Hull speed

Discussions about Cape Dory, Intrepid and Robinhood sailboats and how we use them. Got questions? Have answers? Provide them here.

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Guy Senter

Hull speed

Post by Guy Senter »

I would like the formula for hull speed of a displacement sailboat(as a function of length). I want this so I can get feel for distances small sailboats can be expected to travel during a weekend. Any other
information on typhoon weekend cruising range would be appreciated.



guynapex@att.net
Bob Luby

Re: Hull speed

Post by Bob Luby »

The textbook formula is 4/3 X Square root of Load Water Line in feet.

i.e on a boat with a 25 foot **waterline** this would be about 6.66
kts ( roughly ). Heeling has the effect of lengthening the waterline
so a boat may sail somewhat faster when heeled.

Note! waterline length is not "length over all", which is what people
use to describe boat lengths. A 25 ft LOA boat may have a LWL of
20 ft or less. Check the specs on the Typhoon here.

What really affects cruising are tidal currents. In LI Sound, where I sail, my peak speed over ground can range from 0 or negative kts,
( sailing through Plum Gut against the tide ) to 9 or 10 kts.
( sailing through Plum Gut with the tide. ) From a powerboater's standpoint sailing is really controlled drifting, I suppose.

My rough guess would be 4 - 5 kts max.

Typhoon owners?



Rluby@aol.com
Arnold Amenda

Re: Hull speed

Post by Arnold Amenda »

Guy Senter wrote: I would like the formula for hull speed of a displacement sailboat(as a function of length). I want this so I can get feel for distances small sailboats can be expected to travel during a weekend. Any other
information on typhoon weekend cruising range would be appreciated.

I believe the formula is: (the square root of the waterline length in feet) x 1.34 = hull speed in knots. In Puget Sound I calculate 3 Kt for 8 Hr = 24 mi per day for cruising my Typhoon Daysailer. With fair winds I have made up to 40 mi in a long day. My best velocity made good is 8.1 Kt by GPS with some following current under masthead spinnaker and 20 Kt following wind. I made 24 mi. in 4 hours. That was a great ride for my Typhoon. But I plan on 24 mi per day.



aamenda@ix.netcom.com
M. R. Bober

Re: Hull speed

Post by M. R. Bober »

Guy Senter wrote: I would like the formula for hull speed of a displacement sailboat(as a function of length). I want this so I can get feel for distances small sailboats can be expected to travel during a weekend. Any other
information on typhoon weekend cruising range would be appreciated.
1.34 time the square root of the length of the waterline is the generally accepted formula. Remember that the waterline length increases as the boat heels.
Catherine Monaghan

Re: Hull speed

Post by Catherine Monaghan »

Guy,

You can use this <a href="http://www.image-ination.com/sailcalc.html">sailboat calculator</a>. It will provide you with more information than just the hull speed of your boat.

catherine_monaghan@merck.com
CD32 Realization
Raritan Bay

Guy Senter wrote: I would like the formula for hull speed of a displacement sailboat(as a function of length). I want this so I can get feel for distances small sailboats can be expected to travel during a weekend. Any other
information on typhoon weekend cruising range would be appreciated.


catherine_monaghan@merck.com
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