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Old 06-01-2015, 17:17   #31
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Re: CAT BRIDGE DECK CLEARANCES??

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Originally Posted by 2Hulls View Post
So, please enlighten me as to what took place in 93
Loch Crowther died in 1993, and Christophe Barreau took over.

I have seen boats from 1993 and older, and I've seen boats from 1995 forward.

Hulls from 1995 forward are wider, bridgedecks lower, salons larger, boats heavier.


To the OP: if you look at that picture, you can see the color change at the waterlines/fouling and see where her normal lines fall.
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Old 06-01-2015, 17:50   #32
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Re: CAT BRIDGE DECK CLEARANCES??

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Hulls from 1995 forward are wider, bridgedecks lower, salons larger, boats heavier.
...and boats bigger and fabrication methods improved. And more changes occurred in 98 and 02. This doesn't mean the Catana factory necessarily changed the way they determined where to paint the anti foul. Same factory and, even maybe, the very same people determined the paint lines. This is all presumed when making an "assumption". I was offering a reasonable data point. Why do you feel the need to prove it wrong? To demonstrate some knowledge? It's a stated assumption. By definition it might be wrong and intelligent readers know that.

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Old 06-01-2015, 18:56   #33
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Re: CAT BRIDGE DECK CLEARANCES??

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I don't understand how post production stern extensions will have lower than designed clearances as they are adding some buoyancy.

.

Most stern extensions are added when the boats get so overloaded that they start dragging their sterns. Overloading reduces bridgedeck clearance.

Immersed buoyancy gains are tiny, when compared to the weight of the extension. Even if it gained buoyancy enough to lift the stern then the bow would pitch down. Cant alter physics.
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Old 06-01-2015, 19:07   #34
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Re: CAT BRIDGE DECK CLEARANCES??

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Quite right. I dont agree either. My boats design - Phisa 42 - is the catana 401 mould lengthened in the mould at the stern to amoungst other things carry more weight aft (think bigger tender basically). It doesnt sail bow down when pressed at all probably as the design has been better matched to the real world load placement.
Curious....was the mast positioned in a different position to the Catana 401?
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Old 06-01-2015, 19:14   #35
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Re: CAT BRIDGE DECK CLEARANCES??

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Originally Posted by Seaslug Caravan View Post
Most stern extensions are added when the boats get so overloaded that they start dragging their sterns. Overloading reduces bridgedeck clearance.



Immersed buoyancy gains are tiny, when compared to the weight of the extension. Even if it gained buoyancy enough to lift the stern then the bow would pitch down. Cant alter physics.

Most stern extensions are added because the boat didn't meet design specs and are therefore heavier than planned. From my experiences after having owned two Seawind 1000's, the stern extensions negated the affects of pitching and hobby horsing and the bows would pitch down much less.
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Old 06-01-2015, 20:55   #36
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Re: CAT BRIDGE DECK CLEARANCES??

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Most stern extensions are added because the boat didn't meet design specs and are therefore heavier than planned. From my experiences after having owned two Seawind 1000's, the stern extensions negated the affects of pitching and hobby horsing and the bows would pitch down much less.
Ok , Last attempt. A catamaran hull which is wide in the stern and fine in the bow will naturally assume a bow down trim when the rig loads up and more of the total displacement is taken by the lee hull. This is the nature of the beast.
A double ended hullform like the Wharam will quite obviously depress more evenly as it loads up with more of the total displacement.

Hence adding a transom extension can increase this natural bow down trim as more reserve buoancy has been added aft.

The seawind 1000 hull you refer to was derived from the Jutson designed 850 . This
brand has a good safety record and many owners are very happy with their boats. The 1000 is considered a safe coastal cruiser.
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Old 06-01-2015, 20:59   #37
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Re: Cat Bridge Deck Clearances?

The mast is in exactly the same place as the 401 and she sails nice and flat even beam reaching in 30 knots (if you dont see it then your not gonna).

No increased hobbyhorsing either in fact quite the opposite I would say- longer waterline and more central center of gravity = LESS hobby horsing
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Old 07-01-2015, 02:22   #38
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Re: Cat Bridge Deck Clearances?

Well Guys this isn't getting any clearer, infact its getting more confusing.

Thought a Leopard 42 was a pretty good all round option in a Cat.

Locate the 'Leopard Easy to sail' thread and come away confused as one member says they are atrocious bridge deck slammers and another says that's not the case.
Leopard 42 - Easy to Sail?

