What would cause this behavior - SailNet Community
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post #1 of 24 Old 01-20-2008 Thread Starter
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What would cause this behavior

I thought I was pretty used to sailing a Catalina 27 but last summer I encountered some behavior I'm not sure I can explain.

I was close hauled on a port tack in about 15 knots of wind and 2' seas, making about 4 knots accouding to the knot meter.

I was pinching it a bit on purpose in an attempt to make a mark but I noticed that with the slightest inattention and I would instalntly start to tack. It seem like the the helm (wheel) was very very tender.
The tide was against us supposedly at 2 knots but the GPS said we were standing still or going backwards over ground.
We were near a shoal (about 20' water with 60' all arround).
I suspect that the current was probably faster than the book said right at that point and that combined with the waves and my pinching we couldn't make any forward motion.

But way did the helm feel so strange?
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post #2 of 24 Old 01-20-2008
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If your knot meter is accurate, and your GPS groundspeed was zero, then you were in 4 knots of contrary current.

By pinching you probably negated some weather helm and that, combined with the effects of the current may have caused the "twitchy" feel of the helm.... but if indeed you had 4 knots thru the water then that should have felt more normal. Was your GPS reading VMG to that mark? or raw GS? If VMG then you could have been experiencing some sideways push while not gaining on the mark... (kinda thinking out loud here) and that sideways effect could unload the rudder.

Strong currents, with their eddies and swirls can do some strange things.

Ron

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".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)

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post #3 of 24 Old 01-20-2008
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The current probably speed up due to the shallower area you were in... if you reduce the volume, the velocity increase.. The knotmeter only tells you how much water is going by the hull... not how fast you're moving over the ground...

Was the helm as twitchy as it gets when you're backing the boat??

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post #4 of 24 Old 01-20-2008
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What speed do you usually sail at 15 kts.? 4 knots in that kind of wind, close hauled, in a C27, is slow. Could be you were just to close to the wind and that it why it was squirrely. That speed says to me that you were standing still or slipping sideways in a current. Should have made much better VMG by sailing the wind angle and tacking.
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post #5 of 24 Old 01-20-2008
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Good point Tommy, pinching is rarely worth it.

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post #6 of 24 Old 01-20-2008
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Ahh, the wonders of having actual helm feel I miss them, what with hydraulic steering and all. Wouldn't know what's going on with the rudder if it hit me on the head.
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post #7 of 24 Old 01-20-2008
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If the boat behaviour was unusual, I guess at the effect of the shoal in strong currents, it can set up eddies under the water that play games with your keel and rudder.

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post #8 of 24 Old 01-20-2008
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Could you be draggin something on the rudder?
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post #9 of 24 Old 01-20-2008
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Helm probably felt strange because you had forward motion but no actual forward force over the current that was pushing against you. As an experiment - simply take the boat out and try going in reverse with an idle. The helm will be shaky then too...A Cal-27 is not the kind of boat that handles reverse well (or simulated effects of being in reverse) and the lack of positive forward force the rudder was acting more like it was in reverse when the actual forces are all netted out...

I had an experience once where I was in the Tacoma narrows - current was against me - full sails with +15 knots, I was doing 6.5 knots - getting nowhere... even tried full throttle with the motor.... and nothing... the helm was very tender when normally it would not be..

I got out of the situation by pointing the boat closer to shore which allowed the boat to get some traction...as closer to shore the less effect the current will have.... took some 2 hours finally to break it... when normally it would of been a 15 minute adventure...The good news is that the grill provided plenty of flavor and I ate well...

-- Jody

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post #10 of 24 Old 01-20-2008
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I think Faster nailed this one again. Your knot meter was measuring how fast your boat was moving through the water. As an example, moving 4 knots through the water in a current 6 knots against you indicates you're going backwards over the ground 2 knots. That does not translate into backing up at 2 knots in slack water though. The eddies/currents in fast moving water can cause your boat helm to be squirrely.

We take our boat through Deception Pass all the time when it's running at 6 or 7 knots with us. It can be like a little amusement park ride with all the currents but you just kind of go with the flow, zigging and zagging while trying to keep the bow pointed in the direction you want to go. We've gone through Malibu Rapids a couple of times which runs at 9 knots. That one really gets your attention.

Ray
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Boating for over 25 years, some of them successfully.
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