Center board locking systems?

Boat handling, ideas, questions...
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numbknots
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Center board locking systems?

Post by numbknots »

Does anyone out there have an opinion as to what would happen to a 1,000 lb C/B when one of these boats gets rolled? I'm thinking anyone that has experienced this situation no longer has access to a computer.

Do you think it is safer to raise the C/B in heavy seas and hope for the best? Of course by raising the CB you have raised the CG of boat by quite a bit. Lets see wherer this goes.
Numbknots
... currently experiencing performance anxiety..,

Mike Holibar
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Re: Center board locking systems?

Post by Mike Holibar »

Hi Numbknots, just off the cuff and without any CB experience I would have thought that if the CB can't be locked in the down position, then it ought to be lifted and secured. That amount of weight loose could smah the casing and sink the ship. If your storm tactic is laying a hull, raising the cB would allow the ship to skid sideways and she might be less likely to roll than if the cb was down and "tripped" her up. The lateral resistance of fin type keels is not great when stalled (laying a hull) so the extra leeway from lifting the board might not be all that much.

All the best for Xmas,
Mike Holibar
S/V Fyne Spirit of Plymouth (Freedom 39PHS-1989)
Lyttelton
New Zealand

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Michel
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Re: Center board locking systems?

Post by Michel »

I've had an F33/35 with centerboard, and I agree with Mike. Of course stability is a little less with the board up because the Center of Lateral Resistance moves up. But the board will be secure in the casing and the boat will slide off a wave sideways with less chance to roll over.

A merry Christmas to you all.
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

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Peter
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Location: Bremen, Germany, UK F35 CB Cat Ketch 'Avante'

Re: Center board locking systems?

Post by Peter »

Numbnots,

I've crossed the Atlantic with my F33/35 cat ketch with centerboard in 1996. On the leg from Bermuda to the Azores we had the board up all the time. No clanking noise from the CB. We were hit by a storm during the crossing with puffs up to 48 knots while that wonderful hull was sometime surfing down the waves with 16 knots. At least that's what our GPS said. The boat was steered by our Windpilot wind vane all the time and was going straight ahead as on rails. But then the wind came always from behind. You will only need the CB while going to weather.

Peter

CrazyRU
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Re: Center board locking systems?

Post by CrazyRU »

I had same question. I figure out that I may be capsized only approaching some inlet or in storm conditions offshore. I do raise the board up when I transit from open ocean into inlet. In storm conditions offshore most likely I wont be beating into wind, so the board is up again...
CR
s/v "NEMO" - Freedom 28 Cat Ketch centerboard

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phildowney
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Re: Center board locking systems?

Post by phildowney »

hi after talking to several previous owners of freedoms and reading books on naval architecture my strategy would be to wind the board all the way up even when heaving too, as the board , being like an underwater sail must create a heeling force, the lower ballast probably balances this out in normal sailing but as maurice grifiths said, shoal drafted boats dont trip up over their keels when knocked sideways by a wave thus are less likely to be rolled


plus we are at an advantage over the tall masted modern yacht, take a walk in a marina in a gale and see the heel angle under bare poles of various boats, its quite interesting! remember wind force is not linear , i think its something like the square of windspeed
phil
Owner of Kusi, UK F35 Cat ketch
Southampton UK

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THATBOATGUY
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Re: Center board locking systems?

Post by THATBOATGUY »

phildowney wrote: i think its something like the square of windspeed
phil
This is from my Science Officer aboard S/V Marquesa... (Kerri)

In general, you can use Taylor's formula...

Fw = 0.003 A V^2

Fw = the force of the wind acting normal to a surface facing the wind in lbs
A = the area of the surface facing the wind in square feet
V = velocity of the wind in miles per hour

However, there needs to be a conversion factor/coefficient somewhere - like Marauder said, the force on an object is going to depend on many things, like the density of the medium.

Will this link help?

http://www.sailingusa.info/cal_wind_load.htm

George
George and Kerri Huffman S/V Marquesa Freedom 40 CC CK Sail MarquesaImage

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numbknots
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Re: Center board locking systems?

Post by numbknots »

There was a man and wife from this area in fl that never came back from a trip to bahamas they were in a new freedom 44 I beleive. This was several yrs ago, Many think they rolled that boat in gulf stream and the centerboard came crashing through the trunk. Who knows, maybe a freighter got them. Numbknots
... currently experiencing performance anxiety..,

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Michel
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Re: Center board locking systems?

Post by Michel »

numbknots wrote:There was a man and wife from this area in fl that never came back from a trip to bahamas they were in a new freedom 44 I beleive. This was several yrs ago, Many think they rolled that boat in gulf stream and the centerboard came crashing through the trunk. Who knows, maybe a freighter got them. Numbknots
This must be a 'monkey sandwich', as we call it in Dutch. There were only three (out of a total of 26) Freedom 44s built with a centerboard. This board was kept in a stub U-shaped keel (bottom of the U at the front of the keel) outside of the hull. There was no trunk inside the boat. F44 Angle of Vanishing Stability (AVS) is between 145* and 152*, so the boat will right itself when upside down. I think that even an F40 catketch with CB inside a trunk would survive a roll. The stability of these boats is gigantic. AVS must be over 140 degrees as well. The Gulfstream can be pretty nasty though, I am told. And how about this couple ending up in the Bermuda Triangle? They were perhaps eaten by a gigantic natural gas bubble. :shock:
Michel Capel, Freedom 44 #4 1981 'Alabama Queen', NED8188, cat ketch with wishbones, home port Enkhuizen, the Netherlands, 52*42.238'N 005*18.154'E.

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THATBOATGUY
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Re: Center board locking systems?

Post by THATBOATGUY »

Nothing is indestructibly but the trunk our our 40 is massively built.

George
George and Kerri Huffman S/V Marquesa Freedom 40 CC CK Sail MarquesaImage

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