Modern Hull forms and Motion Comfort - Page 12 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Boat Review and Purchase Forum > Sailboat Design and Construction
 Not a Member? 


Like Tree60Likes
Reply
 
LinkBack Thread Tools
  #111  
Old 04-11-2013
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,166
Thanks: 21
Thanked 96 Times in 80 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Quote:
Originally Posted by SloopJonB View Post
How many rigs have come down, keels fallen off, sailors been rescued and sailors disappeared in the Vendee since its inception?

In the first Whitbread, Sayula, a stock Swan 65 was rolled or pitchpoled, came up with rig intact and continued on to win. The sailors had proper hot meals with wine IIRC during the race and didn't have to wear crash helmets.

THAT is "suitable for offshore" IMHO.
Someone had already explained that. A stock Swan 65 is not a race boat. An Open 60 is a top racing machine. Is like wanting to compare a road BMW with a FM I in terms of durability and speed.

Maybe you have not been following it but the safety of top race boats, namely Open 60's have been increased each year and today's boats are hugely more safe than the first real race sailboats that have done the Vendee Globe to the point of losing the keel and be able to continue to sail without it.

Sure they have a problem with the reliability of keels and I am sure that they are going to address that. Anyway that reliability has to do with the development of canting keels. What they are doing now will permit in some years cruising boats to have safe canting keels and perform better.

If you, instead of looking at boats that, like the F1, are pushing the borders of technology, look for more inexpensive and basic race boats you will find very seaworthy and bullet prove boats, like the 40 class racers, the mini racers or the Figaro II class boats. The number of these boats that finish a Transat is close to 100%, even among 22ft boats. The percentage of these boats that finish ocean races is increasing, not diminishing.

Regards

Paulo
__________________

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

Last edited by PCP; 04-11-2013 at 10:32 PM.
Reply With Quote Share with Facebook
  #112  
Old 04-11-2013
Jeff_H's Avatar
Moderator
 
Join Date: Feb 2000
Location: Annapolis, Md
Posts: 6,579
Thanks: 5
Thanked 95 Times in 71 Posts
Rep Power: 10
Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about Jeff_H has a spectacular aura about
Re: Modern Hull forms and Motion Comfort

Outbound:

Thank you for the generous offer to join you for a sail. The boat with the strange interior plan was at the Annapolis Boat Show probably 5 years ago, and I think was at the show a couple years in a row.

I did want to circle back to the discussion regarding my comment on encapsulated keels. I apologize that some of this was cut and pasted from an article that I had written on the subject a few years ago, and also apologize for the length ( should put that in my signature line). To put my comments into perspective, I will honestly admit that my comments reflect my own personal viewpoint of boats and my own internal filters; a viewpoint that sees boats as a tool; an ideally very complex and sophisticated tool- one whose role in life is to do a wide range of specific tasks exceptionally well. My opinion on specific boats and their details tends to derive from my understanding of the technical, engineering and science based side of issues. As much as I can draw a springy sheer with the best of them, and admire yachts of all eras, I tend to analyze boats at a very technical level.

And in that vein, I see distance cruisers as the pick-up trucks of the sailing world; needing to be purpose oriented, practical, rugged, low maintenance, hauling a small number of people, and a proportionately large amount of cargo. As much as anything else, they need to take a serious beating and keep functioning safely. And that is the foundation on which my opinion of encapsulated keels is built.

I know that are a whole lot of folks who think that encapsulated keels are okay, and to some, encasulated keels may even be preferable, but when I look at the technical implications of how an encapsulated keel is actually constructed from a structural and practical standpoint, and having observed and tried to repair boats with encapsulated keels after they have been damaged, I personally see no reason except cost savings to use an encapsulated keel. I understand that to properly engineer a bolt on keel to withstand the kinds of heavy blows that a keel needs to take, requires a lot of care and a very robust internal structure, but because of the physical location of that structure, it is easier to construct this sturcture in a manner that is reliable over the life of the vessel.

And while an encapsulated keel can get by without the kind of robust internal structure required to make a bolt on keel reliable, if long term reliability and saftety is the goal, then encapsulated keels should have almost the same strength bilge membrane and the same transverse and longitudinal framing as a bolt on keel. But few boats with encapsulated ballast get that level of internal framing.

