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Topic-icon Way to estimate speed potential of different designs....

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5 months 2 weeks ago #197 by multithom
multithom created the topic: Way to estimate speed potential of different designs....
There's a lot of "rating rules" out there that get really really difficult to use...but suppose you only want to know whether one boat is likely to be a fast boat or a slow boat; or want to have a good guess whether one boat design is faster than another. Here's a simple formula that will give a decent guess.

Take the boat length in meters and raise to the 0.3 power (ignore sprits and rudders behind boat).
Take the total sail area (main plus jib plus spinnaker) in sq meters and raise to the 0.4 power.
Multiply those two numbers together.
Take that product and divide by the weight of the boat plus the weight of likely crew in KG raised to the 0.325 power.

Boats with a number of 1 or higher are fast boats.
Boats with a number less than 0.8 are slow boats.

Triak, for example is really slow at 0.71
SeaRail 19 is fast at 1.14
Corsair 24 comes in fast at 1.06

Having sailed two of the boats; I can attest the numbers for the Corsair and Triak reflect reality.

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5 months 2 weeks ago #198 by multithom
multithom replied the topic: Way to estimate speed potential of different designs....
Just for ducks, I did the same calculation for other tri's I've crewed on...
Windrider is .88 with 2 on board and a spinnaker (much slower without the big headsail)
Weta is 1.04 single handed--it's about the same as windrider with 2 on board
Hobie Getaway (catamaran) is .98 with spinnaker and 2 on board.
Based on actual sailing on the same piece of water, these numbers bear up.

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5 months 2 weeks ago #200 by multithom
multithom replied the topic: Way to estimate speed potential of different designs....
In case you are wondering, the searail comes in at 1.08 with two on board.
The new Corsair Pulse (same size as searail) is 1.02. So the searail should be faster (it is 200 pounds lighter, so that makes sense).
Disclaimer, the rule I'm using is not without problems which is why rating rules have so many tweaks; it is just a way to get an idea about relative speeds of different designs. Hull shapes and orientation, rotating mast or non rotating, daggerboard or not, hike out or not ... all these things make a difference on the water-which is the only place you can truly find out which boat is faster.

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