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post #6 of Old 08-31-2004
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Building a New Ruuder

Your rudder construction description has been interesting, thank you. One caution regarding the rudder post, first some background. I believe the Newport 33 was an extended Newport 30. The first two Newport 33''s that made the delivery trip to Alaska both lost their rudders crossing the Gulf of Alaska. Not in storms, just the normal 10'' or 12'' seas. I remember looking at them at the time, thinking the rudder post looked way too skinny. Newport responded by sleeving the regular post with another SS tube - only on the boats coming up here. Your 1-7/8" diameter tube sounds similar to the 33''s post. If you wander around a boatyard looking at rudder posts, suspect you''ll find 1-7/8" unusually slim.

In addition to diameter, there is material and stiffness to consider. Although carbon fiber is very stiff, a composite post will usually still flex more than one of stainless steel. Carbon is stronger than steel by weight, but a much heavier SS post can be stiffer than a light carbon one of equal diameter. On our new boat if you wanted the optional carbon post they mandated spherical bearings to accommodate the greater flex without binding.

I fully appreciate all the reasons to stay with the same diameter. For coastal cruising in good weather you are probably fine. If going off-shore or if you are at all cautious you might want to consider sleeving the interior of the post. Full length wouldn''t be necessary, only the area around the lower bearing. That''s where the 33 rudders broke, at the point of maximum bending moment.

Thanks for the thorough and informative discussion.

jon k

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