My other gripe with an encapsulated keel is the difficulty in doing a proper repair once an encasuilated keel gets damaged. Typically, in a hard grounding a number of things happen to a boat with an encapsulated keel. Typically the skin of the keel encapsulation gets ruptured and separates from the ballast. Sometimes this is a small slit, but often its a larger tear. This allows water into the small cavities between the keel and the ballast and once wet it can mean the ‘beginning of the end’ for the boat as this permanently wet fiberglass blisters itself from the interior and the wet areas spread around the ballast. This is especially a problem on a boat that is hauled out for cold winters where freeze/ thaw cycles can really pry the skin loose from the ballast.

Since the connection between the ballast and the envelope is portion of the keel structure, transmitting lads from one side of the keel to the other much like the web of an I beam, and keeping the ballast from shifting, the loss of connection between the ballast and the skin should be taken seriously.

In an earlier discussion of encapsulated vs bolt-on keels, the question was raised as to how frequently does the ballast actually delaminate from an encasulated keel. Out of curriousity, I walked around a boat yard tapping keels and taking notes on encapsulated keel boats. My recollection is that something approaching 50 % had separated areas in excess of a 1'-6" radius. Most of the delaminated areas were in the upper third of the keel which makes sense when you consider the forces acting on the bond between the ballast and skin. On some of the wost cases, you could literally flex the delaminated area with your hands or could see the bulge away from the ballast near the support blocks.

But getting to the unique aspects of this discussion, I completely disagree with the idea that a distance voyager should worry less about damaging the encapsulation envelope than coastal cruiser. When you go offshore, it is amazing what is floating out there; shipping containers have gotten a lot of press lately, but debris big enough to sink a boat goes far beyond that.

In my sailing career, I have sailed past whole trees, a dumpster, a billboard, a wrecked dinghy complete with outboard motor, what looked like a 2,000-3,000 gal., iron tank of the type that might get used by a gas station, a steel outrigger that we concluded came from a shrimp boat and so on. And the very nature of distance cruising is that you cannot keep the kind of 24/7 watch that would guarantee that you don't hit something just below the surface at speed.

Similarly, distance cruisers, almost by definition, are entering unfamiliar ports of call and so the likelihood of 'messing up big' becomes a greater risk.

So to me, while the odds of any one distance cruiser getting into trouble may be small, the risk of serious consequences is much bigger. And adding to the risk is slicing the encapsulation envelope well below the surface, driving the ballast up through the bilge membrane, and leaving an un-repairable leak while at sea. And on that basis, I don't think that given those risks, an encapsulated keel is the right technology.

I cannot speak for why any individual boat company would chose to use an encapsulated keel. In the case of the Cherubini 44's, to me these boats are a fashion statement and not about the sailing. Fashion statements do not need to be designed for offshore passage making. Consequently, the costs associated with building boats like the Cherubini seem to derive from high levels of fit and finish, vast quantities of material, and exclusivity, rather than from thoughtful structural engineering. The use of encapsulated keels on Shannons is a more complex question in my mind. Since their mission seems more focused on serious cruising, I have no idea why they would elect to use encapsulated keels.

With regards to the description of how the bulbs are added to your Outbound, that gets to my point, that there is not a great way to add bulbs to an encapsulated keel. The solution that you describe is very complex and yet does not succeed in creating as reliable a solution as a bolted keel, especially on a boat which has a generous keel root like the Outbound.

The problems start with the way that an encapsulation envelope is constructed. It is very difficult to lay glass with any precision at the very bottom of cavity the depth of a keel. When I have repaired or observed the bottom of damaged encapsulation envelopes, the quality of the glass work at the bottom of the keel has consistently been dismal. Typically, you see a mix of resin rich cloth with lenses of unreinforced resin, and conversely, dry glass. And that is the surface supporting the ballast and coming between the unstoppable ballast and the immovable submerged object.

Unlike a bolt on keel, the ballast is then just ‘glued’ in, and usually that is done with polyester slurry or worse. This is a brittle material with dubious sheer and tensile strength. On a concentrated impact, this ballast often shifts sheering away from the walls of encapsulation and rotating up against the bilge membrane above. Few boats with an encapsulated keel, have a bilge membrane designed for that kind of load.

