The HULL truth and nothing but. - SailNet Community
 21Likes
Reply
 
LinkBack Thread Tools
post #1 of 74 Old 10-01-2018 Thread Starter
Senior Member
 
outbound's Avatar
 
Join Date: Dec 2012
Location: NE & Windwards
Posts: 6,574
Thanks: 139
Thanked 199 Times in 189 Posts
Rep Power: 8
 
The HULL truth and nothing but.

Being here for a few years I see recurring threads about what makes a BWB. I see arguments about old v new designs. I see discussions about appendages. I also follow Morgancloud.cloud. They recently had a series about balanced ends. In my view recent designs perhaps influenced by recent race boats or the desire for increased interior volume speak to needs not felt by cruisers. I believe there is a increasing schism between cruising designs v race boats or coastal use vessels.
Im quite curious about others opinions on this subject. I think it is the driver of much heat here and want light. There are new designs with balanced ends. There are voluminous boats with balanced ends. There are fast boats competitive except at the professional level with balanced ends. What are your thoughts?

s/v Hippocampus
Outbound 46
outbound is online now  
Sponsored Links
Advertisement
 
post #2 of 74 Old 10-01-2018
bell ringer
 
Don L's Avatar
 
Join Date: Aug 2008
Location: Marathon Fl
Posts: 4,389
Thanks: 10
Thanked 124 Times in 111 Posts
Rep Power: 12
 
Re: The HULL truth and nothing but.

My thought is, cruise on want makes you happy and sail the boat based on it's characteristics.

Far as old design and new design my thoughts are there are; old designs and new designs and all have their pros and cons.

Don't blow air up my rear, be useful and blow it at the sails!
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Don L is online now  
post #3 of 74 Old 10-01-2018
Senior Member
 
SanderO's Avatar
 
Join Date: Jul 2007
Location: Westchester, NY
Posts: 4,278
Thanks: 2
Thanked 108 Times in 108 Posts
Rep Power: 13
 
Re: The HULL truth and nothing but.

One often doesn't have the luxury of sailing lots of boats in different conditions. A sea trial is not much of a test in a sense. We rely on reputation, experts and emotion I suspect.

pay attention... someone's life depends on it
SanderO is online now  
 
post #4 of 74 Old 10-01-2018
Senior Member
 
Join Date: Feb 2010
Location: Narragansett Bay
Posts: 20,810
Thanks: 82
Thanked 588 Times in 564 Posts
Rep Power: 12
   
Re: The HULL truth and nothing but.

I think the average cruiser knows and cares about boat systems, but far less about boat design. Faster makes the modern consumer happy, followed by safer or more durable.
travlin-easy likes this.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Jeanneau 54DS

In the harsh marine environment, something is always in need of repair. Margaritas fix everything.
Minnewaska is offline  
post #5 of 74 Old 10-01-2018 Thread Starter
Senior Member
 
outbound's Avatar
 
Join Date: Dec 2012
Location: NE & Windwards
Posts: 6,574
Thanks: 139
Thanked 199 Times in 189 Posts
Rep Power: 8
 
Re: The HULL truth and nothing but.

Minnie you maybe right. But you can replace boat systems. Much harder to replace the boat. I would think in all the courses people take spending a little time at each level discussing and showing the impact of boat design on function would be well spent.
Example - two pier neighbors. An IP, a Bene, and myself within a foot loa of each other leave for Block at the same time. Light air in the bay but fresh breeze on the nose in Block Sound. Bene gets a few miles ahead going down East channel. IP lags. In the Sound Bene points well but gets beat up. I suppose due to ride they eventually roll the jib and the iron jib goes on. IP and us catch up. IP comfortably chugs along but vmg poor. We reef and get to New Harbor. Any understanding of basic design would predict this. You don’t need to sea trial multiple boats. Yes, it’s good to get on as many different boats as you can. Understanding your judgment about speed, comfort, ride, pointing ability, best heel angle, tracking and all the things that go into what boat is right for you is improved. Still, if possible I’d like the discussion to return to just one facet- balanced ends.

s/v Hippocampus
Outbound 46
outbound is online now  
post #6 of 74 Old 10-01-2018
Senior Member
 
colemj's Avatar
 
Join Date: Jul 2003
Location: On the boat cruising
Posts: 3,149
Thanks: 4
Thanked 126 Times in 120 Posts
Rep Power: 17
 
Re: The HULL truth and nothing but.

