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Desirable and Undesirable Characteristics of Offshore Yachts


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Did I mention how good this thread is? Just wanted to say thanks to all of you chaps, its enjoyable, stimulating and thought provoking just listening.  

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That in no way diminishes the validity of their choices. They are buying the boat for themselves, not for you or me. I happen to prefer a deep fin, spade rudder, tall carbon rig, paradoxically on a wo

This has turned into Desirable and Undesirable Characteristics of Offshore Posters.

You know who to get the best advice from? Delivery skippers. It isn't their boat, they aren't in love with her and blind to her flaws. They have to get the boat from A to B despite the weather or

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19 minutes ago, shaggybaxter said:

Did I mention how good this thread is? Just wanted to say thanks to all of you chaps, its enjoyable, stimulating and thought provoking just listening.  

I hope someone who’s familiar with “Desirable and Undesirable Characteristics of Offshore Yachts” —i.e., the actual book— can tell me (us) if the stability/hull design concepts that have been discussed lately - specifically AVS, RM, etc— are touched on in this book?  It’s a topic I know little about, and a marine/hydrodynamic engineering treatise on it would be over my head - but a gentle introduction —and, critically— application— of said concepts, somewhat in depth, would be nice...

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34 minutes ago, Jud - s/v Sputnik said:

I hope someone who’s familiar with “Desirable and Undesirable Characteristics of Offshore Yachts” —i.e., the actual book— can tell me (us) if the stability/hull design concepts that have been discussed lately - specifically AVS, RM, etc— are touched on in this book?  It’s a topic I know little about, and a marine/hydrodynamic engineering treatise on it would be over my head - but a gentle introduction —and, critically— application— of said concepts, somewhat in depth, would be nice...

jud, yes they are.  It has been a long time since i have read the book so I dont remember the exact treatment.  But it is certainly well discussed.

As  coincidence to this discussion, about a decade ago - several members of the CCA asked Beth and I if we would author/edit a new edition of that book.  I declined.  I think Beth might have done it, but I felt there were too many egos, too many cooks who would have wanted to be in the kitchen and that none of us were really all that wise or knowledgeable.

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35 minutes ago, estarzinger said:

jud, yes they are.  It has been a long time since i have read the book so I dont remember the exact treatment.  But it is certainly well discussed.

As  coincidence to this discussion, about a decade ago - several members of the CCA asked Beth and I if we would author/edit a new edition of that book.  I declined.  I think Beth might have done it, but I felt there were too many egos, too many cooks who would have wanted to be in the kitchen and that none of us were really all that wise or knowledgeable.

Egos...in that hallowed body?!? :-) :-)

Well, the thread I started comes full circle - I think I’ll pick up a cheap used copy of it then, if it touches on these stability topics (notwithstanding the recommendation in the book —apparently— for a Fisherman anchor as a primary hook :-) )

(Does Beth’s book touch on this?  Waiting for a copy to arrive in the mail...)

 

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This has been one of the most interesting threads in CA. I feel like I should print it off in its entirety and tuck it in the back cover of my Adlard Coles' Heavy Weather Sailing.

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1 hour ago, Jim in Halifax said:

This has been one of the most interesting threads in CA. I feel like I should print it off in its entirety and tuck it in the back cover of my Adlard Coles' Heavy Weather Sailing.

Yes, threads like this are what make this place such a hugely valuable resource.

FB- Doug

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12 hours ago, estarzinger said:

jud, yes they are.  It has been a long time since i have read the book so I dont remember the exact treatment.  But it is certainly well discussed.

As  coincidence to this discussion, about a decade ago - several members of the CCA asked Beth and I if we would author/edit a new edition of that book.  I declined.  I think Beth might have done it, but I felt there were too many egos, too many cooks who would have wanted to be in the kitchen and that none of us were really all that wise or knowledgeable.

Are these the same people that don't count a trip to Labrador as an offshore passage? 

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21 minutes ago, Elegua said:

Are these the same people that don't count a trip to Labrador as an offshore passage? 

How could one count that as an offshore passage? True, polar bears will investigate your boat there, but Labrador is connected to North American shores, so ipso facto cannot be offshore :-) :-)  (Newfoundland is offshore.) 

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10 minutes ago, Jud - s/v Sputnik said:

How could one count that as an offshore passage? True, polar bears will investigate your boat there, but Labrador is connected to North American shores, so ipso facto cannot be offshore :-) :-)

It's not, but I'd argue you need to apply more skills than say a "offshore" passage to Bermuda.  

I think an addition to the book would have been invaluable to the sailing community. I understand why it didn't happen and egos or not, it's too bad it didn't. 

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25 minutes ago, Jud - s/v Sputnik said:

How could one count that as an offshore passage? True, polar bears will investigate your boat there, but Labrador is connected to North American shores, so ipso facto cannot be offshore :-) :-)  (Newfoundland is offshore.) 

With this logic, crossing the English channel is an offshore passage whereas crossing the Bay of Biscay is not.... I feel more "at sea" in the middle of the bay of Biscay than in the middle of the English channel!

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13 hours ago, Jud - s/v Sputnik said:

(Does Beth’s book touch on this?  Waiting for a copy to arrive in the mail...)

yea, there are 4 pages on it (61-65) - she covers pretty much everything - some of it is an inch deep  but the book is pretty large as it is and she had to prioritize.

BTW - just to close the loop on a little detail that was mentioned a bit up thread - I asked Andy Claughton (a NA who did a lot of the ground breaking post fastnet stability and capsize tank testing) about stability tank testing using Rc controlled rudders. He confirmed my memory that the original several series of capsize tests and then the subsequent series of drogue tests were all with without steering (eg fixed rudders) - we referred to the results from these a bit up thread.   Since then, with the development of much larger wave tanks, he also confirmed that active steering (both manual and autopilot controlled) are quite common.  He was aware of a stability test series that RNLI did on life boat designs, and he is aware of such tests done on individual high end boat designs (vendee/volvo type programs), but he did not seem to be aware of a test similar to the post-fastnet work (eg broad survey across wide range of yacht designs) on capsize resistance using models with active steering. While looking thru some of the links he gave me - I found this one interesting on multi-hulls, which we have not touched on much in this thread http://www.wumtia.soton.ac.uk/sites/default/files/uploads/pages/CSYS2001BD.pdf

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1 hour ago, Elegua said:

Are these the same people that don't count a trip to Labrador as an offshore passage? 

hmmm, yea, but I believe that is generally true. OCC and SSCA would also not consider it offshore (I think). I get your point, but one has to draw the line somewhere.  "Coastal' can certainly be hard - look at the NWP for instance or Chilean channels - but it is different than offshore.

 . . . honestly even Bermuda is an edge case for 'offshore' .

Most of these definitions were intended to refer to actual ocean crossings but then they got watered down as people tried to find the 'easiest way to meet the standard'.  Practically speaking, 'in the old days' it was sort of settled 'if you needed a sextant it was offshore' . . but gps has made that distinction moot.  

