Passage Speed

[Seaworthy Lass]

Originally Posted by 44'cruisingcat

Today's sail from the Gold coast to Yamba. Fairly brisk northerlies, 100 miles in 10 1/2 hours. Peak speed 19.9 knots.
......

WOW, that must have felt absolutely fabulous!

[Southern Star]

Wow is right. I am truly envious 44C!

Brad

[mikereed100]

100 miles in 10 hours is an awesome day sailing! A 19.9 knot max is also impressive, but consider that my overloaded Catalina 30 once had a GPS max of 14 knots on a day that we never saw more than 5 knots on the speedo. Not bad for a 35 year old liveaboard with old sails and a dirty bottom!

[sneuman]

On Finish time in this year's Carib 1500, a Hylas 54 and Moody 54 both came in ahead of any of the multis and a Jenneau Sun Odyssey 54DS edged out the #3 multihull (by two hours). Much of the monohull fleet beat the remaining two multihulls.

When you correct the time for motoring, the multihulls don't fare as well as that -- 8 monohulls (including an Island Packet 420) are ahead of the fastest corrected time for a multi. The #2 multihull finished an hour later than a Valiant 40 on time corrected for motoring.

http://www.worldcruising.com/content...by%20Class.pdf

[44'cruisingcat]

Originally Posted by Seaworthy Lass

WOW, that must have felt absolutely fabulous!

Yes, when the boat starts to surf it actually gets quieter and smoother. Seems like it's not often we have the wind and swell behind us. Love it.

[cwyckham]

Originally Posted by 44'cruisingcat

Yes, when the boat starts to surf it actually gets quieter and smoother. Seems like it's not often we have the wind and swell behind us. Love it.

What a feeling! The one time I've done a lot of surfing was a hoot. When down below in your bunk, you could tell when you were starting to surf because the boat would all of a sudden go quiet, just like you explained. We knew we were getting a good surf when the canting keel started to hum at around 20 knots, but other than the hum, it was quiet and peaceful.

[Pat Ross]

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 only.

http://www.multihulldynamics.com/comparisonStep2c.asp or

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.