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Rock and Roll Is Not Here to Stay

Posted: September 1, 2011

By: John Beatty

Do any of these situations sound familiar? “This is a lovely spot to spend the night, but what about that ferry wake?” “This is the prettiest cove, and there is a mooring buoy available. We will be out of the wind, but last time the swells marched right around that point and rolled us all night.” “I’d like to anchor off Uncle Evan’s cabin, but it is exposed and there could be some waves.”

If you have spent much time cruising, you have probably been faced with these dilemmas. One solution is to get a slip in an “inexpensive” marina and take a “convenient” taxi to Uncle Evan’s cabin. On the other hand, wouldn’t it be nice to stop where you wanted, spend no money and be sure you would have a peaceful night’s rest? If you said yes, it might be time to look into “at-rest stabilization.” 

A bucket of water weighs a little more than 8 pounds for every gallon it holds. Imagine a 64-gallon garbage can hanging below the surface of the water from a pole sticking 6 feet off the side of your boat, amidships. If nothing is trying to lift it, the can of water weighs nothing (or almost nothing). As soon as a ferry wake arrives, the boat tries to roll, but it has to lift 500 pounds at the end of the pole. It will lift it a little, and the boat might roll a tiny bit, but not like it would without the can. 

Of course, what has been lifted must come down. The descending garbage can will roll the boat back. Not good. How can we get rid of the rollback? Better yet, how can we get rid of the garbage can altogether?

What we need is something that comes up with maximum resistance and goes down easily. A 2-foot-by-3-foot panel of metal would be hard to pull up if it were perpendicular to the direction of force and flat a few feet underwater. If the panel folded in the middle when the stress was gone, it would go down much more easily. The next pull up would cause the panel to flatten out again and be that 2-by-3-foot plank of resistance. Hence, practically no rollback. If I had just thought of this, I would patent the idea and retire. But the people at Magma Products beat me to it. It is called the Rock & Roll Stabilizer.

Putting a System Together

I rigged our Krogen 42 to take advantage of Magma’s at-rest stabilization. We have an aluminum whisker pole, purchased used. Magma sells an outrigger in addition to the stabilizer, but I chose to build my own. My pole snaps into a large pad eye on the edge of the top deck of our boat. A 3/8-inch Dacron topping lift line runs from the masthead to the outboard end of the pole. The stabilizer bridle hangs from the pole with enough line to allow the stabilizer to stay 8 feet deep as the boat tries to roll. The pole is kept from moving fore and aft by two guy lines from the outboard pole end to cleats near the stern and on the bow of the boat. The two guy lines attach to the boat and exert a down force on the pole to keep it from moving up when the boat rolls toward the stabilizer. I am using 1/8-inch Spectra line (2,000-pound test) for the guys and 3/16-inch Spectra (5,100-pound test) to attach the stabilizer to the pole. I can set the pole out and have all these lines in place before I put the stabilizer in the water. 

To avoid that sinking feeling, I ensure that the pole and stabilizer are hooked to the boat two different ways before I let them go. Have the pole hooked to the pad eye and the topping lift, with the stabilizer hooked to the pole and the retrieval line. 

There is a place to attach a retrieval line to the stabilizer, which lets you pull up one end of the stabilizer when you wish to haul the rig out of the water.

Loads and Forces

Before starting this project, I tried to figure out how long the pole should be. The length of the pole and the size of the panel underwater determine some of the forces involved. There are many other factors to consider, such as the boat’s vertical center of gravity, the roll rate and the rolling moment. Rather than hire a naval architect, I think overbuilding the system is the more practical approach.

I double-checked the steps required to deploy the stabilization panel, and we took our boat to Elliott Bay. In an area free from container ships and ferryboats, I put the pole out and lowered the panel into the water using the retrieval line. The wind was about 15 knots, and our downwind drifting caused the panel to pull laterally as well as down. Nonetheless, the roll was significantly reduced. Even in open water with a bit of chop, launching and recovering the 18-pound panel was easy. I did it from the aft deck. Doing this from a swim step (while wearing your PFD) would work equally well. 

At-rest stabilization is a good thing when you want a good night’s sleep or wish to hang on the hook for lunch. The next time we anchor off Sucia Island in the San Juan Islands, I want to sit rock steady while I watch the “unstabilized” boats wallow around in beam rollers when a south wind comes up. Think about it.