that matter, measure everything, chainplates too, to see if it is actually the same on both sides.

Something is out of whack

FB- Doug

Doug, I had not even considered that the jib tracks might not be symmetrical but I will do some measuring there for sure. As I think about it, should I measure from the bow for fore/aft placement and the outside of the deck for P-S? 

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22 minutes ago, Nettles said:

Check to see if your partners are in the center of the boat.  This can absolutely give you the shits.  You didn't say, but I'm assuming the masthead is in the center?

 

Not having ever owned a keel stepped boat, I am not exactly certain what partners are. My boat is deck stepped with a plate on deck bolted through to a compression post. 

We measured to the rail with the main halyard to try and establish center for the masthead and think it is there but it is difficult to be very precise due to stretch in the halyard as we pulled it down. The North Tuning Guide suggests hanging a bucket on the end of it down the topsides to get it more precise and so I am going to try that. Certainly we are currently within a half inch at most. 

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From your comments about different sail shapes tack to tack I would concentrate on measuring the boat first to see if it is symmetrical. Many are not. Then see if mast is truly vertical in boat - the measurement points you used to center the mast may have been different.

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18 minutes ago, danstanford said:

Not having ever owned a keel stepped boat, I am not exactly certain what partners are. My boat is deck stepped with a plate on deck bolted through to a compression post. 

We measured to the rail with the main halyard to try and establish center for the masthead and think it is there but it is difficult to be very precise due to stretch in the halyard as we pulled it down. The North Tuning Guide suggests hanging a bucket on the end of it down the topsides to get it more precise and so I am going to try that. Certainly we are currently within a half inch at most. 

On my J88, I use a fish scale and a meter stick.   hook the fish scale to the main halyard and pull it down to say 25lbs.  they have a little marker there that you can measure from... then you can reach your port side chain plate bolt at say 25" and 25 Lbs... then measure the starboard with the same halyard pressure.   the bucket works but is unwieldy.   mast head is centered pretty well this way as long as the deck/step/chain plates are also pretty good.

My own port-starboard variance is blamed on the paddlewheel not being on center line.  In a blow, with more heel, it gets worse.   However, I am going to take a look at the keel and stern hung rudder for "centerness" when i get it pulled next.

 

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22 minutes ago, Bobjanander said:

Which speed sensor do you use?

Do use twa as refference?

is it centreline?

Are the electronics well calibrated

 

etc

 

 

Are you basing this off Speed over Ground or Through the Water?  Is your speed sensor on center line if using speed through the water.

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Really only using the speed log and it is not centered in the boat. I hadn't thought the amount it is off center could show this much difference. The TWA instrument is not correctly calibrated and I was not using it but rather using telltales to get to maximum height with some confirmation from the windex. We seemed to be able to point as high but with less speed and a less wide groove one one tack over the other. 

Next time I will see about using GPS to confirm the speed since we have very little current here. 

 

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18 minutes ago, dbcorbin said:

On my J88, I use a fish scale and a meter stick.   hook the fish scale to the main halyard and pull it down to say 25lbs.  they have a little marker there that you can measure from... then you can reach your port side chain plate bolt at say 25" and 25 Lbs... then measure the starboard with the same halyard pressure.   the bucket works but is unwieldy.   mast head is centered pretty well this way as long as the deck/step/chain plates are also pretty good.

My own port-starboard variance is blamed on the paddlewheel not being on center line.  In a blow, with more heel, it gets worse.   However, I am going to take a look at the keel and stern hung rudder for "centerness" when i get it pulled next.

 

Not being much of a fisherman I don't have a scale but this is a genius idea and I will get one! 

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3 hours ago, danstanford said:

Doug, I had not even considered that the jib tracks might not be symmetrical but I will do some measuring there for sure. As I think about it, should I measure from the bow for fore/aft placement and the outside of the deck for P-S? 

Don’t measure from the outside, measure from centerline. Some boats are not symmetrical side to side. 

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Make sure you are actually seeing this effect on different days.   It's really common with the cold water and warm air over the lakes right now to have a lot of twist in the wind, add a little current and you will have what you describe, without anything being asymmetric.    You can have days where the wind is twisted 30 degrees in the height of the rig, it's usually lightish air and the water is cold so the air is stuck to the water.   

Most lake sailors have had the experience of a main that is flying every leach telltale and yet the top is twisted off to a reach while the boom is on center.  On the other board you'll have vang on and the trav way down.

