Full or fin keel? - Page 54 - 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 > Out There > Cruising & Liveaboard Forum
 Not a Member? 


Like Tree241Likes
Reply
 
LinkBack Thread Tools
  #531  
Old 10-09-2012
Senior Member
 
Join Date: Sep 2011
Location: Michigan
Posts: 180
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 3
BryceGTX is on a distinguished road
Re: Full or fin keel?

Quote:
Originally Posted by PCP View Post
I say that one is more stiff than the other? You have any doubt?

The stifness of a boat is directly related with the boat displacement and the sail area the boat can carry (SA/D). You can see that big difference yourself. Paulo
Yes, I definitely have a doubt that you know the racer is more stiff than the Benneteau Oceanis. Stiffness is a characteristic of the hull dimensions and weight distribution and has nothing to do with SA/D.

I am sure there are many readers scratching their heads at your post.

Specifically, stiffness is related to the moment of the area of the waterline and the volumetric displacement. It has nothing to do with sails.

You are inferring the stiffness from the SA/D. Problem I see is that the racer would tend to carry more dacron that the cruiser given the same stiffness. The way I see it, most good racers have a hull design that increases the stiffness dramatically with heel angle. This could even lead to a boat less stiff than the Oceanis at low heel angles.

Quote:
Originally Posted by PCP View Post
There are several ways of obtaining a seaworthy boat and mass and a relatively high CG is one of them, unfortunately one that gives slow sailboats.
My discussion is not about seaworthyness. That discussion has been hashed out in the multitude of threads about "Bluewater".

My discussion is specifically about rough water characteristics. And a higher CG by any stretch of the imagination most generally results in a poor rough water boat.

But ignoring that for a moment; again, you are assuming that everyone is willing to sacrifice everything for performance. Most cruisers are not.

Quote:
Originally Posted by PCP View Post
You should try to understand how that massif seaworthiness (that is a fact) is obtained in a boat that contradicts the ways it was obtained 50 years ago instead of, against the reality, assuming that boat cannot be seaworthy because it is not designed accordingly with the principles that 50 years ago were used to design seaworthy boats.
The principles of boat design have not changed in 50 years. Only the boat designs have changed in 50 years.

Again my discussion is not about seaworthy boats. And this thread is not about seaworthy boats.

My discussion is specifically about a charateristic of boats. That characteristic is pretty much what most cruisers are concerned with.

To put it into words that you might understand: Most people prefer that their masts stay pointed up and their keels stay pointed down.

To further this idea, people prefer that their masts stay pointed up even when the boat is going over waves.

Your two boats are boats that exhibit the above characteristic poorly. Rather, their relatively high hull siffness causes both boats to heel exactly with the waves. In this case I am relying on your clearly poor interpretation of stiffness.

Bryce

Last edited by BryceGTX; 10-09-2012 at 07:09 AM.
Reply With Quote Share with Facebook
  #532  
Old 10-09-2012
Senior Member
 
Join Date: Sep 2011
Location: Michigan
Posts: 180
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 3
BryceGTX is on a distinguished road
Re: Full or fin keel?

Quote:
Originally Posted by PCP View Post
The question here is if the strength we can achieve with a fin keel boat is sufficient to make a safe sailboat (and if so we can have better sailing boats) or if fin keel boats are dangerous.

The huge number of fin keel boats without problems and the very low percentage of problems show that modern materials and building techniques can provide safe fin keel boats.

Paulo
I think you are missing barefootnavigator's point. Clearly, by any measure a 9 foot fin keel that is thinner and shorter will be much more subject to damage from a hit than a 2 foot keel that is both wider and longer. This is a characteristic of the dimensions that cannot be argued.

Presumably both boats have the same construction materials and techniques because they are built in the same years. Lets ignore racing boats for a moment as these guys have bottomless pocket books.

So in this discussion, you are relating how great this racer 40 is because it has a very long keel. Which as we know can create some quite large forces. And you say this is very good. However, earlier in this thread you are concerned about a boat tripping over its keel. This very long keel on this racer presents exactly the same scenario as your earlier discussion of the boat tripping over the keel given the same sea conditions. And I had just got finished talking about the same thing only a few posts back with Jeff discussing why this happens.

So which is it Paulo.. do we use a very deep keel to cause our boat to trip over its keel and more likely to break in a hit, or do we use a longer/wider keel (not deeper) that has neither problem.
Bryce

Last edited by BryceGTX; 10-09-2012 at 06:37 AM.
Reply With Quote Share with Facebook
  #533  
Old 10-09-2012
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,160
Thanks: 21
Thanked 95 Times in 79 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Full or fin keel?

