# Unequal upwind performance



## TSOJOURNER (Dec 16, 1999)

Howdy all,
I have a problem that has me stumped at the moment so I am looking for some 3rd person sugestions. 

My problem is that I am unable to achieve equal boat speed up wind in my Ross 780 trailer sailer. On starboard tack I can easily acheive 6.4 knots pointing high. The boat accelerates well after being slowed by chop. However on port tack I will only achieve 5.8 knots and that is at a lower ponting angle. The boat is easily slowed by chops and powers up poorly. It "feels" like it is stalling or on the verge of stalling. The boat heels over easier on port making me let out the main traveller.

It does not seem to matter what sail/reef combination I have up, the result is the same, starboard better than port. I have noticed that in heavy wind the difference in speed is more pronounced, up to 1.1 knots. In heavy winds it is very difficult to maintain a good boat speed and pointing angle. 6 - 6.2knots starboard an a max of 5knots port. It is also difficult to keep the hull below 20 degrees of heel angle on port.

I have visually checked to see if the mast is 90 degrees to the hull ie not leaning to one side due to unequal stay length.
I have visually checked to see if the mast is straight, ie no s bend.
The keel is of the drop version. I have checked for damage to the box holding the keel which would maybe allow for incorrect positioning ie slightly turned or leaning to one side but can't see anything obvious ( not ruling this out).

I have not been able to check the keel yet when fully extended in the water to see its positioning and alignment.

This is not a problem that has developed over time. The boat is three years old and I am its second owner. I have owned it for 6 months. I have noticed the difference since starting to race the boat 1 month ago ,prior usage was only cruising. Previous owner says he did not experience the problem (may not be true?).

Has anyone had a similar problem that may shed some light on this and possibly give me something to measure or check that we have not thought of or have overlooked in our overanalysis (its always the simple things)?

Thanks. (sorry for the length)


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## jorgenl (Aug 14, 2006)

I had a similar problem and had a rigger perform a dynamic tune on the rig, i.e the rig is tuned while under sail.

I do not know exactly what magic stuff he did but it certainly seemed to fix the problem.


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## TSOJOURNER (Dec 16, 1999)

I agree it's probably rid tension. But what about weight? When the boat was designed, does it appear they distributed the interior components equally, (ie, settee and head on the port side, but nothing on the other). Do you have water or fuel tanks or a bunch of heavy gear on the port side? An extra hundred pounds or so might make a difference.


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## Sailormon6 (May 9, 2002)

On a trailered boat, the most common reason I've seen for such a pronounced difference in performance on opposite tacks is because the prop of the outboard motor drags in the water slightly on one tack, but not the other. It might only drag in stronger winds, so, check it in different windstrengths. If it's dragging, study the motor's tilting mechanism. Often the motor can be tilted more than the owner realizes.


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## Zogumwesterly (Jul 24, 2007)

I used to crew on a lightning and the upper rudder pintle on the hull had shifted(the bolt holes had enlarged and the rudder was cocked at about 5-10degrees. it took us a season to figure out, about an hour to fix and made a world of difference.


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## TSOJOURNER (Dec 16, 1999)

Thanks for the quick replies. I appreciate all your feed back. 
I'm going to check all your suggestions out. I had not even thought of the rudder suggestion, cheers.
I'll keep you up to date on what I check and the results.
When I find the fault I will post the remedy. 

Thanks again. I will check back later for any other suggestions.


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## 6string (Oct 19, 2006)

A couple of things you can do to check your mast rig on your own. With the boat level, on the trailer or in the water, hoist a tape measure with your halyard and lock halyard into place as you would for your main sail. Measure both port and starboard to the deck at your chain plate, being careful that it is exactly the same spot on both sides. The measurement should be the same. Also, while under sail to weather on each tack, with same mainsheet tension, (mark your mainsheet at a block and trim the same on each tack) sight your mast and note any bend it may have. Is it the same? On the boat I sail we want some bend but it is the same on each tack. Check stay tension to be sure it is the same on each side.

Is this a keel boat or centerboard? That could also be suspect.

I would also be sure that sail shape looks the same on each tack. Is the boom bending different on the opposing tacks? Are the jib leads coming to the same points on deck, is the travelor set the same on each side? These are the main things that I would look at as well as any slop that may be in the rudder.

