Now THAT is a centerboard...

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Now THAT is a centerboard...

Postby Richincident » Mon Oct 11, 2010 8:28 pm

This year I have gone crazy and had THE INCIDENT hauled with straps so I could take a look at the centerboard--especially the shackle that fastens the stainless steel pennant to the centerboard.

Once we had the boat out Eddy Vachon, sailboat magician and sailor, lowered the board all the way. According to specs I have seen the Soverel 28 draws 3' with board up, 6' with board down.

Slight revision. With board down it appears that THE INCIDENT draws 8.5' at least. Pretty amazing. All in all the boat looked good after a very busy season!

Image

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Re: Now THAT is a centerboard...

Postby Rachel » Mon Oct 11, 2010 10:06 pm

I wonder if the draft discrepancy is accounted for by the fact that the boat was not meant to be sailed with the centerboard lowered all the way to vertical like it is in your second photo?
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Re: Now THAT is a centerboard...

Postby Richincident » Tue Oct 12, 2010 7:09 am

Well I sure haven't sailed with the board fully extended! I usually lower it 20 turns on the winch. Eddy V thinks that you CAN sail with it full extended judging by the heft of the board and the size of the pin.

109 turns to return it to full upright position!

While I doubt I will ever fully extend it while sailing, I am ready to go a lot further than previously.

Single handing I would never have enough time to wind the crank that many times!
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Re: Now THAT is a centerboard...

Postby Figment » Tue Oct 12, 2010 9:07 am

I'll hazard a guess that lowering the board that far (moving the CLR forward) will induce a lot of weather helm.
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Re: Now THAT is a centerboard...

Postby Richincident » Tue Oct 12, 2010 10:33 pm

MORE weather helm is not what I am looking for! I feel the amount I have now is about right, but would like to decrease it slightly. I will not be able to test your thesis until next year, but it sounds right.

THANKS,

RIchard
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Re: Now THAT is a centerboard...

Postby Sailor Simon » Tue Dec 28, 2010 10:12 pm

I'm new to this centre board on a cruiser idea. Always had a full keel pilot boat from west coast England. Real slogger in the heavy stuff no matter where you were pointing. I've just bought a Phillip Rhodes Swiftsure33 centre board sloop. Will I be that much more maneuverable whilst beating to windward in a narrow channel? Will I run any faster off and down with the board up, or partially so? Tell me so, or no and why... Sailor Simon[ Big waves and Big wind make Swell stories.
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Re: Now THAT is a centerboard...

Postby Hirilondë » Tue Dec 28, 2010 11:03 pm

The biggest advantage to a centerboard on a full keel boat is the draft. The boat can be designed with a shallower keel that utilizes a board to make up for the loss of lateral surface. I don't think the Swiftsure is any more maneuverable because of it.

It would be slightly faster off the wind and down wind with the board up, but not significantly so. Reducing wetted surface, when it is not needed is always faster.
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Re: Now THAT is a centerboard...

Postby Tom Young » Wed Dec 29, 2010 9:10 am

Richincident wrote:This year I have gone crazy and had THE INCIDENT hauled with straps so I could take a look at the centerboard--especially the shackle that fastens the stainless steel pennant to the centerboard.

Once we had the boat out Eddy Vachon, sailboat magician and sailor, lowered the board all the way. According to specs I have seen the Soverel 28 draws 3' with board up, 6' with board down.

Slight revision. With board down it appears that THE INCIDENT draws 8.5' at least. Pretty amazing. All in all the boat looked good after a very busy season!


Nice boat! I would suspect the board is not designed to lower that far. It would be interesting to see if windward performance improves with the full lowering though,.....

I wonder if someone just added length to the pendant last time it was replaced?

Here is the full drop position on my boat. Image

But I would be concerned that the pivot pin placement and board depth are designed for a certain lowering angle that protects the board in the even of some sideways force such as in a grounding. Say it came off a wave an onto the bottom, would the board kick back toward the trunk or push straight up?

I'm sure you'll find the info on how it's designed over the winter. Good luck.
Last edited by Tom Young on Wed Dec 29, 2010 9:27 am, edited 1 time in total.
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Re: Now THAT is a centerboard...

Postby Tom Young » Wed Dec 29, 2010 9:20 am

Sailor Simon wrote:I'm new to this centre board on a cruiser idea. Always had a full keel pilot boat from west coast England. Real slogger in the heavy stuff no matter where you were pointing. I've just bought a Phillip Rhodes Swiftsure33 centre board sloop. Will I be that much more maneuverable whilst beating to windward in a narrow channel? Will I run any faster off and down with the board up, or partially so? Tell me so, or no and why... Sailor Simon[ Big waves and Big wind make Swell stories.


