Riding a mooring

[ifmdalvey]

Last weekend i took a run up the lovely 12 mile Kennebec river to the city of Bath in Maine. Some nice old wood lighthouses to look at and moored at the Maine Maritime museum with the view of BIW and two DDG 1000 destroyers parked 1/4 mile away.

Now there is a good current on this river, up to 4 knots both in and out with a extremely short slack period. I notice in the morning that my bow was parallel with the mooring buoy, the 15 pennant was 90 degrees to my bow. My boat was not hunting around , it was just holding steady, by moving the rudder, with no engine i could move across and put the buoy on the other side of the bow but still at 90 degrees rather than down current.
Why did the boat hold this position?

 

[Benny17441]

It is likely the boat was skiing over the water at a slight angle against the current until it got placed back in line by the mooring pendant.

 

[ifmdalvey]

No Benny, the boat was completely stationary, 90 degrees to the mooring ball which was 10 foot away, (length of pennant). I expected to be directly down current with the pennant almost horizontal with 3 knots running past me.

 

[agprice22]

Where was the wind? Was the hull sailing the wind in opposition of the current?

 

[justsomeguy]

Weird stuff. Eddy? Eddies? Gyre?

 

[ifmdalvey]

No wind and i could sit on either side of the mooring ball, no eddies that i could see.I have never seen anything like it.

 

[Boomer54]

Perhaps the Navy was messing with you below the waterline?

 

[jssailem]

Would that be a Navy vortex. Thought they were banned after the Philadelphia Incedent .

 

[Benny17441]

No Benny, the boat was completely stationary, 90 degrees to the mooring ball which was 10 foot away, (length of pennant). I expected to be directly down current with the pennant almost horizontal with 3 knots running past me.

I understood what you were saying but there is water moving past the keel and the rudder in a similar way as if the boat was underway. If the pendant is pulling on the boat in one direction the boat has to be exerting a force in the exact opposite direction. Whether it be because of the hull shape, the keel or the rudder that boat is trying to steer away from the mooring only to be restricted and steered by the pendant. It is like a car that pulls to one side but is held going straight by the hand of the driver in the steering wheel. If let loose it would have floated back and away It just so happens that the equilibrium between the two opposing forces was found at 90 degrees. Perhaps with a lesser current it could have been 45 degrees or a stronger current could have had the bow ahead of the mooring. I don't know how else to explain it; I understand that you would expect the boat to remain down current but the boat was not tracking straight. It could be conditions or it could be the boat.

 

[Tom G P-21]

Did you look at the charts? Chart 13296 shows a spot on just north of the Maine Maritime Museum where the depth goes quickly from 23 to 12 ft. That might be in the mooring field and this could of caused some currents.

 

[ifmdalvey]

Tom, the mooring field is at least 200 yards south of that shallow spot, which is just west of the green can on the chart, we were a fair distance from that point.

 

[Gunni]

Congratulations, your keel works, it lifts the boat!