Jeff


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## TSOJOURNER (Dec 16, 1999)

Howdy all,

Just thought I'd update. I haven't been able to do anything yet. We have had a low pressure sitting off the coast for the past week generating 40 - 65 knot winds with rain flooding etc. Quite a bit of a change to the drought conditions and water shortages we are experiencing latlely.

Hoping to do something next week end.

Cheers


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## TSOJOURNER (Dec 16, 1999)

Hi 

Had the same problem on my Elite-37. Couldn't for the life
of me figure it out. Asked Around got all kinds of answers/suggestions. Then one light air day I noticed the roller furled jenny had taken a set , kind of like a rolled up piece of paper.My sail, furls up clockwise, resulting in which it lifted great to starboard & lousy to port. If it were to furl counter-clockwise I would expect it to lift vice-versa.
Hope this helps

Metalcrafter


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## TSOJOURNER (Dec 16, 1999)

Thanks for the input Metalcrafter, unfortunately my rig doesn't have a self furler (wish it did).

I was able to have a close look at the mast this weekend without sails on. I noticed it had a very slight sideways bend to port. My type of rig uses an adjustable forestay tension system. With light tension the bend is very slight and hardly noticable, but when tension is applied the bend is quite severe. This would explain why the difference in performance is more noticable in heavy conditions when more forestay tension is applied.

As a result of this discovery I will be retuning the rig. I'm just trying to get the suggested mast rake from the boat builder and the suggested mast prebend from the sailmaker. This rig is fractional with heavily raked spreaders and is a bit unique in that you can adjust the forestay tension through a pulley system, should be quite an interesting challenge.


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## sailingdog (Mar 19, 2006)

Pentium7-

if the mast has a curve to port... the shrouds are probably the problem, not the forestay. You need to correct this rather quickly... since having the mastout of column is a good way to lose it.


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## Sabre66 (Feb 3, 2007)

Ditto what sd said. You can pull the main halyard down, hard, along the mast track to tell when you get the mast in column.


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## sailingdog (Mar 19, 2006)

Sighting up along the mast will usually give it away too.....take the boom off and lie on the deck and look up...along it... it's usually pretty obvious if it ain't straight.


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## RichH (Jul 10, 2000)

Where is your speedo mounted? ..... EXACTLY on the centerline or offset to one side?

A speedo mounted offset from a boats centerline will most times give output readings similiar to what you describe ..... different flow patterns going across the paddle wheel versus heel, different flow patters due to different immersion depth tack to tack, etc. etc. 

Inotherwords if your speedo is not set directly ON the boats centerline and/or is not **calibrated** versus which TACK you are on, the speedo is probably giving FALSE readings when the boat is heeled on one side versus being heeled on the 'other side' .... and that's probably your problem.

For a boat to be over 10% faster (6.4/5.8 = 1.103) on one tack than the other tack and not having 'something' grossly noticeable (like a 300kg purple knobby tumor growing off one side of the mast, etc.) .... is nigh on impossible. Betcha its your speedo -- mounted off-center and is giving you misleading readings due to the dissimilar hydrodynamics at the speedo ... when on port tack versus starboard tack.


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## sailingdog (Mar 19, 2006)

RichH-

He didn't say if he was getting boat speed from a knotmeter or off of a GPS.


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## TSOJOURNER (Dec 16, 1999)

Update:

RichH, the speeds are Gps. 

Ok, I was able to get the prebend spec from the sailmaker and suggested rake from the manufacturer.

I have reset the shrouds and now have a mast that has the the correct rake and prebend and is now in column  . Original settings by previous owner had to much rake (explains the excessively heavy wetherhelm I suffered on windy days) and to much prebend ( explains why I was always chasing shape in the main) and the bend to port. 

I'm looking forward to the test sail and a bit of rig tuning on the water. Might be a couple of weeks away due to work commitments.


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## maxmunger (Dec 29, 2005)

Sounds like a lot of incongruous criteria to me.

GPS speed is meaningless on different tacks. Waves, current, trim all effect speed which the GPS will not measure. To evaluate trim, you need an eye for sail shape, lead locations, sheet tension and finally measure speed thru the water in a consistent environment on consecutive tacks.

The port bend is obviously a looser SB shroud, just needs tightening.

Why would the sailmaker define prebend? seems the mast mfr should specifiy that. and the sail would be made to fit the mast. And the rake would depend upon the boat itself and the weather you sail in. Of course the trim of the main would also determine whether you had too much or too little rake.

The discussion of too much mast bend with too much tension on the headstay is DUH!