On my other thread 'OZ CAT QUESTION' I was told the Corsair 3600 was going to be a slammer as well because it had trenches going down into the hulls.
OZ CAT QUESTION - Page 2 - Cruisers & Sailing Forums

And looking at this pic of the underside of the Leopard 42 there are also trenches.....

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Old 07-01-2015, 02:39   #39
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Re: Cat Bridge Deck Clearances?

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Hi Guys.... anybody done some research into bridgedeck clearances from best to worst and whether they could post up a list of makes and models for us newbies?
Hi,

If You need no any other numbers, but just bridgedeck clearance, take it @ 6% of LOW.
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Old 07-01-2015, 02:42   #40
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Re: Cat Bridge Deck Clearances?

Alias
Maybe you should look at another way and enquire if any cat does not "slam" in certain conditions.
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Old 07-01-2015, 05:15   #41
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Re: CAT BRIDGE DECK CLEARANCES??

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Originally Posted by Seaslug Caravan View Post
Ok , Last attempt. A catamaran hull which is wide in the stern and fine in the bow will naturally assume a bow down trim when the rig loads up and more of the total displacement is taken by the lee hull. This is the nature of the beast.

A double ended hullform like the Wharam will quite obviously depress more evenly as it loads up with more of the total displacement.



Hence adding a transom extension can increase this natural bow down trim as more reserve buoancy has been added aft.



The seawind 1000 hull you refer to was derived from the Jutson designed 850 . This

brand has a good safety record and many owners are very happy with their boats. The 1000 is considered a safe coastal cruiser.

Incorrect. When you ad stern extensions to the Seawind your not making the stern any wider but exactly the opposite. The stern sits clear of the water when at rest but you are gaining about two feet of waterline which follows the shape of the hull. Trust me, we sailed Seawinds without stern extensions and with, and the boats with stern extensions have a MUCH more sea-kindly ride. Also I think the Seawind 1000 has done enough blue water passages to be considered a good offshore boat.
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Old 07-01-2015, 05:36   #42
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Re: CAT BRIDGE DECK CLEARANCES??

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Hence adding a transom extension can increase this natural bow down trim as more reserve buoancy has been added aft.
This wasn't the experience of the Manta when it lengthened the transoms to go from 38' to 42' as production models.

This wasn't our experience when we added 27" to our transoms. We pitch much less and don't bury the bows anymore than before. If it matters to your point, we added ~1200lbs of reserve buoyancy once the build weight is subtracted.

I know many who have added transom extensions and none of them relate the experience you claim.

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Old 07-01-2015, 07:03   #43
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Re: Cat Bridge Deck Clearances?

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And looking at this pic of the underside of the Leopard 42 there are also trenches.....
I don't think those are "trenches" as originally discussed on the other boat. I think the poster in that case was describing an athwart ship discontinuity caused by the walkway in the saloon. The fore/aft discontinuities you see in the Leopard 42 are probably structural stringers in the center portion and what are commonly referred to as "knuckles" along the hulls that serve to increase interior volume. Both of these things are not uncommon in cats of multiple builders. Their effect on the overall bridge deck "lowness" is open to discussion. But the bad effect of athwart ship protuberances is pretty easy to imagine, IMHO.

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Old 07-01-2015, 13:03   #44
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Re: Cat Bridge Deck Clearances?

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Originally Posted by ALIAS View Post
Well Guys this isn't getting any clearer, infact its getting more confusing.

Thought a Leopard 42 was a pretty good all round option in a Cat.

Locate the 'Leopard Easy to sail' thread and come away confused as one member says they are atrocious bridge deck slammers and another says that's not the case.
Leopard 42 - Easy to Sail?

On my other thread 'OZ CAT QUESTION' I was told the Corsair 3600 was going to be a slammer as well because it had trenches going down into the hulls.
OZ CAT QUESTION - Page 2 - Cruisers & Sailing Forums

And looking at this pic of the underside of the Leopard 42 there are also trenches.....

Those kinds of boxy protrusions aren't desirable either, but certainly better than one which goes the full width of the bridgedeck.
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Old 07-01-2015, 16:16   #45
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Re: Cat Bridge Deck Clearances?

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Well Guys this isn't getting any clearer, infact its getting more confusing.
hhahahaha Welcome to CF!

Lots of armchair experts on here and just as many with extensive relevant experience. You will need to get a nose to filter the former from the latter to make the most of it

Also theres a big difference between a slam and a slap. those knuckles will slap in certain conditions but not slam (based on my experience with catana knuckles)
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