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1 hour ago, Elegua said:

It's not, but I'd argue you need to apply more skills than say a "offshore" passage to Bermuda.  

I think an addition to the book would have been invaluable to the sailing community. I understand why it didn't happen and egos or not, it's too bad it didn't. 

I was totally joking about Labrador not being an “offshore” passage - certainly is in “my book”.

Re: book...yeah, I agree, an updated/revised version of “Desirable...” would’ve been a great contribution to the sailing community, but such great ideas are often stymied by the wrong circumstances, alas.  So, we have Evans’ expertise here instead, which is great!

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10 minutes ago, estarzinger said:

hmmm, yea, but I believe that is generally true I think. OCC and SSCA would also not consider it offshore. I get your point, but one has to draw the line somewhere.  "Coastal' can certainly be hard - look at the NWP for instance or Chilean channels - but it is different than offshore.

 . . . honestly even Bermuda is an edge case for 'offshore' .

Most of these definitions were intended to refer to actual ocean crossings but then they got watered down as people tried to find the 'easiest way to meet the standard'.

Fair enough. I get the idea you have to draw the line somewhere and that is a simpler way.  Imagine the controversy if you had to grade passages and locations by difficulty? I was just commenting it might be simplistic.  And although Bermuda is an edge case for offshore, the trip from Bermuda to Baltimore was much rougher and felt more challenging than the transatlantic trip to Bermuda.  

1 minute ago, Jud - s/v Sputnik said:

So, we have Evans’ expertise here instead, which is great!

100% agree. This has become a very educational thread. 

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In French we have 3 words: côtier, Large, Grand Large. From Brittany going to the Azores would be Grand Large, going to Ireland or Spain would be Large and crossing the English channel would be an edge case between Côtier and Large depending where you do it.

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Pretty soon we're gonna have ta append the discussion of 'offshore'  to an anchor thread somewhere...

Me bones is achin' and I'ma feelin' like it's gonna blow...

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8 hours ago, estarzinger said:

............. just to close the loop on a little detail that was mentioned a bit up thread - I asked Andy Claughton........ he also confirmed that active steering (both manual and autopilot controlled) are quite common.  .......

Importantly the snippet you cut out from Wolfston before is only applicable to a boat lying beam on which is misleading since even Heaving-To is significantly more effective at preventing capsize.

As I said earlier. Importantly in those test the trad models were never knocked down or rolled over while underway and even surfed ahead retaining full directional control while at the other extreme the lighter beamier models were often uncontrollable, and tended to violently capsize (fully invert) every time, and that in waves the trad model took with complete impunity every time.

And I liked his words to the 98 S-H Coroner to the effect that they have done the research time and again as to what makes a boat seaworthy and that people just don't seem to get it.

For smaller offshore boats, not extreme types like large ULDB catermarans or Open/Vo series 60's 70's...   (which are seaworthy but the effects don't scale down).

In wave impact inversion prevention: Beam is bad, weight is good, a higher static stability limit is good, a high roll gyradius(roll inertia) is good. A larger lower aspect rudder is beneficial, Keel area is beneficial.

 

Having established all these factors relative to seaworthiness it was decided that  LPS_AVS was the easiest to use for the MCA commercial code which I think is a good guide.

 

 

 

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7 hours ago, MikeJohns said:

As I said earlier. Importantly in those test the trad models were never knocked down or rolled over while underway and even surfed ahead retaining full directional control while at the other extreme the lighter beamier models were often uncontrollable, and tended to violently capsize (fully invert) every time, and that in waves the trad model took with complete impunity every time.

Depends what you call "trad boats", when you look at the golden globe race, the long keel designs didn't fare particularly well, even the extremely experienced Van Den Heede struggled to sail one of these designs in the South. On the other hand a Contessa 32 (narrow, lot of ballast and fin keel which is somewhere between trafitional and modern) showed during the "Longue Route" that a small boat could behave well in those conditions. I was not surprised at all as I've seen them perform in RORC races.

As for beamier models, IMHO they aren't all equal, they give away some AVS but those with twin rudders are very easy to control even when heeling (try to recover a full keel boat which has started to roundup... when it starts to go, rudder stalls and it's gone!). IMHO a relatively beamy boat that is well ballasted is not such a bad choice as long as you keep sailing the boat even under bare pole.

Then there are the centreboard boats, as explained by @estarzinger above, being able to retract your foil is a big plus in term of safety as you are less likely to be rolled by a wave....

So it is a bit quick to oppose trad boats vs the rest...

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2 hours ago, Panoramix said:

Then there are the centreboard boats, as explained by @estarzinger above, being able to retract your foil is a big plus in term of safety as you are less likely to be rolled by a wave....

Thought that one had already been shot down? That the boats didn't trip over their keels, they tripped over their deck edges, and this was exacerbated by increased beam?

FKT

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39 minutes ago, Fah Kiew Tu said:

Thought that one had already been shot down? That the boats didn't trip over their keels, they tripped over their deck edges, and this was exacerbated by increased beam?

FKT

On a flat bottom IME it works at least to some extent as the boat weathercock downwind and slides, if not convinced get out on a 420 on a breezy day and lift the board.

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sigh . . . I  dont really want to engage in a debate about 'general' answers to the desirable/undesirable/seaworthy question  . . .because it is damn complicated and there is no one answer, they 'all depend' on compromises one wants to make. 

But, let me just point out that the design space is rather not generally moving toward narrow/heavy/full keel/barn door rudders - it is rather moving in exact the opposite direction (wider beams, lighter, fin-er keels and spade-er rudders).  And that is NOT because the clients and their NA's are complete morons, but because that direction makes sense in the totality of the sailing they do. And there is no evidence that direction is particularly 'unsafe'. Just to quote from the official Sydney to Hobart report "There is no evidence that any particular style or design of boat fared better or worse in the conditions. The age of yacht, age of design, construction method, construction material, high or low stability, heavy or light displacement or rig type were not determining factors."  

As to the expedition centerboards - that feature is primarily for the important task of being able to sneek into shallow enough water that truck size ice bergs can't follow you.  They ground outside you.  And for being able to take the ground well.  It also DOES happen to make those boats (generally) run really well, with really good directional stability - which means they (generally) dont round up and they dont need to even test whether keels are a primary or secondary or contributing cause to roll overs.  But, I would suggest it is rather clear that keels can and do have complicated hydrodynamic effects on capsize.

MikeJohns  seems to like narrow/heavy/full keel/barn door boats and that's just fine.  They can be fine boats.  But they bring their own set of compromises. And they are NOT (at all) immune to breaking waves, and he continues to rather overstate what the tank testing determined. No-one (that I know) is 'against' RM or AVS - they just bring compromises.  There are rather a wide range of people 'against' full keels and barn door rudders - but again they just bring compromises.  Narrow vs Wide is honestly the most interesting discussion - there are great boats along that whole spectrum from pencil thin ones to square multihulls - all seaworthy.

