Blue Jacket 40 (new racer/cruiser) - Page 12 - SailNet Community
Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

This discussion between Brian and Paulo has been very interesting. In a way they might both be right. At great personal risk of getting caught in the cross fire, allow me to reference this web site: Understanding monohull sailboat stability curves | M.B. Marsh Design by Matthew Marsh (boat designer).

Marsh defines tenderness/stiffness as the slope of the stability curve at low angles of heel. At low angles of heel, a stiff boat has a steep slope and a tender boat has a shallow slope. Initial stability, therefore, is the key to the difference between stiff and tender. Stabilty and stiffness, however, are not the same thing. A tender boat will likely have a higher ultimate stability than a stiff boat that derives her stiffness from beam.

According to Marsh, sail carrying capacity is a function of righting moment in the 15-30 degrees of heel portion of the curve, since this is the area where most sailing occurs. The more righting moment one has in this region, the more sail a boat can typically carry. Righting moment, by the way equals GZ x displacement, so there is no difference between RM and GZ when it comes to determining stiffeness/tenderness and stability (unless you start considering the added dispalcement associated with flooding).

So regarding the Catalina 400 versus the First 40.7. Would have to see the stability curves to be sure, but likely the Benateau has a higher ultimate stabilty, but is more tender than the Catalina 400. The answer lies in the slope of the stabilty curves at low angles of heel (less than 15 degrees, I'd say). Whichever boat has steeper slope is the stiffer boat, by definition. My guess - the Catalina based on my experience. Whichever has the highest angle vanishing stability (where G=Z) is the more stable boat. I'd surmise the First 40, since her stabilty does not come from her beam.

Anyone have reliable curves? That would settle the debate as long the definitions that Marsh are acceptable to everyone.

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Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Quote:
Originally Posted by PCP View Post
Brian, they did not pull anything. They have asked to Catalina Yachts stability curves regarding the boats they have tested.

Those stability curves were provided by Catalina. The AVS were taken from the delivered curves.

Do you mean that the Catalina designers don't know how to do the stability curves of their own designs?

Regards

Paulo
Well, given my previous statements about inconsistencies in the data, do you really want me to answer that!!? I guess I could ask Gerry. I am just not sure I want to get in his crosshair if we get into a dissagreement on it! If it came from the published C400 data, it may very well be incorrect. But that would only make the stability curve better.

BTW, I am not accussing in any way gerry of doing anything wrong. Gerry is a class act and has to be one of the most owner-driven designers ever. I am simply telling you that the data is incorrect. My boat draws nigh on 6 feet.

Brian

PS You're sure Catalina provided that information? I was not aware they were required to do so. I know there are some basic formulas out there, but I don't think they really take everything into account.

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Last edited by Cruisingdad; 01-16-2013 at 04:03 PM.
Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Quote:
Originally Posted by johnnyquest37 View Post
This discussion between Brian and Paulo has been very interesting. In a way they might both be right. At great personal risk of getting caught in the cross fire, allow me to reference this web site: Understanding monohull sailboat stability curves | M.B. Marsh Design by Matthew Marsh (boat designer).

Marsh defines tenderness/stiffness as the slope of the stability curve at low angles of heel. At low angles of heel, a stiff boat has a steep slope and a tender boat has a shallow slope. Initial stability, therefore, is the key to the difference between stiff and tender. Stabilty and stiffness, however, are not the same thing. A tender boat will likely have a higher ultimate stability than a stiff boat that derives her stiffness from beam.

According to Marsh, sail carrying capacity is a function of righting moment in the 15-30 degrees of heel portion of the curve, since this is the area where most sailing occurs. The more righting moment one has in this region, the more sail a boat can typically carry. Righting moment, by the way equals GZ x displacement, so there is no difference between RM and GZ when it comes to determining stiffeness/tenderness and stability (unless you start considering the added dispalcement associated with flooding).

So regarding the Catalina 400 versus the First 40.7. Would have to see the stability curves to be sure, but likely the Benateau has a higher ultimate stabilty, but is more tender than the Catalina 400. The answer lies in the slope of the stabilty curves at low angles of heel (less than 15 degrees, I'd say). Whichever boat has steeper slope is the stiffer boat, by definition. My guess - the Catalina based on my experience. Whichever has the highest angle vanishing stability (where G=Z) is the more stable boat. I'd surmise the First 40, since her stabilty does not come from her beam.