Also, as pointed out above, use your GPS and compass to study speed from board to board.   That's not to say SOG is the right tool to use, but it's a great reference when you are not confident of the water speed sensor calibration.

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4 hours ago, dbcorbin said:

On my J88, I use a fish scale and a meter stick.   hook the fish scale to the main halyard and pull it down to say 25lbs.  they have a little marker there that you can measure from... then you can reach your port side chain plate bolt at say 25" and 25 Lbs... then measure the starboard with the same halyard pressure.   the bucket works but is unwieldy.   mast head is centered pretty well this way as long as the deck/step/chain plates are also pretty good.

My own port-starboard variance is blamed on the paddlewheel not being on center line.  In a blow, with more heel, it gets worse.   However, I am going to take a look at the keel and stern hung rudder for "centerness" when i get it pulled next.

 

Why bother with the meter stick? Hook the fish scale to the halyard and trim the halyard until the fish scale is at the chainplate with a tension reading in the working range of the scale. Without adjusting the halyard, bring to the other chainplate and see if it's the same tension reading.

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You dont need any fancy fish scale

Tie a heavy weight ( I use a 12kg kettlebell) to a halyard exiting at the hounds - usually the jib halyard but might be a spinnaker halyard if its just above forestay.

Make sure the mast is central in the boat before doing anything else.

Also check speed with a gps not your log and try doing it in flat water with no tide

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6 hours ago, danstanford said:

Really only using the speed log and it is not centered in the boat. I hadn't thought the amount it is off center could show this much difference. The TWA instrument is not correctly calibrated and I was not using it but rather using telltales to get to maximum height with some confirmation from the windex. We seemed to be able to point as high but with less speed and a less wide groove one one tack over the other. 

Next time I will see about using GPS to confirm the speed since we have very little current here. 

 

The paddlewheel being off-center has a big (negative) affect on the entire instrument system. I have seen up to 1kt difference from tack to tack with an off-centerline paddwheel sensor. Set your instruments to GPS speed, then take data on long tacks to confirm what you are seeing isn't simply a speedo issue.

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21 minutes ago, F18 Sailor said:

The paddlewheel being off-center has a big (negative) affect on the entire instrument system. I have seen up to 1kt difference from tack to tack with an off-centerline paddwheel sensor. Set your instruments to GPS speed, then take data on long tacks to confirm what you are seeing isn't simply a speedo issue.

I think that was my comment in the other thread.  The first rule of instruments is they're probably wrong.  The 2nd rule is...

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Just use a gps and check your SOG and COG on both tacks....mark your sheets so that everything is duplicated on each tack. You can also use the Navionics app on your phone. 

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What way is your boat moored?

I am tied up on the Southern side of an East/ west orientated marina leg in Ireland.

The difference in marine growth between the south facing side and the north facing side has to be seen to be believed.

Easily a knot between tack speeds when she is fouled up 

Speed differential not marked when she is clean.

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How about the heel angle. May be your boat carries more weight on one side than the other. May be she is sailing more upright on one tack than the other.

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40 minutes ago, Omer said:

How about the heel angle. May be your boat carries more weight on one side than the other. May be she is sailing more upright on one tack than the other.

I don't have a way yet to measure heel angle but from seat of the pants there wasn't much difference. The biggest reason for me to go down this rabbit hole is the difference in sail shape in the main which indicates something is amiss. 

Dan

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15 minutes ago, danstanford said:

I don't have a way yet to measure heel angle but from seat of the pants there wasn't much difference. The biggest reason for me to go down this rabbit hole is the difference in sail shape in the main which indicates something is amiss. 

Dan

If the mast top is plumb and the sail shape is different, then your lowers are the problem.

Your mast shape when loaded is different between tacks.  If the middle of your mast falls to leeward a bit it will hook your main.  If it stays straight or a few mm to windward it will flatten it.  Does not take much and you will not see it at the dock.

Get the spanners out and tweak the lowers till you get the same shape both sides.

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We sometimes tend to look for a single factor . It is also possible that there is not just one reason but many acting on top of another if you are unlucky enough that they all act negatively in the same direction. If there are four different reasons each causing quarter of a knot difference, you probably would not notice it if the other three was not there. 

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14 minutes ago, random. said:

If the mast top is plumb and the sail shape is different, then your lowers are the problem.

Your mast shape when loaded is different between tacks.  If the middle of your mast falls to leeward a bit it will hook your main.  If it stays straight or a few mm to windward it will flatten it.  Does not take much and you will not see it at the dock.

