# Average Speed of a Sailboat



## Heloboarder (Jan 9, 2009)

What are the average cruising speeds for a 30-40' displacement and semi displacement hull sailboat?


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## CharlieCobra (May 23, 2006)

6-9 knots depending on conditions and the boat.


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## CBinRI (May 17, 2004)

CharlieCobra said:


> 6-9 knots depending on conditions and the boat.


If you are talking about averages over the course of a long sail, I think that is a bit high.


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## JohnRPollard (Mar 26, 2007)

This is a tricky question -- so many variables. Length, displacement , rig, crew, windspeed, upwind, downwind, etc. 

There's a fairly large speed difference between a typical 30 footer and the typical 40 footer. I would say Charlie's estimate is pretty high for a 30 footer, but in the ballpark for a well-crewed performance oriented 40 footer. 

I'm wondering what you plan to use this average speed figure for? Is it for planning a passage? IF for that purpose, I would use a figure closer to 4.5 knots for the 30 footer and maybe 5.5 knots for the 40 footer.

If you are trying to compare the speeds of displacement vs. semi-planing hulls, that's another conversation. A bit more info, perhaps?

P.S. Welcome to Sailnet!


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## btrayfors (Aug 25, 2006)

As was said, this is a tricky question.

But, for consideration, a well-sailed cruising boat on passage will make about 75-80% of her hull-speed potential over a 24-hour period.

Example:

Waterline length: 34'
Hull speed: 5.8*1.4 = 8.2 knots
80% of hull speed: 6.56 knots
24-hour run: 157.4 nm

Mine does a bit better, averaging 6.7 knots or 160 nm per day on offshore passages on a 34.2' waterline (27K lbs displacement, 42' LOA).

Obviously, there are many variables. But, the "80% rule" often comes close, I've found.

Bill


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## nolatom (Jun 29, 2005)

I'd agree with what our esteemed moderator has said.

Low, about 4 knots. High, about 6 knots. Subject of course to weather being higher or lower than usual. With GPS, you'll know your speed over the bottom. With a wood or stryofoam chip, timed from bow to stern, you'll know what your speed through the water is. They you'll know if you're sailing in current.

But our estimates on the web don't mean much to you on the water, you'll have to take both an over-ground and a through-water speed, then compare to see if you are in a current and if so what its direction is.


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## Faster (Sep 13, 2005)

All these guestimates also need to take into account the point of sail and the wind speeds vs the different designs. I suspect there's little difference between "displacement" and "semi-displacement" designs. However a boat that can outright plane in certain conditions will have a much higher potential threshold with the right wind speed, course and sea state.

JRP's estimates for overall average speed look good.


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## chucklesR (Sep 17, 2007)

To figure out how long it will take to get somewhere, figure 5kts as a average. When bragging at the local sailing bar, figure the hull speed plus 10%.

Unless you are in the trade winds, then figure on 75% of hull speed depending on the skipper, condition of sails, the load of the boat multiple times a random number derived from adding up the letters of the words "silly question". 

Sorry, had to do it.


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## rayncyn51 (Aug 8, 2008)

I measure average speed in quarts of rum per hour. Is that incorrect?!?


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## N0NJY (Oct 19, 2008)

What are the average cruising speeds for a 30-40' displacement and semi displacement hull sailboat?

I think you have to add up all the displacement hull boats at 30', then all the semi's at 30', then all the 31s, 32's etc and divide by the actual number of boats for this problem.



That ought to give you some good, round, averages. hehe


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## sailortjk1 (Dec 20, 2005)

chucklesR said:


> To figure out how long it will take to get somewhere, figure 5kts as a average.


We too use the 5 knot average when calculating the time for our planned cruise.


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## xort (Aug 4, 2006)

I'd better get busy with my sailing skills...especially in light winds  
Or else get better with my BS ability


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## TSOJOURNER (Dec 16, 1999)

> What are the average cruising speeds for a 30-40' displacement and semi displacement hull sailboat?


... to calculate the average you need to measure the speeds at various points and then add them all up and then divide that figure by the number of speed measurements that you took....


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## Heloboarder (Jan 9, 2009)

Thanks for all the feedback. Everyone's answers was exactly what I was looking for.


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## TSOJOURNER (Dec 16, 1999)

One variable no one mentioned is where you are cruising. When we crossed Lake Michigan years ago, we used to figure 5 knots as minimum speed, because the run was about 60 NM where we usually crossed, and we always liked to do it in the 7 AM to 7 PM time frame. If the wind fell off and our speed dropped below 5 knots, we would start the engine. However, when crossing an ocean, you really don't want to start the engine because you don't carry enough fuel to run the engine for a couple weeks!


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## GySgt (Jun 11, 2007)

RAGTIMEDON said:


> One variable no one mentioned is where you are cruising. When we crossed Lake Michigan years ago, we used to figure 5 knots as minimum speed, because the run was about 60 NM where we usually crossed, and we always liked to do it in the 7 AM to 7 PM time frame. If the wind fell off and our speed dropped below 5 knots, we would start the engine. However, when crossing an ocean, you really don't want to start the engine because you don't carry enough fuel to run the engine for a couple weeks!


I agree. paddling a 30' with a boat hook never gets you very far. Of course judging by some of the boats at the Marina, I would say 0. I never see them leave the dock.


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## camaraderie (May 22, 2002)

Gunny!! Yer back!! Where ya been??


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## genieskip (Jan 1, 2008)

I'll chime in on the 5 kts average. That's what I use when cruising under conditions that don't allow for long term use of engine when the wind dies. The times you are bombing along at 8 kts are offset by the times when you are drifting in circles. And of course all bets are off it you are going to windward in light stuff.


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## bubb2 (Nov 9, 2002)

I use a 6 knot average when I am planing a cruise. I find it easier to do the time, distance and speed calculations in my head when I use 6 knots. I aways late though.!!!


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## Boasun (Feb 10, 2007)

Of course you all realize that the amount of marine growth on the bottom makes a difference also. 
Ultra clean bottom 6+ kts
Average clean bottom 5+ kts
grassy bottom 4+ kts
botanical gardens on the bottom 2+ kts

Now how close am I??


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## GySgt (Jun 11, 2007)

camaraderie said:


> Gunny!! Yer back!! Where ya been??


Hey CamJ
Just living life. Merger-ed myself out of a job, took up selling health and life insurance. That took sometime to get the license and learn selling skills. I still get out in the bay. Have more time to go thru the board since I work from a "home" office, (read bunny slippers, coffee, computer, and telephone.) (Ok I really don't wear bunny slippers).


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## camaraderie (May 22, 2002)

Kewl...good to have ya back for our Winter Dementia series!


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