Cruise speed planning

[Roger Long]

When I did my tightly scheduled science cruise last spring I based my planning on an average through the water speed of 5 knots but wished at the time I had better data. This season, I've been having fun with the Trip Odometer function on my GPS, making sure to set it at the yard when I launched and using a different unit for anchor watches.

This is my sailing so far this season:

It's mostly daysailing but with a two overnight cruise to Boothbay Harbor. My boat is about midway between a traditional, long keel cruiser and a modern cruiser/racer in performance. I like motoring nearly as much as sailing so I don't spend a lot of time ghosting. I think these tracks are pretty representative of long coastal cruise where you are trying to cover ground as opposed to just puttering around.

Let's do the numbers:

Miles covered: 310
Max Speed over ground 8.9 knots (We've had some great winds and a fair tide one day.)
Moving Average: 5.0 knots.

The last number has remained remarkably consistent for most of the time. The square root of my waterline length is just a hair over 5 so I conclude that a speed / length ratio of 1.0 is a good figure to use for cruise planning unless you have similar data from your own boat (or a multi-hull).

 

[Bad Obsession]

I have almost 3000 miles on my GPS. The GPS is 7 years old and it covered some of my Hunter 22 as well as my Catalina 30. My average speed is around 4 knots. This does account for some of my time fighting tide, sailing only a few knots, and other things. I was impressed that I have put about 3000 miles in the Chesapeake Bay Region .

 

[Dan Johnson]

Roger...

I've found that using a 4 knot average in planning has worked for me here on the Chesapeake, where a four to six hour "trip" is the most common one we take between points.

When under power we average around 6 knots, but when sailing the average drops due to tacks and the common light winds of summer here on the Bay. Sorta validates Obsession's findings.

 

[RichH]

I do a lot of long distance sailing, 3-4000 miles per total 'trip' (in/out) is typical. When I 'back out' the lift or drag corrections for 'currents' like the Gulf Stream .... my overall average is quite close 5 kts. or ~120 miles per day, and this is in spite of my desired 'target speed' of 6-6.5. This from both GPS and Speedo paddle wheel logs.

Most long distance serious *cruisers*, whether sailing, motor sailing, or just plain motoring, usually only get 100-120 miles per day = ~5kts. average. A 100-120 mile 24 hour day is considered - very good distance made.

 

[sailaway78]

I always figure

When doing offshore work, I always use the figure of 100 miles per day. Most times I manage more than that, but I use the 100 mile figure for planning. Rather do better than planned than make plans I can't keep to. GPS shows a moving average, for a total of close to 10,000 miles of 4.9 knots.

 

[Roger Long]

Most long distance serious *cruisers*, whether sailing, motor sailing, or just plain motoring, usually only get 100-120 miles per day = ~5kts. average.

Such cruising is going to have a lower S/L average because the impracticality of fuel replenishment makes sailing slowly in light winds necessary. My figure is for close in coastal cruising where you can use as many polar bear cubs as your conscience allows.

 

[kloudie1]

Sound like fine numbers to me.. about 6 when motoring, about 5 over the water and 4 VMG total.. I use http://www.sailflow.com/ for wind planning .. they have a pretty good forecast.. these guys http://www.windfinder.com/forecast/lake_pontchartrain_mandeville_harbor
are pretty good too.. I don't find them very accurate after about three days.. but very useful..

 

[RichH]

I prefer www.passageweather.com

Also, the noaa 'ocean prediction center' - www.opc.ncep.noaa.gov/index_2.shtml .... then choose your 'area' from the listed sub-listings for: 500mb, surface, wind/wave for 24, 48, 96 hrs. ... its where most of the 'others' get their basic forecasts from.

 

[Ross]

For fuel conservation motoring at about 4-4.5 knots is very efficient in myIslander 30 pushing much above that and the fuel consumption curve gets pretty steep.

 

[druid]

For me, it depends on where I'm going and how. I can maintain 5 knots (ie if I drop much below that sailing, I fire up the Iron Spinnaker), even taking tidal currents into consideration. If I'm going to be sailing upwind, I use 4 knots - maybe a bit optimistic for directly upwind, but it's usually kind of a sawtooth course anyway.

Strangely enough, I used 5 knots for planning in the Catalina 36 as well.

druid

 

[RichH]

Such cruising is going to have a lower S/L average because the impracticality of fuel replenishment makes sailing slowly in light winds necessary. My figure is for close in coastal cruising where you can use as many polar bear cubs as your conscience allows.

Roger - are you SURE that youre not actually subliminally coveting a (dreaded) 'stinkpot' ?
*<))))

 

[Roger Long]

Roger - are you SURE that youre not actually subliminally coveting a (dreaded) 'stinkpot' ?

I've already got one. If "Strider" were a 32 foot trawler yacht, I would be delighted with her performance and motion. I've got the best of both worlds.

The one thing I do covet is a pilothouse. If I ever do get one, I want it on a slightly larger boat a lot like the one I have now. Another lifetime, perhaps.

 

[Peter Ennis]

Hull speed:Wind speed

How much wind speed does it take to get to hull speed? How dependent is boat speed on point of sail, assuming reasonable trim and not pointing excessively? Seems like these factors also must be considered in trip planning.

Thanks,

Peter

 

[Hermit Scott]

I like the warning on the chart that says 'danger explosives'. Where are you sailing again, the beautiful waters of Afghanistan?