Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 16-02-2012, 08:33   #1
Registered User

Join Date: Nov 2011
Posts: 66
What Makes a Seaworthy Boat ?

Over the past several months, I have been Very actively looking for my ideal boat. I have concrete plans for what I intend to do with her and I have a pretty good idea of the size and type of boat I want and need.
Seaworthiness is one of the major features my boat must have. And with that, the question arises, what is a seaworthy boat?

I read various things about keel weight and types - full, modified full, fin, etc. And I have read various things about displacement, narrow beam vs wide beam, sail area in relation to displacement, blah, blah, blah.

What the heck does all that mean? Is my boat going to be tender or stiff? Is the boat going to get knocked down by a 20 foot wave or 50 knot wind? Will my boat capsize with the same 20 foot wave or 50 knot wind? And more importantly, will it right itself and how quickly?

I found this great site that offers formulas for everything from hull speed to capsize screening to angle of vanishing stability.
Sailboat Design and Stability

With all that, I have laid out a few MINIMUM characteristics my boat Must have. For one, I want a ballast to displacement ratio of at least 35% but would prefer something closer to 40.
But, looking at different boats, this factor seems not to apply. For example, if you look at Beneteau boats, you will find they have light displacement and very poor % for ballast. I looked at the Beneteau Oceanis 323 and discovered the displacement is around 9350 with a ballast around 1550. That calculates to a 29% ratio. Unacceptable by any formula but I know these boats have crossed oceans, even the 32 footer.
On the other hand, a Com-Pac 27 is light, 6000 lbs with a 2500 pound ballast which calculates to a 41% ratio. Does that mean you would cross an ocean with a Com-Pac 27?

What does all this mean? I believe every and any boat can get knocked down and unfortunately every and any boat can get capsized. But, which ones will right themselves quickly, if at all?

Are there any engineers, boat designers, people in the know that have a clue as to what all these formulas and calculations translate to in a practical sense?
__________________

__________________
Notpopeye is offline   Reply With Quote
Old 16-02-2012, 09:37   #2
Registered User
 
Sabbatical II's Avatar

Join Date: Apr 2009
Location: Lake Macquarie
Boat: Bluewater 420 CC
Posts: 756
Images: 1
Re: What Makes a Seaworthy Boat ?

There are many factors which might make a "seaworthy vessel" and not all boats will have all desirable features and not all sailors will agree on which features are important.

However on the issue of ballast ratios there are some points to consider. A ballast ratio of around 40% would be rare in a modern production boat and 25 - 30% is common. If this ballast is placed at the bottom of a vessel with a 3 metre deep keel, all other things being equal, it would have a greater righting moment than if it was in a shoal draft keel that was only 1 metre deep. For similar reasons if the keel ballast was cast iron it will be less dense than lead and therefore a ton of cast iron can not be concentrated as low in the hull as a ton of lead. I yesterday read of an early Whitbread yacht have ballast material of spent uranium rods because it was more dense than lead and therefore for the same weight produced a greater righting moment. Because the ballast ratio is a percentage it can be enhanced by lightening the hull structure as well. You will find some extremely lightweight racing boats that have ballast ratios around 50% with a deep keel. These might be very safe as far as "righting moment" but may have sacrificed the strength of the structure and maybe seaworthyness, to achieve it.
__________________

__________________
Greg
Sabbatical II is offline   Reply With Quote
Old 16-02-2012, 09:39   #3
CF Adviser
 
Bash's Avatar

Cruisers Forum Supporter

Join Date: Dec 2008
Location: sausalito
Boat: 14 meter sloop
Posts: 7,260
Re: What Makes a Seaworthy Boat ?

Boating by the numbers? I can't imagine a worse starting point.

Don't buy a boat because it has acceptable ratios. Buy a boat that you've fallen in love with because it's simply impossible to do otherwise. Buy it because, when you take the helm to determine how high she'll sail before pinching, it feels as if the boat completes you. Buy it because it's so damned good-looking that you take pleasure rowing the dink away and then just staring at it.

Unless all you're hoping to do with the boat is survive a capsize, the ballast/displacement ratio means very little until informed by the sail area/displacement ratio and the displacement/length ratio. You gotta examine the whole package.