Quote:
Originally Posted by outbound View Post
Still, if possible Id like the discussion to return to just one facet- balanced ends.
You can't focus on one facet while using anecdotes of boats having completely different keel shapes, hull designs (outside of the ends), weights, sail areas, skipper/crew expectations and immediate desires, etc to support/refute arguments.

Frankly, your story about an afternoon sail to Block Island immediately led me to thinking that the owners of those boats had different opinions on how they wanted to spend the afternoon or how they approached sailing. I didn't see anything in it that touched on "balanced ends". Do you not think that the owners of that Bene would have done the same in an IP?

Discussing a single facet can be done in a few objective and descriptive bullet points - and then what? Can't draw any conclusions without getting into subjectives and purpose.

Mark

Dolphin 460 Catamaran "Reach"

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Current boat

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Previous boat
colemj is offline  
post #7 of 74 Old 10-01-2018 Thread Starter
Senior Member
 
outbound's Avatar
 
Join Date: Dec 2012
Location: NE & Windwards
Posts: 6,574
Thanks: 139
Thanked 199 Times in 189 Posts
Rep Power: 8
 
Re: The HULL truth and nothing but.

Mark have a look at the discussion at morgancloud. Then come back to this thread. It seems many decisions are predicated on the the basic shape of the canoe body and the ends in some significant degree to predict the the middle as well as features you mentioned.

s/v Hippocampus
Outbound 46
outbound is online now  
post #8 of 74 Old 10-01-2018
Senior Member
 
colemj's Avatar
 
Join Date: Jul 2003
Location: On the boat cruising
Posts: 3,149
Thanks: 4
Thanked 126 Times in 120 Posts
Rep Power: 17
 
Re: The HULL truth and nothing but.

The website goes straight into a paywall. There is no article that I can see.

Mark

Dolphin 460 Catamaran "Reach"

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Current boat

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Previous boat
colemj is offline  
post #9 of 74 Old 10-01-2018
Senior Member
 
colemj's Avatar
 
Join Date: Jul 2003
Location: On the boat cruising
Posts: 3,149
Thanks: 4
Thanked 126 Times in 120 Posts
Rep Power: 17
 
Re: The HULL truth and nothing but.

However, if they are saying that the design choices made in the boat are predicated on those made on the ends, then that is simplistic. A boat hull is designed as a whole - it is just as valid to say that the design choice of the ends are predicated on all other decisions.

Except for the old IOR boats - they do seem to be put together using unrelated design "parts".

Mark

Dolphin 460 Catamaran "Reach"

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Current boat

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
- Previous boat
colemj is offline  
post #10 of 74 Old 10-01-2018
Administrator
 
Jeff_H's Avatar
 
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 8,880
Thanks: 43
Thanked 439 Times in 369 Posts
Rep Power: 10
     
Re: The HULL truth and nothing but.

That article does not seem to understand that no matter how the boat may look statically, when you talk about the newer designs, when they are properly designed, the part of the boat that is in the water does have 'balanced ends' relative to the center of gravity of the boat. But that is a very broad generality and does not apply to all of the new designs.

Here is what is not readily apparent to most people looking at the shape of a modern boat is they tend to think of what they see above the water as the shape in the water. But typically these boats are designed to remarkably balanced shapes in the water, which as they heel (up to a point) become even more balanced fore and aft as well as amidships. While it is true that these designs do tend to carry more buoyancy towards the stern than they do forward, and tend to have their centers of buoyancy a little further aft than some more traditional designs, this is offset because they also carry their center of gravity further aft as well. What is not understood is that the actual waterline beam on these boats is surprisingly very narrow, especially when they have a some heel angle. It may actually be narrower than more traditional designs of 20-30 years ago.

Its important to understand that these wider hulls are modeled so that the center of buoyancy moves quickly to leeward with heel angle. Since the center of gravity does not move, they very quickly develop huge amounts of stability without the usual penalties associated with excessively beamy hulls. In order to prevent developing large amounts of weather helm due to the immersed hull shape, the hull shape is carefully modeled so that it results in a comparatively symmetrical immersed hull form (closer in shape to a multihull than a traditional monohull) that is balanced around an axis that starts at the bow but which rotates to leeward at the stern. While this hull form is not parallel to the center line of the hull, it is none the less parallel to the way that water is moving over the hull. (That shifted angle means that the hull in the water is actually pointing slightly upwind and helping to resist leeway)