Anecdotally, the only boat I know which has been knocked over (and then abandoned near S Georgia)) while streaming a series drogue was in this general (heavy/full/barndoor) design space - this happened primarily because it was a single hander trying to a solo RTW, who was just too fried and tired and was making mistakes.  Which to my mind points out the more important contributing factors than boat design - skipper skill and knowledge and raw (bad) luck, and in the 'design space' raw size is the only thing (yea in the general middle of the design space, if you go to a corner of the space you can ofc create problems) which systematically effects outcomes (both in tests and empirically). 

 

 

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I own it and love it.  I don't care anything about, and generally loathe, modern boats so it's right up my alley.  For me one of the most interesting takeaways was that a heavier rig was much more stable and less likely to be knocked down than a light one, all other things being equal.  So if you've been looking for a justification for switching over to a solid timber mast with galvanized shrouds and stays, you can point to this.

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8 minutes ago, low bum said:

I own it and love it.  I don't care anything about, and generally loathe, modern boats so it's right up my alley.  For me one of the most interesting takeaways was that a heavier rig was much more stable and less likely to be knocked down than a light one, all other things being equal.  So if you've been looking for a justification for switching over to a solid timber mast with galvanized shrouds and stays, you can point to this.

High inertia in roll. Easy to do, hoist something heavy up your mast.

FB- Doug

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2 minutes ago, Steam Flyer said:

High inertia in roll. Easy to do, hoist something heavy up your mast.

FB- Doug

Well I guess, in theory, but I've never known this to be a storm tactic.

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14 minutes ago, low bum said:

I own it and love it.  

That is awesome :)  It is rather the attitude that cruisers out in remote anchorages away from internet forums take.  I actually don't remember EVER having a debate about anchors or boat design with fellow distant cruisers.  There was a decently high base level of knowledge and then we all pretty much just did ourselves and did not much worry about other  people's choices or justifying our own.

We did occasionally have discussions about techniques and best practices - but honestly even those were rare and they may have only been because both Beth and I are curious  'process people' by nature.

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4 minutes ago, Steam Flyer said:

High inertia in roll. Easy to do, hoist something heavy up your mast.

FB- Doug

are you volunteering?

if so, we hope you don't have a heart attack up there half way across the tropical pacific (lol).

 

sorry - just felt like being childish for a moment there :)

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29 minutes ago, estarzinger said:

are you volunteering?

if so, we hope you don't have a heart attack up there half way across the tropical pacific (lol).

 

sorry - just felt like being childish for a moment there :)

Hey jump right in the pool, here

Just having fun, the boundaries of where theory meets practice are a good place to lighten up IMHO

 

33 minutes ago, low bum said:
36 minutes ago, Steam Flyer said:

High inertia in roll. Easy to do, hoist something heavy up your mast.

 

Well I guess, in theory, but I've never known this to be a storm tactic.

Me neither. But that's what a heavy mast or rigging is doing, increasing roll inertia. Obviously it's not a simple case of "more is better."

Part of the challenge in studying yacht design is to pick out the common elements, on the basic level that the laws of physics 'see' your boat, and trying to apply them in general to boats of differing configuration. A lot of times, it's confusing or even misleading. It's amazing we don't argue more.......

FB- Doug

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1 hour ago, low bum said:

Well I guess, in theory, but I've never known this to be a storm tactic.

In the square rig days, they actually did the opposite - bringing bits of the rig down to deck in preparation for a storm.

That's because the 'all things being equal' in your original post is a bit of a trap.  If you add weight to a rig, you do increase roll inertia which is good, but you also (almost inevitably) also decrease RM (and AVS) which is bad and (usually) the net effect is bad. 

It shows the challenge of pulling isolated bits of completed dynamics out and singling them out.

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4 minutes ago, Steam Flyer said:

 

Me neither. But that's what a heavy mast or rigging is doing, increasing roll inertia. Obviously it's not a simple case of "more is better."

Part of the challenge in studying yacht design is to pick out the common elements, on the basic level that the laws of physics 'see' your boat, and trying to apply them in general to boats of differing configuration. A lot of times, it's confusing or even misleading. It's amazing we don't argue more.......

FB- Doug

The "argument" in so much of this stems from that period where boats transitioned from wood construction (with it's form defining limitations) to fiberglass (which freed designers up amazingly and liberated the underbody from basically any restrictions).  It's a spaghetti junction where aesthetics and intended uses crash together at rush hour.  Witness the hostility that the Valiant 40 was met with.  "That's not what a safe cruising boat looks like!"

The whole race rating scam/scandal nonsense that led to so many lousy boats laying on their beam ends never to return is on one end of the spectrum, in opposition to cruising oriented boats that are comically heavy and slow and built based largely on nostalgia and aesthetics rather than common sense - the "character" boats that come to mind. The retro-grouches of course crowed and said "See?  Next time will you listen?"  But the famous survivor of the Fastnet was not a pilot cutter but a Contessa 32 with a very non traditional underbody that was made possible by new materials and new thinking.

There's plenty to learn, and has been learned, from both ends of that spectrum and prudence lies in the middle.   "Desirable Characteristics" tries to take a look at this and I think if you're interested in that subject, it's an important work.  But if you're a total modern and play with carbon fiber this, and foiling that, then it's not particularly pertinent.  There really is no argument any more - modern boat design has simply moved on.  People that point at this book, and this time, and chuckle sagely to themselves about those dim witted ancients do not cover themselves with glory.

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1 minute ago, estarzinger said:

In the square rig days, they actually did the opposite - bringing bits of the rig down to deck in preparation for a storm.

That's because the 'all things being equal' in your original post is a bit of a trap.  If you add weight to a rig, you do increase roll inertia which is good, but you also (almost inevitably) also decrease RM (and AVS) which is bad and (usually) the net effect is bad. 

Yes you're right - strike the topmasts down on deck.  I wonder how much of this was tradition and standing orders, how much was hard learned experience, and how much was fear of the fidded mast junctions that could twist and splinter across the grain.  

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10 minutes ago, low bum said:

The "argument" in so much of this stems from that period where boats transitioned from wood construction (with it's form defining limitations) to fiberglass (which freed designers up amazingly and liberated the underbody from basically any restrictions).  It's a spaghetti junction where aesthetics and intended uses crash together at rush hour.  Witness the hostility that the Valiant 40 was met with.  "That's not what a safe cruising boat looks like!"

The whole race rating scam/scandal nonsense that led to so many lousy boats laying on their beam ends never to return is on one end of the spectrum, in opposition to cruising oriented boats that are comically heavy and slow and built based largely on nostalgia and aesthetics rather than common sense - the "character" boats that come to mind. The retro-grouches of course crowed and said "See?  Next time will you listen?"  But the famous survivor of the Fastnet was not a pilot cutter but a Contessa 32 with a very non traditional underbody that was made possible by new materials and new thinking.