Get the spanners out and tweak the lowers till you get the same shape both sides.

I probably should have asked the initial question citing this possible solution as it makes sense to me. I don't want to get too far from standard settings but it does make sense to me that if there is a hook in the mast resulting in asymmetry of sail shape I should be adjusting the lowers to bring back evenness on both tacks. 

I will start with a review of shroud tension and centeredness and work from there.  It is difficult to get all the back stay tension off due to its rigging but I know I should be extra careful there to review mast column. 

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1 minute ago, danstanford said:

 

I will start with a review of shroud tension and centeredness and work from there.  

Good place to start, but my point was that everything can checkout, apparently, till it's loaded.   I'd sail it and take a photo up the mast on each tack.

Is it a masthead or fractional rig?

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3 minutes ago, random. said:

Good place to start, but my point was that everything can checkout, apparently, till it's loaded.   I'd sail it and take a photo up the mast on each tack.

Is it a masthead or fractional rig?

Very large fraction, 7/8 or so. 

Great idea about taking a photo, I had even thought about rigging a gopro there to look at how the mast is acting. Due to the way the backstay is rigged, I often think full-on is not enough. 

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10 minutes ago, danstanford said:

Very large fraction, 7/8 or so. 

I'd still put my money on the lowers.  Fractionals can magnify any sag in the middle because 10mm sag to leeward below the hounds can create a 5mm hook to windward above them creating a 15mm total 'out-of-column'.  The uppers act like a pivot.

Add that to to difference on the other tack and you have a serious shape difference between tacks.

 

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Mid, I am going to give the centeredness one more go round before I proclaim it there but it is reasonably close if you are talking about the top of the mast. If you are talking about the mast base I have never really worked on that so I will look with a measuring tape. As for the keel and rudder, they look fine by eye but I have never attempted to measure them. 

Trying to imagine how to measure these accurately....

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19 hours ago, danstanford said:

We are finding the boat a full knot quicker on port than we are on starboard and for sure we have a fairer shape to the main on port with quite the bubble in the luff of the main on Port. 

We tuned the mast using the North Guide and a Loos Gauge when we stepped the mast and I plan to go back to review it now in pursuit of a solution. Looking at the sail it occurred to me that a hook in the middle of the mast might cause this but sighting up the mast one is not obvious. 

Where would you Folks look first for a solution? We are comfortably hitting our polar target on the weaker tack though perhaps not able to point as high as we might like, especially at higher wind speeds where we are managing the traveller to keep the heel in range and the rudder engaged. 

Dan

19 hours ago, danstanford said:

We are finding the boat a full knot quicker on port than we are on starboard and for sure we have a fairer shape to the main on port with quite the bubble in the luff of the main on Port. 

We tuned the mast using the North Guide and a Loos Gauge when we stepped the mast and I plan to go back to review it now in pursuit of a solution. Looking at the sail it occurred to me that a hook in the middle of the mast might cause this but sighting up the mast one is not obvious. 

Where would you Folks look first for a solution? We are comfortably hitting our polar target on the weaker tack though perhaps not able to point as high as we might like, especially at higher wind speeds where we are managing the traveller to keep the heel in range and the rudder engaged. 

Dan

Assuming your mast is in the middle of the boat , your keel is symmetric and weight distribution is equal 

 

First check your speedo for accuracy 

second check your wind instrument for accuracy

third check for wind sheer 

forth record your rudder angle ....tack to tack 

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4 minutes ago, danstanford said:

Trying to imagine how to measure these accurately....

:) , almost all yachts are asymmetrical , however your discrepancy of a whole knot is extreme .

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btw , mast base then tune the rig  , bottom up and measure top down .

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3 minutes ago, slug zitski said:

First check your speedo for accuracy 

second check your wind instrument for accuracy

slug has a couple of valid points also , Saints be praised , :blink:

it's not unusual for the knot meter to have a favored tack , it's guaranteed to be off center , and a slight bias in the anemometer will also throw things .

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1 knot is a huge difference tack to tack.   Make sure the data you have on performance is correct.   Bring a GPS.   Understand current.   Assume that the data from your instruments is WRONG until you prove it otherwise.   

Once you have correct data, if you really have 1 knot difference tack to tack, look at big stuff.  Are your foils symetric?   Is the rudder straight?   Is the keel on straight?   Are both foils on center line.   Then look at the rig.   Is it on center line and straight?

