Pilothouse Variations -- Boreal

[TheThunderbird]

Boats are currently designed either to win, or to offer comfy interiors, or to catch the eye.

Few sail as seriously as DH, in difficult seas...

A brand new HR64 may top the 2mEUR tag, or more... quite hard that they design it for the very few....

Pilot Houses exist only in some fine steel motorsailers from the 60/70s, of Dutch and Italian production (Sangermani, Valdettaro, Mostes...) in the 60-80' range, but possibly 2 masts... not perfect upwind.
They have length and fine hulls, thus may prove efficient with tuned-up rigging

Lot of class granted.

With efficient re-rigging, it could be an interesting project to go for, imo

Btw, I accept s PH in the old tradition, of a 2nd steering position.

Sailing into a closed environment full time is no sailing, to me

[TheThunderbird]

Originally Posted by Cadence

Originally Posted by Dockhead View Post

....
Few of the boats shown in Polux's posts in this thread have anything to do with normal cruising boats. They are like the Lamborghinis, F1 cars, and fantasy concept hot rods taped to a teenage boy's bedroom wall.

Ditto

I can not disagree....
Salona, pogo,... all boats derived from the Wallys concept, good for day-light and delight cruising.
Ad far as i see a cockpit 9'+ large, i disagree, too dangerous

[Snowpetrel]

Found another very interesting titbit from the farr design group regarding bow slope and fashion.

"The plumb or relatively upright stem angle's typical of today's boats are a product of fashion that has aligned itself with the common box rule type race boats we wish to emulate. When unconstrained by rules, designers are free to look for advantages in alternative concepts. In the case of this boat two major areas have pushed us in the direction of a more angled stem. The first is the desire to tack a removable masthead genoa forward of the forestay. This sail would be used in light air when racing under handicap systems that do not unfavorably treat such a sail. When sizing that masthead sail the resulting foot length positioned its tack well forward of the forestay requiring some form of structure to support it. The structure alone could have been provided by some other means like a portion of fixed bowsprit tube. When looking at the required structure we considered that a section of extended bow slope could also provide an added volume and flare to the topsides forward. The reserve buoyancy in that added geometry will be a benefit in waves and high speed running conditions where nose diving can be a concern. When discussing these possibilities with our client we decided together to pursue the less fashionable but perhaps more technically correct solution"

http://www.farrdesign.com/613faq.htm

Admittedly this is a 2007 design. But shows once again how fashion, fads and yacht design all converge at times.

I guess I do like the pogo's and their ilk. They would be lots of fun to sail. I suppose given no restrictions for the same money I could make the boat narrower but longer, then I could get away with single big rudder. Keep the same rig size, but with a longer J for a big code sail without needing a prod. It probably would be similar speed to the pogo, faster in some conditions, slower in others, but more to my style, and happier at displacement speeds, to windward and in light airs.

[Polux]

Originally Posted by Juho

I believe Nauticat 385 has a 180° AVS. It must be the pilothouse that does it. Probably not a very rolling boat.

Maybe 170° AVS would be as good in practice. Maybe a strong righting moment at 95° (when the mast hits the water) would be a useful property.

Yes that 180ºAVS has to do with the pilot house and does not reflect (comparatively) the safety stability (over 75º to 100º).

The stability and the relation between the Weight/ RM of the boat at those angles is very important to seaworthiness in what regards stability.

A boat with a big weight/RM ratio when capsized to 90º by a wave will rise itself quickly and when the next wave comes it will have all its stability to counteract the rolling effect of a new breaking wave.

A boat with a low weight/RM ratio when capsized to 90º by a wave will rise to its feet slowly, so slowly that it can sustain another wave while at a big heeling angle and that means that it will only have available a small part of its stability to counteract the new breaking wave.

From the few boats that are rolled many are rolled by a set of two breaking waves that come closer: The first lay the boat flat (taking away almost all positive stability) and the next one will do the job.

[Polux]

Originally Posted by Snowpetrel

----
Rules like IMS try to be much more balanced, producing boats that are often much better all rounders.
....

That do not make any sense: How can a rule raises much more limitations to the designer (to make a fast and better sailingboat) can produce better all rounders?

By the way IMS was better regarding IOR but ended up giving bad results and producing not fast boats but boats adapted to the rule. Since 2000 almost all serious handicap rating passed to IRC rule, that give more balanced results.

Only recently a much bettered follow up of the IMS have been giving some good results, it is called ORC or ORCI on its more sophisticated version but it is still way less used than IRC.

