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  #1  
Old 08-18-2014
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What does a centerboard do?

Okay, a stupid question. The centerboard stops the boat from sliding to the side when the wind pushes it. But....

I have a 12' Petrel; it is basically an aluminum row boat rigged for sailing.
Yesterday there was a steady 12mph wind from the NW; that is a bit much for me, so I went out without the jib.
I sailed a few miles north, raised the centerboard, and turned to sail south. Then I turned west. I expected I would get blown by the wind SE more than making any headway west, but to my surprise it sailed west pretty normally.
In other words, it sailed pretty normally upwind without the centerboard being done.

So I am confused. Is the centerboard less important than I thought? Or does it serve another purpose?
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Old 08-18-2014
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Re: What does a centerboard do?

A centerboard provides lift, in the same manner as a deep fin keel(though not as efficiently for the typical compromises of a centerboard).

It is lift(that the board provides), that lessens your boats slide to leeward.

It's not unusual to not feel a difference in the way a boat sails, board up or down, especially in larger boats.

Subtle indicators, like your wake narrowing as the board provides lift to windward. At times, better speed as apparent wind increases.

The biggest difference(I find) will be a more weatherly course that you may see on a GPS.

My boat will usually pick up 5 to 10 degrees to windward, with the board down.

The board increases draft to 7'6" from 4'. You may see a similar(better?) change in your course to windward with your board down. Try it.
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Old 08-18-2014
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Re: What does a centerboard do?

We use the board almost all the time. We use it from down only 6" to down all the way. We use it to balance the boat, taking out lee or weather helm, stop rolling down wind and at anchor, and to prevent leeway, though honestly, I don't think we get any lift from it. We always reef, rather than sail on our beam ends, so the board is doing it's job, down there in the briny.
If you play around with it, trying varying depths, I think you will get a significant increase in both performance and comfort, once you have found the correct depth for the point of sail and the conditions. A centerboard is certainly not an all or nothing proposition.
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Old 08-18-2014
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Re: What does a centerboard do?

As Tom says, try it. But this time try it with a control against which to measure the effect. Since there probably isn't another Petrel to sail against, use a GPS or smart phone to record your track (I use iNavX). Take a control tack upwind or beam reaching with the board down, then go back to the same place (set a waypoint) and do it again with the board up. I'll wager that you make much more leeway than you think with the board up.
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Old 08-18-2014
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Re: What does a centerboard do?

I notice my centerboard, which is made of wood, will float up out of the trunk some when the load goes off it, when I am going downwind etc. But it is hard to move when there is some wind and the boat is heeling some, this I think, shows it is doing something,a steering vane that the rudder can act against instead of just slipping the boat sideways. If you notice little difference with it up or down I suspect the hull has some chines or runners along it, my Pirateer has a totally smooth rounded bottom and will not steer easily with it pulled up.
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Re: What does a centerboard do?

Okay, so the centerboard is useful for best sailing, but it isn't the vital component I always thought it was, is that about right?

Other boats I have had were pretty flat on the bottom, while the Petrel a bit of V to it. Not really pronounced, but certainly not flat. Perhaps that explains it.

I always had it up or down; I will experiment with other positions.
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Old 08-19-2014
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Re: What does a centerboard do?

Quote:
Okay, so the centerboard is useful for best sailing, but it isn't the vital component I always thought it was, is that about right?
No, that's not the correct conclusion. For a boat without a permanent keel, such as yours, it's critical to upwind performance. You will fall off and your effective course will be nowhere near what it could be. On SailNet we often see new sailors puzzle why they can't go to windward and achieve their objective. Not having the centerboard down is a major contributor.

One reason the Volvo boats use dagger boards is to prevent leeway and provide lift because their canting keels don't when going to windward.
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