There's plenty to learn, and has been learned, from both ends of that spectrum and prudence lies in the middle.   "Desirable Characteristics" tries to take a look at this and I think if you're interested in that subject, it's an important work.  But if you're a total modern and play with carbon fiber this, and foiling that, then it's not particularly pertinent.  There really is no argument any more - modern boat design has simply moved on.  People that point at this book, and this time, and chuckle sagely to themselves about those dim witted ancients do not cover themselves with glory.

Very well put, thank you

FB- Doug

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On a tangent . . . good wood is a truly marvelous material.  If it were 'invented' today it would be hailed as a wonder material. And careful wood construction is quite awesome.  

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It's amazing.  And building boats in wood leads to the most beautiful shapes imaginable.  It's like how trout fishing necessarily takes you to the most beautiful places in the world.  Serendipity.  But this isn't good enough for a lot of people.  Smith wants to beat Jones and money is no object, the materials seem to have no strength or weight limitations, so you get the twisted shapes we see now in sailing.  

 

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24 minutes ago, estarzinger said:

On a tangent . . . good wood is a truly marvelous material.  If it were 'invented' today it would be hailed as a wonder material. And careful wood construction is quite awesome.  

The only real default of wood is that it is time consuming (thus expensive) to build.

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5 minutes ago, Panoramix said:

The only real default of wood is that it is time consuming (thus expensive) to build.

The defect with wood is the countless secondary bonds 

 

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16 minutes ago, slug zitski said:

The defect with wood is the countless secondary bonds 

 

Yep.  Fiberglass becomes all one thing.  A wooden boat, however well made, is still a whole lot of small things held tightly together.  And sometimes not very tightly.  And apparently it's delicious.

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12 minutes ago, low bum said:

Yep.  Fiberglass becomes all one thing.  A wooden boat, however well made, is still a whole lot of small things held tightly together.  And sometimes not very tightly.  And apparently it's delicious.

Wood epoxy boats are just as much monocoque structures as any fiberglass boat.  Sometimes more so depending on how interior liners are installed and hull-to-deck-joints are done.

30 minutes ago, slug zitski said:

The defect with wood is the countless secondary bonds 

 

Really? I've never heard of wood epoxy boats having delamination issues.  Most damage I've seen has been the wood splintering or giving way, not the glue joint.

Wood has its "limitations" as a material:

  • it burns
  • material properties vary from tree to tree
  • it's hard to work with in very small or thin geometries
  • it's very bulky for its strength
  • it's not isotropic, i.e. it has a grain.
  • its very soft
  • it rots
  • it's not dimensionally stable with changes in moisture content

Most of these are either non-issues, or are easily managed/mitigated for hull construction.

 

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On 4/17/2021 at 2:22 PM, accnick said:

That would depend on who you ask, on any particular day. I once thought I knew a lot more than I probably do. Ironically, thinking you know a lot can get you started in the direction to understand how much more there is to learn.

I take some things as truths, others as guidelines, some as absolute BS. The trick is differentiating between them. Experience can help in that regard, provided you survive and learn from your mistakes.

"Ah, but I was so much older then, I'm younger than that now."

The more I learn, the less I know.

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7 hours ago, Panoramix said:

The only real default of wood is that it is time consuming (thus expensive) to build.

And time consuming (thus expensive) to maintain - at least ordinary timber construction is. I've owned a wood boat...and sailed on and cared for other wood boats. It's just an entire extra bucket of time/money on top of everything else on a similar fiberglass boat. Some people sail to mess about with boats - I prefer to mess about with boats to sail. 

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16 minutes ago, CapDave said:

And time consuming (thus expensive) to maintain - at least ordinary timber construction is. I've owned a wood boat...and sailed on and cared for other wood boats. It's just an entire extra bucket of time/money on top of everything else on a similar fiberglass boat. Some people sail to mess about with boats - I prefer to mess about with boats to sail. 

Traditional wood construction but a modern wood epoxy isn't that bad, I think purchase price aside the minimal extra hassle makes sense to get a light, rigid and solid boat. Solid GRP boats are a bit heavy and flexible and a cored boat probably needs as much attention as a wood epoxy boat.

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11 hours ago, estarzinger said:

 

As to the expedition centerboards - that feature is primarily for the important task of being able to sneek into shallow enough water that truck size ice bergs can't follow you.  They ground outside you.  And for being able to take the ground well.

FWIW I am quite a fan of these sorts of hulls for the reasons you state. I've been in the pack with a disabled engine and seen icebergs carving their way through and knowing there was nothing we could do should their course intersect ours. The ability to get into shoal water to avoid them & big floes/bergy bits is essential if you want to go far south.

In fact were I to build 2 more boats, the second one would be a hull of this type. Unfortunately due to age I doubt I'll build even one more boat, but who knows...

And as a point of interest Mike Johns currently owns 2 ocean capable cruising boats, both in steel, and neither are of the 'crab crusher' hull form. Both by 2 different Australian naval architects.

But also neither are of the modern lightweight 'skimming dish' form made possible by modern composites. They're heavy displacement cruising boats with the ability to carry tonnes of stores.

And my own boat is a relatively light/medium displacement shoal draft hull in steel with a heavy junk rig for simplicity of handling. I have absolutely zero plans to take her further south than we already are though.

FKT

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36 minutes ago, Fah Kiew Tu said:

In fact were I to build 2 more boats, the second one would be a hull of this type. Unfortunately due to age I doubt I'll build even one more boat, but who knows...

 

I have 6 boats (with various stages of designs) I would like to build.  I hope we get the opportunity to build one of them. I doubt we will go south again, but I have some unfinished business north.

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11 hours ago, estarzinger said:

sigh . . . I  dont really want to engage in a debate about 'general' answers to the desirable/undesirable/seaworthy question  . . .because it is damn complicated and there is no one answer, they 'all depend' on compromises one wants to make. 

But, let me just point out that the design space is rather not generally moving toward narrow/heavy/full keel/barn door rudders - it is rather moving in exact the opposite direction (wider beams, lighter, fin-er keels and spade-er rudders).  And that is NOT because the clients and their NA's are complete morons, but because that direction makes sense in the totality of the sailing they do. And there is no evidence that direction is particularly 'unsafe'. Just to quote from the official Sydney to Hobart report "There is no evidence that any particular style or design of boat fared better or worse in the conditions. The age of yacht, age of design, construction method, construction material, high or low stability, heavy or light displacement or rig type were not determining factors."  

As to the expedition centerboards - that feature is primarily for the important task of being able to sneek into shallow enough water that truck size ice bergs can't follow you.  They ground outside you.  And for being able to take the ground well.  It also DOES happen to make those boats (generally) run really well, with really good directional stability - which means they (generally) dont round up and they dont need to even test whether keels are a primary or secondary or contributing cause to roll overs.  But, I would suggest it is rather clear that keels can and do have complicated hydrodynamic effects on capsize.