The article suggests that these boats tend to go bow down when surfing in big waves. While that is true on some of the early broader stern designs and boats like the 6.5 meter Mini TransAt boats, with their huge reaching and running sail plans flown over very short waterline lengths, that has not proven to be the case once these more modern designs get longer and with more normal SA/D's. What is not all that apparent when looking at these boats is that the bow at the deck line is typically a lot fuller then more traditional designs and so while the waterline at the bow might be pretty fine compared to traditional cruising boats. these boats have huge amounts of reserve buoyancy, which occurs further forward of the longitudinal axis of rotation (pitch axis) and therefore has a longer lever arm to dampen pitch angle than more traditional designs. Moving the point of entry of the bow forward allows the boats to experience the impact with waves more progressively and so do not have the sharper impacts that are in more traditional designs of the same displacement. The huge amounts of reserve buoyancy in the stern also helps to damp pitch as well and reduce the likelihood of being pooped. The net result is that these boats tend to pitch through much smaller angles than traditional hull forms and remain closer to parallel to the wave face than more traditional hull forms.

Similarly, they tend to have much greater roll damping as well. The net result is that the non-planning versions of these hull forms generally have a more comfortable motion than something like an IP which transmits much greater wave impacts to the crew and boat, and which tends to pitch and roll through much greater angles.

Designing boats that behave like that takes more care than more traditional designs. The hull shape above and below the waterline needs to be optimized to remain balanced within the intended sailing heel angle. Without computer design and the ability to precisely track hull shape and its effect on trim (all directions) at various heel angles, it would be almost impossible to produce boats that employed versions of these modern hull forms and yet which were still well behaved,

And that gets back to the problem with citing anecdotal evidence. Since these modern designs require more sophisticated design analysis, and not all visually modern boats receive that level of care, its hard to cite any particular design as a case study for the general design principal. This is especially true since many of the production designs that are out there have adopted, "the look" with adopting the science. There is no doubt that these designs neither perform as well nor offer the motion comfort that a more carefully modeled hull will provide. Often 'the look' is employed as a way to cram in some additional accommodations or meet some other design parameter. And, as in many things in life, the pendulum may have swung too far and may need to swing back a little.

As far as the schism between race boats and cruising boats, there is no doubt that race boats have taken a very different route than cruising boats, becoming wildly lighter and more stripped out, living with much greater form stability, and in many cases, employing movable ballast and foils to achieve speeds which would have been inconceivable a few decades ago. From a design standpoint, while they may look like the newer cruising designs above the waterline, they are operating on very different design principles, principals that I do not envision bleeding down into cruising designs unless people are willing to live with huge compromises.

But that is the opposite of the direction that the cruising boats version of the wide body look are going. When I look at the current crop of modern looking 38 footers on the market, they are nearly 5,000 lbs heavier than my four decade old designed 38 foot performance cruiser, and roughly the same weight as a Pacific Seacraft of the same length. Similarly, a Sense 46 is roughly the same displacement as your Outbound. And while the Sense 46 has less ballast, it carries in a larger bulb lower below the canoe body and so probably has more initial stability, and probably a similar angle of positive stability (but with much larger area under both the positive and negative stability curves).

Alright, my lunch is over, I need to get back to work!

Jeff


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Curmudgeon at Large- and rhinestone in the rough, sailing my Farr 11.6 on the Chesapeake Bay

Last edited by Jeff_H; 10-01-2018 at 07:32 PM.
Jeff_H is online now  
The Following 2 Users Say Thank You to Jeff_H For This Useful Post:
outbound (10-01-2018), Telesail (10-01-2018)
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now



In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.


User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Similar Threads
Thread Thread Starter Forum Replies Last Post
Nothing but the truth A.C.A. Alibaba Politics, Current Affairs, Guns & HOT Topics 12 04-22-2014 01:28 PM
"The" truth, or, "A" truth? bwalker42 Politics, Current Affairs, Guns & HOT Topics 0 05-19-2012 01:50 PM
Nothing but smooth sailing for Oakland (The Daily Progress) NewsReader News Feeds 0 12-07-2006 03:15 PM
Nothing but smooth sailing for Oakland (The Daily Progress) NewsReader News Feeds 0 12-05-2006 02:15 AM
Afloat: Nothing else matters but wind, water and sky - Providence Journal NewsReader News Feeds 0 08-07-2006 02:15 AM

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome