predicting behavior from design

Hi.
Can you tell me if behavior at sea can be predicted from design?
If so,
- to what extent is this possible
- how much information on the design is required

Example : attached is a very simple sketch. How much can one tell from this?
Nothing or ...?

 

OK, sorry. It's upside down. Here is a better view.

 

What do you mean by "behaviour at sea"? Are you talking about speed, ability to hold a course, vertical accelerations, angle of heel, pitch and roll, etc.... it's possible to make an educated guess at these things, and to spend a lot of money making educated guesses at them, but you'll have to be more specific as to what you're thinking of.

 

Behavior at sea can be predicted, but it takes a significant engineering effort to do it. Programs like the US Navy's Standard Ship Motion Program (SMP) can take in tables of offsets and particulars like keel shape and mass properties, and predict the motion in regular and irregular seaways.

SMP doesn't include the effect of sails, but it would not be too big a stretch to add it in. There would have to be some other tweaks, since a "small boat" in SMP is 80 ft long. But it would be do-able. I mention SMP because it was used for most of the results in Vol III of Principles of Naval Architecture, and because the source code is available at a reasonable price from DTIC.

There are other organizations with other programs that are more modern than SMP, but you're probably talking real money to have them do an analysis for you. Your boat will probably cost less to build.

And that is why a seakeeping analysis is rarely done for a boat like yours. It's cheaper just to make it like boats that have proven to have good seaworthiness characteristics and modify or replace it if it doesn't work out.

For the maxi-boats, AC campaigns, and the like it's a different story. It's worth it to them because they get the additive drag in waves out of it, and that can be the difference between winning and losing.