Keels

 This is really just information for me, as I'm sure everybody else already knows it.  But it's my blog so I'm putting it in here anyways :)  As my dreaming/planning stage continues I need to figure out what I want out of a boat (which of course will change many times over this journey I'm sure).  So today I'm going over the different types of keels.  Grab some caffeine and try and stay awake please! This is just information I've pulled together from various blogs/forums/info on the net.

Full Keel

A full keel by definition runs the length of at least 50% of the hull.
The forward edge curves vertically while the aft edge often connects to
a rudder. The main advantage of a full keel are safe grounding and
directional stability.Safe grounding means a full keel is safer when you lie on hard ground.
Whether along the coastline or in travel lift slings, the full keel
provides a strong, stable balancing point for the hull. A full keel
boat will not tip on its bow or stern. When you ground then, the boat
will lay on her side in shoal water and take less damage. In a travel
lift, the full keel is easier to sling with the longer keel line.

Blocked up on the hard, the full keel provides a line of balance. Be it
an unintentional or intentional grounding, a full keel has more stability.
A full keeled boat points well when in the water. It has good
directional stability. Put the boat in a compass direction and with a
properly designed full keel is likely to stay pointing in that compass
direction. The full keel has longer waterline length so controls the
flowing water more than shorter keels. The water rushes by for a longer
distance and smoother flow. Turbulence is less likely to generate
forces to twist the boat. The full keeled boat is less likely than a
fin to fall off because this smoother flow. The boat has greater
directional stability than a fin.

Pros: A lot more headroom in the cabin because there is no trunk, ususally very good
ultimate stability (the ability to right itself, even from full turtle). 

Cons: When you run aground, you can't just raise the keel to free yourself,
you have to employ interesting tactics like getting a crewman to hang
on the boom, and then swing out over the side.


Fin Keel

By the classic definition of a fin keel any keel whose bottom is less
than 50% of the length of the boat is a fin keel. Fin keels came into
being in an effort to reduce drag. Cut away the forefoot or rake the     
stem, as well as, move the rudderpost forward and rake it sharply and
pretty soon you have a fin keel. Today we assume that fin keels mean a
separated rudder (skeg hung or spade) but in fact early fin keels had
the rudder attached in a worst of all worlds situation. They offer all
of the disadvantages of both full and fin keels, but with none of the
virtues. Unknowing or unscrupulous brokers will often refer to boats
with fin (or near fin) keels as full keel if they have an attached
rudder.

Pros:  They have less drag as explained above so they typically make less 
leeway and go faster. You can get the ballast down lower so in theory 
they are more stable for their weight. They are more maneuverable. 
They take better advantage of the high efficiency of modern sail plans and materials.

Cons:   They have less directional stability than long keel
boats so the tend to wander more under sail.Fin keels are harder to
engineer to withstand a hard grounding and when aground they 
are more likely to flop over on their bow or stern. Fins typically have 
deeper draft. They are easier to pivot around and get off in a simple grounding.

Bulb

The bulb is a shoal draft fin keel. Basically, you saw off a deep fin
keel and attach a torpedo shaped bulb of lead to the keel bottom. This
shallower keel is a compromise between the performance of a fin but the
realities of cruising in the Bahamas, Cheasapeake Bay, and other shoal    
water holes. Often makers these days produce shoal and deep versions of
their designs. Hylas, Valiant, and Tayana come to mind. If you plan to
sail in shoal waters, they recommend a bulb keel but otherwise you will
enjoy the deep fin keel. As a side benefit if you do ground on a soft 
bottom and sink in, the bulb keel is the easiest to free. The bulb does
not stick way down into or catch the muck like other designs. The bulb
at the bottom plops out easily.



Wing Keel

Wing keels are a specialized type of bulb keel. Instead of a torpedo
shaped bulb there are small lead wings more or less perpendicular to
the keel. These concentrate weight lower like a bulb and properly             
designed they also are very efficient in reducing tip vortex. There has
been some discussion that wings increase the effective span of the keel
when heeled over but this does not seem to be born out in tank testing
of the short wings currently being used in production sailboats. Not
all wings are created equal. They potentially offer a lot of
advantages, but they are heavily dependent on the quality of the design
and I really think that many wing designs are not really working to
their potential.

Pros:  The wing has better performance than the bulb because
she reduces tip vortex turbulence. The draft can be even less. Because
the two bulbs are offset they do not mess with the leading keel edge
and generate turbulence like a simple bulb keel. 

Cons: As a drawback, the wing is the most difficult to free if you slide
into muck. The wings have a way of gripping down into the bottom. In 
2002, the Naval Academy did  a study of keel types and grounding. They
found that the popular perception that wing keels are harder to free is accurate. In their
study, wing keels were extremely harder to free. Straight fins were
much easier to free, especially when heeled, and the easiest keel to
free was the bulb keel.


Centerboards

Centerboards are appendages that can be raised and lowered on or near
the centerline of the boat. They can rotate up into a trunk or rotate
below the boat. Daggerboards are a type of centerboard that raises   
vertically or near vertically in a trunk. Swing keels are a type of
rotating centerboard that actually contains a substantial portion of
the boat’s ballast. They may be housed in a trunk like a Tartan 27 or
34 or hung below the boat like a Catalina 22. In the case of the Tartan
27 or 34 they are more frequently referred to as a Keel/ Centerboard
(abbreviated k/cb). A swing keel is intended to act as a fin keel when
lowered and allow some sailing in the partially raised position.

Pros: The centerboard keel has a base keel with a dagger than 
rotates downward. When the water is deep, you stick the centerboard down.
When shoal, you sail centerboard up. You get the performance of a deep
keel and the manuverability of the shoal – a perfect idea, right? 

Cons: The drawback is maintenance with the centerboard. As with any 
moving part, problems arise. The centerboard has to be maintained.


Ok - it's time to wake up now. Obviously there are other types of keels out there, and variations of the above.  But if I went through it all, you really would be asleep.  This seemed like a decent set of the more common keels to me (I know - I'm a novice, so don't take it as the end all be all of keel knowledge).  Rest assured that none of the information is mine.  It's all pulled from people much more knowledgeable then me.  My thoughts on keels for me is that I want something that doesn't have moveable parts - simpler is better I've been told.  I like the idea of the stability of the full keel, but am worried that the draft may be too much for where I potentially want to travel.    Of course if budget was no concern I'd like a catamaran.  I of course say that without comparing cat's versus monohulls in person.  So that may change once I get on board some boats.

If you've made it all the way down to here congratulations - you've earned yourself a drink!

Good sailing to you and yours!