(This response written by someone whose current boat has a b/d ratio of 37, a sa/d ratio of 18.15 and a d/l ratio of 186.08. Try keeping up with that with a Com-Pac 27! I'll be over the horizon before you can clean my spray off your binoculars.)
__________________
cruising is entirely about showing up--in boat shoes.
Bash is offline   Reply With Quote
Old 16-02-2012, 09:42   #4
Registered User
 
stevensuf's Avatar

Join Date: Dec 2010
Location: Back in Scotland!
Boat: Gib sea 43
Posts: 840
Images: 10
Re: What Makes a Seaworthy Boat ?

ballast ratios tend to be smaller on production boats & newer boats in general, a narrow boat with high ballast ratio will self right quicker than a beamier boat with lower ballast ratio. a beamier boat will heel less under normal conditions, so requires less ballast under normal use.

hence older narrower boats have greater ballast ratios compared to beamier newer boats.

lead is more dense than steel, which means less drag (smaller surface area) and technically a slightly smaller lead ballast can give the same effect as a larger steel ballast (this is underwater only).

very few modern boats have ballast ratios of 40% or more.

you are really talking old narrow boat style versus new beamier style.

just remember youll be safer in a 40ft 30% ballast boat than a 30ft 40% ballast boat.

A breaking wave that can capsize a 40ft yacht will capsize it weather the ballast is 30% or 40% , just the 40%one will right much quicker.

this is my understanding, no doubt ill be said to be wrong.

also bear in mind weight distribution of a boat, a boat that holds 1000kg in fuel and water, vs one with 500kg, the 1000kg tankage boat will be more stable when full. does the boat have lockers up high?

is the keel, bulb or fin? bulb will have more weight further down than a simple fin, so more lever moment on the hull.

lots of other factors come in to play
__________________
http://nicnsteve.blogspot.com/

If the pen is mightier than the sword, then my keyboard must be a nuclear missile!
stevensuf is offline   Reply With Quote
Old 16-02-2012, 09:57   #5
Senior Cruiser
 
rebel heart's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Posts: 6,190
Images: 3
Re: What Makes a Seaworthy Boat ?

This guy sailed (and is still out there) a 27' Albin Vega that I would barely feel comfortable taking to Catalina. He sailed it through the Northwest Passage, the Bering Straits (including two cyclones), and rounded Cape Horn via Drakes Passage.

Solo Around the America's Under Sail | An audacious attempt at sailing the Northwest Passage and circumnavigating entirety of both continents, to benefit Chesapeake Region Accessible Boating

The lack of typical "seaworthiness" of this vessel is made up by the experience and talent of the sailor onboard. The smarter you are the less you'll need a boat to overcompensate for your mistakes.

Here's him leaving:

__________________
rebel heart is offline   Reply With Quote
Old 16-02-2012, 10:14   #6
Registered User

Join Date: Nov 2011
Posts: 66
Re: What Makes a Seaworthy Boat ?

Quote:
Originally Posted by Bash View Post
Don't buy a boat because it has acceptable ratios. Buy a boat that you've fallen in love with because it's simply impossible to do otherwise. Buy it because, when you take the helm to determine how high she'll sail before pinching, it feels as if the boat completes you. Buy it because it's so damned good-looking that you take pleasure rowing the dink away and then just staring at it.

(This response written by someone whose current boat has a b/d ratio of 37, a sa/d ratio of 18.15 and a d/l ratio of 186.08. Try keeping up with that with a Com-Pac 27! I'll be over the horizon before you can clean my spray off your binoculars.)
I have looked at many boats in my exhaustive search. I fell in love with the Dana 24 but it is outrageously expensive and very small -- too small. And I fell in love with Pacific Seacraft 31 and the Island Packet boats but they are also pretty expensive - exceed my budget.
I also saw a Com-Pac 27 and just you stated above, I really like the boat but everything I have tells me this is not the boat for me - it is not seaworthy, it is small, and on and on.
But the Com-Pac 27 has a SA/D of 18.41, a D/L ratio of 187.83, a Angle of Vanishing Stability of 220.43. The bad numbers are the Motion Comfort ratio which is 18.31 and the Capsize screening ratio - 2.09. These numbers are way better than a Beneteau or Hunter (oh lord, why even bring Hunters into this?)
So, there ya go, the Com-Pac 27 numbers keep up with your numbers you so proudly posted.
__________________
Notpopeye is offline   Reply With Quote
Old 16-02-2012, 10:18   #7
Registered User

Join Date: Nov 2011
Posts: 66
Re: What Makes a Seaworthy Boat ?