"IMS racing declined seriously in the early 2000s. A raft of new technology developments in yacht design led to a situation where the very largest and most expensive yachts were able to gain a significant technology advantage which the rule was less able to account for. Smaller yacht owners began to feel unfairly disadvantaged under the rule and between 2003 and 2007 much handicap racing around the world changed to using the newer IRC rule.
However, an improved, revised version of IMS has been developed recently (2006-2008), known as the Offshore Racing Congress (ORC) rule. "

The main reason those two formula give less interesting hulls for cruising is mainly because they design boats to be sailed by a big crew, much more demanding boats in what regards control than the ones designed on the Open classes, that are designed to be solo sailed and also because the boats are not designed towards absolute sail efficiency but mostly to beat a rule.

While on IRC or ORC it is not the faster boat (and the more efficient hull) that wins but simply the boat that plays better with the rules (assuming identical crews) on the Open classes the faster and more efficient boat wins since they race in real time.

Design development derived by handicap racing (IRC, ORC) goes on the direction to propose boats that can beat or adapt better to a rule, not towards pure sail efficiency.

Open class design developments goes on the direction of pure efficiency and faster boats, since they race in real time.

[Polux]

Originally Posted by Snowpetrel

Found another very interesting titbit from the farr design group regarding bow slope and fashion.

"The plumb or relatively upright stem angle's typical of today's boats are a product of fashion that has aligned itself with the common box rule type race boats we wish to emulate. When unconstrained by rules, designers are free to look for advantages in alternative concepts. In the case of this boat two major areas have pushed us in the direction of a more angled stem. The first is the desire to tack a removable masthead genoa forward of the forestay. This sail would be used in light air when racing under handicap systems that do not unfavorably treat such a sail. When sizing that masthead sail the resulting foot length positioned its tack well forward of the forestay requiring some form of structure to support it. The structure alone could have been provided by some other means like a portion of fixed bowsprit tube. When looking at the required structure we considered that a section of extended bow slope could also provide an added volume and flare to the topsides forward. The reserve buoyancy in that added geometry will be a benefit in waves and high speed running conditions where nose diving can be a concern. When discussing these possibilities with our client we decided together to pursue the less fashionable but perhaps more technically correct solution"

Farr Yacht Design

Admittedly this is a 2007 design. But shows once again how fashion, fads and yacht design all converge at times.
....

Yes and about a boat that was designed for a particular client that wanted that type of bow on his sailboat (they had to justify that odd choice didn't they? After all they wanted to sell more boats):

You should look at the new Farr designs, the one that did not result from a command of a particular client but represents what Farr thinks about it.

The 2015 IRC 13m concept:


The 2015 53ft Infinity:

The IRC 44 racer concept (2014)

[Polux]

Originally Posted by Snowpetrel

...
Racing rules often apply constraints. If you constrain length you end up with wide boats....

Because they will be more fast and efficient. So we finally agree

What matters in what regards cruising is the length of a boat since costs, building costs, marina costs are associated with length and because regarding the same length beamier boats are more efficient (in a global way) that's why most modern cruisers opt by beamy boats that offer the added advantage of offering a bigger interior.

[reed1v]

Originally Posted by Polux

Yes that 180ºAVS has to do with the pilot house and does not reflect (comparatively) the safety stability (over 75º to 100º).

The stability and the relation between the Weight/ RM of the boat at those angles is very important to seaworthiness in what regards stability.

A boat with a big weight/RM ratio when capsized to 90º by a wave will rise itself quickly and when the next wave comes it will have all its stability to counteract the rolling effect of a new breaking wave.

A boat with a low weight/RM ratio when capsized to 90º by a wave will rise to its feet slowly, so slowly that it can sustain another wave while at a big heeling angle and that means that it will only have available a small part of its stability to counteract the new breaking wave.

From the few boats that are rolled many are rolled by a set of two breaking waves that come closer: The first lay the boat flat (taking away almost all positive stability) and the next one will do the job.

Intersecting wave trains, especially at shallow angles, can really create havoc with any type of boat. Not only will they produce unusually high waves, breaking at the intersection; but set the boat rolling in a way that gets amplified until it topples over. Happens at sea, happens in test tanks.

A monohull with deep keel can absorb some of the wave's slope without becoming perpendicular to its surface. Not so a shallow keeled or multi hulled vessel. They will tend to maintain their perpendicular position to the wave's surface as it slides beneath the vessel. If the intersecting waves reach a certain periodicity, the shallow draft vessels will ultimately either topple over or plow directly into the extra deep trough created by the two wave trains.

Or in simple terms: maximum depth, maximum stability.

[Juho]

Originally Posted by Polux

Yes that 180ºAVS has to do with the pilot house and does not reflect (comparatively) the safety stability (over 75º to 100º).

