rhinorhino
Well-Known Member
I have a HR36 - why is there upto a 20% difference between performance on the two tacks, especially upwind?
Anyone got any ideas
Anyone got any ideas
Different Tacks - Different Speeds?
- Thread starter rhinorhino
- Start date
jimi
Well-Known Member
Rig tension?
Impeller well off to one side?
Impeller well off to one side?
rhinorhino
Well-Known Member
Impeller central - in any event sog from gps is also different. Rig tension equal.
We have been wondering about this one for about five years, no one has yet come up with a convincing argument. Most boats seem to favour starboard tack (or at least in the northen hemisphere) any Aussies out there care to comment.
Does your boat have a favoured tack?
We have been wondering about this one for about five years, no one has yet come up with a convincing argument. Most boats seem to favour starboard tack (or at least in the northen hemisphere) any Aussies out there care to comment.
Does your boat have a favoured tack?
jimi
Well-Known Member
My boat does seem to have a favoured tack (port) but what I've noticed is that some helms tend to pinch more when on starboard than port (might be a rubbish observation?)
rhinorhino
Well-Known Member
could be, but also happens under autohelm!
Mudplugger
Well-Known Member
Mast offset to one side??...Keel not straight??... just a couple of thoughts!!
jimi
Well-Known Member
Wind indicator not straight?
Lakesailor
Well-Known Member
How about this.
Even if the weight distribution gives you an 'even keel' at rest it may be that masses are not equally distributed about the centre line.
That is a heavy mass quite outboard on the port may be balanced by several masses nearer the centre line on the starboard. I'm thinking gas bottle, batteries etc.
When you heel the masses further from the centre line have a greater effect thus creating more heel, more wetted surface or diffent underwater dynamics one side to another?
Ok. I'll go back to sleep.
Even if the weight distribution gives you an 'even keel' at rest it may be that masses are not equally distributed about the centre line.
That is a heavy mass quite outboard on the port may be balanced by several masses nearer the centre line on the starboard. I'm thinking gas bottle, batteries etc.
When you heel the masses further from the centre line have a greater effect thus creating more heel, more wetted surface or diffent underwater dynamics one side to another?
Ok. I'll go back to sleep.
twisterkai
Well-Known Member
Rig tension may be equal, but is the mast perfectly upright?
What about other HR 36's?
Other than that, no other help really, sorry!
What about other HR 36's?
Other than that, no other help really, sorry!
peteandthira
Well-Known Member
We notice this too. We have a much better port tack than starboard, we think it is due to genset and batteries being on the port side of the boat. Extra water tanks shortly to be added to the starboard side may even out the balance. We will be interested to see if theres any change. The boat has a barely perceptible (2deg?) heel in the marina which is not noticeable down below. If I remember, I'll report back later after water tank fitting.
Pops
Pops
Talbot
Well-Known Member
my vote is for the wind indicator being slightly misaligned (I have the same problem) and a couple of degrees will make a big difference.
Neraida
Well-Known Member
2 things.
Most likely rig tuning.... Get a pro in.
Secondly could be the weave/impregnation of your cloth (assuming you dont use lammies).. According to a chum this can be "roller syndrome" where the sails dont work properly on one side. Could be cobblers tho. /forums/images/graemlins/crazy.gif How old are your sails?
We had this issue, rig was tuned, problem went away. The mast was straight, and the rig "felt" even, but it did the trick.
Cheers
James
Most likely rig tuning.... Get a pro in.
Secondly could be the weave/impregnation of your cloth (assuming you dont use lammies).. According to a chum this can be "roller syndrome" where the sails dont work properly on one side. Could be cobblers tho. /forums/images/graemlins/crazy.gif How old are your sails?
We had this issue, rig was tuned, problem went away. The mast was straight, and the rig "felt" even, but it did the trick.
Cheers
James
Peppermint
Well-Known Member
Re:Most boats I sail have the same problem
I'd say 20% was quite a large variation but a bit of difference is about par. Reasons I'd suggest are structural, like rig alignment, ballast and/or payload differential, something dragging off centre ( bathing ladder or windvane) or trim based ie you think your setting the boat up the same on both tacks but your not.
Another thing can be perception based. We tack through the wind. So the force of wind is equal on each tack. Waves on the other hand lag behind the wind. So say the wind is westerly the waves will be coming from one side of west. That can make a difference to the feel and performance of one tack over another.
One guy told me he thought it was because weed grew more on one side of the hull than the other, because he moored so that one side got more light than the other.
With my boat I'd say it was load based. It's only slight but it is noticeable. The wind instrument idea is easy enough to check but I don't have wind instruments so that won't stand up for me.
I'd say 20% was quite a large variation but a bit of difference is about par. Reasons I'd suggest are structural, like rig alignment, ballast and/or payload differential, something dragging off centre ( bathing ladder or windvane) or trim based ie you think your setting the boat up the same on both tacks but your not.
Another thing can be perception based. We tack through the wind. So the force of wind is equal on each tack. Waves on the other hand lag behind the wind. So say the wind is westerly the waves will be coming from one side of west. That can make a difference to the feel and performance of one tack over another.
One guy told me he thought it was because weed grew more on one side of the hull than the other, because he moored so that one side got more light than the other.
With my boat I'd say it was load based. It's only slight but it is noticeable. The wind instrument idea is easy enough to check but I don't have wind instruments so that won't stand up for me.
EagerV
Active Member
Often noticed pointing better on Starboard tack, particularly when gusty. I always put it down to the fact that the wind almost always veers in gusts in Northern hemisphere. Also wind direction veers with altitude due to loss of surface friction. Hence the reason aircraft will always use a left crosswind, if at 90 degrees, for take of and landing.
