Hull form, Keel and rudder design... merits and hazzards.

[s/v Faith]

I am really surprised we have not discussed this much here.  I found several threads with some limited discussion but no dedicated thread.

I have got to start with the disclaimer that there is a 'right' boat for any given Sailor and intended use.

I have had a bias for more traditional designs.  I like the old story about why so many Scandanavian designers drew similar boats...

"We build boats for thousands of years.  The men would build their boats and go down to the sea.  The boats that would venture forth and return.  The men who lived to teach their sons to build boats all built boats that looked like this"



  Of course those boats mostly looked a lot like Faith does. ;D

Full keel, maybe a cutaway forefoot.  Good for holding a course, tracks well with little steering effort.  Narrow beam with heavy lead ballast down low.. very stable right-side-up... not stable un-side-down. , Some overhang, reserve buoyancy fore and aft....

A nice wineglass shape with a fine entry  that won't pound in a heavy sea, and increases stability as it heals.

An attached rudder, that sits in a heavy bronze shoe.  No part of the rudder is lower then the keel, so groundings are much less of a problem unless you ground on a large pile of rocks...while sailing backwards.


Of course the design 'evolved' at least in part from the medium...  wood.  The design also lends it's self well to fiberglass, since the curves are very 'mold friendly' and all of the first production designs used the proven hull form to sell boats in this new material (that many were suspicious of).

There were some designers who wanted to get specific aspects of the traditional hull to work differently.  Two areas that could be easily addressed in the new material were 'wetted surface' and the 'advance and transfer' of the keep hung rudder. 

  The same thing that improves 'tracking' or the boats ability to maintain a course also make it harder to make very tight turns around buoys.  The cutaway forefoot helps, but the keep hung rudder works like a flap on an aircraft wing.. it makes drag which tries to slow one side of the boat to make the turn.  This takes longer which means the boat travels farther after the rudder is turned (advance) before it starts to turn... it also saps speed.  Making a rudder that is a plane in the water that can pivot independently of the keel allows for less drag and quicker turns.  The rudder could also be made very narrow.  The keel was also easier to make skinny with fiberglass supporting higher point loading a narrow iron keel could be bolted onto a hull that could resist lateral movement well, with a significant decrease in wetted area. (drag).

  These 2 aspects of hull design rapidly gained favor, and the market started to shift. 

Another significant market force was the decreased cost of fiberglass construction.  The market opened up to segments that had not been able to afford hand built wooden yachts.  This brought the 'family' into the picture and more interior space was quickly bumped to the builders design priorities.

  Ok, I got into a lot of stuff here beyond what I intended.

Of course there is a lot that can be challenged in what I have written, but my intent was to discuss the general characteristics and some ideas about why they came to be.

[s/v Faith]

  An interesting look into this trend was to look at early Pearsons.  The Triton is widely accepted as the first mass produced fiberglass sailboat.  From the late 50's when it was first marketed it was a very successful design.  No one can depute either the Triton's proven performance as a world cruiser, or the way it changed sailing history.

  The market seemed to be asking for a slightly smaller version of the Triton so Pearson had Carl Alberg draw a smaller boat with the same formula.. and drew the Ariel (and Commander).  They sold well through most of the 60's but the competition rapidly increased as several builders struggled to establish themselves in this new market.

  By the time the 70's rolled around Pearson was having trouble getting Carl Alberg to deviate from his design parameters (or his license fee).  They wanted (and the market demanded) a 30' interior in a 25' boat.  The young family with little experience really liked the idea of a boat that could 'sleep 5' in the same LOA as a boat that could only 'sleep 4'... and their buying reflected this.

  Most sailing was done on inland or coastal waters... so the 'blue water' features that had carried over from earlier drawings fell by the wayside.   The bridgedeck on my Ariel is great for offshore... but an annoyance for a woman in a skirt stepping aboard at a boat show.  It was eliminated in Pearson's successor to the Ariel.. the Pearson 26.

