March 6, 2012

Seaworthy centerboards

THIS COMMENT just in from someone called Hugo:

"Hello Mr Vigor! As per your book The Seaworthy Offshore Sailboat, boats with a combination of keel and centerboard may not be seaworthy. Since I am considering buying a Jeanneau Sun Rise 35 with a combined pivoting centerboard and stub keel, I am writing to you for advice. Would you consider this particular boat safe and seaworthy enough to cruise from Bermuda to Polynesia and sail around the islands, with side visits to New Zealand and Australia?.

"I shall very much appreciate your expert opinion.

"Best regards,


Well, Hugo, I don't recall saying that keel/centerboarders are not seaworthy.  What I said was that the seaworthiness of such a boat is very difficult to evaluate in terms of its recovery from an upside-down position.   And I don't remember claiming to be an expert  on the subject, either.  So take what advice I have to offer with a liberal dose of salt.

I must say that Jeanneau has had a lot of experience with keel/centerboarders of various sizes, even if they weren't exactly designed for ocean voyaging in the first place. Most of the type are designed as coastal cruisers in areas where shallow waters prevail.  There is no profit in building a centerboarder if your usual cruising waters are deep enough for a fixed keel.

On the other hand, many of the hardest-working ocean-going sailboats are deep-sea racers, and there was a time when, for rule-cheating reasons, many of them were built with centerboards protruding from a stub keel.  The stub keel gave them ballasted stability, of course, and the deep, thin centerboard made them very efficient to windward.

According to Ted Brewer, the well-known naval architect, "One true rule beater was the 1950s Olin Stephens-designed Finisterre. This beamy keel/centerboard yawl took advantage of the rule without really bending it. Her wide beam (moderate by today's standards), shoal centerboard draft, hefty displacement, modest ballast, and yawl rig combined to give her a favorable rating. Combined with Olin Stephen's design genius and Carleton Mitchell's expert handling, she was the boat to beat in any race she entered, and won a room full of trophies. Finisterre's success inspired a host of keel/centerboard yawls, ranging from Bill Shaw's lovely little 24-foot MORC racer, Trina, to Bill Tripp's handsome Block Island 40 and Bermuda 40 and big 50-plus footers such as the beautiful Innishfree, designed by George Cuthbertson, founder of C&C Yachts." 

Eventually, this combination of keel and centerboard gave way to fin keels and spade rudders, but when the keel/centerboard combination ruled the roost, such boats went to sea in all weather conditions and did just fine.

I don't think you have anything to worry about on the score of seaworthiness, Hugo.  These boats are not terribly popular now because it's more expensive to build in a centerboard, which, incidentally, also introduces another thing to go wrong at the most awkward time.

There are advantages, though.  Besides allowing you to sail in water less than 4 feet deep, your Sun Rise 35's centerboard will help you balance the boat to its sailplan by moving the board back or forward to change the center of lateral resistance.

At least, that's the theory.  I don't think you're likely to bother too much with this while you're swanning around the South Seas distracted by the rustle of grass skirts, but it's nice to know that you could if you wanted to.

So go for it, Hugo.  Happy Sun Rise to you.

Today's Thought
 The fruit of my tree of knowledge is plucked, and it is this: "Adventures are to the adventurous."
— Benjamin Disraeli, Ixion in Heaven

"What's the orchestra playing now?" 
"According to that board over there, it's a Refrain from Spitting."

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