 

 

 

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I experienced this on a Peterson 34. It was the sails trimmed differently tack to tack was our clue. After measuring everything including tracks and mast centering that lead to the conclusion the hull and/or chain plates were the culprits. We finally just kept tuning the rig to one side until the sails trimmed equally tack to tack. The difference was about 5/8ths of an inch difference to the mast head.

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Can’t be said enough. Make sure your on board instruments are accurate first. A lot can throw it off. 
 

the boat I race on has a .3knot difference at 6knots of boat speed between tacks upwind. And the difference gets bigger the faster we go (and smaller the slower) We given up trying to solve it, and just sail it with two sets of polars. 
 

also If you don’t have a hand held gps to get speed, Is there anyone around you with a j99 you can test yourself against? Go pace someone before a race? That would tell you if you are actually slow on one tack. 

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Hi,

as others here I do not trust speedo so much. I had the same problem a while back, and I will pass over the advice they gave me: look for something else than the speedo to measure the assymetry.

Do you see anything different from tack to tack if you look somewhere else than your speedometer? Try to look from different angles. I could tell you where I looked, but I am sure you know better where to look: it is your boat.

Generally, I find that I do too much pronostics (actions), and too little diagnostics (measurements).

 

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18 hours ago, NicoW said:

Hi,

as others here I do not trust speedo so much. I had the same problem a while back, and I will pass over the advice they gave me: look for something else than the speedo to measure the assymetry.

Do you see anything different from tack to tack if you look somewhere else than your speedometer? Try to look from different angles. I could tell you where I looked, but I am sure you know better where to look: it is your boat.

Generally, I find that I do too much pronostics (actions), and too little diagnostics (measurements).

 

Nico, it has been the inability to trim the main properly on port while easy on starboard combined with the speed difference that has prompted the questions.

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On 7/2/2021 at 8:20 PM, slug zitski said:

Assuming your mast is in the middle of the boat , your keel is symmetric and weight distribution is equal 

 

First check your speedo for accuracy 

second check your wind instrument for accuracy

third check for wind sheer 

forth record your rudder angle ....tack to tack 

fifth, learn to spell fourth

 

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This is another one of those "a good coach in a coach boat would probably see the problem in about 15mins"  type problems.

Let's assume the performance difference is real.  And that when trimming both sails, exactly the same way on one tack over the other,  and sailing the boat exactly the same way on both tacks, you get a bubble in the front of the main on one tack and not on the other.  

This means one of two things:

1) the pressure at the front of the main is higher on one tack than the other

2) the angle of attack of the main sail is different on one tack than the other

If it is 1) then the mostly likely causes are:

  • Your jib is not sheeted the same way on both tacks. 
  • The sheeting positions, relative to the main are different on both tacks
  • The position of the main relative to the jib is different on both tacks (that is the mast is moving disproportionately on one tack to the other.)

If it is 2) then the most likely causes are:

  • The main is not sheeted the same way on both tacks
  • The sheeting positions, relative to the mast are different on both tacks
  • The position of the tack and luff of the main is different on both tacks. 
  • The tension on the luff is different between tacks.

The last two points might occur if say the tack is not in the middle of the mast, or say the cunningham pulls the tack to one side.

In lieu of a coach or coach boat.  Mount a go-pro to your spinnaker pole ring looking straight up the mast, then go do a couple of tacks.  Also, take some photos at the gooseneck looking to the top of the mast on each tack.  

Another option is to tie a piece of string to the clew of your main.  Run it to the clew of your jib and mark it.  then tack and repeat.  If it gets longer or shorter then the trim of the main compared to the jib is different.  

Other possibilities are you're pinching on one tack more than the other, or something really wonky with your boat.

On 7/2/2021 at 1:08 AM, danstanford said:

We are comfortably hitting our polar target on the weaker tack though perhaps not able to point as high as we might like, especially at higher wind speeds where we are managing the traveller to keep the heel in range and the rudder engaged. 

Not pointing as high compared to what?  do you hold the lane on what tack but not the other?  If you're hitting your polar then is there a problem?  Are you subconsciously creating a problem?  How much faster than polar are you on the other tack then?  1 knot up?  You recently stepped the mast, was there a problem before you stepped the mast?

My gut feel is a few things:

1) your speedo is reading differently on one tack than the other

2) you're subconciously or unknowingly sheeting sails differently on one tack to the other.  Either because of the way you're sailing the boat or because gear is not in the same position on both tacks.

3) your mid mast is sagging between the hounds on one tack more than the other.  I would have thought it'd have to do that a lot to make such a big difference.  But I could be wrong.