The failure of the membrane at least on the one boat that I looked at, occurred in part because of the nature of the construction of the membrane which is added after the keel has been set, and so typically has a secondary bond between the membrane and the hull. The membrane in that case was actually surprisingly thick, but it peeled away from the hull on the line of the secondary bond. I suppose that this could be improved if the membrane were laid up in epoxy with its much greater secondary bond strength, but that is almost never the case.

Moving onto the bulb, while through-bolting the bulbs to the keel makes sense from the bulb side, the question in my mind is what is actually supporting the bolts. By that I mean, are the bolts supported by the encapsulation skin? Or are they supported by the lead ballast that is glued into the encapsulation skin.

If supported by the skin, then that places a concentrated load on a very small bearing surface of a material that does not do great with those kinds of loads. A direct impact to the bulb would try to sheer those bolts through the skin creating a point of entry for water. If the bolt loads are placed on the ballast, then it places a load on the slurry adhesive, not a great way to go long term. If the “glassed over” skin is adding to the support strategy, you are counting on the secondary bond peel strength of the polyester-glass matrix where the load is concentrated at the point that the outside glass skin joins the hull.

In the end, what you describe is probably about as good as can be done to add a bulb to an encapsulated keel, and yet, it is a cobled together solution that would have been far easier design as a properly engineered, bolted in place, keel in the first place and in my opinion, end up with a more reliable and safer keel design over the life of the boat.

Respectfully,
Jeff
jameswilson29 and One like this.
__________________

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

Last edited by Jeff_H; 04-12-2013 at 10:20 AM.
Reply With Quote Share with Facebook
  #113  
Old 04-11-2013
SloopJonB's Avatar
Senior Moment Member
 
Join Date: Jun 2011
Location: West Vancouver B.C.
Posts: 10,721
Thanks: 56
Thanked 51 Times in 48 Posts
Rep Power: 4
SloopJonB will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Quote:
Originally Posted by PCP View Post
A stock Swan 65 is not a race boat.
It WAS - then, before they became so extreme.

I also much preferred it when Le Mans racers drove to the track instead of being carried in megabuck transporters.

Not all change is for the better. And before you say it, obviously boats are a lot faster now. I simply disagree with the elimination of everything but speed for ocean racers - that mindset should be reserved for inshore racing IMHO.
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
Reply With Quote Share with Facebook
  #114  
Old 04-11-2013
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,166
Thanks: 21
Thanked 96 Times in 80 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Quote:
Originally Posted by SloopJonB View Post
...

Not all change is for the better. And before you say it, obviously boats are a lot faster now. I simply disagree with the elimination of everything but speed for ocean racers - that mindset should be reserved for inshore racing IMHO.
I guess you make a confusion between performance cruisers and race boats. There was a time were almost all race boats were performance cruisers but that was some decades back. Now the difference is very clear in performance...and comfort for the crew. Yes, the one that race on offshore racing boats are professional and make the boats more comfortable and less fast (more weight) would make as sense as making a F1 more comfortable.

But you are wrong when you say that modern offshore racers care only about speed: they are also the safest boats around, the ones with a bigger stability, with the bigger demands in safety. Many are unthinkable and some have to pass a test showing that they can right itself by their own means. Uncomfortable but very seaworthy

Regards

Paulo
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Share with Facebook
  #115  
Old 04-11-2013
SloopJonB's Avatar
Senior Moment Member
 
Join Date: Jun 2011
Location: West Vancouver B.C.
Posts: 10,721
Thanks: 56
Thanked 51 Times in 48 Posts
Rep Power: 4
SloopJonB will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Quote:
Originally Posted by PCP View Post
I guess you make a confusion between performance cruisers and race boats. There was a time were almost all race boats were performance cruisers but that was some decades back. Now the difference is very clear in performance...and comfort for the crew. Yes, the one that race on offshore racing boats are professional and make the boats more comfortable and less fast (more weight) would make as sense as making a F1 more comfortable.

But you are wrong when you say that modern offshore racers care only about speed: they are also the safest boats around, the ones with a bigger stability, with the bigger demands in safety. Many are unthinkable and some have to pass a test showing that they can right itself by their own means. Uncomfortable but very seaworthy

Regards

Paulo
Paulo, you never answered my original question.