MikeJohns  seems to like narrow/heavy/full keel/barn door boats and that's just fine.  They can be fine boats.  But they bring their own set of compromises. And they are NOT (at all) immune to breaking waves, and he continues to rather overstate what the tank testing determined. No-one (that I know) is 'against' RM or AVS - they just bring compromises.  There are rather a wide range of people 'against' full keels and barn door rudders - but again they just bring compromises.  Narrow vs Wide is honestly the most interesting discussion - there are great boats along that whole spectrum from pencil thin ones to square multihulls - all seaworthy.

Anecdotally, the only boat I know which has been knocked over (and then abandoned near S Georgia)) while streaming a series drogue was in this general (heavy/full/barndoor) design space - this happened primarily because it was a single hander trying to a solo RTW, who was just too fried and tired and was making mistakes.  Which to my mind points out the more important contributing factors than boat design - skipper skill and knowledge and raw (bad) luck, and in the 'design space' raw size is the only thing (yea in the general middle of the design space, if you go to a corner of the space you can ofc create problems) which systematically effects outcomes (both in tests and empirically). 

 

 

 I am not advocating that boats that exhibit extremes in seaworthiness should be sought just that awareness of the compromises be acknowledged.

There's a common theme in these sorts of discussions where individuals try and subvert research. That research has been done for a long time. It's repeated and validated, it's not highly theoretical.

Of course skill can make up for deficiencies and compromises in vessel design.

No one has ever suggested anything about designers as you said "being morons" , but they they are designing for a commercial market that dictates the compromises.

Performance influences designers more than seakindliness or inate seaworthiness. Performace is more easily achievable with a light boat. There's nothing inately slow about a heavy boat. It's the sail area ratios and the power to carry sail that determine speed. But heavy boats performance are expensive to produce......

For example, design trends; you use the terminology "a Barn Door" for a lower aspect rudder.  That a lower aspect rudder stalls at much higher loads than a high aspect rudder. But a high aspect rudder has a more desirable lift/Drag ratio and a lower wetted surface area.

If you ask for the most seaworthy controllable hullform they will or should design something else. Because they design they design a Pogo and they are skilled qualified designers doesn't mean the design trend is necessarily desirable.

Seaworthiness and seakindliness especially aren't current trends in the majority of production boats.

The plumb stem is a really good illustration of current trends.

As for the 1998 S-H the outcome was well predicted by the research done on the Fastnet. It's a pretty clear example of people misled about the level of safety of the boats they are buying.

Just look at the data. There was a clear trend of the less seaworthy boats being rolled ( fully inverted) and the more seaworthy boats coping very well.

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10 hours ago, estarzinger said:

And careful wood construction is quite awesome.  

I was lucky enough to see the famous Taleisin up close once - Larry (and Lin?) Pardey did extraordinary, detailed work on that boat.

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1 hour ago, estarzinger said:

I doubt we will go south again, but I have some unfinished business north.

Drifting with the Arctic pack ice has already been done (a re-enactment of the original Otto Sverdrup Expedition in the Fram)... :-) :-) 

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21 minutes ago, Jud - s/v Sputnik said:

I was lucky enough to see the famous Taleisin up close once - Larry (and Lin?) Pardey did extraordinary, detailed work on that boat.

you should look up Noel Barrott - very low profile but I guess google might find something. A kiwi wooden boat builder - took two of his boats Masina and Sina - rtw generally in decently high latitudes (higher than the Pardeys generally used).  The first one was engineless.  Super impressive guy - one of only a handful that I know who I think would have thrived on one of the old cape horn tall ships.  

we had Larry and Noel on board for some nice Chilean red.  Larry did not know Noel's background/experience and it was a bit funny to watch, both excellent seaman but such different personalities - the discussion came around to heavy weather at one point and Larry started with 'well I wrote the book on heavy weather', and Noel just sat and nodded his head - nothing to prove.  I really liked him.  He got laid low later on by bad metal in his blood, we assumed from the boat building, but he also ate a lot of fish up in Iceland/Spitzbergen and there was apparently also a lot of toxic Russian metal in those.

On the first boat Noel broken his rudder off with an ice impact, and sailed 1500 miles to a pin point landfall on a Chilean port with no rudder (and this was ofc pre-gps).

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1 hour ago, estarzinger said:

I have 6 boats (with various stages of designs) I would like to build.  I hope we get the opportunity to build one of them. I doubt we will go south again, but I have some unfinished business north.

Hear that tick tock noise?? Building boats takes too long, and you have to make a lot of decisions about things you don't care about that much. So many boats for sale.....

That may be my delivery skipper background talking - take them as I find them, go sailing....

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14 minutes ago, estarzinger said:

On the first boat Noel broken his rudder off with an ice impact, and sailed 1500 miles to a Chilean port with no rudder (and this was ofc pre-gps).

No rudder, hard. Latitude sailing to a North-South coast by sextant, easy. 

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9 minutes ago, CapDave said:

No rudder, hard. Latitude sailing to a North-South coast by sextant, easy. 

hmmm, sure they were pretty sure to hit something . . but  . . . 'easy' . . idk if that's the word I would use, Someone else here used the word 'easy' for a different passage in the 40's and 50's and I was not so confident about that usage of the word either. . . . . The rudder came off in the '50's - so it was a NNE course to Valparaiso. There is often not much sky down there and it is generally pretty rough in a small boat.  And if you get in too close you are on an ironbound lee shore.

  

11 minutes ago, CapDave said:

Hear that tick tock noise?? Building boats takes too long, and you have to make a lot of decisions about things you don't care about that much. So many boats for sale.....

I hear you.  I have told many people exactly that.  But I personally am perhaps a bit spoiled by having had a custom boat - I find most of the used stuff pretty uninspired. A few of my 6 'concepts' I could find something, but for a few others I dont think anything exists I would be happy with.  Look up mv Polar Bound - how many of those do you think are on the used market?

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11 minutes ago, estarzinger said:

but  . . . 'easy' . . idk if that's the word I would use,

Yeah, this is where internet forums fall so far short of conversation - because if we were talking I'd agree with you, and then qualify my agreement with some further observation, etc. But even in near real time (or generally with more latency), it gets old quickly....

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11 hours ago, estarzinger said:

On a tangent . . . good wood is a truly marvelous material.  If it were 'invented' today it would be hailed as a wonder material. And careful wood construction is quite awesome.  

I can attest. My previous boat was nearly as good as glass gets, a Hinckley, carefully built and very well sorted.

My current boat is cold molded by Brooklin BY, and, so far as I can tell, better in almost every way. Plus beautiful beyond imagine. 

She's not everybody's cuppa. Since my size limit on boats is driven not by money but by what my wife and I can easily handle by ourselves. She's a 48' with the pricetag of a 60' and the accomodations of a 40' or less, but she is perfect for us, now, while I am still doing a little offshore racing, but mainly cruising with my love of 47 years. 

