Hull Speed Cats

[mikewilkes]

A wee while ago I saw a formula for power and sail speeds of a cat.
Copied it to my laptop but since then the dreaded machine has lost everything and need to get stuff back.
If whoever had the formula would not mind posting it again I will file a hard copy away - somewhere SWMBO knows the location.
Mant thanks and apologies.


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[snowleopard]

don't know if these are the ones:

sail: 5 x sq root( sail area x LWL / displacement)
units ft, lbs


power: sq root (power x LWL / displacement)
units metres, tonnes, horsepower

odd mixture of units but both give answers in knots.

for my boat the results are sail: 7.9 (I use 7-7.5 knots for passage planning) and power 10.5 (about right, i get 11 if the bottom is really clean.)

the guy who worked them out reckons the power formula gets a bit optimistic in the higher speed ranges (20 knots+)

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[mikewilkes]

Magic thats the one. Many thanks will give 'er indoors a copy as soon as I get home.


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