May also explain why a broad reach on port tack is faster...? Or perhaps I'm writing rubbish..!
May also explain why a broad reach on port tack is faster...? Or perhaps I'm writing rubbish..!
Lizzie_B
Well-Known Member
The two boats(a 36foot gaff sloop and a carter 30) I've sailed in that had a noticeable difference between tacks have both had their water tanks under saloon settee.
In the case of the gaffer, her identical sister hull, had central water tank and sailed like a dream on both tacks, while her sister slid sideways like a pig on roller skates when tank to leeward, as did the Carter 30.
Both appeared perfectly trimmed when sitting sedately alongside.
My current boat and my last boat both had central tanks and had no noticeable performance difference between tacks.
In the case of the gaffer, her identical sister hull, had central water tank and sailed like a dream on both tacks, while her sister slid sideways like a pig on roller skates when tank to leeward, as did the Carter 30.
Both appeared perfectly trimmed when sitting sedately alongside.
My current boat and my last boat both had central tanks and had no noticeable performance difference between tacks.
Jeannius
Well-Known Member
I thought my cat had a preferred tack as well as I could get much closer to the wind on stbd than I could on port. After much investigation it turned out that the wind indicator was offset around 4 degrees.
Swagman
Well-Known Member
[ QUOTE ]
Impeller central - in any event sog from gps is also different. Rig tension equal.
We have been wondering about this one for about five years, no one has yet come up with a convincing argument. Most boats seem to favour starboard tack (or at least in the northen hemisphere) any Aussies out there care to comment.
Does your boat have a favoured tack?
[/ QUOTE ]
I lived and sailed in Auz so can affirm this is not an extension of the bath water down the plughole type scenario. It will be one or more of rig set up, keel fairing or alignment, or weight distribution.
Cheers
JOHN
Impeller central - in any event sog from gps is also different. Rig tension equal.
We have been wondering about this one for about five years, no one has yet come up with a convincing argument. Most boats seem to favour starboard tack (or at least in the northen hemisphere) any Aussies out there care to comment.
Does your boat have a favoured tack?
[/ QUOTE ]
I lived and sailed in Auz so can affirm this is not an extension of the bath water down the plughole type scenario. It will be one or more of rig set up, keel fairing or alignment, or weight distribution.
Cheers
JOHN
bbg
Well-Known Member
You are the first to mention keel fairing. It would be unlikely to account for a 20 degree difference, but certainly could account for several of those degrees - if the shape of the keel is not the same on each side.
Robin
Well-Known Member
Disturbance of the waterflow into the log impeller is a start, even if it is central. The actual flow into the impeller could be disturbed by something else, like a skin fitting or echosounder transducer either ahead of or behind the log. HRs have pretty chunky keel profiles and even behind the log will inevitably skew the waterflow past the log especially when heeled one way or the other.
Rig setup is another possibility, mast not central or not vertical or falling off to leeward on one tack and hooking to windward on the other. Sails, especially if the originals from HR rather than quality ones might be stretched and the genoa leech hook on one tack and not on the other if a roller sail with a sun strip.
Then there is sea state and windspeeds. Rarely is the sea from the same direction on both tacks, so will tend to slow you more on one than the other, especially upwind. If you try and sail the same wind angle apparent upwind especially on each tack then for sure one will be faster, but then if you free of on one (for sea state) and not on the other then the speeds will differ too. In gusts the wind tends to free and more so on starboard (don't ask me for the scientific explanation) so if you don't 'follow the wind' and head up to keep the same apparent wind angle then the boat will go faster because you are temporarily sailing more freely whilst the gust lasts. Equally if you keep the same compass course (especially relevant on autopilot) then gusts when the wind heads you the speed will drop because you are temporaily pinching too high.
A 20% difference is huge (1.2kts at 6kts average) and I suspect very unlikely in actuality rather than true waterspeed. SOG from the GPS isn't definitive either because tide will usually have a greater effect on one tack than another. Is this proven in passage times? For example if closehauled on starboard over say a 60ml trip do you really get there over 2hrs earlier than if on port tack? If that is really the case it might be time to change boat!
Robin
Rig setup is another possibility, mast not central or not vertical or falling off to leeward on one tack and hooking to windward on the other. Sails, especially if the originals from HR rather than quality ones might be stretched and the genoa leech hook on one tack and not on the other if a roller sail with a sun strip.
Then there is sea state and windspeeds. Rarely is the sea from the same direction on both tacks, so will tend to slow you more on one than the other, especially upwind. If you try and sail the same wind angle apparent upwind especially on each tack then for sure one will be faster, but then if you free of on one (for sea state) and not on the other then the speeds will differ too. In gusts the wind tends to free and more so on starboard (don't ask me for the scientific explanation) so if you don't 'follow the wind' and head up to keep the same apparent wind angle then the boat will go faster because you are temporarily sailing more freely whilst the gust lasts. Equally if you keep the same compass course (especially relevant on autopilot) then gusts when the wind heads you the speed will drop because you are temporaily pinching too high.
A 20% difference is huge (1.2kts at 6kts average) and I suspect very unlikely in actuality rather than true waterspeed. SOG from the GPS isn't definitive either because tide will usually have a greater effect on one tack than another. Is this proven in passage times? For example if closehauled on starboard over say a 60ml trip do you really get there over 2hrs earlier than if on port tack? If that is really the case it might be time to change boat!
Robin
PeteMylett
Well-Known Member
I had the same problem.
Decided it was primarily due to non calibration of wind instrument. Recalibrated and there has been some improvement. I guess I'll look at the rig next.
Decided it was primarily due to non calibration of wind instrument. Recalibrated and there has been some improvement. I guess I'll look at the rig next.
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