Quote:
How many rigs have come down, keels fallen off, sailors been rescued and sailors disappeared in the Vendee since its inception?
__________________

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
I, myself, personally intend to continue being outspoken and opinionated, intolerant of all fanatics, fools and ignoramuses, deeply suspicious of all those who have "found the answer" and on my bad days, downright rude.
Reply With Quote Share with Facebook
  #116  
Old 04-12-2013
mitiempo's Avatar
Senior Member
 
Join Date: Sep 2008
Location: Victoria B.C. Canada
Posts: 7,109
Thanks: 0
Thanked 71 Times in 62 Posts
Rep Power: 7
mitiempo will become famous soon enough mitiempo will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Or how many machines - F1 or Indy cars for example - have failed to finish? It doesn't really matter because at the top levels of any sport that involves a car or boat or any machine and speed is involved the last possible ounce has been removed. If the Vendee boat can go around a second time without a refit it was too heavy to start with.

Better to ask how many performance cruisers have lost their keels or rigs or have sailors been rescued or have disappeared from same.
__________________
Brian
Living aboard in Victoria Harbour
Reply With Quote Share with Facebook
  #117  
Old 04-12-2013
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,166
Thanks: 21
Thanked 96 Times in 80 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Quote:
Originally Posted by SloopJonB View Post
Paulo, you never answered my original question.
Quote:
How many rigs have come down, keels fallen off, sailors been rescued and sailors disappeared in the Vendee since its inception?
I don't understand your point. That only proves what I have been saying that modern racing boats, particularly Open 60's have improved greatly in what regards safety over the years. NA Jean Marie Finot had a great role in that.

Answering to your question about deaths on the race, since its beginning 23 yeas ago two sailors lost their live on the race, in both cases they were lost overbore and their boats were found intact on distant shores. The last one died 16 years ago.


YACHT RACING - Solo Sailor in Global Race Found Dead Off Spain's Coast - NYTimes.com

Regarding the boats we can see that the reliability is increasing even with the introduction of a canting keel that was extensively tested first on this race, there was an increase. Canting keels for extensive use are much on the border of development and this year for instance they found unsuspected problems due to metal fatigue.

Even so regarding keels you can see that this year three boats out of 20 lost their keel, 3 abandoned after collisions and only one boat lose the mast. One of the boats that lost the keel keep racing without it since Brazil to France, lost only one place and finished in 4th. Last edition another boat managed to finish the boat without a keel and another one was sailed to safety without one. This year of all boats that have problems with the keel (4) only one could not sail the boat back to port.

Even with that unusual and unexpected number of collisions and those new problems regarding metal fatigue in the canting keels, 55% of the boats finished the race against 53% on the first edition and 47% on the second one.

So how this proves your point that racing boats are becoming more dangerous and less reliable?

Everybody, including sailors and designers find that the canting keels have to be made more reliable and they will be working on that. There is talk about all the designers to join in research producing a single canting keel on a box that will be used by all boats. That will permit to have more information that will allow a faster resolution of all technical and fatigue problems.

This kind of work and experimentation carried on top racing boats is what allow the development of technologies and materials that will be used later, when the reliability is found, on cruising boats. The number on innovations tried first on these boats and used later (many times by the same designers) on cruising boats is huge, ad allow us to have better, safer and faster cruising sailing boats.

Regards

Paulo
One likes this.
__________________

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

Last edited by PCP; 04-12-2013 at 07:55 AM.
Reply With Quote Share with Facebook
  #118  
Old 04-12-2013
Senior Member
 
Join Date: Dec 2012
Location: new england
Posts: 1,698
Thanks: 31
Thanked 30 Times in 27 Posts
Rep Power: 2
outbound is on a distinguished road
Re: Modern Hull forms and Motion Comfort