4) some combination of all the above

There are a lot of controls that can affect the way your boat is sailing from one tack to the other, and especially the way alu masts are manufactured (if it's Alu) plenty of reasons why it might be stiffer on one tack than the other.  Without pictures or video, if we as a group happen to stumble on an answer in this way I'll be amazed.  

But IMHO start with " what is the angle of attack of this main on one tack to the other"  and " what might be causing increased pressure on the leeward side for one tack than the other"  or even "is the difference real and measurable outside of the boat" and go from there.  



 

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8 hours ago, Spoonie said:

This is another one of those "a good coach in a coach boat would probably see the problem in about 15mins"  type problems.

Let's assume the performance difference is real.  And that when trimming both sails, exactly the same way on one tack over the other,  and sailing the boat exactly the same way on both tacks, you get a bubble in the front of the main on one tack and not on the other.  

This means one of two things:

1) the pressure at the front of the main is higher on one tack than the other

2) the angle of attack of the main sail is different on one tack than the other

If it is 1) then the mostly likely causes are:

  • Your jib is not sheeted the same way on both tacks. 
  • The sheeting positions, relative to the main are different on both tacks
  • The position of the main relative to the jib is different on both tacks (that is the mast is moving disproportionately on one tack to the other.)

If it is 2) then the most likely causes are:

  • The main is not sheeted the same way on both tacks
  • The sheeting positions, relative to the mast are different on both tacks
  • The position of the tack and luff of the main is different on both tacks. 
  • The tension on the luff is different between tacks.

The last two points might occur if say the tack is not in the middle of the mast, or say the cunningham pulls the tack to one side.

In lieu of a coach or coach boat.  Mount a go-pro to your spinnaker pole ring looking straight up the mast, then go do a couple of tacks.  Also, take some photos at the gooseneck looking to the top of the mast on each tack.  

Another option is to tie a piece of string to the clew of your main.  Run it to the clew of your jib and mark it.  then tack and repeat.  If it gets longer or shorter then the trim of the main compared to the jib is different.  

Other possibilities are you're pinching on one tack more than the other, or something really wonky with your boat.

Not pointing as high compared to what?  do you hold the lane on what tack but not the other?  If you're hitting your polar then is there a problem?  Are you subconsciously creating a problem?  How much faster than polar are you on the other tack then?  1 knot up?  You recently stepped the mast, was there a problem before you stepped the mast?

My gut feel is a few things:

1) your speedo is reading differently on one tack than the other

2) you're subconciously or unknowingly sheeting sails differently on one tack to the other.  Either because of the way you're sailing the boat or because gear is not in the same position on both tacks.

3) your mid mast is sagging between the hounds on one tack more than the other.  I would have thought it'd have to do that a lot to make such a big difference.  But I could be wrong.

4) some combination of all the above

There are a lot of controls that can affect the way your boat is sailing from one tack to the other, and especially the way alu masts are manufactured (if it's Alu) plenty of reasons why it might be stiffer on one tack than the other.  Without pictures or video, if we as a group happen to stumble on an answer in this way I'll be amazed.  

But IMHO start with " what is the angle of attack of this main on one tack to the other"  and " what might be causing increased pressure on the leeward side for one tack than the other"  or even "is the difference real and measurable outside of the boat" and go from there.  



 

What a great piece of writing and loads of things to think about. 

Thanks for your very reasoned response and please know I will spend the time to get through all of these and report back.

Dan

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Is the keel true? (i.e. properly aligned along the centre line of the boat) and is it vertical?

Don't laugh:- I've seen instances when this hasn't been the case.

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Measure EVERYTHING. Invent stuff to measure:

 

Measurement suggestions  I didn’t notice while skimming through the posts:

 

* bow chainplate to jib sheet leads

* side shrouds to jib leads 

* spreaders to deck

 

* spreader sweep

* standing behind boat. Sight over a level held crosswise ..  are the spreaders symmetrical?

* put an long foot lEvel across the deck and see if the chainplates and jib leads are at symmetrical heights below said level

***I am not suggesting below the water keel and rudder measuring because the sail shapes are different. The keel and rudder may be out of whack but that has zero to do with asymmetrical tack to tack sail shapes


*maybe the boat is bending, or an important bulkhead is lifting under load

Maybe you can measure whether the chainplate is riding with respect to the mast and deck and other chainplate?? Maybe put a straight edge across the boat and go sailing. Do the numbers change?

