Backing a sail when dropping the mooring

Gunni · Aug 1, 2017

It is part and parcel of CE/CLR. What would be the purpose of sailing about a mooring?

mcrow33 · Aug 1, 2017

When you back wind the jib to starboard. You are creating more surface area on the starboard side for the wind to push to port. If you didn't do anything, once the wind interacted with one side or the other naturally, the boat will drift to the opposite side.

Southpaw · Aug 1, 2017

It has to do with the location of the sail on the boat.The main sail is more in the middle of the boat and over the keel it pushes the aft of the boat. The jib is at the bow so it pushes the bow in the opposite direction.

Gunni · Aug 1, 2017

jimshipsky said:
What would be the purpose of sailing about a mooring?
The purpose is not to sail about a mooring, but to turn the boat off the wind before dropping the mooring.

OK. If you want to control the boat when dropping the mooring (or pulling your anchor) do it with the mainsail. One control sheet.

Dennis Kitchen · Aug 2, 2017

Gunni said:
OK. If you want to control the boat when dropping the mooring (or pulling your anchor) do it with the mainsail. One control sheet.

When you're on a mooring, unless there is a strong current, the boat feathers into the wind. You're in irons , therefore the main sheet is useless, except to release it so you can push the boom forward to start moving the boat backward against a cocked rudder until the boat has fallen off to a reach. Now pull in the main sheet and you're sailing.
Dennis

Gunni · Aug 2, 2017

Dennis, what is this "boat feathering into the wind" stuff? Sailboats don't stop sailing just because they are on a mooring.

Joe · Aug 3, 2017

When a sailboat turns, it is essentially rotating around the center of its keel. The head sail has more influence on the bow section.. the main has more on the stern section. Since the boat cannot drop backward while still attached to the mooring, a back winded jib is simply pushing the bow causing it to rotate around the keel. A similar thing happens with the main (in a sloop rig)... pushing out the stern to rotate it in the other direction.

This is a good example of what you should be aware of when balancing your sails. Getting the correct amount of helm pressure, rudder angle... etc. It's all about balancing the pressure on the headsail with the main to make the boat controllable. It also illustrates how a sailboat turns from the back... rotating around its keel's center point.

Dennis Kitchen · Aug 3, 2017

Gunni said:
Dennis, what is this "boat feathering into the wind" stuff? Sailboats don't stop sailing just because they are on a mooring.

Gunni,
I guess I don't know how to explain it better than I already did.

One of us is missing something? Apples vs Oranges?

weinie · Aug 3, 2017

your diagram is incorrect.
The vector from the wind is pointed directly down. (assuming the wind is coming from dead ahead which is typical of a boat in a mooring sans current).
The lateral force comes from the fact that the sail is TURNING the wind to the right causing the resultant force to the left.
This is newtons second law where Force= change in momentum (with respect to time).
The velocity component of the momentum vector of the wind is being redirected by the sail from downwards to right (and down).

Gunni · Aug 3, 2017

I'm thinking one of us has actually sailed onto and off of a mooring (and anchor) and the other is just talking about it. A skilled and experienced sailor can control the motion of a sailboat on moor with a mainsail and mainsheet in hand and the tiller in the other. You can creep up to a mooring to allow a bowman to hook or release a pennant and you can precisely veer off and sail away. The mainsheet is far from useless, it is essential and key to this essential skill. It is what you do when you are sailing and you don't have a working engine.

Dennis Kitchen · Aug 3, 2017

jimshipsky,
I think thats pretty close. In your illustration you show the boat still attached to the mooring. That will of course inhibit any force from your sail and you wouldn't want sail pressure working against you as you're trying to unclip from the mooring. Symantics.....I know. For clarity you have drawn the wind vector perpendicular to the average jib surface. In reality it wouldn't be so but regardless you would still get an element of "side" vector that would begin to turn the boat.
Dennis

Parsons · Aug 3, 2017

Gunni said:
It is part and parcel of CE/CLR.

As far as your vector diagrams, let's focus on the first part of Gunni's comment about the center of effort (CE) and center of lateral resistance (CLR). Obviously, most of the posters on this thread know this already, but for the rest of the readers ... The center of effort (CE) of the foresail is in front of the CLR on the keel, therefore that sail acting along forces the boat in the same direction as the wind. The CE of the main acting alone is behind the CLR so the main forces the aft of the boat in the same direction of the wind and the bow into the wind. Think of a sideways see-saw.

Dennis Kitchen · Aug 3, 2017

Guni,
You have an amazing boat! On my boat when it is lying still I can turn the rudder any which way and it has absolutely no effect. I know boats at anchor or moored will " ride around" and often this is countered with an anchor riding sail to cause the boat to stay streamed back ( or feathered if you please) from the rode or pennant. Seems to me if you sheet in the main you've just created a big anchor riding sail. Now if you have current working counter to the wind and creating power over your rudder I can see you out there hobby horsing around until something favorable happens but I wouldn't call that sailing. And yeah I know I don't have much experience at it so I would just luff the main, hard over the rudder, pull in the pennant to get enough slack to unclip, let the boat fall off and then go sail. Maybe you can teach us your technique in detail?
Dennis

Disclaimer: No sailors were injured or killed in this exchange.

Gunni · Aug 3, 2017

Dennis; Sounds like you are stalling your boat, diminishing lift from your mainsail and/or creating drag from fiddling with your rudder. Your actions have to be very precise you are dealing with less power and low speeds. The best way to learn is to take your boat out and practice sailing up to, and stopping at a mooring ball or Nav-aid. Then power back up and sail away. Each boat has it's own tendencies. But being able to sail your boat like this may one day save you from a very bad day. So it is worth developing the skill. Good luck.

Dennis Kitchen · Aug 3, 2017

Thanks Gunni!
I get the part about learning to maneuver on close points of sail but I guess what I'm missing is if I'm already hanging from a mooring, head to wind I am stalled by default, the main is streaming aft and luffing even without sheeting in. That's why I would push the boom out into the wind to get some action started. Then are you saying there is enough slack in a mooring to make enough way to head up and unclip from the ball?
Dennis

Gunni · Aug 3, 2017

Dennis Kitchen said:
if I'm already hanging from a mooring, head to wind I am stalled by default, the main is streaming aft and luffing even without sheeting in.

Head-to-wind if you sheet in your main it will slowly power up and start to sail the boat and veer. You then have the forward motion to make your rudder capable of steering back up to wind...or sail off. Practice will show you how fast your boat reacts to sheeting and how much forward motion you need to make the rudder effective. Typically you want very small changes to a centered rudder.

Backing a sail when dropping the mooring

.

Attachments

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.

.