Very nice boat. What you should get with your centerboard over you last full keeler, is a few degrees higher pointing to windward. With my full keel centerboarder, I get an average of 10 degrees higher angle to weather on the gps with the board down. It's varies due to seastate, wind strength and a zillion other variables. The effect off the wind becomes less obvious although in my case, for balancing the boats CL, it can be helpful. At least it's fun to think so....

Centerboards are tricky as many sailors I've met can't tell if they're up or down. I think they're looking for the wrong things. You won't generally feel a difference in much of the boats immediate performance but look to it's actual course change over the ground. Then you may begin to see the subtle differences in actual changes in apparent wind and at times speed. If you like to sail, you'll adjust your centerboard as if it's a part of the sail trim.

You may find the boat will turn through the wind a bit quicker with the board down in some conditions(you'll never be a fin keel boat with detached rudder though,...), but it's main purpose, especially in beating out a narrow channel, will be the extra lift it will give you.

Mine is a bronze centerboard that takes the draft from 4' to about 7 1/2'.
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Re: Now THAT is a centerboard...

Postby Paulus » Wed Dec 29, 2010 9:51 am

The vertical position of the centerboard looks very awkward...

I also know of several boats with centerboard design (smaller boats) where the board can be removed once taken off the cable and lowered beyond its maximum position, by simply lifting it off - I would not operate the boat with any centerboard lowered beyond its design max position without checking into that first...

My $02.
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Re: Now THAT is a centerboard...

Postby Duncan » Wed Dec 29, 2010 10:48 am

Figment wrote:I'll hazard a guess that lowering the board that far (moving the CLR forward) will induce a lot of weather helm.

I doubt it, I think that would be a pretty serious design error.

Centreboard boats are designed and balanced to be sailed with the board down,
on the points of sail where it helps, i.e. on the wind.

Raising the board to reduce lateral resistance allows leeway,
so it's a pretty sloppy way to reduce weather helm, by skidding through the water!

On most boats, too much weather helm means they are overpowered.
The answer is therefore better sail trim (i.e. flatter sails, take a reef, etc.),
not reduced lateral resistance.

If the board is not supposed to go down all the way to vertical, it will be designed that way in the first place, e.g.

Image

This drawing is of a Paceship Westwind 24, by Ted Hood.
When I sailed this boat, my rule of thumb was board down on the wind,
board up off the wind, and down about 1/3 on a broad reach.

The hull was very rounded and slippery,
so it was easy to feel when it needed the board to keep going straight.
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Re: Now THAT is a centerboard...

Postby Richincident » Wed Dec 29, 2010 11:47 am

I agree that my board has MUCH too much cable on it. I can't imagine there is a lot of benefit to going all the way to that position, and I sure never did that sailing. I also never realized that I had that much additional cable!

My experience has been that the boat does point higher and tack more easily with more centerboard, but not by an earth shaking amount. I am going to try recording a track next year and see what happens with and without. It does not seem like a dramatic difference at all to me. With all centerboard boats I usually sailed with full board up wind, half (depending on feel) on a tight reach, and little or none DDW or on a broad reach. The whole operation is different on the Soverel.

What kind of boat do you have there Sailor Simon? Looks gorgeous in the straps!
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Re: Now THAT is a centerboard...

Postby Sailor Simon » Wed Dec 29, 2010 7:36 pm

Richard, that's not my boat in the straps, that's Tom Young's boat. Mine is in a thousand pieces in 4 barns near Wasaga Beach in Georgian Bay. AURORA will be a hull up restoration/repair. Presently I sail a 1967 Bristol Channel pilot boat, named HOLDFAST, (see her at http://www.woodenboatholdfast.yolasite.com). Eastern Georgian Bay is the world's largest fresh water archipeligo. Georgeous beyond gorgeous and nobody around. They call the area the 30,000 islands. It's the 60,000 island that lie in the 6" to 7' zone that concern me. That's how the centre board idea was born for me. Much work to do, so if anybody has good ideas on just about anything, send them along to me... Sailor Simon
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Re: Now THAT is a centerboard...

Postby Duncan » Wed Dec 29, 2010 7:47 pm

Richincident wrote:I agree that my board has MUCH too much cable on it.
I can't imagine there is a lot of benefit to going all the way to that position, and I sure never did that sailing....

No, no, your centreboard is supposed to be all the way down going to windward, making it a slender, high-aspect foil.
High aspect ratio = High lift/drag ratio = greater speeds to windward with less leeway.