She finds the aesthetics, inside and out, of the woody to be simply irresistible. I find the sailing characteristics downright addictive. With this  boat I have a boat that sails like I think a boat should sail, looks how I think a boat should look, treats her crew how I think a crew should be treated. 

Back to the original topic, the book really only has a couple of sections on hull design. Jim McCurdy, designer of my Hinckley, I think wrote the section on scantlings, while we have much advancement in materials science, that is still worth reading.

A much neglected area in modern boats, I think, is interior ventilation. My current boat has 4 large dorades and 6 opening hatches with integral bug screens. The Dorades have interior plugs so they may be sealed from inside in the event of truly horrendous weather. The result  is a boat is a joy to be abaord during rainstorms. A stuffy boat is not my idea of fun, but I see so many with only hatches for ventilation. We have a spray over our forward hatch, which allows us to keep it open in moderate conditions offshore, and makes sailing quite pleasant

 

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1 hour ago, MikeJohns said:

As for the 1998 S-H the outcome was well predicted by the research done on the Fastnet. It's a pretty clear example of people misled about the level of safety of the boats they are buying.

Just look at the data. There was a clear trend of the less seaworthy boats being rolled ( fully inverted) and the more seaworthy boats coping very well.

G'day Mike,

I thought the summary from the 98 S-H was the yachts getting into trouble was more about the locale the boat found itself in rather than the seaworthiness of the boat? I do believe there were some new boats that simply were too focused on speed vs manners for those conditions but a lot of good boats got caught out too.  

Winston Churchill springs to mind, a Percy Coverdale wooden cutter that IIRC was immaculately prepared and loved heavy weather, it was simply in the wrong spot. 

Happy to be corrected! 

Cheers,

SB

    

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3 minutes ago, Cruisin Loser said:

My current boat is cold molded by Brooklin BY, and, so far as I can tell, better in almost every way. Plus beautiful beyond imagine. 

yea, your current boat in fact fits smack dab in one of my 6 concepts - a 'gentleman's boat' - Beauty and style, but also fast enough to (at least potentially) crush the competition.

When I was planning Hawk, I had dinner with two of the Maine high latitude fraternity, and they tried to talk me into thick wood. They had compelling arguments, and I'm sure something excellent would have resulted.

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2 hours ago, MikeJohns said:

For example, design trends; you use the terminology "a Barn Door" for a lower aspect rudder.  That a lower aspect rudder stalls at much higher loads than a high aspect rudder. But a high aspect rudder has a more desirable lift/Drag ratio and a lower wetted surface area.

 

Not really technically correct - a low aspect rudder stalls at high angles of attack. It does not necessarily generate higher loads, other things equal it will generate lower loads. The lower lift slope and less distinct stall can be a benefit if you are under ruddered or have a ham fisted helmsman (or autopilot). 

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21 minutes ago, shaggybaxter said:

G'day Mike,

I thought the summary from the 98 S-H was the yachts getting into trouble was more about the locale the boat found itself in rather than the seaworthiness of the boat? I do believe there were some new boats that simply were too focused on speed vs manners for those conditions but a lot of good boats got caught out too.  

Winston Churchill springs to mind, a Percy Coverdale wooden cutter that IIRC was immaculately prepared and loved heavy weather, it was simply in the wrong spot. 

Happy to be corrected! 

Cheers,

SB

    

For a start the organizers hired a professional public relations damage control specialist. That influenced the media, a lot of people's opinions and set the theme for the language used.

There was a lot of mention  about the awesome and unpredictable power of the sea, It was also loudly promoted that it was a once in 100 year storm.

Localized storms of that magnitude occur in that area 4 to 5 times a year. The records of the oil platforms and testimony from Naval commanders and commercial boat operators who were there were different.

The conditions were well forecast the day before and warnings were current. The coronial inquest revealed that many participants didn't properly understand marine forecasts and that the wind and wave height were not expected maximums.

As for Winston Churchill; The Displacement was 21.4 tonnes Length On deck 50.6 ft Built in 1942 as a performance craft.

At 56 years of age and plank on frame the quality of the plank fastenings was poor  Importantly she was partially refastening but the job was not complete She lost a topside plank along with her Bulwark after a wave strike and sank from water ingress. The boat was lightly built and had a prior history of major damage in rough weather.  It had nearly sunk some years prior when the mast pushed through the bottom of the hull and was only saved when it was run aground. Similar damage to old plank on frame boats has been very common over the years. 

Also WC was not what you'd class as very stable with a LPS of only 124 degrees. It certainly wasn't a traditional solid, heavy displacement, highly stable craft.

Here's a plot showing S-H boats that were  rolled ( as in fully capsized ) overlaid on the UK MCA commercial requirement for sailing craft produced by Wolfston. This is from Kim Taylors paper on the event.

rolled sydney Hobart.JPG

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1 hour ago, DDW said:

Not really technically correct - a low aspect rudder stalls at high angles of attack. It does not necessarily generate higher loads, other things equal it will generate lower loads. The lower lift slope and less distinct stall can be a benefit if you are under ruddered or have a ham fisted helmsman (or autopilot). 

Sure with the same foil section and planform scales just for AR but  lower aspect rudders are commonly skeg partial skeg and even flat plate.

Fully attached rudders like the flat plate "barn door" also work quite differently, they move Cp of the keel rather than being a lifting foil.

Rudders are interesting,  do you have you read Molland's Marine rudders and control surfaces ? Look at Flat plates and even Naca sections used backwards you get more lift for a given angle and more robust control at the cost of Drag....... 

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1 hour ago, MikeJohns said:

For a start the organizers hired a professional public relations damage control specialist. That influenced the media, a lot of people's opinions and set the theme for the language used.

There was a lot of mention  about the awesome and unpredictable power of the sea, It was also loudly promoted that it was a once in 100 year storm.

Localized storms of that magnitude occur in that area 4 to 5 times a year. The records of the oil platforms and testimony from Naval commanders and commercial boat operators who were there were different.

The conditions were well forecast the day before and warnings were current. The coronial inquest revealed that many participants didn't properly understand marine forecasts and that the wind and wave height were not expected maximums.

As for Winston Churchill; The Displacement was 21.4 tonnes Length On deck 50.6 ft Built in 1942 as a performance craft.

At 56 years of age and plank on frame the quality of the plank fastenings was poor  Importantly she was partially refastening but the job was not complete She lost a topside plank along with her Bulwark after a wave strike and sank from water ingress. The boat was lightly built and had a prior history of major damage in rough weather.  It had nearly sunk some years prior when the mast pushed through the bottom of the hull and was only saved when it was run aground. Similar damage to old plank on frame boats has been very common over the years. 

Also WC was not what you'd class as very stable with a LPS of only 124 degrees. It certainly wasn't a traditional solid, heavy displacement, highly stable craft.

