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Port tack faster than starboard tack, same point of sail?

13K views 28 replies 15 participants last post by  anthemj24 
#1 ·
On my boat I've noticed that sometimes when I'm close hauled, wind and waves from the same direction, that starboard tack is faster than port tack, sometimes by a whole knot. I can't figure out why.

My rig is balanced, straight mast, I've tuned the shrouds at very nearly the same tension. I do have a bit of a rake, about 2-3 inches. Rudder isn't bent, keel isn't either.

At dock there is a slight list to the port side as there's more weight there, but I can't imagine that's the reason. If anything, shouldn't that make me faster on a port tack?

Am I missing something?
 
#2 ·
At dock there is a slight list to the port side as there's more weight there, but I can't imagine that's the reason. If anything, shouldn't that make me faster on a port tack?
That is quite a good reason. The boat will sail flatter on a starboard tack than on a port tack.

Is this true in all winds? In very light air, it might be faster on a port tack. The slight amount of heel will keep the boom over on port. Many boats sail better with a some heel.
 
#5 ·
Some fiberglass boats, and all boats I suppose, are not perfectly symmetric. Even a very small asymmetry in the hull, particularly with respect to the alignment of the keel and rudder, could cause a noticeable difference in performance on different tacks. Moore 24's were supposed to have this problem in some of the early boats. That, and/or the listing you've noticed could easily explain the performance difference you're seeing.
 
#6 ·
Well, I guess to "scientifically" confirm the diagnosis I'll have to remove the list completely, put more weight starboard.

What's confusing me is that if the list were to starboard that would be the equivalent, when sailing on a starboard tack, to having rail meat on the starboard side. But I guess, now that I think of it, putting meat on starboard causes the port side to dig in more....

JackDale: I haven't really sailed much in lighter winds lately, mostly 10+ knots. It's happening in 15-20 knots and 1-2 meter waves.
DrGamble: It's a CS30, so yep - light displacement boat.
SlowButSteady: I don't think my model of boat is known for it, but I guess it's possible. Love the sig, by the way!
 
#8 ·
#9 ·
zAR,

You said it's noticeable when you're close-hauled.

Are the sails absolutely symmetrical? Like, does the jib have luff foam or luff rope on it? Could be disturbing wind at the leading edge.
It could even be dissimilar shroud tensions; the are a myriad of possibilities. I will stick with my first guess based on your list to port.
 
#10 ·
Unless I'm confused the OP said he has a list to port (more weight on port side) and he consistently sails faster on a starboard tack. If weight distribution was the cause you would think that the boat would be faster on port tack because it would sail flatter (as the OP said). I would suspect rigging tension but there are a lot of unknowns to explore.
 
#11 ·
It all depends on the boat. In light winds, the port list may help to lower the wetted surface area of the hull a bit on a starboard tack. At slow boat speeds (e.g., in light winds) wetted surface area has a disproportionately large effect on overall drag.
 
#14 ·
Is the speedo paddle wheel on one side or the other? if so, this has been a reason for one tack being faster per say than the other. At least on "MY" boat it is! The paddle wheel is about 8" ff center to port, so many times since the wheel is deep and flat when on starboard tack, we are faster than on the port tack where the wheel will be pointing sideways for lack of better term or way to say it!

I list to port also a bit.

My rig is pretty well centered, as I had a crew up to the top, measured side to side a the top, upper then lower spreaders etc. tension is equal on both sides........

marty
 
#17 ·
When you haul the boat this winter check keel + rudder + center of hull alignment.

You can either use a plumb bob and eyeball it or buy a new fangled laser levelers at a hardware store.
 
#18 ·
More heel can lengthen the waterline, and influence hull speed. It would depend on the boat. For a full knot difference, a 30' waterline would have to become 34'. (Someone please check my math...) That's easy enough to test by moving rail meat around.

A roller furler has some asymmetry. Still guessing on the boat and rigging.
 
#19 ·
More heel can lengthen the waterline, and influence hull speed. It would depend on the boat. For a full knot difference, a 30' waterline would have to become 34'. (Someone please check my math...)
sqrt30 X 1.34 = 7.5 knots
sqrt34 X 1.34 = 7.8 knots

You would need at least a 40 waterline to get to 8.5 knots.
 
