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Thread: Port tack faster than starboard tack, same point of sail? Reply to Thread
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  Topic Review (Newest First)
09-06-2011 05:57 PM
Originally Posted by zAr View Post
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.
09-06-2011 10:57 AM
Sailormon6 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.
09-06-2011 07:22 AM
tempest I might try using a couple of instruments to measure and compare speed. Check your speed over ground with a GPS, get a knot compare to your paddle.

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

I know you don't have currents as we know 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 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.....
09-06-2011 02:39 AM
DSnider748 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.
08-29-2011 09:39 PM
Originally Posted by captflood View Post
GREETINGS EATHLINGS ' Please look up water line length and effects the more wieght the longer the waterline the greater the achiveable speed. this does involve the type of tummble home and many other factors on and off the boat. GO SAFE
Yeah, but by a whole knot for maybe 1/3 of an inch list at the waterline? I wonder....
08-29-2011 08:43 PM
Originally Posted by jackdale View Post
Would that be UV protection on the leech and foot? That might affect air flow, but it would be minimal.
Yup, that's it. I didn't think the effect on air flow could be that dramatic.
08-29-2011 04:04 AM
captflood GREETINGS EATHLINGS ' Please look up water line length and effects the more wieght the longer the waterline the greater the achiveable speed. this does involve the type of tummble home and many other factors on and off the boat. GO SAFE
08-29-2011 12:03 AM
Originally Posted by zAr View Post
Both my jib and genoa have protectors on one side, hrm.
Would that be UV protection on the leech and foot? That might affect air flow, but it would be minimal.
08-28-2011 11:58 PM
Originally Posted by MikeWhy View Post

A roller furler has some asymmetry. Still guessing on the boat and rigging.
I do have a roller furler. Why would that produce asymmetry though?
08-28-2011 11:56 PM
Originally Posted by jjablonowski View Post

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.
Both my jib and genoa have protectors on one side, hrm.
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