twistedtree
Guru
When anchored, most, if not all boats swing back and forth. Some swing quite a bit. Why? What causes it, and what, if anything, can be done to reduce it?
The bigger and heavier the boat, the less it will move. Buy a bigger boat!
A boat yaws at anchor because it is an unstable system trying to find equilibrium. Generally speaking the distributed forces applied by the wind and water change relative to the center of gravity of the boat.
Steadying or riding sails aft or using an anchor bridle to a side cleat forward changes the centroids of these forces and lessens the effect.
Greetings,
P/F. "...hanging them while we are under way...". You CAN'T be serious!
That's it in a nutshell. What to do about it? Try to anchor out of the current and protected from the wind.A boat yaws at anchor because it is an unstable system trying to find equilibrium. Generally speaking the distributed forces applied by the wind and water change relative to the center of gravity of the boat. .....
Fortunately the Mrs is totally on-board with the Nordhavn.
People mention greater displacement as being more stable, but what got me wondering about this again is a very experienced Nordhavn delivery/training captain who commented on how much they sail at anchor.
Sure, a shift of wind here or there will cause a boat to move around, but many seem to just constantly oscillate no mater what.
As for sail boats vs power boats, what you say about different windage etc makes sense, yet the worst boat I ever saw sailing at anchor was actually a sail boat. At times I though it was going to hit it's neighboring boats it was so bad. The dock guy said that boat always does it.
All this suggests to me that we don't REALLY know what the detailed dynamics are. Where are the rocket scientest when you need them......
the worst boat I ever saw sailing at anchor was actually a sail boat. At times I though it was going to hit it's neighboring boats it was so bad. The dock guy said that boat always does it.
That is the best take away from this discussion as the cause of swinging.The further the center of windage is from the bow attachment point and the closer to the center of gravity, the less it will sail.
I just found this Rode Dynamic Behavior 3 which help illustrate and explain whats going on.
How to counter it when the center of windage and effort is on the opposite end from center of gravity and resistance ... and a back sail is not an option? Bridles? What else?
Right, this is what I said #22 ...Two important design factors are also involved in a typical anchoring situation: Center of Effort and Center of Lateral Resistance.