Quote:
Originally Posted by BryceGTX View Post
Yes, I definitely have a doubt that you know the racer is more stiff than the Benneteau Oceanis. Stiffness is a characteristic of the hull dimensions and weight distribution and has nothing to do with SA/D.

I am sure there are many readers scratching their heads at your post.

....

Bryce
Jesus, I give up on you Bryce

You fail to acknowledge even the most obvious facts

So you have doubts that a 40 class racer is more stiff than a 40ft Oceanis?

The 40 class racer has much more hull form stability, being much beamier with a much flatter hull and the 40class boat has also a much bigger B/D not to mention that it has all ballast in a torpedo at the end of a 3 m draft while the Oceanis has only a 2 m draft and a keel with the weight more distributed.

How the hell do you think stiffness it is obtained in a sailboat?

I am out!

Hey guys, you can keep scratching your heads

Regards

Paulo
Reply With Quote Share with Facebook
  #534  
Old 10-09-2012
Senior Member
 
Join Date: Jun 2007
Posts: 530
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 8
GBurton is on a distinguished road
Re: Full or fin keel?

Quote:
Originally Posted by PCP View Post
Jesus, I give up on you Bryce

You fail to acknowledge even the most obvious facts

So you have doubts that a 40 class racer is more stiff than a 40ft Oceanis?

The 40 class racer has much more hull form stability, being much beamier with a much flatter hull and the 40class boat has also a much bigger B/D not to mention that it has all ballast in a torpedo at the end of a 3 m draft while the Oceanis has only a 2 m draft and a keel with the weight more distributed.

How the hell do you think stiffness it is obtained in a sailboat?

I am out!

Hey guys, you can keep scratching your heads

Regards

Paulo
On the contrary Paulo, Bryce makes a lot of sense whilst you resort to personal attack.
Reply With Quote Share with Facebook
  #535  
Old 10-09-2012
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,160
Thanks: 21
Thanked 95 Times in 79 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Full or fin keel?

Quote:
Originally Posted by GBurton View Post
On the contrary Paulo, Bryce makes a lot of sense whilst you resort to personal attack.
Quote:
Originally Posted by GBurton View Post
On the contrary Paulo, Bryce makes a lot of sense whilst you resort to personal attack.
Can you explain where is the personal attack?

Regarding sense do you mean do you also believe that an Oceanis 40 is more stiff (or as any comparison in what regards stiffness) than a 40class racer?

Or maybe you don't know the boats?

Take a look at the huge amount of sail this boats can carry even with lots of wind and bad weather and see how they remain steady and resist heeling.


The 40 class boats are these boats:






You saw how the huge stiffness of a 40Class racer allows it to sail with an huge sail area and even so resist heeling?



Now the Beneteau Oceanis 40:

Look how with less wind the boat sail with more heel and with much less sail, resisting much less to the force of the wind on its sails:










That means the Oceanis 40 is (obviously) much less stiff than a 40class racer, resisting a lot less to the wind force that it is applied in its sails. With the same sail area the 40class carries, the Oceanis 40 would not be able to resist heeling and would capsize.

and since "stiffness (is) the ability of the boat to resist the heeling force of the sails" how can someone say than an Oceanis is less Stiff than a 40class racer?

It is obvious that the 40class boat can carry much more sail area and even so heel less than the Oceanis. This is not obvious to you?

That quote about stiffness is from a well known NA. I cannot copy the article but you can read it here. It is very interesting article:

Performance Cruising

More definitions about stiffness in a sailboat:

stiff - A boat that resists heeling.

Boat Mall, the online boat shop, sell or find your dreamboat, classified boat ads

Regards

Paulo

Last edited by PCP; 10-09-2012 at 03:00 PM.
Reply With Quote Share with Facebook
  #536  
Old 10-11-2012
Familycruisers's Avatar
Senior Member
 
Join Date: Dec 2011
Posts: 134
Thanks: 4
Thanked 3 Times in 2 Posts
Rep Power: 3
Familycruisers is on a distinguished road
Re: Full or fin keel?

Bilge keels are better than both, so there :-)--
Trekka and GBurton like this.
__________________
S/V Never Land
Westerly Centaur
Reply With Quote Share with Facebook
  #537  
Old 10-11-2012
Senior Member
 
Join Date: Jun 2007
Posts: 530
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 8
GBurton is on a distinguished road
Re: Full or fin keel?