I think you need to spend more time on the water sailing and trimming with different rig tuning to determine that point of equilibrium you seek. All those "specs" are just starting points. have your sailmaker go out with you.


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## TSOJOURNER (Dec 16, 1999)

Hi Maxmunger,

It would seem from your post that you have some sort of attitude problem.
Your suggestions have been written with an amount of contempt for anyones knowlege base and sailing experience. From the tone of your writings I take it you are an expert in sailing, probably a winner of an Olympic medal or such.

However doubt arises in my mind in regards to your knowledge when you refer to the manufacturer of masts determining prebend settings for a mast. If you have an existing mainsail that has been cut to meet a certain prebend setting, why would you ask the mast manufacturer how much prebend the sail was cut for? Did the mast manufacturer cut the sail. How would the mast manufacturer know what the sailmaker cut the sail to? Maybe they have mindreading abilities..... Sorry I'm getting sarcastic.

In regards to Gps speed being meaningless, a few questions by yourself would have revealed that measurements taken have been during several races which have been in varying wind, chop and trim settings. Current does not play a part here due the bay enviroment area I race in.

By the way I am not a novice. I have won 5 consecutive national titles, 6 consecutive state titles and have come 2nd in the Australian National Open School Titles(300+ starters). 

So don't jump in disrespecting everyones contributions to my thread effectively treating us all like idiots.

Go flame some other thread.


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## Idiens (Jan 9, 2007)

If you have fixed all the asymmetries above the water line, that leaves those below. As water is about 1000 times denser than air, it only takes small underwater asymmetry to give an effect. It can get right down to the foil shapes of your keel, let alone a small misalignment of the keel with the hull. Try checking if you need exactly the same rudder setting to counterbalance weather-helm on both tacks.


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## maxmunger (Dec 29, 2005)

I think you had better look in the mirror to see who has attitude.

Not once did you indicate you knew anything about sail trim much less being a certified jock. Nor your sailing environment.

For someone who didn't know why or how to fix a port bend in the mast or the effect headstay tension had on mast bend, I clearly got another impression. Other contributors listed the basics of mast setup, but you didn;t chastise them.

I clearly laid out that the mfr has a prebend in mind when the mast is designed and the sailmaker should have consulted mfr to determine that before making a sail. Not the other way around. You are trying to fit an old main to a boat/mast that by your description, won't fit or trim properly.

If you are gradually making all these adjustments yourself then why are you asking this forum for help? You get what you ask for.

OH, and I am a national champion too!


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## Sabre66 (Feb 3, 2007)

maxmunger said:


> Sounds like a lot of incongruous criteria to me.
> 
> GPS speed is meaningless on different tacks. Waves, current, trim all effect speed which the GPS will not measure. To evaluate trim, you need an eye for sail shape, lead locations, sheet tension and finally measure speed thru the water in a consistent environment on consecutive tacks.
> 
> ...


Whatever happened to speed over ground then? Why do We use the knot log Vs GPS to determine VMG? The comparison shows the effect of tide, current and, ultimately the amount were being set. Gps is not affected by tide...etc..conversely the knot log reflects boat speed VS tide or current so
the knot log will almost always, be slower on one tack than the other.


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## RichH (Jul 10, 2000)

FWIW
take a closer look at the battens especially the aft ends and their interaction with leech shape. 
I race scows which are extremely sensitive to the dissimilarities caused by the normal mounting the battens on ONE single side of the sail. Watch for any leech exit shape problems (leech hooking to weather, etc. more on one side than the other) which can become additionally mishaped because the leech pucker line is also slightly offset to the same side that the battens are attached. Leech symmetry problems will definitely cause differences in pointing ability on different tacks.


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## TSOJOURNER (Dec 16, 1999)

Update:

Howdy all, I finally have had a chance to take the yacht out. We have had an outbreak of horse influenza here in Australia and I'm part of the disaster management team that is trying to manage it. This equates to no time to go sailing.
Anyway... the problem is fixed...yah. The retuning of the rigging seems to have made a world of difference. Amazing the difference a straight mast makes.lol. Went straight past a catalina 34, he was not happy. 
A big thankyou for all the input received and suggestions given.
I am still looking at shifting some weight (as suggested) from the starbord side to the port side as all extras such as fuel,outboard motor and portable toilet are on starboard. Looking at moving the fuel tanks and honda genset.
Going to keep working thru all the other suggestions just to rule out any other possible gains. I will let you know how I go.

Thanks


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