Anyone have reliable curves? That would settle the debate as long the definitions that Marsh are acceptable to everyone.
I think the interesting thing will be getting the good curves. But great post and welcome to the debate.

Now, Paulo, put him in your crosshairs!! Ill take the other side. (snicker)

Brian

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Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Quote:
Originally Posted by johnnyquest37 View Post
... allow me to reference this web site: Understanding monohull sailboat stability curves | M.B. Marsh Design by Matthew Marsh (boat designer).

Marsh defines tenderness/stiffness as the slope of the stability curve at low angles of heel. At low angles of heel, a stiff boat has a steep slope and a tender boat has a shallow slope. Initial stability, therefore, is the key to the difference between stiff and tender. ....
.... That would settle the debate as long the definitions that Marsh are acceptable to everyone.
Jesus, I believe you didn't make it deliberately but that is quite frustrating. You should have a look at who is the one you quote on that definition of stiffness:

"Matthew is an engineering physicist, with interests and expertise spanning many fields. He has played key roles in two NASC/WSC solar car projects and has experience with composite materials design, solar power systems, construction industry QA/QC, building envelope design/testing, and LEED program implementation. He is an avid boater and boat builder, mainly in small power craft, and has extensive knowledge of small boat design and construction.

Matthew holds two engineering physics degrees from Queen's University (M.A.Sc. in medical physics, class of 2012, and B.Sc.E in engineering physics / mechanical, class of 2009). He is currently conducting research in radiographic image reconstruction and Co-60 radiotherapy at Queen's University and the Cancer Centre of Southeastern Ontario.

A Few Recent Projects
Computed tomography / digital tomosynthesis imaging system for cobalt-60 radiotherapy
Experimental cobalt-60 intensity modulated radiotherapy system
Hardware upgrades, software enhancements, data centre migration and user support for a 100+ core distributed computing cluster
Non-destructive testing of radiation shielding concrete using megavoltage CT imaging
Parametric array for nonlinear ultrasound-to-audio demodulation
Quality assurance program training, implementation and auditing on eight major construction projects
Composite aeroshell and hybrid carbon/spaceframe chassis for the solar cars Aurum and Ultraviolet"

I have quoted on the subject one of the greates contemporary American NA,
Rodney S. Johnstone, the designer of Jboats:

Where does performance come from? ...

A cruising sailboat’s performance also depends on stability, or "stiffness"-the ability of the boat to resist the heeling force of the sails. Good all-around speed is possible only if the boat is stiff; a stiff boat can carry more sail... If stiffness comes from a wide waterline beam, the boat’s motion tends to be bouncy and abrupt in waves; as soon as this type of boat heels, it usually exhibits excessive weather helm and may be difficult to steer. ..
The most important characteristic of a performance cruiser is that its stiffness be derived from a low center of gravity. ...

The preponderance of heavy-displacement boats ... reflects a modern trend in cruising sailboats toward increased accommodations and decreased ballast/displacement ratios-a trend that has raised the height of the center of gravity of this type of boat. ...

.. Whether light or heavy, a narrow boat with a low center of gravity will have a rock solid feel, an easy motion, and positive control-the unmistakable aura of power, stability, and passagemaking speed.

Who do you think it deserves more credibility?

For the ones that want to understand this subject better a good way is to run this article on a translator, I mean for the ones that cannot read French. It makes also very clear why the GZ curve is a basic instrument to access boat stiffness.

I will translate the first paragraph:

"La Raideur à la toile est la capacité du voilier à porter de la toile"

Stifness in a sailboat is its ability to carry sail area.

Regards

Paulo

Last edited by PCP; 01-16-2013 at 08:05 PM.
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Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Quote:
Originally Posted by Cruisingdad View Post
Well, given my previous statements about inconsistencies in the data, do you really want me to answer that!!? I guess I could ask Gerry. I am just not sure I want to get in his crosshair if we get into a dissagreement on it! If it came from the published C400 data, it may very well be incorrect. But that would only make the stability curve better.

