About keels...

[ErikG]

I visited a boatshow today and of all the cruisers (no racers if you don't count the old J80) most including x-yachts uses keels that don't have a "normal" bulb but an extremely thick lower section. What are the benefits for this kind of keel compared to a "normal" bulbkeel?

My guesses are that theere is less turbulence since the change from normal keel to fat ass keel is smooth and not a drastic change as there would be on a bulbkeel. On the other hand there is no reduction at all (end plate effect) when it comes to overflow between the sides of the keel.


Are there any other benefits for keels of this type, or is it just a fad?

[tspeer]

I think you have it the other way around - I'd say the keels you describe are the "normal" ones, and the move to fin and bulb is the more recent fashion. Not that fin and bulb hasn't been around since the 19th century.

If you center a bulb on a keel, it will project forward and be prone to catching seaweed, lobster pots, etc. If you line the nose of the bulb up with the leading edge of the keel, the bulb projects aft. This moves the center of area forward compared to the c.g. of the keel. It also means there's a torsion load on the keel when the boat is heeled that tries to twist the keel bolts.

With fin and bulb, you have to design and build a fin and attach it to the bulb and to the hull. With the keel you describe, you cast the ballast into the shape of the keel and attach it to the hull. Much simpler.