Here's a plot showing S-H boats that were  rolled ( as in fully capsized ) overlaid on the UK MCA commercial requirement for sailing craft produced by Wolfston. This is from Kim Taylors paper on the event.

rolled sydney Hobart.JPG

Thanks very much for the very informative response. Albeit I need more coffee to absorb the chart, is the vertical axis intended to be the AVS? 

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46 minutes ago, MikeJohns said:

Sure with the same foil section and planform scales just for AR but  lower aspect rudders are commonly skeg partial skeg and even flat plate.

Fully attached rudders like the flat plate "barn door" also work quite differently, they move Cp of the keel rather than being a lifting foil.

Rudders are interesting,  do you have you read Molland's Marine rudders and control surfaces ? Look at Flat plates and even Naca sections used backwards you get more lift for a given angle and more robust control at the cost of Drag....... 

None of which is particularly relevant. A fully attached flat plate is not going to develop more steering moment than a proper spade rudder on any vaguely normal hull form. This has been known for 100 years. Nat Herreshoff knew it. Running sections backwards isn't going to give you better control, the lift slope is slightly increased at the cost of greatly reduced stall angle - not at all what you want. Molland does not appear to address sailing yacht rudders, rather ships. They have very different requirements from rudders. If you're reading stuff, Vacanti's writings would be far more relevant to sailing yachts.

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2 hours ago, DDW said:

None of which is particularly relevant. A fully attached flat plate is not going to develop more steering moment than a proper spade rudder on any vaguely normal hull form. This has been known for 100 years. Nat Herreshoff knew it. Running sections backwards isn't going to give you better control, the lift slope is slightly increased at the cost of greatly reduced stall angle - not at all what you want. Molland does not appear to address sailing yacht rudders, rather ships. They have very different requirements from rudders. If you're reading stuff, Vacanti's writings would be far more relevant to sailing yachts.

I like to gauge peoples reaction to the foil reversal... ;-)  And yes for equivalent areas.

Molland spent a lot of time with small craft including sailboat rudders, did a lot of free stream tests that have useful data on a raft of different forms.  He really pioneered current empirical  methods for load derivation used by class societies for small craft as well as ships.

I'd like to come back to your claim that  "although  low aspect rudder stalls at high angles of attack. It does not necessarily generate higher loads....." what  AR.e are you considering there ?

Also Vacanti and his code are all about ideal free stream flow.  The problem I have is that in a seaway the inflow is nothing like ideal.

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3 hours ago, shaggybaxter said:

Thanks very much for the very informative response. Albeit I need more coffee to absorb the chart, is the vertical axis intended to be the AVS? 

Yes, static limit of positive stability.

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6 hours ago, MikeJohns said:

Here's a plot showing S-H boats that were  rolled ( as in fully capsized ) overlaid on the UK MCA commercial requirement for sailing craft produced by Wolfston. This is from Kim Taylors paper on the event.

 

Presented like this, this plot would tend to show that there is no strong relationship between being rolled and being on the safe side of this graph! But then these are just 5 data points, so statistically not very robust, it would be more interesting if boats that didn't capsize had been included. This is from a report, may be there was another graph somewhere in there showing the full picture.

Also I am a bit wary of a graph effectively saying you can't go offshore in a yacht less than 7m long as experience shows that it is possible.

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3 minutes ago, Panoramix said:

Also I am a bit wary of a graph effectively saying you can't go offshore in a yacht less than 7m long as experience shows that it is possible.

Of course it's possible, it's been done heaps of times.

The question for people who do this is - do you feel lucky?

Quite a few of the small boat people disappeared at sea. Christopher Ridding comes to mind - left NZ headed for Australia but never made it.

FKT

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17 minutes ago, Fah Kiew Tu said:

Of course it's possible, it's been done heaps of times.

The question for people who do this is - do you feel lucky?

Quite a few of the small boat people disappeared at sea. Christopher Ridding comes to mind - left NZ headed for Australia but never made it.

FKT

On the other hand every 2 years 80 solo skippers race across the Atlantic with overpowered 6.5m boats... I can't remember when was the last accident but that was a long time ago, probably safer than things people do daily on earth!

If you go offshore on a small boat, you need to do it right but it can be done safely...

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3 hours ago, Panoramix said:

Presented like this, this plot would tend to show that there is no strong relationship between being rolled and being on the safe side of this graph!

As I directly quoted in a post above - that was the exact conclusion of the coroner report.  "There is no evidence that any particular style or design of boat fared better or worse in the conditions. The age of yacht, age of design, construction method, construction material, high or low stability, heavy or light displacement or rig type were not determining factors."  

 

Reading various posts and considering his own boats - Mike's 'theoretical' position on RM and AVS may actually be pretty simple and agreeable - (A) That if boat A is twice the displacement of boat B and they are both excellent examples of the NA craft, then boat A is probably more roll resistant than boat B. and (B) If Boat A and Boat B are identical designs and you take weight out of the interior of boat A and put that same weight in the keel, then boat A is probably more roll resistant than boat B. As I commented several times above - no-one is 'against' RM and AVS per say - it is just the bring compromises and for each 'mission' there is some sort of optimal compromise (which would depend on the individual owners).

With (A) the more empirical evidence suggests enough extra size does matter and can make a difference. With (B) - type gains however, they may be slight enough to be easily swamped by the power of breaking waves - and where you are related to the storm, if you end up in the most intense part of the breaking waves or not - along with how the skipper handles the situation, becomes the primary factor in whether you roll or not.

I am unable to see how his position on some of the other matters, like rudder shapes, are  likely to generate much agreement.

  

13 hours ago, MikeJohns said:

 But heavy boats performance are expensive to produce......

And this comment made me lol - be fun sometime to ask an owner of say a custom Persico or MULTIPLAST if they bought lightweight boats because the heavy ones were too expensive B)

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1 hour ago, estarzinger said:

I am unable to see how his position on some of the other matters, like rudder shapes, are  likely to generate much agreement.

I read your earlier post but didn't realise that the graph was from this report, should read more carefully! As for the bit I quoted, that would mean that a lot of people are wrong.... I've sailed old gaffers (just a bit), I love all the history behind them and as a boat geek I am just curious, Nevertheless despite all the efforts and cleverness that went into their design and construction, it is hard to ignore that boat design has progressed vastly. For a start rudder authority on these boats is - to modern standards - approximative.

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27 minutes ago, Panoramix said:

, it is hard to ignore that boat design has progressed vastly.

The coroners report was just empirically commenting regarding the SH fleet, and this particular incident, not trying to encompass the broader full assortment of all possible sailing craft.  As shown in the graph, design distinctions did not make much differences empirically in who got into trouble. The next sentence which I did not quote was, as we have all discussed/agreed before, that the primary factor was where exactly you were regard to the worst breaking waves - there are almost always small zones which are much more intense that other places.

