Stability improvements

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Mark Barrett

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Aug 15, 2019, 7:09:24 PM8/15/19
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Hello all,
We have a 1978 34’ Sedan, it’s hippiness makes me nervous. It has tendency to broach, especially in following seas. I’m doing research to see if any one has found ways to improve stability.
Also has anyone installed the Underhull modification
and has it helped,
Thanks for your input.

thedoug...@comcast.net

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Aug 20, 2019, 3:56:01 PM8/20/19
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Try moving weight from the bow to the stern. 

WKleiser

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Aug 23, 2019, 10:03:14 AM8/23/19
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I don't know about Tollycraft but I had experience in the distant past with a 34' Uniflyte that had the same broaching issue  The Uniflyte was very 'broachy' in a following sea, you had to use a lot of rudder to keep it in line.  This was partly because we were not planning (this was off the SF gate), so the small rudders were not adequate and the hull had no skeg at all.   The planning hull design with low / moderage deadrise and a broad transom is naturally more prone to broaching than say a canoe stern (to take the opposite extreme).  

A keel skeg can improve that tendancy though Tollycraft generally had those already (Uniflyte didn't).  Larger rudders could help in terms of directional responsiveness but I'd be worried about loading on the rudder bearings.  wever, I know my 40' has a skeg already, not huge but its there.    If you have a skeg you could investigate lengthening it.  Years ago I saw the Vic Frank yard adding a keel skeg to a 36' Uniflyte for this same reason.  However this isn't a cheap solution.

WKleiser

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Aug 23, 2019, 10:10:57 AM8/23/19
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One other comment.  Tollycraft was pretty strict about the stability of his boats.  He required that they be 'Columbia Bar' capable.  I know this because I met one of the guys who used to test boat designs for them, if they didn't perform well, they didn't get built.   So if the boat isn't 'stable' then look to what has been changed. Weight up on the fly bridge, an added 'radar arch', added hard tops, etc.  Also, many of us often run all  chain anchor rodes adding hundreds of pounds to the bow.  Sail boats often use chain/rope (e.g. ~30' of chain then all rope) to keep bow weight in control.  
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