Flopper stopper question.

I have enjoyed reading "Voyaging under power by R Beebe". This book has convinced me it is safe to cross the Atlantic in a small motorboat of 40' or more. However possible and safe it is (for experienced sailors) I think for a great number of weekend sailor types it would be an act of lunacy.

Flopper stoppers which according to Beebe reduce rolling by about 60% would be a must. What I would like to know is at what point on the beaufort scale should they be deployed.

 

Well, it depends;
On the boat, it's trim, speed, fuel reserves, crew tolerance and endurance, wind direction, wind direction vs. current direction, wave state and direction, etc.
That ought to narrow it down a bit...

 

I run what you call flopper stoppers (we call them staybies don't know the correct spelling if there is one) on my salmon troller, almost all of us do. Like Milehog said it depends on a lot of things. But the easiest way to put it might be when the barf inducing roll becomes worse than the loss of speed, increased fuel consumption ect. about half a knot on my boat and a lot of strain on my rigging if I'm trying to go full speed. So really they slow me down about a knot, knot and a half. I pretty much only run them if I am in a following sea unless I am fishing. I guess to sum up you'll love them if you have them. Just make the rig strong. Keep them clear of the prop. Sink them deep enough so that they don't pop out of the water when your rolling in the big combers and take out a window or something. Watch out for s#@t in the water kelp wads, crab pots (those suck!) ect. And lastly I am sure you will know when you want to put them out, but you should never have to. If you do then you have a bigger problem.

 

At what sea state must you retreive your floppers ?


How effective are they at anchor ?

 

Most folks going offshore will rig the poles and required stays on departure .

Then its fairly easy to deploy one or both fish .

The half K of speed loss is tolerable to keep the cook on station.

 

Staybies work quite well at anchor. Not as good as when your moving but I almost always have them out when I'm on the hook. That brings to mind one more thing. It is possible to get them wound up around your anchor gear. This doesn't happen to often but it can be a pain in the butt. Also be careful dragging them in to shallow. I got mine hooked on a rock once and broke my pole in half.

 

Once they go in they stay in until the weather lets up or you get were your going.

 

If you can aford it active fins or a gyroscope stabilizers can do the job in some ways better than polled floppers.

 

I was watching some yachts at a marina the other day, rolling in quite small wash. I could imagine how sick-making it would be if you were actually living on one.

There would be a good case for live aboard boats having easily deployed 'fins' to vastly increase livability.

I wonder if a non fuel powered 'active fin' could be designed, working on wave and/or wind action ?

I suppose just extended flat planes would be useful, if not as effective as actively adjustable ones.

 

The correct term is "towed paravanes".

As mentioned above, if you are voyaging "outside" folks usually drop the poles after leaving harbour.....then drop or pull the paravanes as conditions warrant. For West Coast fishermen and Beebe originally, this is a strenuous manual exercise. Today (and for many years) Passagemaker is equipped with twin electric drum winches to do the job. I've seen a number of boats with manual open drum sailboat winches on the inboard end of the pole, but this is awkward at best.

Properly sized active fins or gyroscopes will reduce rolling more effectively than paravanes, but they require many more dollars to install and maintain, they require power, are mostly ineffective at anchor (brains are too slow), and active fins add drag 100% of the time, whereas the gyro just adds a bunch of weight to haul around 100% of the time.

I believe it was Nils Lucander who conceived a passive drive for active fins. The fins were coupled to a system of swinging counterweights inside the hull and those moved the fins appropriately. It would take huge interior volume.

Bill Garden tried manually operated fins, handled by the helmsman......if you loose the plot you increase roll depth...... I think a better idea he proposed was a water tank on the masthead with a fill, drain, and pump to adjust the level. A passive way to change VCG and adjust roll period.

A Dutch company offered a transverse track with large moving weight as a possible solution....it was interesting but again ate interior volume and needed to be up high (close to the main deck).

Pat Bray advocates bilge fins, fixed foils that extend to keel depth and sometimes include active fins on their trailing edge. On this coast "bat wings" are popular on older, round bilged, fishing vessels. These are really large thin steel plates extending horizontally from the keel the full width of the ship. They are supported at the outboard edge by a vertical leg from the rail. Another local idea was to glass big lengths of open-ended fiberglass pipe on the chine of seiners, the idea being that another 1000 pounds of water would slow the roll......

Flume tanks are an interesting passive option. A box tank up high (on the cabin roof) extending most of the ship's beam. With a series of baffles at each end they set up a flow of water in opposition to the roll, damping that effectively.

Avard Fuller advocated the use of a passive vertical daggerboard deployed through a trunk on centerline. This can be very effective but it is draggy and vulnerable to damage.

And finally I'll mention the system used on a mini-trawler yacht called Papaza (sp?)......This was a passive system using twin bilge boards (plywood) deployed almost horizontally from a case in the topsides (slightly above waterline) aft. When deployed at cruising speed they where immersed into the stern wave.....I though this a clever idea with great possibilities though I know nothing of the actual results.......

 

I'll be sure next time to tell my deckhand to deploy the "towed paravanes"
Just kidding around. Thanks!

 

Did anybody mention retractable pontoons. ON a sail boat this would convert to a tri with the design criteria mainly to dampen roll. There have been several motor tris with small outiger hulls recently. I do not know if they fold alongside which would be a necessity for marina freindliness.

 

"Avard Fuller advocated the use of a passive vertical daggerboard deployed through a trunk on centerline. This can be very effective but it is draggy and vulnerable to damage."

Buy using a wide centerboard style trunk the board could be lifted when not in use. The board would be wider to roll from side to side more easily.

Today an air powered ram as used in many industries could give the blade the proper computer controlled anti roll input at very low coat.

The danger of a grounding and having the anti roll fins knock or tear a hole in the boat is absent, as centerboards take the ground with no damage for hundreds of years .

The budget version could have two rudder pedals for the helmsman , and cheap push pull cables or rope to control the board with.

Even a sawed off bottom of a bike with pedals and chain could work.

 

Twin Bilge Centerboards / Roll-Dampening fins

Lots of variety there Tad.

How about something like this ??....
....make the twin bilge 'fins' as retractable 'centerboards'.

In other words these bilge boards would be more like shark fins that would retract inside the hull. These fins I have in mind for roll dampening would be just plain old flat plate boards,...perhaps steel or another material.

Now I know most sailboaters know how difficult CB slots and boards can be to keep anti-fouled. I'm thinking that the 'trunk' would be a relatively wide-mouthed rectangular box glassed to the hull's bottom inner skin, or in the case of a steel vessel, welded to the hull's inner skin,....with its 'mouth' open to the sea.

Into this rectangular box (trunk) there would be inserted, as an assembly, a rectangular block of UHMWP that has a slot carved into it that holds the pivoting 'centerboard/fin'.

What I'm seeking to do is have a fairly wide-mouthed trunk that on occasion can be cleaned out and recoated with anti-foul. The innards are made out of a block of UHMWP that is virtually anti-fouling by itself, and it can fit a fairly close-tolerance pivoting board that gets 'wiped' each time it is withdrawn or kicked back into its slot.

All self lubricating, and no penetrations to the integrity of the hull itself.

 

There you go! Bringing up the obvious ....