BTW, I am not accussing in any way gerry of doing anything wrong. Gerry is a class act and has to be one of the most owner-driven designers ever. I am simply telling you that the data is incorrect. My boat draws nigh on 6 feet.

Brian

PS You're sure Catalina provided that information? I was not aware they were required to do so. I know there are some basic formulas out there, but I don't think they really take everything into account.
Yes, I am sure.

One thing is a typo error regarding measures but that is impossible with a stability curve. A stability curve is a basic instrument that is used to design the boat and to be sure he has a good performance and stability. Stability curves are not made by the boat builder but by the designer and are necessary for the boat CE certification.

I doubt very much that a NA would make a wrong stability curve while designing a boat. I would rather not say what that would mean.

Regards

Paulo

Last edited by PCP; 01-16-2013 at 08:17 PM.
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Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Quote:
Originally Posted by Cruisingdad View Post
.. I guess it all comes down to what your definition of a performance cruiser is. My definition is a boat that in normal conditions will meet or exceed hull speed while FULLY LOADED with cruising gear. ... Because if it is simply the fastest boat that you could cruise on, a First or J122 wouldn't even make the list. ...

So, what is cruising for you? TO me, cruising is Fulltime living aboard and travelling on a boat for year(s) at a time... and certainly not less than six months at a time. It is going to different places, anchoring out and adventuring. It is a combination of marinas, mooring fields, and sitting on the hook (with a fair amount of being on the hook). I do not feel that cruising is taking a weekend and sailing down to the next marina. THat is weekending. I do not feel cruising is taken several weeks or a couple of months to sail to a few different places and then returning to your house. That is vacationing. So that is my definition. Again, what is yours?

... Now Paulo mentioned this couple that is in the Antarctica on their First. Was that their boat of choice, or was it what they had and fit their price and them made do? I can certainlty think of a lot of better boats to go to ANtarctica with... I bet they can too. ALso, is it a stock boat? Doubtful. I suspect, like ALL cruising boats, they are loaded to the brim with clothes, pots and pans, gas tanks, diesel tanks, extra water jugs, solar panels, a generator, many weeks (we do over a month) of food stocks, etc. Now, when they are done with that boat, does it still look like and perform like a stock J or First? Heck no. We wouldn't expect it to. But now my question is: How fast is that boat really now? WHat is its true RM now with all that crap all over the deck and above the waterline? How long can they go without having to pump out... or do they dump in the bay? ....
Yes, that First 40.7 is their boat of choice and yes it is a fast boat and yes they travel light and yes, they are circumnavigating.

You insist in not understanding that other sailors can have an idea different of yours in what regards a cruising boat. Yes there are many sailors to whom sailing pleasure is a very important part of cruising.

What I think or not is irrelevant to the way other sailors like to cruise and the sailboat they chose according with that. Believe me like you I know very well the boat I want and you can be sure that is not the boat you would want and vice-verse. There is not a perfect cruising boat but many different types of cruising boats for cruisers with different tastes, even for circumnavigating.

You prefer to sail a relatively slow boat (by modern standards) full of stuff inside. Ok, that's your type of pleasure, your type of cruising but I am amazed at your incapacity to understand that some would prefer a slower and heavier boat (some would even prefer an heavy old design) but others will prefer a faster and more enjoyable boat to sail.

On the interesting sailboat we have been following the circumnavigation of Capado, a small and very light cruiser boat. The crew is a young couple, they are top sailors, much better than you or I and I am quite sure that was the boat they wanted. They have the hull made and finish the rest but for the money they spend on a new boat they would have enough money to buy a used 40ft Catalina.

I am quite sure if I would suggest such a boat to them they would laugh at me, the same way you would laugh if I had suggested such boat to you for doing a circumnavigation.

Here some pictures of their boat:

Regards

Paulo
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Old 01-16-2013
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Re: Blue Jacket 40 (new racer/cruiser)

My dock mate has a C400 WK; i have the Bene 400. The Cat is definitely more cruiser friendly. We ride each other's boats and run against each other all the time. The PHRF is the same and his boat does feel "stiffer"; but, i definitely feel that my Bene is more manurveable and more under control. I just don't feel the pointing ability in the C400.
The First 40 is fast and beautifull; but, as a cruiser it's a compromise. The C400 is much nicer, but no where near as fast. Not even in the same league for speed. Would i take a C400 over my Bene400, don't think so. Mines less beamy, shorter, easier to manuever and i believe faster over the long haul.

