Cruising Under Power and Anchoring

[N4061]

Two questions for the experts:

1. Does a mid size (30' - 40') monohull sailboat moving under power move similar to a full displacement hull powerboat without stabilizers? Does it rock from side to side in a beam sea or does the long keel act as a stabilizer? I recognize this may be a multi-part answer.

2. Watching sailboats at anchor they appear to move (all directions) more than a FD trawler which brings up the question - why? Doesn't the keel act like a flopper stopper used on some trawlers and provide resistance? Granted the trawler will be heavier and hull shape not as round but still without hard chimes I would think the sailboat keel would equal things out?

3. OK, I added a third question: what about the forward motion of a sailboat under power or sail? Assuming hull speed is it the same as a trawler in similar conditions what should we expect?

Thanks

John T. - A lot to learn...

[jt11791]

Originally Posted by N4061

Two questions for the experts:

1. Does a mid size (30' - 40') monohull sailboat moving under power move similar to a full displacement hull powerboat without stabilizers? Does it rock from side to side in a beam sea or does the long keel act as a stabilizer? I recognize this may be a multi-part answer.


It rocks. The keel helps some, but it will rock and roll. If there is any wind at all motor-sailing is much more comfortable as the pressure on the sail reduces or stops the rolling.


2. Watching sailboats at anchor they appear to move (all directions) more than a FD trawler which brings up the question - why? Doesn't the keel act like a flopper stopper used on some trawlers and provide resistance? Granted the trawler will be heavier and hull shape not as round but still without hard chimes I would think the sailboat keel would equal things out?


Rolling is a harmonic motion, like a pendulum. Pushing the keel through the water damps the motion some, but not completely and the heavy keel has a lot of momentum so it doesn't stop easily once moving.


3. OK, I added a third question: what about the forward motion of a sailboat under power or sail? Assuming hull speed is it the same as a trawler in similar conditions what should we expect?

Thanks

John T. - A lot to learn...

The forward motion doesn't change things much at all. You'll need wind pressure on a sail to get a smooth ride.

[sailorboy1]

Been watching the 38’ trawler next to ne for 2/weeks now and they have dancer, rolled, and rocked a lot more than out boat. And our boat sails around at anchor a lot in general.