 

[s/v Faith]

Here is the hull of a Triton;



An Ariel;


and a (Bill Shaw drawn) Pearson 26;



 Ok, I am tempted to go over the many differences, but lets focus on the hull (since that is the intent of this thread).

The Ariel has an 8'beam.. for a short distance nearly amidships.  The P-26 is slightly longer but 8" wider... and carries the width much farther along it's length.  

 The most significant changes I want to point out are the fin keel, and the rudder design.  These changes brought both an increase in speed (longer WWL, less wetted area) and lower advance & transfer (quicker turns, more agile near the buoys).


 I have raced against a P-26.. they are faster (in light to moderate wind).  They do not track as true as the Ariel, but are not difficult to maintain a course with.  

I found a photograph of a P-26 Rudder.





 

For me, the choice of hull is important.  I am very pleased with the boat I have.  

WHat about you?  What features do you see that you like (or dislike) in a given hull?



   
   

[tomwatt]

Funny, but that (the Ariel) could so easily be the drawing of my Bristol Corsair. Mine's only a bit smaller, but lacking the inboard, makes up for the little bit of loss. I just 'knew' somehow that the full keel design was what I wanted... nothing else interested me (even though I could have gotten a better deal on a couple of other boats).
I love the form, and the design of a keelboat. Now, how well I do with one in the water remains to be seen... so far, I'm just an Internet sailor, but I'm sure that by June I will have enough hands-on and sandpaper on hull experience to know this boat inside and out.
Really glad this thread got started - hadn't even considered the implications for the origins of the hull form. Neat stuff to ponder. I'll do some digging and see what I come up with.

[s/v Faith]

....Really glad this thread got started - hadn't even considered the implications for the origins of the hull form. Neat stuff to ponder. I'll do some digging and see what I come up with.

That is really nice to hear Tom.  Thanks.

My Ariel has an outboard also, most of those sold came with the 'outboard in a well'.  I think I recall reading that something like 10% of the Ariels and Commanders were sold with the inboard (Atomic 4).

[Pablo]

I have limited sailing experience, I sail mostly dinghies with center boards but have sailed some Ensigns and on a Hunter 34' .  For my "big" boat I have pretty much limited my search to full keel boats 30' or less.  With the Cape dory 27 and the Columbia 29 MkII (S&S designed) being some of my top choices. But lately another boat caught my eye, the Yankee 30 (again S&S designed), it is a modified keel with a Partial Skeg protected rudder.  With this I have been wondering how this affects the boats "off shore" qualities. 

The Columbia 29 MkII


The Yankee 30 MkI

[CharlieJ]

Craig- That line drawing of the Triton could be almost a photocopy of the drawing for the Rhodes Meridian 25. Ours is of course the version with the OB in a well.

Tehani has onlyy a 7 ft beam to th Ariel's 8 ft, but is otherwise a very close match.

I've long contended that Rhodes, Alberg and others of that era learned their craft designing wooden boats, thus the flowing lines so a Plank could be easily hung.  Which also allowed an easy flow of water contributing to the more seakindly motion. Of course we DO give up some interior space because of that, but that's a trade off we can live with.

I know Laura is definitly in love with the boat- grin.

[Captain Smollett]

I'll offer a slightly different take on the topic and say that in my opinion, one of the biggest drawbacks of the move toward 'fin' type keels has been the reduction (in the minds of 'modern' sailors) of heaving-to as a survival tactic.

Years ago, when fin-keelers first appeared, folks had trouble getting them hove-to using the 'traditional' technique and thus was born the 'myth' that they cannot heave-to.  In turn, heaving-to was lost (among modern sailors who have essentially learned to sail with this belief firmly entrenched) as a 'final' or 'go-to' technique.

So, lying ahull and running off under bare poles has replaced heaving-to in the popular mindset.  Heaving-to has been relegated to a 'convenience' technique when conditions are not-so-terribly bad.  "No Sail Up" has replaced "Sail The Boat" in the minds of many modern-boat sailors.