REBEL HEART - Albin Vega 27's are reported to be extremely good bluewater seaworthy boats.
Albin Vega 27 Review : Bluewaterboats.org
__________________
Notpopeye is offline   Reply With Quote
Old 16-02-2012, 10:31   #8
Registered User
 
Rhapsody-NS27's Avatar

Join Date: Oct 2010
Location: VA, boat: Deale, MD
Boat: 1981 Nor'sea 27
Posts: 1,409
Re: What Makes a Seaworthy Boat ?

Quote:
Originally Posted by Notpopeye View Post
REBEL HEART - Albin Vega 27's are reported to be extremely good bluewater seaworthy boats.
Albin Vega 27 Review : Bluewaterboats.org
A couple days ago I found a series of videos of a couple sailing their Albin Vega 27 to Hawaii.
Their site: Voyaging Under Sail, Cruising Lealea Home
Their videos: vega1860's Channel - YouTube

Looking at their videos, you can tell they had a great time. I enjoy(ed) watching their videos.
__________________
Daniel - Rhapsody Blog,
“A sailor’s joys are as simple as a child’s.” — Bernard Moitessier
"I don't need therapy, I just need my boat"
Rhapsody-NS27 is offline   Reply With Quote
Old 16-02-2012, 10:40   #9
Senior Cruiser
 
rebel heart's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Posts: 6,190
Images: 3
Re: What Makes a Seaworthy Boat ?

Quote:
Originally Posted by Notpopeye View Post
REBEL HEART - Albin Vega 27's are reported to be extremely good bluewater seaworthy boats.
Albin Vega 27 Review : Bluewaterboats.org
Well hey, good luck in your search then bud.
__________________
rebel heart is offline   Reply With Quote
Old 16-02-2012, 10:46   #10
Registered User
 
taildragerdrive's Avatar

Join Date: Sep 2010
Location: Halfway, Oregon, USA
Boat: Swan, 1968, 36'
Posts: 102
Re: What Makes a Seaworthy Boat ?

This is an interesting discussion. I thought about a lot of things when I bought my boat a little over a year ago and since I wanted to do and now have done some open water cruising I used several factors to determine the seaworthiness of the boat I eventually bought. I have sailed her in 40 kt winds (unplanned) and she was comfortable and felt safe.

First I looked at the history and reputation of that boat and the designers. Sparkman and Stevens boats have a great track record. Since the boat I bought is relatively old there was a lot of information available. Her stats show a ballast ratio of 55.5% although as fitted out for cruising I suspect it is closer to 50%. The design has proven to be seaworthy in many past races and other occasions I was able to read about. 36 feet is considered a bit short for off shore by todays standards so I factored that in. I believe seaworthiness must include much more than ballast ratio. If the boat stays upright but the porthole get blown out by a wave and the top gets knocked off because of weak design the boat will sink even if it never gets knocked over.

I also agree with Bash. I absolutely fell in love with the boat since I have owned it. I tried to stay objective about the technical aspects during the buying process knowing that I would love the boat once it was mine.

So to me seaworthiness is much more than the numbers but the numbers need to be there to fit your planned use or you are simply stand a larger chance of getting into trouble if you get into that storm we all try to avoid.

Fortunately in the world today there is a ton of information on the internet we can all use to learn before we decide what to buy. That was not true 30 years ago when I bought my airplane but the same kind of rules applied so I had some experience I could apply as I did the research.

To me the rule is do the research enough to feel comfortable that the thing you are looking to buy meets the technical need for what your are going to do. Than find one that fits into those specifications you can love because for most of us this is a big investment and we will live with the result for a long time.

Good luck
__________________
Taildraggerdriver - Flying in the mountains of the west. Sailing/cruising as much as I can.
taildragerdrive is offline   Reply With Quote
Old 16-02-2012, 10:51   #11
Senior Cruiser

Cruisers Forum Supporter

Join Date: Jul 2006
Location: Chesapeake Region and Maine
Boat: 42' Bob Perry sloop
Posts: 4,038
Images: 4
Re: What Makes a Seaworthy Boat ?

