Desirable and Undesirable Characteristics of Offshore Yachts

[estarzinger]

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.

 

[Jud - s/v Sputnik]

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...)

 

[Jim in Halifax]

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.

 

[Steam Flyer]

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

 

[Elegua]

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? 

 

[Jud - s/v Sputnik]

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.) 

 

[Elegua]

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. 

 

[Panoramix]

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!

 

[estarzinger]

(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

 

[estarzinger]

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.  

 

[Jud - s/v Sputnik]

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!

 

[Elegua]

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.  

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

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

 

[Panoramix]

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.

 

[Veeger]

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...

 

[MikeJohns]

............. 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.

 

[Panoramix]

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...

 

[Fah Kiew Tu]

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

 

[Panoramix]

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.

 

[estarzinger]

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). 

 

[low bum]

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.