That's what you have with your centreboard, a fast, high-lift foil, like this one:

Image

Cranking it up partway cuts the lift, but still leaves you with all the drag. Not a very good trade.

I think the issue here is maybe too high a gear ratio on the cable (too many turns)?
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Re: Now THAT is a centerboard...

Postby Tom Young » Thu Dec 30, 2010 10:10 am

Richard, my boat is an Alden Challenger built in 1961. Somewhere there must be some design specs for your boat and centerboard arrangement. If my boats centerboard was lifted by a cable and reel instead of the screw on the cabintop that limits the travel, it could also be dropped to vertical. But it would be very vulnerable in that state. Here's the original drawing from 1959. Visualizing the board lowered to vertical and little of it left in the slot, you can imagine how vulnerable and easily damaged it would be.

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Re: Now THAT is a centerboard...

Postby Rachel » Sun Jan 02, 2011 8:46 pm

Seems like there is a good chance that if you lower the centerboard until your boat drafts the designed amount (in feet/inches), then the resultant centerboard angle would be the designed one (vs. vertical).
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Re: Now THAT is a centerboard...

Postby Paulus » Sun Jan 02, 2011 9:27 pm

I have sailed several boats with centerboards or swing keels - one thing I always considered (worried about) was that if the board would run over an obstruction, such as a rock, once the obstruction cleared, the board/keel would basically free-fall back to its previous position, stopped only by the cable.

There is a point where the cable can no longer stop this swing motion effectively... the narrower the angle between the cable and the board at the point where it connects to the board, the more severe the abuse will be the cable will "see" in order to stop the keel/board.

Should the cable fail, the only next "stop" the board/keel will find will be structural fiberglass - not designed to take such a hit.

Others have made excellent points about other items to consider - be cafeful to use the centerboard as it was intended by the designer...

FWIW
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Re: Now THAT is a centerboard...

Postby EKE » Tue Jan 04, 2011 1:42 pm

My experience is that most keel/CB designs in the CCA era carried their boards swept back at a fairly dramatic angle.

On my Dolphin 24, there is a "tooth" on the radiused top end of the board that hits a stop on the trunk and prevents it from lowering beyond the designed angle. The cable doesn't stop it. Some Dolphin owners have ground away the tooth to allow the board to go lower, but I think it's bad practice, and it puts stress on the cable. Besides, having it down further means moving the center of lateral resistance forward, and that means more weather helm, as has been noted.

Here's a shot of Robin Lee in slings to show the Dolphin board in its full down position:

Image
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Re: Now THAT is a centerboard...

Postby Duncan » Tue Jan 04, 2011 6:19 pm

I think that Ted Hood would have to be counted as one of the foremost proponents of keel/centreboards.

Here's a set of hull outlines from his brochure " A History and Technical Overview of the Hood Design Philosophy"

Image

Here are "Robin" and "Freestyle", the winners of the Newport-Bermuda race, in 1968 and 1992, respectively.

Image

It looks to me as if these centreboards are narrower and more vertical than shown on Tom Young's Alden Challenger,
while not being straight up and down like the fixed racing foil I showed on the Open 60, a few posts above.

So, I think it all depends what designer, what boat, and so on.
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Re: Now THAT is a centerboard...

Postby Tom Young » Tue Jan 04, 2011 7:22 pm

Duncan wrote:
So, I think it all depends what designer, what boat, and so on.


It sure does. I've had fun studying the centerboards on boats like Finesterre(a sister ship actually), old style, and newer high aspect centerboards like those designs of Bruce Kirby and a few other performance designers of canoe body and centerboard only for best performance.

These days though, some of my favorite boats are Jboats. The new daysailing designs are impressive from many designers/builders. Now from Jboats, we have 2 shoal draft models. A successful 30'er and now the new J108, a bit bigger(36' or so). Most interesting(to me) is J is building a "stub" fin keel, innovative design, and a centerboard.

Some new ideas, and some old ideas, coming around again.

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Re: Now THAT is a centerboard...

Postby Duncan » Thu Jan 06, 2011 1:07 pm

Tom Young wrote:Some new ideas, and some old ideas, coming around again.

That's an eye-opener, for a J boat!
I went Googling around to find out more about the J108 and J109. One thing led to another, and I came across this:
Chuck Paine wrote:It’s taken me most of my working life to discover that in some ways
I haven’t been able to contribute very much that is really “new” to the field of yacht design.
However, I do believe that when I was finally able to master those aesthetic principles
developed years earlier by Alden, Herreshoff, Crocker, Rhodes and other famous designers,
I was able to create my finest work. And that has made it all worthwhile
.
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