Back to the OP.

I like the looks of the new Blue Jacket, but, it doesn't stand out enough to make me want one. Fast? I doubt it. It needs a little Juan K. to break it into the 21st century. I think there are a lot better boats out there for the money. The Europeans i think are on the right track for boat design and pushy the envelop for cruisers. IP, Cat and hunter need to do some serious review of there rivals before they get swallowed up.
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Old 01-17-2013
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Re: Blue Jacket 40 (new racer/cruiser)

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Originally Posted by benesailor View Post
..
I like the looks of the new Blue Jacket, but, it doesn't stand out enough to make me want one. Fast? I doubt it...
Fast is a relative concept. Yes much faster than your boat or the Catalina 40 but less faster than a First 40 or J122. I like fast performance cruisers and I would not mind to have one of those, provided they would modify the rigging, nothing difficult but expensive. The boat will be fast for a cruiser and those modifications would be related with a better control of the sail shape and they will not be important to most cruisers. Fact is that only performance cruisers have them, not mainstream cruisers.

I like the hull, rudder, keel, B/D and even the global look of the boat, a bit to classic for me but with good quality in what regards design. Take a look at that beautiful hull:

Blue Jacket 40 360° View | BlueJacketYachts.com

Regarding what is called in Europe the luxury cruiser segment, the bluejacket is the American design I like more. Personally I would prefer a J122 but that is more of a performance cruiser that supposedly has a less luxurious interior, one that will be enough for me. Well, we have only saw the designs we have to see if the Bluejacket will be delivering that or not.

The Bluejacket will not be on the same market sector of the Catalina or Benetau, neither on the one of the First or J122, it will be on the market that in Europe is called "Luxury cruisers" that includes fast and less fast cruisers but all with luxurious interiors and off course, very expensive boats. The only American modern design that could be competing with the Bluejacket is the Tartan 4100, even if they are very different boats. I would clearly prefer the Bluejacket but I am not sure that will be the case for most cruisers and they are really not the same type of boat nor do I think they will be addressed to the same public, except in what regards money.

I guess the boat will be competing with the Arcona 410 and Swedestar 415, for instance:

http://www.arconayachts.com/images/410/410b.jpg

http://www.arconayachts.com/images/4..._sail_plan.gif

The question will be at what price and if America has a market for that type of boat. Europe has but it is a small market and in Europe the sailing market is much bigger than the American one (new boats).

Anybody knows if they are really making the boat and when will the first one hit the water?

Regards

Paulo

Last edited by PCP; 01-17-2013 at 09:51 AM.
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Old 01-17-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Haven't read the whole string of posts here, so this may have been mentioned earlier, but anybody heading to Strictly Sail Chicago may be able to see one of these close up and personal. We're headed there next week and in checking out the website to see what boats are going to be on display I believe I saw the Bluejacket listed as the sole boat IP was exhibiting there this year.

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Old 01-17-2013
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Re: Blue Jacket 40 (new racer/cruiser)

Quote:
Originally Posted by PCP View Post

Who do you think it deserves more credibility?

For the ones that want to understand this subject better a good way is to run this article on a translator, I mean for the ones that cannot read French. It makes also very clear why the GZ curve is a basic instrument to access boat stiffness.

Raideur à la toile - Wikipédia

I will translate the first paragraph:

"La Raideur à la toile est la capacité du voilier à porter de la toile"

Stifness in a sailboat is its ability to carry sail area.

Regards

Paulo

Paulo - no question that the stability curve describes a boat's tenderness or stiffness. I still say that both of you may be correct. You are saying the ultimate stability describes stiffness. Marsh, Dave, and most boat owners I know consider stiffness to be related to initial stability and describes boat motion at lower levels of heel.

You (and others with credibility) have your definition of stiffness and others have equally acceptable, but different, definitions of stiffness. Regardless, it is clear that ultimate stability is the criterion that sail area is based upon. As I understand it, the area under the postive part of the curve defines this.

[/B]S/V Wind Orchid
Catalina 350 (hull# 273)
Annapolis, MD

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