Originally Posted by Adelie
The best predictor of CRUISING speed for monohulls that I have found is the Leonard/Starzinger formula.
L/S formula is Daily Average Mileage =24*(2.62 + 0.066*SA/D+ 0.051*LWL ) obtained from their website and based on reviewing the logs
of a bunch of boats they met while cruising and running the data thru a mathematical regression to determine what the important variables are.
If your passage
is short enough that you can expend a racing
level of effort to keep the boat going or you have a larger than normal crew I expect that this formula can be bettered by a significant amount.
For multihulls we use Richard Boehmer's formula for "Base Speed" on the Multihull Dynamics website. His formula is a 24 hour prediction formula.
You can calculate specifications for a specific boat using the Custom Evaluation page. This page is helpful for a boat that is not in the database or a boat that is in the database but you believe the specifications are different that we have in our database. All our calculations are based on "Working Sail Area", full main and 100% jib
you can review the calculations based on the specifications we have in the database:
Multihull Dynamics, Inc. - Standard Comparison Step 2
The best way to view these results is rather as a comparative result vs. an actual expectation of what will happen in the real world. i.e. Given the accuracy of the data and all things being equal, if the result say boat A is faster or more stable than boat B, we believe the relative difference is accurate.