Re: What Makes a Seaworthy Boat ?

First and foremost, an experienced and knowledgeable captain.

Most everything else is in the noise.

Bill
__________________
btrayfors is offline   Reply With Quote
Old 16-02-2012, 10:56   #12
Registered User
 
Ironhorse74's Avatar

Join Date: Dec 2010
Location: Vancouver Washington
Boat: Ed Monk designed 34' Sloop Second Wind
Posts: 400
Images: 1
Re: What Makes a Seaworthy Boat ?

Have you read John Vigor's "The Seaworthy Offshore Sailboat"? http://www.amazon.com/Seaworthy-Offs.../dp/0071343288
__________________
Ironhorse74 is offline   Reply With Quote
Old 16-02-2012, 11:24   #13
Registered User
 
Nadejda's Avatar

Join Date: Jan 2012
Location: At large
Boat: Colin Archer RS-22 46' LOD
Posts: 34
Re: What Makes a Seaworthy Boat ?

I am going to go ahead and open the proverbial can of worms here, so be warned.

Most modern boats are designed for racing and going fast to windward. They are not designed to heave to and most will require running in a storm or running various forms of sea anchors. Their construction has also been getting lighter as engineers push the limit on how little FRP can be used and still have an acceptable lifespan. In the earlier production boats made of FRP you will find hulls that are severely over built due to the relative newness of the product and designers not knowing how it would hold up.

I started my quest for a "seaworthy" boat several years ago and after much research settled on buying a Colin Archer design. Most of his boats were designed either as pilot boats or rescue boats for some of the worst conditions possible. Colin Archer was a genius of nautical architecture and his work is still consulted by designers today. They are heavy, gentle, heave-to well, and will take most of what the ocean can throw at them (there are alway exceptions to everything). Here is a link to a video on the Satori which after the Coast Guard removed her crew in the famous "Perfect Storm" sailed her self onto a beach and was later re-floated. She is now still sailing on the east coast.

The Dana 24 you mentioned has the reputation of not heaving to well, which is one of the most important characteristics a boat can have for surviving a storm in relative comfort. So I would pass on one of those although they are they are lovely little boats in most other aspects. I would look at Westsail 32, Ingrid 38 (made by different companies like Bluewater), A Dreadnought 32 which I know of one of these for sale locally (PNW) if you are interested contact me. The boats above are not necessarily fast but they should get you there and take care of you when you can no longer take care of the boat.

Hope that helps give you a direction.
__________________
S/V Nadejda
Nadejda is offline   Reply With Quote
Old 16-02-2012, 12:26   #14
Senior Cruiser
 
rebel heart's Avatar

Cruisers Forum Supporter

Join Date: Oct 2005
Posts: 6,190
Images: 3
Re: What Makes a Seaworthy Boat ?

Probably took those 90MPH winds for the wetsnail 32 to finally hit hull speed.
__________________
rebel heart is offline   Reply With Quote
Old 16-02-2012, 12:42   #15
cat herder, extreme blacksheep
 
zeehag's Avatar

Cruisers Forum Supporter

Join Date: Jul 2008
Location: furycame alley , tropics, mexico for now
Boat: 1976 FORMOSA yankee clipper 41
Posts: 17,781
Images: 56
Send a message via Yahoo to zeehag Send a message via Skype™ to zeehag
Re: What Makes a Seaworthy Boat ?

if a catalina 27 named my sweet lord can circumnavigate successfully, and a bendy toy can(markj) then the moire seaworthy sailing boats such as albin vega and formosa and others are certainly a good to go example of seaworthiness. albin vega has been performing well on open oceans for decades.
__________________

zeehag is online now   Reply With Quote
Reply

Tags
seaworthy

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

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

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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Replacing a Fuel Tank on a Tartan TOCK rhhmadry Engines and Propulsion Systems 5 10-09-2012 14:21
Boat Suggestions for Circumnavigation Robes Monohull Sailboats 18 18-02-2012 08:26
What Makes a Seaworthy Boat ? Notpopeye Monohull Sailboats 22 16-02-2012 14:53
What I really do... red_sky Off Topic Forum 3 16-02-2012 08:54



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 15:38.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.