 

* simple at dock measurement :

On many boats with “sick” compression posts or loose bulkheads I can feel the movement at the dock. I reach out and grab the lower shrouds. If the deck goes up and down when I pull them together, we have a problem 

**
cracking or loose keel cross braces ( floors)? If the keel is bending to weather and lifting the entire weather side of the hull or pulling the leeward side down inappropriately the parts above it could be thrown out of whack

* are the deck chocks letting the mast move only one sideways direction? Is the deck soft right next to the hole where the mast goes through?? Maybe it takes more load to push the mast sideways than is noticeable standing at the dock

* maybe you need to measure distances like bow chainplate to jib leads, mast to jib leads, and spreader tip to jib leads out on the water. It might take a couple thousand pounds to deflect whatever is moving. 
 

….. 

Sorry if I am suggesting a lot of time at the boat and sailing.  Perhaps if you drink beer while doing all of the above you will feel better

 

 

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One whole knot!! Are you sure you aren't dragging your outboard along on one tack? 

In all seriousness what kind of boat is it? I would check:

  • Jib tracks from CL
  • Keel alignment 
  • double check mainsheet car is the same distance from CL on both tacks
  • double check the backstay is on the CL (forestay, mast base and Backstay must all be on CL (or at least symmetrical if using runners)

Then it's into the rig setup which isn't always as simple as the guide. 

  • Assume rake is OK (it may not be but isn't a tack to tack issue) 
  • Check chain plates are same distance from Forestay both sides
  • Check spreaders are same length and same angle 
    • Length with a tape measure
    • angle by tying a string between the tips and between the shrouds near the deck - sight up (or down) and make sure lines are parallel 
  • Take all tension off lowers (or D1s and D2s - can't remember what boat type
  • Tension main shrouds 
  • measure if the hounds are in the middle of the boat (fish scale technique above is a good one) 
  • if mast step is not on CL then do some head scratching but ultimately get it on the CL 
  • if spreaders are square and hounds are on CL the mast should be straight sideways 

Next go to your D1's

  • Tighten them evenly so they are a little tighter than the guide (a higher tension makes one turn more sensitive) 
  • Adjust them so that the mast is straight side to side 
  • Now do the same with your D2's (if you have them) 

Now you can adjust shrouds and D's to your tuning guide but make sure you do even turns on port and starboard - small D tension variation side to side can make your main look different tack to tack. The fact you have a bubble at the luff means the main is either to deep or the jib is sheeted closer to CL or firmer in the leech on one tack. 

Failing all this then bend test your mast. It is possible that the wall thickness isn't even on port and starboard which would cause a difference but that's pretty unlikely. 

Also the only real way to know if you are fast is to line up against other boats on both tacks. Who cares what the speed says. That's a whole other problem on instrument calibration. 

Hope that gives you some ideas. I would check the keel alignment as the other factors won't make a knot of difference. 

 

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Reason keel would make a big difference is that if it's 1 degree off the rig will effectively be 2 degrees more open or closed to the wind from one tack to the other. Imagine if you are always footing one degree on one tack and pinching one degree on the other. It's going to be a significant factor. 

Also the jib would effectively be sheeted closer to AWA on one tack than the other even if the deck is symmetrical so this may explain your luffing main on one tack even if the rig is perfectly aligned with the deck. 

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On 7/1/2021 at 5:08 PM, danstanford said:

We are finding the boat a full knot quicker on port than we are on starboard and for sure we have a fairer shape to the main on port with quite the bubble in the luff of the main on Port. 

We tuned the mast using the North Guide and a Loos Gauge when we stepped the mast and I plan to go back to review it now in pursuit of a solution. Looking at the sail it occurred to me that a hook in the middle of the mast might cause this but sighting up the mast one is not obvious. 

Where would you Folks look first for a solution? We are comfortably hitting our polar target on the weaker tack though perhaps not able to point as high as we might like, especially at higher wind speeds where we are managing the traveller to keep the heel in range and the rudder engaged. 

Dan

You might consider the coriolis force.

"Cruising and the Coriolis Force

Wind shear: Due to the Coriolis force, the angle of the wind turns from the mast top downwards, counterclockwise, i.e. to the left (shears). Consequence: The pressure point is different depending on which bow you are sailing on. Wind shear reaches values of up to 20 percent.

On starboard tack (i.e. with wind from starboard) the wind at the masthead comes more aft, the boat heels more strongly. The helmsman lets himself be tempted by the failure of the clicker to steer a little higher, but this leads to greater drift and the speed drops.

