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Old 19-10-2010, 22:35   #31
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Take a look at this discussion on the Onvi, especially the comments in the Southern ocean
SSCA Discussion Board • View topic - Alubat Ovni 435 .poor AVS, is that so bad?
Paul L
Something I've noticed is that posters are conflating centerboard boats (ie. Tartan 34) and dropkeel boats (Ovni, Clearwater).

With a centerboard boat the ballast is in the fixed portion of the hull, usually a stub or short keel and a lightly weighted centerboard drops thru this. Some of the previous posters have indicated that losing the board was no big catastrophe, the boat sailed acceptably afterward.

With a dropkeel, the 'centerboard' is the ballast and it usually retracts mostly or completely into the canoe hull. Framing for the heavier board has to be much more substantial and loss might be fatal.
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Old 20-10-2010, 09:01   #32
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There are two T34's

B/D of 35%++ for my own needs is desirable.

The Tartan 34-C numbers I have here are 11,200 displacement and 5000 ballast = BD radio of 45% which is pretty good. She also has a D/L of 320 = heavy cruiser

The Tartan 34-2 numbers I have here are 11K displacement and 4400 ballast = BD radio of 40% which is just over the mark. She also has a D/L of 205 = light cruiser

From a numbers perspective, where she seems to fail is in SA /D (slow in light winds); L/B, Capsize, Roll Period, Roll Acceleration (knockdown and roll recovery); Motion Comfort. Experience probably proves otherwise.

The T37 is a better boat IMHO.
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Old 20-10-2010, 09:09   #33
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There are two T34's

B/D of 35%++ for my own needs is desirable.

The Tartan 34-C numbers I have here are 11,200 displacement and 5000 ballast = BD radio of 45% which is pretty good. She also has a D/L of 320 = heavy cruiser

The Tartan 34-2 numbers I have here are 11K displacement and 4400 ballast = BD radio of 40% which is just over the mark. She also has a D/L of 205 = light cruiser
The 34C is a center board boat, the 34-2 has a moderately deep fixed which is why I did not mention it.

Why did you pick the specific value of 35% min B/D?
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Old 20-10-2010, 09:37   #34
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This is stating the obvious, but the righting moment of the ballast also depends on the length of the arm. So a keel boat with 30% B-D might have the same rolling stability as a centerboard version with 40% B-D. The centerboarder will displace more, and this could affect performance.

The nice thing about a centerboarder is that you can move the center of resistance aft (board partway up), or eliminate it (board up). This is really nice in high winds and breaking waves. Example: when overpowered in a high performance dinghy you simply raise the centerboard part way instead of reefing.

I believe the Ovni's are true centerboarders. The Atlantic is another example of a lifting keel.
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Old 20-10-2010, 09:50   #35
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Centerboards

Have been sailing one for 30+ years and shes been around 53 years. Not sure I'd every own a non-centerboard for crusing New England.
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Old 20-10-2010, 10:08   #36
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Why did you pick the specific value of 35% min B/D?
It's my reasonable choice based on YD principles and other BWS characteristics I've researched, as well as other number-head YD cruisers testimonials, and the fact I cannot have hedges and fuzzy variables in a spreadsheet. So, if something is say 33%, its still a consideration but something I need to weigh against other factors. It's only numbers.

What are you suggesting? 5%? Pick your own poison.
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Old 20-10-2010, 10:14   #37
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An important point here I think - some centerboard boats are "keel/centerboarders" in that they have an external ballasted keel with a centerboard for additional draft. Many of these boats will sail fine even upwind without the board down. Other boats are "true centerboarders" in that they have no external keel, the ballast is all internal inside of the hull and the centerboard is usually pretty necessary for tracking especially upwind(often retracted fully downwind). The French (Ovnis, Garcias etc) have long built boats that are "true centerboarders", deriveurs integrales in French, that are often aluminum and have many thousands of miles of blue water and high latitude sailing. Lifting keel boats are another animal altogether that have externally ballasted keels that have a mechanism to lift them to reduce draft-these boats would be more like conventional keel boats, other than the mechanisms. Many of the Ted Hood boats, for instance, are "true centerboarders" whereas a Tartan 37 is not. Good to keep these vital differences clear I think.
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Old 20-10-2010, 10:16   #38
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This is stating the obvious, but the righting moment of the ballast also depends on the length of the arm. So a keel boat with 30% B-D might have the same rolling stability as a centerboard version with 40% B-D. The centerboarder will displace more, and this could affect performance.
Thats a misconception. You need to consider the beam when calculating capsize or period along with displacement. Also via AVS.

A real measurement would be STYXX but the input values are hard to come by,
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Old 20-10-2010, 10:18   #39
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Can we try and build a list here of "true centerboard" boats that might be on market?

I'm fixated on the OVNI, which I will never be able to afford.
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Old 20-10-2010, 11:32   #40
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Thats a misconception. You need to consider the beam when calculating capsize or period along with displacement. Also via AVS.
Notice that I was writing about the "righting moment of the ballast," not the capsize moment. Clearly you're correct - beam also affects a boat's stability. The point is that some posts were comparing boats of the same hull shape, and comparing the B-D ratios, but not mentioning the moment arms of the ballast.
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Old 20-10-2010, 11:36   #41
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Doesn't matter. All i want is a boat I can afford. I wish there was a poor mans OVNI somewhere...=(
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Old 20-10-2010, 12:12   #42
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I hear you. The new Boreal is also beautiful.

How about Garcia? There are some older ones on Yachtworld, but still not cheap. Maybe with time....
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Old 20-10-2010, 14:27   #43
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oh gad that Boreal is fantastic
Bienvenue chez Boreal

Garcia is up there $$$
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Old 21-10-2010, 04:25   #44
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the list

Southerly will be on the list, I am not sure if all of them.

There are also LK Jeanneaus I think, and Bennetaus too.

Then there is the Ovni and a good bunch of other French alloys.

b.
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Old 21-10-2010, 07:00   #45
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The Southerly has a true swing keel, not a centerboard. I believe that is also true for the Atlantics made in Holland.

The French boats are all centerboarders. If I wanted a centerboard, I would buy one of Ted Hood's Little Harbors before I bought an Ovni.

And if you are on a budget, what's wrong with a Pearson 35? It's a nice sailing boat.
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