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post #1 of 9 Old 08-18-2014 Thread Starter
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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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post #2 of 9 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.

Tom Young sailing a 1961 38' Alden Challenger, CHRISTMAS out of
Rockport, Maine.
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post #3 of 9 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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post #4 of 9 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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post #5 of 9 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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post #6 of 9 Old 08-18-2014 Thread Starter
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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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post #7 of 9 Old 08-19-2014
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Re: What does a centerboard do?

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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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post #8 of 9 Old 05-08-2015
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Re: What does a centerboard do?

Hello Toller:
Some Lessons from Managing a Centerboard
See John Rousmaniere, The Annapolis Book of Seamanship, 4th ed., 2014, p.22. John talks about “the centerboard as a pivot point under a balance beam where the mainsail and jib push in opposite directions.” I like that concept with the centerboard providing upwind side force, and it helps me to visualize this. This helps me to balance my helm and point upwind. But how do I manage my centerboard as the wind pipes up? I know that your question is for the smaller boats but I did not find much guidance for this question on the larger boats. My centerboard is 6 ft. and keel draft with board up is 6.5 ft. so a heft 12.5 ft. down. Some lessons from my Sail & Power, USNA, 1967, and learned long ago on their racing Luders 44 yawls, I still use today:
1. When maneuvering, have the centerboard all the way down, otherwise she makes leeway (remember that pivot point discussed above)
2. Small boats – lower the centerboard to allow you to step up on it next to the keel to right a capsized boat (No, not much help to me on a Hinckley SW59)
3. Resistance to making leeway or lateral resistance - covered above
4. When running, the board is usually all the way up. When beating, it is all the way down. Note: I leave mine down in any wind above a light breeze until the wind is abaft the beam, and then start drawing it up gradually.
5. When jibing in a breeze the board should usually be about a quarter of the way down. Some good discussion around this one, but their (USNA) consensus was all the way down and the boat may trip on her centerboard, all the way up and she can slip to the side causing roll and yaw in heavier seas.
6. When reefing when the wind pipes up and on a beat or close reach, and heel becomes excessive for the boat (17 degrees is my magic number but boat specific) and the helm becomes heavy, the centerboard may be pulled partially up. (Note: I use 45 degrees and have my centerboard pendant marked so) to move your center of lateral resistance (CLR) back while topside you reef the main and then the jib, if required, to move your Total Lateral Resistance (TLR) forward. Note: That you are using both CLR and TCE to balance the boat to conditions.
7. In light air you will probably make better headway with the centerboard up if you have any keel at all on your boat as the board presents too much resistance to forward motion.
That is how we learned managing your centerboard at the academy on the small boats and applied it on the big boats. That was 45 years ago for me. There are some fine sailors on this forum. Maybe they have something more current than this? Well, I hope these old lessons from the “sunny swells of long ago” are helpful. They serve me well.
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post #9 of 9 Old 05-08-2015
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Re: What does a centerboard do?

Are you confusing Heading and Course? Perhaps you "turned" the boat to point west, however were actually making a course to the southwest? How would you know?

The centerboard is vital anytime the wind is not aft, as written above.

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