The stability and the relation between the Weight/ RM of the boat at those angles is very important to seaworthiness in what regards stability.

A boat with a big weight/RM ratio when capsized to 90º by a wave will rise itself quickly and when the next wave comes it will have all its stability to counteract the rolling effect of a new breaking wave.

A boat with a low weight/RM ratio when capsized to 90º by a wave will rise to its feet slowly, so slowly that it can sustain another wave while at a big heeling angle and that means that it will only have available a small part of its stability to counteract the new breaking wave.

From the few boats that are rolled many are rolled by a set of two breaking waves that come closer: The first lay the boat flat (taking away almost all positive stability) and the next one will do the job.

Of course also righting moment above 75°-90°-95°-100° is important. It is nice to come also back after capsizing. 180° AVS is thus ideal. It can be arranged together with good 75°-100° stability / righting moment.

I didn't quite understand your "weight/RM ratio". (RM = righting moment ?) Did you say that a heavy boat would be good, and a high righting moment bad?

[Polux]

Originally Posted by Juho

....
I didn't quite understand your "weight/RM ratio". (RM = righting moment ?) Did you say that a heavy boat would be good, and a high righting moment bad?

That means that regarding that (right itself up quickly) the absolute value of RM at 90º is not what matters but the relation of that value with the boat weight.

See it this way: A heavy boat can have a lot more RM at 90º and be much slower to right itself up than a lighter boat with a considerably smaller RM at 90º. On the the heavy boat the RM needed to right it up it will be much bigger than the one needed to right the lighter boat. That's why that relation is what counts.

You can compare different boats (with different weights) regarding this using the GZ curve (arms curve)

[Juho]

Originally Posted by Polux

That means that regarding that (right itself up quickly) the absolute value of RM at 90º is not what matters but the relation of that value with the boat weight.

See it this way: A heavy boat can have a lot more RM at 90º and be much slower to right itself up than a lighter boat with a considerably smaller RM at 90º. On the the heavy boat the RM needed to right it up it will be much bigger than the one needed to right the lighter boat. That's why that relation is what counts.

You can compare different boats (with different weights) regarding this using the GZ curve (arms curve)

I think I understand how the righting moment and the weight of the boat do interact and will right the boat. I was just confused about the math representation of your formula, where high weight is good and high RM bad.

(Also the shape of the boat (keel etc.) and location of the weight should be considered to fully evaluate the righting behaviour of a boat.)

[TeddyDiver]

Originally Posted by Polux

That means that regarding that (right itself up quickly) the absolute value of RM at 90º is not what matters but the relation of that value with the boat weight.

See it this way: A heavy boat can have a lot more RM at 90º and be much slower to right itself up than a lighter boat with a considerably smaller RM at 90º. On the the heavy boat the RM needed to right it up it will be much bigger than the one needed to right the lighter boat. That's why that relation is what counts.

You can compare different boats (with different weights) regarding this using the GZ curve (arms curve)

Utter BS.. To know that you need to know the moment of inertia which by the way can make the outcome opposite what you are suggesting, or not. Totally depends of the boats in question, how they are loaded etc..

BR Teddy

[Polux]

Originally Posted by Juho

I think I understand how the righting moment and the weight of the boat do interact and will right the boat. I was just confused about the math representation of your formula, where high weight is good and high RM bad.
...

Yes you are right, the relation is RM/Mass (weight) and that will give you the arm. The arms curve is the GZ curve.

[Snowpetrel]

Originally Posted by Polux

Because they will be more fast and efficient. So we finally agree

You do not understand the word efficiency as it relates to cruising. It is a very elusive thing for cruising because almost every cruiser has a different set of proirities that help define what efficent really means for them. Racing is pretty easy to quantify. Winning on line or handicap is pretty much all that counts. Sometimes speed for the doller is important. But basically speed is king. On a cruiser absolute speed is not what makes a boat efficient.

This is the whole problem with you. Your idea of what looks good, or your set of priorities is what you think is perfect. You fail to realise that others may have different proirities, and different definitions of efficiency. Eg I want a boat that can use a windvane 99% of the time. That pretty much rules out surfing. So a big surfboard shaped hull optimised for drag racing downwind is pretty inefficient for me.



Sent from my SM-G930F using Cruisers Sailing Forum mobile app

[Snowpetrel]

Originally Posted by TeddyDiver

Utter BS.. To know that you need to know the moment of inertia which by the way can make the outcome opposite what you are suggesting, or not. Totally depends of the boats in question, how they are loaded etc..

BR Teddy

^^ +10000

Sent from my SM-G930F using Cruisers Sailing Forum mobile app