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Go Back   SailNet Community > General Interest > General Discussion (sailing related) > What does the Centerboard Do...?
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Thread: What does the Centerboard Do...? Reply to Thread
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Topic Review (Newest First)
09-19-2012 08:45 PM
chef2sail
Re: What does the Centerboard Do...?

We have a 35 ft k/c boat and there is a substantial enough difference pointing ability and also righting moment to use it in winds over 12 knots, especially on the windward legs.

Our draft is 4'6 witout and 7.5 with. Without the centerboard down we would reef at 15-16 knots ( no gusts), with it down we can remain with fuull sails and no terrible weather helm till 20 ( no gusts). Our pointing ability is 4 degerees higher also

Also the drag of the centerboard will depend on its thickness and shape. Ours is quite heavy (Laminate over metal)( my wife once dropped the line when deploying it and the boat shuddered when it swung down into place. It is also very tapered with a very thin leading edge to reduce its drag.

We use ours quite frequently to gain an advantage on windward legs and often can sail inside ( point higher) many boats because of it ( not the only reason). It is on our checklist when entering shallower waters to raise it also.

We deploy it every time out to at least clear the trunk of inwanted critters so it doesnt get frozen into place through lack of use.

Dont get rid of it and learn how to use it to your advantage. Big differnece in useage from a small sailboat using it for its keel.

Dave
09-19-2012 08:12 PM
sawingknots
Re: What does the Centerboard Do...?

squid!I haven't had the c.b. down on my py in a couple of years,I've never been able to see much difference,but then I'm not a racer so a tiny bit of extra speed doesn't concern me one way or the other,the py c.b. is fiberglass so it doesn't weigh that much
09-19-2012 06:04 PM
Irunbird
Re: What does the Centerboard Do...?

Quote:
Originally Posted by flo617 View Post
Actually the centerboard down could make broaching worse, during an accidental jibe for example. At least that's the case on a dinghy.
Yep- done it at least a couple times in our 18' Buccaneer!
09-19-2012 05:56 PM
flo617
Re: What does the Centerboard Do...?

Actually the centerboard down could make broaching worse, during an accidental jibe for example. At least that's the case on a dinghy.

When broaching with the centerboard down, the centerboard prevents the boat from slipping and makes heeling even worse (that's sometimes referred to as tripping over the centerboard).

However, at the same time, the centerboard can add stability when running (downwind) as it can dampen the lateral oscillation due to the sail and the waves.

Now I'm not expert nor am I a racer but this is my experience.

On a bigger boat, with a ballast and a higher drag, I'm not sure how much the centerboard will affect the behavior but it should be along the same trends.
09-19-2012 05:34 PM
CalebD
Re: What does the Centerboard Do...?

Squid,
Trust your GPS. You were going faster although not necessarily in the exact direction you were pointing. Hopefully your GPS can also show you your bearing (actual course) as this can help you know your VMG (vector made good?).
My Tartan 27 sounds very similar to your PY 26 in hull design. We have been racing her against other fin keel boats (Tartan 30, Catalina 30 etc).
For one light wind race our CB was stuck up in the slot and would not come down. We ended up winning anyway. No CB deployed = less underwater drag + a little extra leeway. In higher winds I'd speculate that with no CB you would end up with more leeway that trumped the lack of drag. In other words, there is a point of diminishing returns on keeping the CB up as the wind speed increases.
The cut in stone recommendations for deploying the CB given above are more for dinghy sailboats that only have a CB and no keel. Our boats have a keel and track well even without the CB deployed. I'd recommend that you play with different settings of the CB on different points of sail in different wind strengths.
For instance, in high winds (10 - 18) to reduce weather helm on a beat (close hauled) we can raise the CB to 1/2 way, which moves the center of lateral resistance aft. Counterintuitive perhaps but true. This website explains the sci-fi details better than I can: Helm Balance – Center of Effort, Lateral Resistance, Centerboard, Mast Rake - Waves « Jordan Yacht Brokerage

PACESHIP PY26 sailboat specifications and details on sailboatdata.com
09-19-2012 04:55 PM
SchockT
Re: What does the Centerboard Do...?

As others have stated, your lead keel is what provides most of your righting moment. The centerboard's primary function is to generate the lift required to sail upwind. It will certainly reduce leeway when reaching, but the big benefit is allowing you to point much higher when beating. I would not advise removing it! You don't NEED it but without it your upwind performance will suffer. Off the wind it is nothing but drag, so go ahead and retract it and you will sail faster.
09-19-2012 04:18 PM
CapnBilll
Re: What does the Centerboard Do...?

My Aquarius has lead keel in addition to Centerboard. I would like a way to lock it down. It is so light compaired to ballast it mostly just keeps boat from sideslipping on a beam or close reach.
09-19-2012 04:06 PM
NateCP16
Re: What does the Centerboard Do...?

Some people with keel/CB designs end up removing the CB due to maintenance issues. My ComPac 23 only has a 2' keel (no CB), and it sails just fine (though it would make less leeway if it did have a CB or deeper keel).
09-19-2012 04:01 PM
kwaltersmi
Re: What does the Centerboard Do...?

We use to sail a 25' swingkeel boat and found her relatively stable/stiff without the board down, but that boat (Helms 25) did have a very shallow (~6") keel running the length of the hull.

As mentioned above, dropping the board will allow you to sail to weather more easily without moving excessively to leeward. We put the board all the way down when sailing close hauled, about half down on a beam reach, and fully up when we were broad reaching or running downwind. Our centerboard (swingkeel) was heavy, so it also provided a good amount of ballast and therefore changed the boat's center of gravity depending on the amount it was lowered or raised. You'll just have to experiment with your board and see what she likes.
09-19-2012 03:57 PM
peterchech
Re: What does the Centerboard Do...?

Ditto what irunbird says. You start crabbing with the board up. Running downwind it's not an issue, and the extra drag can be safely lost by lifting the cb. Dinghy sailing 101 It should be progressively lower the closer you get to the wind, to fight the side slip and turn the power of the sails into velocity made good (vmg).

Most of your ballast is in your shallow keel, but I'm pretty sure that your cb has significant weight to it and keeping it down low can't hurt, esp upwind. Might want to see if there's a way to lock it down, if you are concerned about broaching/knockdowns, but unlike a catalina 22 or something, your boat doesn't seem to rely on the cb for ballast.

True dinghy or c-22 racers will post here soon I'm sure and explain how raising/loweing the cb effects the center of lateral resistance (clr) since I don't understand that as well as they probably do...
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