Hull form, Keel and rudder design... merits and hazzards.

[skylark]

http://thesimplesailor.com/articles.html

Thank you for this link.  Roger Taylor also has some interesting youtube videos.  I really like the concept of his boat, he stays in the cabin all of the time and rarely is in the cockpit when at sea.  The boat is set up to be sailed from inside the cabin.

[SeaHusky]

I too like Roger Taylor's "unconventional" thinking and agree on some more than other. The idea of hardly ever leaving the cabin would for me take a lot of the fun away but then I haven't spent as many years getting cold and wet as Mr Taylor. I do very much like his idea of making his boat unsinkable but I think filling half the cabin with foam to achieve positive buoyancy when swamped only works on small boats with a special purpose. A more realistic approach is James Baldwins idea http://atomvoyages.com/projects/UnsinkableBoat.htm to make every storagelocker and compartment of his boat into a watertight compartment which will contain a leak or hullbreach to a small part of the hull adding maybe hours of repairtime before sinking. I find this so logical that I am astonished that it is not common practice to do this with at least the V-berth.
Have any of you done something similar?     

By the way, thanks for the grog! :)

[AdriftAtSea]

Nicely said... grog to ya for it. :)

Computer modeling, whether it's the weather, structural engineering, aeronautical engineering, fluid dynamics or whatever, is only as good as the person doing the modeling using the computer as a TOOL.

Therein lies much of the problem that many "lay" people don't appreciate.  There are a TON of people using computers tools that DO NOT understand the models or how to apply them.  So, they run a model, the computer spits out a number or a pretty picture and blammo...the number or picture gets reported/use/quoted/debunked.

I'll give a little case history from just a couple of weeks ago.  I was contacted by a client to do some modeling of something that is VERY dangerous and could have life-ending consequences for both my client and INNOCENT bystanders.

In my reply, I cautioned the client that ANY results we get from our models MUST be thoroughly and carefully tested with real-world, hands-on engineering tests.  The modeling results can guide the process, but it's NOT a 'model this, and go into production' type solution.  The potential costs are too high.

He absolutely agreed and was already thinking on that page.  I like to work with professionals that understand this sort of thing, and only felt compelled to mention it because all too often, the prospective client does NOT appreciate this.

Would you 'ask' a circular saw to build a house?  No, of course not.  Nor should one entrust the results of a computer model, which are nothing but numerical calculations, to provide a solution to a contextual problem.  The computer is only calculating numbers based on the equations it is programmed to use and only using the base data it is given.

Back to the topic at hand....the ONLY conclusion that can/should be drawn by ANY scientist or engineer using modeling is "this model says that cannot be done."  He SHOULD understand that the model could be limited (on purpose) or flawed.  The discussion should then go into "why might this model suggest that" and the thinking, problem solving HUMAN BEING should evaluate the results.

So, yes, there are many cases where a model says something cannot happen (or happens differently than reality).  That's often not the fault of the model itself or theory upon which it is based.  Rather, it is either (a) the fault of the USER applying a model in an incorrect context or (b) there is something unknown that the model is not taking into account.

Further, that's how models are improved...just like any other science, it is the FAILURES that teach you more than the successes.

Just some near-random thoughts from a dude who does the following professionally:

Quantum Chemistry Modeling
Molecular Dynamics Modeling
Computational Fluid Dynamics
Reactive Flow (Detonation) Modeling

[Captain Smollett]

Sometimes, the hull form is such an integral part of the boat's safety and the shape plays into stability in ways we often forget.  Too many times, we associate the stability of the boat coming from ballast, keel shape or some combination.

What about when a ballasted boat loose her keel completely?  Can the boat remain upright?  This happened to an Alberg 30 (lightning and age damaged keel bolts failed).

... the boat rolled completely from one side to other every ten
seconds. There was no longer anything counter-balancing the force of the mast. It felt
like rounding the Horn on a windjammer. It was a startling demonstration of Carl
Alberg?s genius. For her lines, her beautiful lines would capture and hold her right
there at the edge of the roll, and come back despite the fact that she was so badly
crippled.

(emphasis added)

I would be VERY interested to read about 'keel failure stability' of modern  (post CCA era) designs.

[CharlieJ]

I got the new ports I installed in our previous boat from a Catalina 30, that lost it's keel off Matagorda Island. The boat washed ashore and other than parts salvage, was a total loss. They burned the hull and deck, since there was no way to get any kind of tow vehicles or trailers down that 12 miles of virgin beach.

I happen to have the masthead fitting, if anyone is interested.

[Captain Smollett]

It seems we are not the only ones that "debate" the merits of hull design in various seas.

I found this gem of a post in a fishing forum, of all places.  The general discussion had veered to taking an open canoe out Bogue Inlet (which had nothing to do with the OP's question, but thread creep was kicking in).  Someone replied with what appeared as a snarky comment regarding what kind of "boat is needed" to run the inlet.  The comment also seemed to suggest only double bladed paddles had merit.