Ofc the naval architecture profession has progressed. They were not trying to suggest it had not.  Just that across the SH fleet the size and power of the worst waves washed away the distinctions that existed within the fleet.  It is in fact similar to the quote I posted from the fastnet testing - that sufficiently sized breaking waves could easily capsize all the models.

I have sat on a few of these sorts on incident/accident investigations, and they tend to try to stick at least initially reasonably narrowly to their brief.  It is hard enough to draw conclusions and agreement when doing that.  Trying to encompass the whole possible world of sailing would tend to make it impossible.  Sometimes you get follow up activities that are intended to be broader - like the investigation into Cheeki Rafiki was extended into a look at the whole school of plexus pan liner structural construction (that ball was then just totally ignored/dropped dropped by the industry). These sorts of incident reports, including the SH corner's one, are typically quite worthwhile reading. Usually the team writing them has a quite good knowledge base and worked quite hard to tease out the best conclusions (yea, sometimes they fail at that, but usually they are a worthwhile read anyways).

(edit: these things are difficult to discuss in twitter size bites. I suspect we would all have more agreement if we were face to face with some nice red wine).

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6 hours ago, MikeJohns said:

I'd like to come back to your claim that  "although  low aspect rudder stalls at high angles of attack. It does not necessarily generate higher loads....." what  AR.e are you considering there ?

Also Vacanti and his code are all about ideal free stream flow.  The problem I have is that in a seaway the inflow is nothing like ideal.

Aspect ratios in rudders on normal sailboats range from about 1 to about 8 or so. The rapidly varying region is in the lower numbers. I'm talking here about real AR, not a doubled version that some speak of. The mirror effect requires gap sealing rarely seen on boats. Some of the data from tests that are published is polluted by rake, causing spanwise flow. In classic wind tunnel testing going back to about the Wright Bros., very low AR foils have a lower lift slope and stall at (at best) the same or (usually) lower CL. This has been shown to be because the tip vortex wraps to the low pressure side, having two effects: it delays separated flow on the low side and releases pressure from the high side producing the measured effect. Load or lift is proportional to CL, area, and dynamic pressure; lower CL means lower load.

Now, when operated well beyond stall angles, you may find the lower AR foil producing more load because the flow separation is soft, and filled in by the vortex. At 35 deg angle of attack, an AR 1 rudder may produce more lift than an AR 5 rudder. This is how lifting strakes on jet fighters, crab claw rigs, and hang gliders can fly at very high angles of attack. If you are frequently operating your boat's rudder like that, you have a serious rig balance problem or are under ruddered. 

I'll agree that in a seaway the flow is not an ideal free stream but it isn't that far off either. Most normal rudders behave in practice just as aerodynamic theory suggests they should. 

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33 minutes ago, estarzinger said:

(edit: these things are difficult to discuss in twitter size bites. I suspect we would all have more agreement if we were face to face with some nice red wine).

I was actually agreeing with you, I don't take time to make long paragraphs with qualified sentences but what I just meant is that there is no reason to be nostalgic on stuff like barn door rudders. They existed at some point for good reasons but now that design knowledge and material science are completely different, saying it works because it was done like this in 1950 has little value. Chances are that there is a better way to do it nowadays. When I go down a wave that is much steeper than I would like, I definitely want to choose where I bury my bow!

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Can the following generalizations be made about heavy weather survival?

For running downwind and actively steered - Light boat/high AR spade rudder is better.

For points above beam (hove to, fore reach, lie ahull) - Heavy boat/low AR barn door rudder is better.

 

Disclaimer: I don't know anything about this subject.

Steve

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1 hour ago, Panope said:

Can the following generalizations be made about heavy weather survival?

it is an interesting question - the reverse of how this is usually asked - usually you have a boat of a particular design and the question is what is the best tactic for this boat.  You are asking for a particular tactic, what is the best boat. 

And at least for me idk the general purpose answers to that off my head. I would guess that the answer - to for instance what in the best design for running in breaking waves - would be niche boats that would not be great at general purpose cruising.

I personally felt a successful cruising boat needed to be able to go both directions (up and down) in harsh weather.  But I know some which were not able (just for example, the Pardey boat could fore reach and heave to but did not run well).

I did build a custom boat specifically to be good in a wide range of hard conditions and it was more in a middle ground that the edge choices you mention - a mid-weight displacement, mid size-fin/bulb, very large not super high AR spade rudder.  We were near the outer achievable limits of RM and AVS (given some constrains on practical draft and construction strength and materials).  This boat both ran well and forereached well.  It forereached much better than it hove-to, so we generally did not heave-to. And we did not lie ahull ever in hard conditions.  It did benefit from a drogue in some running conditions.

Another way to answer your question, from various empirical findings we have already discussed, is perhaps to say that rather more important than the parameters you mention is raw boat size (get the biggest one), and skipper skill and experience (duck those intense small hot zones and know what tactic is best for each condition in the particular boat and make sure everything on the boat is maintained)  . . . and then some amount of raw luck.

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just as an aside. . . . I understand the focus on storms . . . but light air is really the cruising challenge - there is (generally) a lot of it. It is both highly desirable and seaworthy to be able to move well in light air under sail.

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Also CL = coefficient of lift, a primary characteristic of sections and planforms. 

When hove to classically, you are backing down with both keel and rudder stalled. You could argue that a low aspect ratio rudder would be better under these circumstances, because it has a greater and more predictable slope of lift vs. angle of attack after separation (stall). I have the feeling all of that is greatly overwhelmed by other factors in the hull, keel, and rig. Perhaps the biggest impediment to heaving to properly is a sloop rig, it lacks options to vary the CP (= center of pressure) of the rig. Pretty easy on a ketch or yawl, impossible on a una rig, sloop is in the middle but tending toward the una in that there is no way to get the CP aft very far. 

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6 hours ago, estarzinger said:

Sometimes you get follow up activities that are intended to be broader - like the investigation into Cheeki Rafiki was extended into a look at the whole school of plexus pan liner structural construction (that ball was then just totally ignored/dropped dropped by the industry).

This is a surprise?  The majority of industry build boats with pans, it's quick and cost effective.  They aren't really repairable and not especially strong but does anyone believe it's going to change.  Look at the problem the Lagoon 45 owners (+1,000 owners) are facing, the builder just walks away and blames the sailor.

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Interesting discussion on capsize, especially the rubbery relationship between design characteristics and capsize history.

My take is capsize is a rare event, determined by multiple variables, and what matters is the boat doesn’t sink under you, you are not seriously injured, and the boat retains some degree of function.

So the details of construction are more important to me than the overall design. Things like fixed batteries and floorboards, effective restraints, a mast and boom that remain standing, hatches and windows that don’t pop open, and keels that stay attached to the boat.

I grew up racing dinghies and skiffs, capsize was inevitable, what mattered was the recovery and getting back into the race.

As far as offshore design characteristics go, I am more interested in comfort and maintaining a good passage speed.

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