Jeff- I sure you have more offshore miles and I but:
cherubini's are no fashion statement. Many have done serious outshore miles. One did the last Marion- Bermuda and did just fine. I've raced against them in prior ones as well. Quick boat up wind. I know how they ride in force 8 and it stands up well. One went aground in Marion with the bad storm last year. She was brought down to N.J. repaired and will be sailing agan soon. Shannons speak for themselves. Like Valiants they've been everywhere.
Running aground is a question of when not if. If you picked up the floor boards of a Outbound you would see it's a belt and suspenders system. The weak point of all fins ( the junction of aft cord root to the canoe body) is heavy glass internially supported by both transverse and longitudial stringers of glass and high density closed cell foam. The bulb is fasioned so in event of hard grounding the lead will absorb impact. Should the glass be breached given the bolts are more than sufficent to support the structure the boat will contnue to function until repair can be effected. Given these boats are built as voyagers and need to function for weeks or months before yard access is available this design creates greater safety than the bolt on keel. Given the glass encapsulating the bulb is done after the hull/central keel has left the one piece mold even if it is necessary to grind all the glass away from the bulb the structure can be reglassed with out any loss of the initial strength of the structure. This is a state of affairs not feasible on a bolt on keel as the canoe body aft of the keel stub usually oilcans with resultant rupture of the fibers ( glass or carbon or unattainium) and loss of strength.
As to you're last statment my old tayana had occassion to hit a car ( yup a car) just north of St George. Apparently fell off a ship and had enough air in it to float just below the surface. So far have missed shipping containers, milled logs, sleeping whales, one half sunk fishing boat, and a big steel nav bouy but have seen them all. Happy I have a watertight bulk head 7' aft of the bow on the new boat.

As regards the Paulo discussion. There has been only one death in the Marion Bermuda race since it's inception ( much older race for cruisng boats only). I was on that race. Guy jibbed his boat boom took off his head. This race involves folks like us not professional young buck racers. Remarkable safety record given the thousands of untrained unblooded sailors involved through the decades. It was my first offshore experience 30+ years ago.
__________________
s/v Hippocampus
Outbound 46

Last edited by outbound; 04-12-2013 at 09:22 AM.
Reply With Quote Share with Facebook
  #119  
Old 04-12-2013
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,166
Thanks: 21
Thanked 96 Times in 80 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Modern Hull forms and Motion Comfort

Quote:
Originally Posted by outbound View Post
...

As regards the Paulo discussion. There has been only one death in the Marion Bermuda race since it's inception ( much older race for cruisng boats only).. This race involves folks like us not professional young buck racers. Remarkable safety record given the thousands of untrained unblooded sailors involved through the decades...
Outbounf there is anything to be compared. You talk of a race with mostly cruising boats and some performance cruisers that sail relatively slowly (I mean the boats are slow compared with race boats) with full crewed boats. They should be able to pick up someone that falls overboard.

The vendee Globe is a race with only racing boats that go many times over 20k and sometimes at 30K with only a sailor aboard. If he falls overboard nobody there to turn the boat around and pick him.

Regarding age, even if they racing in top racing boats these here there was several over 50 and most of them has between 40 and 50. I would not call that "young buck" sailors

Regards

Paulo
__________________

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

Last edited by PCP; 04-12-2013 at 09:48 AM.
Reply With Quote Share with Facebook
  #120  
Old 04-12-2013
Senior Member
 
Join Date: Dec 2012
Location: new england
Posts: 1,698
Thanks: 31
Thanked 30 Times in 27 Posts
Rep Power: 2
outbound is on a distinguished road
Re: Modern Hull forms and Motion Comfort

Argee with you Paulo as view your comments as self evident. However, still think JonB's comments have merit. Think with some designs there is an increasing dversity between racing and cruising designs as weight carrying and liveability is sacifriced for desire for speed. Further agree many very recent designs accomendate these conflicting desires better then others. Just saying stock cruising designs of the past have functioned quite well. Many finish that race and then just keep on cruising in comfort and safey. Focus on the single handed ocean races is a great platform for design advancement but remain concerned you don't accept there is a bifurcation where some of the advances may not be appliable to cruising boats.
__________________
s/v Hippocampus
Outbound 46
Reply With Quote Share with Facebook
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Seakindly Boats vs.the rest rmf1643 Boat Review and Purchase Forum 14 04-10-2013 03:26 PM
What can you tell from the numbers? brazilnut Boat Review and Purchase Forum 10 07-01-2009 04:09 PM


All times are GMT -4. The time now is 10:39 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.