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Sailor Thom Davis shared the following with me last week as pertaining to guessing the speeds of trimaran designs. I’d love to hear from others as to whether or not they feel this little formula reflects a general “accuracy” or not.

Thanks for sharing this with us Thom … perhaps this post will inspire input from others that have some thoughts on this topic.


Just in case smalltrimaran readers are interested in guesstimating the speed potential for different trimaran designs, here’s a formula that works reasonably well for a good guess.

1) Take the Length in Meters raised to the 0.3 power.
2) Take the Sail Area (main, jib, spinnaker all added together) in Square Meters raised to the 0.4 power.
3) Multiply those together.
4) Divide by the boat weight plus crew weight in KG raised to the 0.325 power.

… Numbers above 1 are fast boats.
… Numbers below 0.8 are slow boats.

I didn’t arrive at this, those Aussies developed it. It can’t be really accurate since you can’t tell how a boat will point (or fail to point) and hull shape will definitely slow some boats down more than others…but your readers might want to know if the boat they are considering is fast or slow.

The Aussies use it as the start for a rating formula. Basically, just take the elapsed time and multiply by “the number”. Lowest result wins. In friendly competition, numbers should be adjusted so the same person/boat doesn’t win all the time.

Thom Davis