Remedy: trim more twist on the starboard tack and flatter on the port tack.

Nevertheless: With the wind from starboard you can point higher due to the wind-shear effect.

Incidentally, the neglected wind shear is usually the reason why boats sail at different speeds depending on the bow. The true angle of incidence of the wind is different on the starboard and port tack.

 

windvonstbtable50.gif   Windshear im Segel - Quelle: Nexus/Silva

(edited translation from https://www.sailpress.com/richtigkreuzen/index.html  as port and starboard "tacks" are the other way around in Germany).

Discussion started...

 

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Took the great advice from this thread to the boat and did some review for a few minutes yesterday. I found a couple of things which might be a start and perhaps when combined with the speedo would get me most of the way there. The lowers D1 were much tighter than spec'd and a bit asymmetric plus I found the starboard inhauler jammed up which probably means it was set in when it should not have been which was likely the cause of the bubble. The breeze was quite heavy for the canvas we had up so everyone was on the rail and nobody went to check the jib sheet angle....won't happen again. 

 

The tuning guide calls for 7 on the Loos 2 gauge for the D1's and the Euro version of the tuning guide calls for these to be 28! 7 is so loose as to be floppy, why would they be so loose? 

Sailing Wednesday and will report back.

Dan  

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9 minutes ago, danstanford said:

The tuning guide calls for 7 on the Loos 2 gauge for the D1's and the Euro version of the tuning guide calls for these to be 28! 7 is so loose as to be floppy, why would they be so loose? 

Depends on what the other settings are.  Someone is trying to induce bend lower down the mast.  Typically that results in a straighter mast from the spreaders upwards.   Means a flatter main at the bottom but fuller mid and top sections.  Also might result in less forestay tension as the mast compresses so your jib knuckles up.  

Where as tight D1's result in a more rigid lower section pushing the bend further up the mast.  That means the mid/head of the main is likely to flatten more and the forestay remains tighter, so a flatter jib.

I'd say, and I could be wrong, the 7 setting is medium to light air in sloppy water and the 28 setting is heavier air/flatter water setting.  

With two very different settings between two different tuning guides, I'd say the respective authors have different philosophies on how to sail your particular boat.  The 7 guy is probably fatter and likes to sail low "bow down" in the groove while vang sheeting.  The the 28 guy is probably lighter and likes to pinch.

Someone is surely going to come along and tell me I'm wrong though I'm sure... 

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1 hour ago, danstanford said:

Took the great advice from this thread to the boat and did some review for a few minutes yesterday. I found a couple of things which might be a start and perhaps when combined with the speedo would get me most of the way there. The lowers D1 were much tighter than spec'd and a bit asymmetric plus I found the starboard inhauler jammed up which probably means it was set in when it should not have been which was likely the cause of the bubble. The breeze was quite heavy for the canvas we had up so everyone was on the rail and nobody went to check the jib sheet angle....won't happen again. 

 

The tuning guide calls for 7 on the Loos 2 gauge for the D1's and the Euro version of the tuning guide calls for these to be 28! 7 is so loose as to be floppy, why would they be so loose? 

Sailing Wednesday and will report back.

Dan  

Dan I have only popped into this thread to read a post here and a post there.... so maybe this has been said before.

Loos gauge readings or rather shroud tensions are dynamic, not static. Everything affects everything else. So if say you have 38 on the port upper and 36 on the stb upper, it is likely an error. if you put 38 on one side, you should have 38 on the other.....unless you have a whale of a hook!

The other thing I would suggest to you, people all the time sight up the main track and try and determine if the mast is in column. Uhhhhhh....okay.
What I do is establish a reference point both port and starboard as discussed above I do believe. Then take a sail slug. run that up the mast on the halyard and tape measure and measure at the termination of the uppers, intermediates and lowers from side to side.... adjust as necessary. You may have to back everything off to just snug to remove any odd influences you have cranked into the rig. But then you take an accurate measure to determine the rig is centered and in column. Once you establish that, which is by far step 1, then worry about adding tension to the caps, d1 and d2, 3 4,5,6 etc. Always add or subtract the same number of turns on a given set of shrouds once you establish center and column...... which is easier said than done!

Good luck.

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1 hour ago, Spoonie said:

Depends on what the other settings are.  Someone is trying to induce bend lower down the mast.  Typically that results in a straighter mast from the spreaders upwards.   Means a flatter main at the bottom but fuller mid and top sections.  Also might result in less forestay tension as the mast compresses so your jib knuckles up.  