#26 ·
Recently, I became aware of the same issue; while tacking close hauled for both port side and starboard side, I encoutered distinctly different handling and speed differences. Thinking about the many reasons for what was happening, I noted that I handled the boat differently (handling of main sheet, and tiller) depending on port or starbard. I made a conciencious point of handling the boat the same way on both port and starboard tacks... and alot of the issue dissapeared. The efficientcy, and coordination process I was deploying was asymetrical, hence the sailing proficientcy suffered accordingly.
 
#27 ·
I might try using a couple of instruments to measure and compare speed. Check your speed over ground with a GPS, get a knot stick..to compare to your paddle.

There's also the effect of 1 to 3 meter waves...approx..3 to 6 ft..in americanese..
Is it always the same angle of attack to the waves?

I know you don't have currents as we know them..here near the ocean...but I believe you have some current up there due to river flows, wind driven, outflows from storm sewers etc....

Waves, and currents will affect speed. Here on the hudson river...we have a big underwater profile called a keel...if sailing at a right angle to the current..it will have a greater effect..

The fact that your speed is affected always on the same tack..may rule these issues out...but something to consider.....
 
#28 ·
When I first bought my boat, I noticed that it sometimes sailed better on one tack than the other. I have learned that, after I shut down the engine, if I set the 2-blade prop so that it is locked in a vertical position, it sails equally well on both tacks. If you have a 2-blade prop, try locking the prop vertically, and see if it helps.
 
#29 · (Edited)
On my boat I've noticed that sometimes when I'm close hauled, wind and waves from the same direction, that starboard tack is faster than port tack, sometimes by a whole knot. I can't figure out why.

My rig is balanced, straight mast, I've tuned the shrouds at very nearly the same tension. I do have a bit of a rake, about 2-3 inches. Rudder isn't bent, keel isn't either.

At dock there is a slight list to the port side as there's more weight there, but I can't imagine that's the reason. If anything, shouldn't that make me faster on a port tack?

Am I missing something?
Reading the words I bolded from your post, I take it that the effect is not always there and when it is there not always in the same amount. There are a number of things that could cause your boat to be slower on one tack than the other. Start making notes when you go out, and keep track of what the conditions (wind, current, sea state, trim) are when you experience the effect and note the level of the effect as well. Also make note of the wind direction and your heading for each tack. Are you pointing higher and slower on port, lower and slower, or equal pointing and slower. Try also to determine the amount of leeway on each tack by comparing GPS heading vs magentic heading (adjusting for variation) and speed over water with your knotmeter vs GPS speed. That kind of information would be very helpful in diagnosing the problem.

You also state that the shrouds are very nearly the same tension. How did you measure this? If it was by hand and not with a Loos guage, your estimate could be surprisingly wrong. If you have not already, put a Loos guage on it. Also, make sure that the mast is truly centered. This can be a surprisingly difficult thing to measure since boats are rarely perfectly symmetrical, but is important to get right. Measure to the rail, and not to any deck hardware, and make sure the point you are measuring to is equal on both port and starboard by measuring the distance to the bow and transom from both points. Once you know the mast is centered, check to see if the deck hardware is placed in the same exact location on both sides of the boat. It is not unheard of for a boat builder to work with a hangover, leaving your sheeting angles on one side less than ideal.

Lastly, don't be surprised if your keel is actually not on straight or if the shape is not symmetrical (many boats came from the factory this way), either of which could cause a difference in speed and/or pointing from one tack to another.

I am going to make a wild guess that it is actually rig tension, and that the lowers and/or uppers are different tension on one side vs the other. you may not notice this in 8 knots, but when the wind picks up to 15 or 20, the mast is probably bending different on one tack vs the other. Could be that the uppers on stbd are lower and so the top is bending off, and keeping the boat flatter when the wind kicks up, or maybe the port lowers are not as tensioned and so the center sags to leeward on port tack giving you a not so fast shape. Of course this is just a wild guess, and I am just as likely to be wrong as right having never sailed on your boat.
 
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