Paulo, this open 60 does not appear to be very stiff. Perhaps it has something to do with the way it is being sailed?

Reply With Quote Share with Facebook
  #538  
Old 10-11-2012
PCP's Avatar
PCP PCP is offline
Senior Member
 
Join Date: Dec 2004
Location: Portugal, West Coast
Posts: 16,160
Thanks: 21
Thanked 95 Times in 79 Posts
Rep Power: 10
PCP will become famous soon enough
Re: Full or fin keel?

Quote:
Originally Posted by GBurton View Post
Paulo, this open 60 does not appear to be very stiff. Perhaps it has something to do with the way it is being sailed?

I assume(and hope) you are kidding

The stiffness of a boat has not to do with the way the boat is sailed and an Open 60 is one of the stiffest boats you can have. Only because it is so stiff it can be sailed that way and remain steady on that position allowing that Alex to be on the keel of Hugo Boss with a Hugo Boss suit. cool





Regards

Paulo

Last edited by PCP; 10-11-2012 at 04:37 PM.
Reply With Quote Share with Facebook
  #539  
Old 10-11-2012
Senior Member
 
Join Date: Jun 2007
Posts: 530
Thanks: 0
Thanked 3 Times in 3 Posts
Rep Power: 8
GBurton is on a distinguished road
Re: Full or fin keel?

Whooooooosh....
Reply With Quote Share with Facebook
  #540  
Old 10-12-2012
Senior Member
 
Join Date: Sep 2011
Location: Michigan
Posts: 180
Thanks: 0
Thanked 0 Times in 0 Posts
Rep Power: 3
BryceGTX is on a distinguished road
Re: Full or fin keel?

Quote:
Originally Posted by PCP View Post
Jesus, I give up on you Bryce

You fail to acknowledge even the most obvious facts

So you have doubts that a 40 class racer is more stiff than a 40ft Oceanis?

The 40 class racer has much more hull form stability, being much beamier with a much flatter hull and the 40class boat has also a much bigger B/D not to mention that it has all ballast in a torpedo at the end of a 3 m draft while the Oceanis has only a 2 m draft and a keel with the weight more distributed.

How the hell do you think stiffness it is obtained in a sailboat?

Paulo
Stffness is invariably created by hull design.. plain and simple. You can roll your eyes all you want, but it does not change that fact. However, for this discussion, not sure why we care.

Here are the facts. Modern wide bodied racers get their righting moment from wide hulls. They are lightened as much as possible to reduce hull resistance. This provide the best acceleration. Because they are lightened so much, their center of gravity is often higher than a good rough water boat.

The most obvious example of a high CG boat having a large righting moment is a catamaran. Clearly the righting moment is created by hull design, not mass. Wide racers use the exact same idea, only with a single hull.

For a modern racer, the keel mass only needs to be as heavy as required to provide a certain amount of moment to balance the standing rigging and to allow the boat to have a RM diagram that extends to a large heeling angle. The total weight is often defined by rules. So the goal is to reduce the hull weight to an absolute minimum and instead place any left over weight on the keel.

Your suggestion that the Class 40 boat is a good rough water boat undoubtably comes from racers whose goal is to go fast in spite of the weather.

Lets put a 65 year old couple on that POS racer and let them get unexpectedly caught in mid Atlantic like the big blow last year November?? north of Bermuda for 3 days. Since there is only two of them, they will not be able to sail through, so they will be forced to resort to stabilizing tactics. I bet they will have a radically different viewpoint than you on what a rough water boat is. Not everything is about performance.

As far as I am concerned neither of these boats are rough water boats. Picking one over the other is like asking which one will be less miserable in rough water.
Bryce

Last edited by BryceGTX; 10-12-2012 at 06:47 AM.
Reply With Quote Share with Facebook
Reply

Tags
boat buying , newbee advice


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
Full Keel Vs. Fin or Modified Full Keel AjariBonten Sailboat Design and Construction 51 11-16-2013 02:52 AM
Full Keel vs. Wing Keel small boats Kyhillbilly General Discussion (sailing related) 4 07-26-2011 11:51 AM
4 ft draft, full keel, 30' and over? birdlives Boat Review and Purchase Forum 6 09-17-2010 11:00 PM
Older Full Keel boats JerryO39 General Discussion (sailing related) 30 06-09-2010 09:06 AM
Bristol 32'' full keel johnblsc Boat Review and Purchase Forum 2 12-13-2002 05:37 AM


All times are GMT -4. The time now is 10:56 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