Hull Speed & Book Review

[TexasPhil]

Wow, what a book "The Annapolis Book of Seamanship" by John Rousmaniere (Click Here for the review of the book on messing-about.com.)

My loving wife and daughter found this one at the library and for some unknown reason thought of me    I guess they LOVE me!  

I have been reading this and found, for the first time, an explenation that makes sense about the hull speed.  It is basically a physical property based on the wavelength created by the bow wave.  It also points out how to calculate your speed based on the number of waves along the side of your boat.  For example, if you have three waves from bow to stern, you are going 1/3 hull speed, 2 waves is 1/2 hull speed, 1 wave is hull speed.

The reason you can't go faster is due to the fact that you can't break through the wave.  Planing boats get up and over it, so they can go faster, but the displacement boats cannot.  Since (bow) waves move at a fairly consistant rate, the boat has a limit based on the LWL.  But, as we have discussed before, some boats are more apt to hit that limit than others, and some will hit it more quickly, while others can plane and go even faster.

So, the "Theoretical hull speed", in knots, is determined by multiplying the square root of the LWL by 1.34

[Frank Hagan]

Thanks for the plug about the books on the site.  I edited your "insert link here" to insert the actual link.  It looks like it is "on sale," at $28 with free shipping right now ... not quite cheap, but much less than the $40 cover price.  

It is a good book; I have also poured over it from the library and its "on the list" too.