Andy
Beatrix, P19-854
-----Original Message-----
From: Gordon <hlg@pacbell.net>
To: wwpotter@tscnet.com <wwpotter@tscnet.com>
Date: Saturday, April 17, 1999 12:26 PM
Subject: Re: Raising Centerboard
>- - - - - - - - - - - - - - - - - - - - - - - - - - -
> West Wight Potter Website at URL
> http://www.lesbois.com/wwpotter/
>- - - - - - - - - - - - - - - - - - - - - - - - - - -
>Great post, Dave. Thanks for doing the math. It does appear that 10 or 15
>degrees aft could be effective in reducing weather helm without affecting
>stability significantly.
>
>Harry
>
>>Soooo, heres a little table which should help us understand why "raising"
the
>>board slightly can change the way the boat handles without imposing
>>significant danger:
>>
>>Angle Cosine Sine
>>0 deg 1.0 0.0
>>5 deg .996 .087
>>10 deg .985 .174
>>15 deg. .966 .259
>>20 deg .939 .342
>>30 deg .866 .500
>>45 deg .707 .707
>>60 deg. .500 .866
>>75 deg. .259 .966
>>90 deg. 0.0 1.0
>>
>>We can multiply each of these entries by 100 to get a percent change in
>>height with angle - So "raising" the board by 15 degrees, as I suggested
>>before, actually leaves the board at 96% of it's original depth while
moving
>>it back 26%. 10 degrees would maintain 98.5% depth while moving the board
>>back by 17%. Going back 30 degrees leaves 86% of the board down while
moving
>>it back by 50% of it's length.
>>
>>At 45 degrees things become even (71% depth, 71%aft), the change in depth
the
>>same as the change in fore/aft position and after that the relationship
>>reverses and we are then quickly lifting the board out of the water.
>>
>>I hope it's obvious here that while raising the board a little is okay (in
my
>>opinion, anyway), raising it more than, say, 30 degrees will have
diminishing
>>returns in balancing the helm and will start to seriously compromise the
>>ability of the boat to "self-right". Coming from a background of sailing
>>dinghies with unballasted boards which are frequently raised all or part
way
>>may make me more cavalier with this than is prudent, so it is probably
better
>>that I suggest that readers of this not interpret it as advice or
>>recommendation. If there is any question in your mind, leave the board all
>>the way down.
>>
>>Best regards to all,
>>
>>Dave Kautz
>>P-15 #1632
>>Palo Alto, CA
>
>
>