This is a reply to that comment:

A large area of the Bering Sea was paddled by single paddle boats. We've all seen the crab fishery shows on television...........just about the worst climate on the planet to paddle in. Remember.........the aboriginal paddlers were not paddling for sport, but to make a living. No radio, no EPIRB, no SAR helicopter to pick them out of the water, and no wetsuits/drysuits to prevent hypothermia. Everything they did, every nuance of boat construction, served a purpose. They used sea mammal air bladders for floatation during recovery techniques, if they came out of their boat. The literature remaining today suggests the original kayakers made few wet exits, due to boat design.

{my emphasis}

I love it!   ;D

Small OPEN boats, Longish Distances on ROUGH SEAS.

(I'll stick to my Alberg-30 for such conditions, though...   ;)  )

[tomwatt]

I love it!   ;D

Small OPEN boats, Longish Distances on ROUGH SEAS.

(I'll stick to my Alberg-30 for such conditions, though...   ;)  )

I remember some of the discussion surrounding the "re-introduction" of the Aleutian kayak design... so different than a Greenland kayak... even the Aleuts had stopped using them, until someone built one based on a museum specimen. Apparently everyone decided the weird bow and stern forms were just some kind of native superstition, without realizing how fast and agile the shapes made them. There's an old video from PBS out on the Internet showing the launch... featuring an Olympic kayaker.
Although it's arguable that Aleut baidarkas (kayaks) are open boats, since they are decked and have hatches. Hull form, and especially those graceful overhang areas, come into play in little boats too... the Aleutian kayak's weird bow form apparently does away with the need for long overhanging bow in a Greenland kayak by splitting the waves and driving through them.
Here's a link to an Aleutian kayak designer/builder:
http://www.wolfgangbrinck.com/boats/baidarka/thealeutiankayak/introduction/index.html

[Captain Smollett]

I remember some of the discussion surrounding the "re-introduction" of the Aleutian kayak design... so different than a Greenland kayak... even the Aleuts had stopped using them, until someone built one based on a museum specimen. Apparently everyone decided the weird bow and stern forms were just some kind of native superstition, without realizing how fast and agile the shapes made them. There's an old video from PBS out on the Internet showing the launch... featuring an Olympic kayaker.
Although it's arguable that Aleut baidarkas (kayaks) are open boats, since they are decked and have hatches. Hull form, and especially those graceful overhang areas, come into play in little boats too... the Aleutian kayak's weird bow form apparently does away with the need for long overhanging bow in a Greenland kayak by splitting the waves and driving through them.
Here's a link to an Aleutian kayak designer/builder:
http://www.wolfgangbrinck.com/boats/baidarka/thealeutiankayak/introduction/index.html

Thank-you, Tom, for that very cool, informative post.

I must cry "Mea Culpa" on the open boat comment.

Not being familiar with the specific boats to which the poster referred, I apparently conflated this boat with one(s) mentioned in later paragraphs where it is very clear he was talking about open boats.  In addition to rolling/righting techniques, he was even talking about bailing with a paddle blade (which clearly cannot be effectively be done with a decked boat).

On the topic, I have a "How-To" canoe book we bought almost 20 years ago in which the author spends a good deal of effort in early chapters laying into the 'myths' of what can be done with an open canoe (provided buoyancy is provided).  This book was also my first introduction to the idea decked canoes (not kayaks).

Anyway, I just find the parallels interesting now that I think about them.  Hull form and design play a larger role than some folks care to admit.  I recently was engaged in a conversation with a colleague who explicitly said "An Alberg 30 will be just as bouncy and uncomfortable as {boat x}," where boat x was a flat bottomed, plumb stemmed tub.

This poster on the fishing forum, like us here and the author of my canoe book, seemed to be fighting the current of "conventional wisdom" in boat design.

Thanks again...,I'm going to see if I can track down that PBS video...

[Cruise]

 I have owned quite a few boats over the years; An Ensenada 20 with a swing keel, a Pearson 26, an Albin Vega, an Olympian 34, and now an Allied 30. I prefer a full keel with a tiller-steered transom hung rudder.

[Captain Smollett]

Thanks again...,I'm going to see if I can track down that PBS video...

Here it is: Rebuilding the Baidarkas

Wow.  Thanks again.  This is good stuff.

[tomwatt]

Just got in from work... yes, I first thought the Greenland kayak design was "pretty" and the Aleut design was weird... but the more I see them (as well as having watched the PBS video over and over again), there is something very wonderful about that little boat.
And yes, a good kayaker (not including self in that category) can not only roll, but cover great distances over open water (deck mounted compass helps) in even rough seas. I have a few kayaking acquaintances who go fairly far out in the Gulf of Maine... I someday hope to have a decent mount for my kayak aboard my boat, so I can do a little fishing from the kayak.
8)