There are ways to get fin keelers to heave-to, but the technique is different from the traditional "back the jib, lash down the helm."

What it boils down to for this discussion is that as boat design 'evolved' (a matter of perspective, I guess), sailing competence has, perhaps, devolved.  Perhaps this devolution, to the extent that it exists, is also linked to the prevalence of the 'casual' sailor that the modern designs (with larger interior volume and bigger cockpits) attract.

[Auspicious]

My more-or-less fin keel semi-balanced rudder boat heaves to nicely. We sat off Great Guana Cay hove-to for a couple of hours a few days ago waiting for light before running the Man of War cut.

Practice is good. *grin*

[okawbow]

The Bristol 24 (Sail Star Corsair) was designed by Paul Coble in the mid 60's

It's funny how similar the hull shape is to the Ariel and many of the other 60's boats. One of the differences of the corsair to many of the other similar boats, is the ballast ratio. The corsair has more than a 50% ballast to displacement ratio. My 76 Bristol 24 still heels quickly, but I find I can carry a 155 genoa and full main in some pretty good wind and still have good steering and not bury the rail too bad.

I also like the keel with attached rudder. Everything is so solid and strong. I ran aground a few times coming down the Tenn-Tom to the gulf. There was no damage whatsoever, and I was able to get off without help. I also didn't worry about snaging pots and such.

[s/v Faith]

...Yet more support for;

the old story about why so many Scandinavian designers drew similar boats...

"We build boats for thousands of years.  The men would build their boats and go down to the sea.  The boats that would venture forth and return.  The men who lived to teach their sons to build boats all built boats that looked like this"

[Bill NH]

One unusual, or at least less common, characteristic of the Yankee 30 is the prop location, extending from the keel rather than in an aperture immediately in front of the rudder (probably accomplished through a V-drive gearbox).  Having the prop so far from the rudder will decrease close-quarters low-speed maneuverability (like when docking), as you can't "kick" the stern one way or another as easily...

Compare this underbody to one of my favorite hulls, the Contessa 32.  Prop right in front of well-protected, skeg hung rudder will give good maneuverability.  I also like the fairly low aspect fin - long enough for good directional stability but with much less wetted surface (drag) than the traditional full keel.  Yes, it's a bit of a compromise, but in this case it seems to get the best of both worlds.  

This might be heresy, but even though I've owned 4 of Carl Alberg's very traditional full keel designs, I think a Contessa 32 might be one of the boats I'd take around the big blue ball...

[Captain Smollett]

Nautical Survival of the Fittest...

I think I may have mentioned this before, but a few years ago, Ocean Navigator had an article on boat aesthetics vs seaworthiness in the design.  The authors thesis:

Our "eye" for beauty in a boat has developed based on what boats we SAW, collectively over decades (or longer).  Boats that lasted, ie that were seaworthy enough to 'survive' got seen more...so commonness was related to seaworthy, safe design.  

Long overhangs fore and aft, a fine entry, rounded forefoot and other design characteristics developed into 'beautiful lines' from the premise that, subconsciously at least, "hey, there's a SAFE boat...a real SEA boat."

I think it's an interesting idea.  It's not to say other design parameters are less seaworthy, but maybe they have not been around long enough to be 'proven' to our eye at an instinctive level.

[s/v Faith]

.... I also didn't worry about snagging pots and such.

Yes, that is a nice added bonus.  The crab pots are not nearly the problem, nor is it as likely for a boat to 'trip over her anchor' with the tide change. ;)

[Bill NH]

Nautical Survival of the Fittest...

...Boats that lasted, ie that were seaworthy enough to 'survive' got seen more...so commonness was related to seaworthy, safe design.

Only scary thing about this is that nowadays boat designs seem to survive or flourish not based on seaworthiness but on marketability... 

