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Question

About what would say your average speed is, on a day with average winds?

Answer 1

On the open sea, if you think in terms of distance sailed in 24 hours, I can give you a good idea of "average speeds" that are sustainable.

At sea, any run less than 100 miles in 24 hours is depressing...  Over a 100 is Ok, and a120 miles a day is a "good" day indeed.  A 150 miles (averaging 6.25 knots) is speed that cruising dreams are made of...  

Monohull sailboats are in a unique "displacement" hull category... by design, their hulls will only travel through the water at a certain speed...

So, to help understand the hull design - if you put a 150 hp engines on sailboat's stern and make an attempt to get her to "plane" - in fact, instead, you will drive her down into the water.  This is why "light winds" slow you down - but hurricane force winds will not speed you up past the speed of you hull's maximum speed.

Here is how to "estimate" your (displacement vessels only) hull speed.

It is the waterline length of a sailboat that determines its maximum speed. This speed is estimated by designers when they design the hull to be about 1.34 x the square root of the waterline length.

So if a sailboat is 25 ft long at the waterline, the square root of 25 is 5, and the boat will probably not exceed 5 x 1.34, or about 6.7 knots or 7.7 mph.

A 36 ft sailboat would has the square root of 6. So the boats maximum hull speed it 6 x 1.34, or 8.04 knots or 9.2 mph.

Course, is you are sailing with the wind, and with the current in the Gulf Stream (for example)... the current could add as much as 6 or 7 mph to your OTG (over the ground) speed. This is why so many sailors take the northern route across the Atlantic and follow the Gulf Stream - you can easily cut 3 days off an Atlantic crossing - even though you boat is not going faster through the water...  Get my drift?

Happy & Safe Boating!

Answer 2

Speed is dependent on waterline length and sail area in a given wind...... let's say ESE at 12.5 that's what it was this afternoon near Baltimore.  Best speed was 9.5 Knots.. but average was 7.8.... So, as you can see it's not always logical.  I've had 20 mile runs @ 10.6    I'm 30ft.   I hope this helps.    Speeds computed by GPS time over distance.