Where as tight D1's result in a more rigid lower section pushing the bend further up the mast.  That means the mid/head of the main is likely to flatten more and the forestay remains tighter, so a flatter jib.

I'd say, and I could be wrong, the 7 setting is medium to light air in sloppy water and the 28 setting is heavier air/flatter water setting.  

With two very different settings between two different tuning guides, I'd say the respective authors have different philosophies on how to sail your particular boat.  The 7 guy is probably fatter and likes to sail low "bow down" in the groove while vang sheeting.  The the 28 guy is probably lighter and likes to pinch.

Someone is surely going to come along and tell me I'm wrong though I'm sure... 

Spoonie, the 28 came from the European Tuning Guide from North and the 7 from the North American one. The other settings are different but not so drastically. 

I wondered if the D1's might be so loose as to allow more mast bend from the back stay tightening.

This is the base setting for 10 knots of wind.

Dan 

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4 hours ago, Knut Grotzki said:

You might consider the coriolis force.

Wrong! Normally compensated for by the sailmaker. Coriolis force is why it is important to inform your sailmaker of your expected  hemisphere, N or S. The sailmaker will select either S or Z twist thread accordingly. 

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North says North American made mast and European mast are very different stiffness and this is why the shroud tensions are different. 

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1 hour ago, danstanford said:

North says North American made mast and European mast are very different stiffness and this is why the shroud tensions are different. 

Well there you go.  that makes sense.

the way I think about this is to imagine bending a batten.   If you take a batten and bend it , it forms a fair curve.   If you push that curve one side or the other, one side becomes more round, and the other becomes more straight.  If you bend the batten more the distance between the two ends gets shorter.

 

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12 hours ago, quod umbra said:

...

The other thing I would suggest to you, people all the time sight up the main track and try and determine if the mast is in column. Uhhhhhh....okay.
What I do is establish a reference point both port and starboard as discussed above I do believe. Then take a sail slug. run that up the mast on the halyard and tape measure and measure at the termination of the uppers, intermediates and lowers from side to side.... adjust as necessary.

Here is another tip to check the mast in column.  Make sure the halyards, vang and backstay are slack so only the standing rigging is positioning the mast.  Stand about 10 feet behind the mast in the center (on my J/109 I stand in the companionway) and take a picture up the mast so you can see the top of the mast and as low on the mast as you can get.  Drop the picture in PowerPoint and draw a straight line up the mast track.  Easiest if you drop the two end points, then blow up the picture and position each end point on the mast center.  It will become very apparent if you have any curves in the column when you expand the view and go up the drawn line.

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On 7/6/2021 at 4:06 PM, Borracho said:

Wrong! Normally compensated for by the sailmaker. Coriolis force is why it is important to inform your sailmaker of your expected  hemisphere, N or S. The sailmaker will select either S or Z twist thread accordingly. 

haha!

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  • 2 weeks later...
On 7/1/2021 at 3:09 PM, Lynch said:

You dont need any fancy fish scale

Tie a heavy weight ( I use a 12kg kettlebell) to a halyard exiting at the hounds - usually the jib halyard but might be a spinnaker halyard if its just above forestay.

Make sure the mast is central in the boat before doing anything else.

Also check speed with a gps not your log and try doing it in flat water with no tide

image.thumb.png.1930bbe90b9e7fbc265240ad019fccac.png    $17.99

image.thumb.png.627265e5c5ee9cb24ae429f80e9954ad.png     ~$25

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On 7/2/2021 at 6:16 AM, danstanford said:

Mid, I am going to give the centeredness one more go round before I proclaim it there but it is reasonably close if you are talking about the top of the mast. If you are talking about the mast base I have never really worked on that so I will look with a measuring tape. As for the keel and rudder, they look fine by eye but I have never attempted to measure them. 

Trying to imagine how to measure these accurately....

just taking a flyer here, but without a template for your boat ... if you can establish a centerline on deck, and all is symmetrical out to the toerail, you could take a soft tape measure around the hull to various points on the keel and rudder.

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I have done one more set of tuning and set the tip of the mast centered once more using the bucket of water and we have it somewhere less than half an inch. My Vakaros just arrived so I am going to get it mounted this week and see from GPS SOG how we stack up. 

Since last tuning we have raced twice and not noticed the difference in the speed but had a lot to think about as well with a short course and lots of boats around.

Will keep this thread posted.

Dan 

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