seakeeping

[Guest]

Hi everyone.

I would like to know if anyone has info about seakeeping like how to calculate, for preliminary design, i know its a quite extended topic, but if someone has refrences, spreadsheet or just some guidence, this info will be much apreciated.

Thanks.

[duluthboats]

This is a good one to chew on.
http://www.boatdesign.net/forums/showthread.php?s=&threadid=272&highlight=stability
There are more like it. The search button is in the upper right.

[Guest]

Thanks for you input much apreciated

[tspeer]

You can buy the US Navy's Standard Ship Motion Program, SMP, from NTIS. This is a linear strip-theory frequency domain code, written in FORTRAN. You supply the table of offsets for the hull and data describing rudder(s), fin(s), or bilge keels and the program does the rest. Depending on the size of boat you're talking about, you may have to modify the encounter frequencies used by the program. It's advertised to have a "small boat" capability - meaning waterlines as short as 90 ft!

There's a companion program called the Simulation Time History Program (STH) that takes the complex numerical transfer functions from SMP and applies them to random (but stationary) waves to create a representative time history of the motion in a seaway. Also available from NTIS.

Finally, there's a third program that is supposed to tie the two together and provide a more convenient user interface. But don't get it - it requires an expensive graphics package that isn't even available any more.

[Guest]

Powersea, from ship motion assoc. is for planing craft seakeeping. SMP can't do planing craft.

SHIPMO and SEADYNE also do seakeeping, and it is possible to use older codes such as SCORES, or to d the calcs directly (with a spreadsheet and the Lewis form charts).

[Guest]

Thanks for your comments, i will look forward to The navy SMP, Ted, do you know any other software that may do small crafts in the range of 35-85 foot waterline?

i may have a couple of boats where i can use the 90ft waterline study, but the most of the designs that i'm involved in are 35 -85ft.

and again thank you for your comments.

guest

thanks you for your comments i will look forward to those softwares, do you know if there is any restriction on lenght-beam etc. like i explained i'm working mostly with small vessels, and seems tha most of what i been capable to find its mostly large ships, thanks again.

[Guest]

Recommend the book "Seaworthiness" by C. A. Marchaj.
Out of print, I think, but a superb analysis of the subject for small yachts, particularly sailboats.