[Tim]

One unusual, or at least less common, characteristic of the Yankee 30 is the prop location, extending from the keel rather than in an aperture immediately in front of the rudder (probably accomplished through a V-drive gearbox).  Having the prop so far from the rudder will decrease close-quarters low-speed maneuverability (like when docking), as you can't "kick" the stern one way or another as easily...

This is one drawback of the outboard well boats such as the Ariel. Maneuverability under power can be challenging. One learns all kinds of dockside tricks to get in and out.

[s/v Faith]

Nautical Survival of the Fittest...

...Boats that lasted, ie that were seaworthy enough to 'survive' got seen more...so commonness was related to seaworthy, safe design.

Only scary thing about this is that nowadays boat designs seem to survive or flourish not based on seaworthiness but on marketability... 

Exactly what I was saying in the first couple posts on this thread.

 I do not think this is insignificant to the SailFar Sailor.  Many discussions take place over what is a 'suitable boat' for an intended voyage.  I believe that the 'intended purpose' it is an important consideration.  Not to say that a boat must be purpose built for bluewater if you are going off shore, but to look at the boat as a system... and consider what the limitations are.   Some limitations can be addressed through modifications, others are dificult if not impossible to overcome.

 Hull form is one of the things about a boat that is very difficult to change.  If one is going to accept some of the weaknesses it it good to at least know about them.

 If you have a wide beam (for a given length) you ARE going to pound in a seaway.  There is NO way around it... you will have to reduce sail, or change course.  

 If you have a weak / unprotected rudder then you ARE going to have a liability that could cause problems at the very worst possible time.  Most hulls / rudders will work fine underway... but a steering casualty when transiting an inlet can cost you the boat... there is NO way around it.  The practice of good and prudent seamanship can reduce the risk, but never eliminate it.

 The devil's advocate would say that a boat that points higher is better able to claw away from a lee shore and less likely to ground... and they would be right in some circumstances.

 The bottom line is that every cruiser must know themselves, and and their limits... and those of their ship equally well.

[s/v Faith]

This is one drawback of the outboard well boats such as the Ariel. Maneuverability under power can be challenging. One learns all kinds of dockside tricks to get in and out.

Actually Tim, with practice the ability to 'vector thrust' with a properly sized outboard can make the outboard in a well a real advantage when docking.  I know some folks on the Ariel site advocate leaving it centered, but I have had great success in close quarter steering with the motor.  It is like having a stern thruster once you get really used to using it.
(not to say I can not mess up a docking, but more to suggest that the design affords me help that I appreciate.).  ;)

[Frank]

 
Practice is good. *grin*

Couple of thoughts.
 I love the "practice is good" quote. The time to figure out how to get your boat to 'heave-to' properly is not when ya need to most. My flicka hove-to best with just the main. A backwinded jib and it fell off too far. This may be because the flicka has a traditional full keel with no cutaway  forefoot.
  One thing I found about the Ariel was it felt....well..."bouyant". It has low freeboard yet would seemingly bob like a cork in waves.Times I thought it would bury the bow it surprised me.I assume it was the reserve bouyancy with the longer overhangs.
  I like the feel of a full keel boat....except at the dock  ;D Backing out is always an adventure. Gun it and hope for the best seems to work.
  Judy and I had a jammed rudder in the Keys once with a crab pot line on a fin keel boat.. Diving under a boat with wave action is no fun.
  I too like the Contessa 32..they are relatively fast as well. Being a 'small boat guy' if money was no object I think a Dana 24 would be my ultimate pick. A 8000lb 24fter with full keel/,attached rudder/cutter rig has to be a great lil ship..
 

[Chattcatdaddy]

My only experience is with a fin keel that was on my Cal-29 Bill Lapworth design. Excellent boat that sailed very well and could turn quickly and tracked well enough. Great light air boat and strongly built.

When I`m in the buying market again in around 2 years I will most likely go with some sort on fin keel with light displacement. I`m seriously considering going engineless and ease of handling will be pretty important.