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  #1  
Old 12-04-2006
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Which tack is faster?

I was on the water yesterday for 3.5 hours in a C&C 24. It had no traveler and the mainsheet was set up on top of the cabin with the control line coming from just the right side into the cabin top. The N wind started at about 8-10 knts , but then died to 2 knts by the time we got back.

On our way out from Shilshole towards Port Madison, we were heading west on a starboard tack. We didn't stay N enough and got too far S below our GPS planned route. So we pointed N as far as we could (going NW) to try to get back to our planned route. The winds were probably around 6-8 knts and the GPS said we were going about 4 knts. We ran out of room because the island is S of our next point and we didnít want it to get shallow so we decided to tack back NE. We were going maybe 3-4 knts before coming about. As soon as we did, the boat lost all power. We were just bobbing. I think that first time we may have been in irons because I had 4 others on the boat with me and it was their first time out and one of them was at the helm. So I took the helm, gybed in the light wind and got us going NW again. The winds were still around 6 knots I'd guess and we got our 3-4 knots of speed back. I was getting our speed indication from the GPS, because the instruments on the boat didn't work.

Setting up to tack again, I made sure we were on the wind as close as possible, then sized up my point 90 degrees to the starboard. I pushed the tiller hard leeward and gave it another try. That time we came about quickly and it easily went past the point I set, but as I tried to settle it in the groove, there seemed to be no wind again and we just sat there bobbing at about 1 knt or less. The 135 genoa was trimmed in tight on the right side. I was starting to think the boat sails better on a starboard tack than on a port tack.

We tried it another time or two and got almost the same results. I couldnít believe it that the boat would have that big of difference between a port and starboard tack. Since it was then looking like the winds were dying to 4 knots, we decided to give up on Post Madison and head home. We didnít want to bend on the iron jib to make it home.

So we sat there at a port tack bobbing for a while and finally got about 2.5 knots on the GPS towards home. We made sure to point N as much as possible so we didnít get stuck below our Marina.

We made it home in time and didnít have to fire up the motor until putting down the sails, but I wanted to see if anyone has an opinion on why the boat might have been slower on the port tacks. One thought that comes to mind is there may have been a current and the GPS was showing us the current speed. The other (more likely?) one is that the winds just died when we tacked and came back when we tacked the other way. I doubt it would be the boat, even though Iíve never seen one with no traveler and the mainsheet line coming from the right of the cabin top. Maybe our weight wasnít distributed correctly? Iím sure we had too much weight aft in the cockpit with all 5 of us there.

What do you think?
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Old 12-04-2006
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"why the boat might have been slower on the port tacks."
Actually, it is not unusual for a boat to be *slightly* faster on one tack than the other. Especially on budget-priced boats, the rudder and keel may not be installed perfectly true and the keel often isn't faired perfectly symmetrically, especially after years of pervious owners. But that's a difference of a fraction of a knot, something to bother racers not stop the boat dead.

"One thought that comes to mind is there may have been a current and the GPS was showing us the current speed. " Probably on the nose. The GPS shows your speed over ground ("SOG") not your speed through the water. You need a regular knotmeter with an impeller in the water to read actual speed versus the water. Consider this:
If you are in a car moving down the road at 30mph...that's like being in a boat moving through the water, and the airflow is analogous to the current moving the water, for our purposes.
Now, stick your hand out the window, fingers together, palm faing you, fingers forward. Your hand/palm/fingers is pretending to be the keel. When the keel is facing straight ahead, into the current, it simply slices through. But pivot your wrist a boat--swing the keel at an angle to the wind--and WHAM, your whole hand moves over.
In the same way, if your keel gets sideways to the current, your boat can be pushed sideways--and that's often not the direction you are trying to go in. And usually not "symmetric" for your purposes of tacking against the wind.
That's where navigation and tactics for racing (or even "We're cruising but we'd like to get ashore for dinner tonight") get more complicated. You need to find out the local currents, if there are current charts in any detail for your area. And then check the charted water depths, because local changes in depth (shallows) will change currents. In some places there will be reverse eddies, too.
Trying to figure out the real net effects, the totals of land shadows on the wind, shoals and currents, wind shifts, and getting the best boat speed OVER GROUND for all of that, is part of why racing can be more like a chess game than just watching the grass grow.

All the rest, hull differences, rig not vertical, crew weight, etc., falls into "tweaking". The gross difference, probably is from the current, as you suspected. If you don't have a knotmeter and can't install one for now, you can still time your speed through the water by throwing a piece of popcorn (biodegradeable, fish & waterfowl food) off the bow and timing how long it takes to get to the stern. A little basic math on speed/vs/distance, and that's how it was done before knotmeters. Still works.
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Old 12-04-2006
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Quote:
Originally Posted by RayMetz100
I was on the water yesterday for 3.5 hours in a C&C 24. It had no traveler and the mainsheet was set up on top of the cabin with the control line coming from just the right side into the cabin top.
The C&C "Niagara" 24 was originally supplied with twin mainsheets in lieu of the traveller. The sheets attached to padeyes either side of the companionway. From the statement above it sounds like someone removed one half of the twin sheet system. This will totally bias your mainsail angle of attack from one tack to the other and may well be the problem with the different performance from one tack to the other.

The port side padeye is probably still there, simply replace the missing tackle from the boom bail to the deck (a twin of what's already there) and you'll be good to go.

Twin sheets enable you to set the boom pretty well anywhere, and can produce results similar to good traveller control, but is more awkward to use, leaves more line on the cockpit floor. A conventional traveller setup is all-around a better deal.
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Old 12-04-2006
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It's a charter boat, so I'm not that familuar with it. I think the mainsheet was rigged like 3 upside down Vs. The middle of the Vs ran through three pullys together on the boom. The left side had one pully, and one end of the rope tied off. The right side had one pully and the loose end mainsheet.

So if you pull the mainsheet all the way in tight, it made a short wide upside down V and kept the boom right in the middle of the boat. As you let the mainsheet in looser, the boom would loosen and hang to one side or the other. I don't see how one mainsheet rigged in this manner would affect the performance of one side vs. the other, even though the mainsheet was controlled from the right side.

If I take it out again, I'll look for hardware where there may have been a twin mainsheet setup like you described.

With the setup I described, couldn't you just let the mainsheet half in, then pull the tied off left side out and that would be the second mainsheet lead. That would be about the same as one lead... Unless you replaced one of the middle pullys with a knot. Then you might have to work with with a different sheet depending on the side. So maybe the modification was to simply replace the knots on the boom with a third pulley and run one mainsheet rather than two. I have no idea how that might affect performance, but we made it out there and back ok I guess.

Ray
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Old 12-04-2006
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Ray

I guess I misunderstood your comment - sorry... but it sounds like someone altered the original arrangement that these boats were provided with.

In any event, your speed differences will be from other things as previously described. As hellosailor points out, the GPS is not a reliable indicator of through-the-water boatspeed since it's affected by currents and is giving you speed over the ground. Another possibility is that your knotmeter impeller is not installed parallel to the centerline of the boat, indicating different speeds on each tack.

The sheeting arrangement you describe will work as well as any non-traveller based system, I suppose, but will not be as performance oriented.

Short of the twin sheet system I described (which is a rather clumsy substitute), there's nothing like a good, easily adjustable traveller, coupled with a powerful vang to give you good control of the main under all conditions.
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Old 12-11-2006
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I would have guessed current also. While boats will be quicker on one tack, it shouldn't be that big a difference. I suspect that if the boat speed indicator was working it would have confirmed that on one of the tacks you were heading into a current of a knot or two.
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