Are flopper stoppers effective on a light yacht?

[Simon F]

Hello all,

Are flopper stoppers less effective on a light boat? (a 1200kg Pandora in this case) I like to anchor up just off the beach of an evening and I'd like to damp out some of the roll. Before I knock up a couple of flopper stoppers to this end, I thought I'd check I haven't missed something basic about the physics of a smaller lighter craft that would render the effort useless. Also, would I scale down the dimensions?

Thanks

Simon.

 

[Catalina36]

Should still work the same but make sure you deploy them deep enough. They don't work so well if they're set shallow because they're in water which is rising and falling in the first place. They need to be at least three times wave height deep.

 

[Simon F]

Thanks for the reply Catalina36. I think I'll go ahead and make some then. Do you think 52cm square would be big enough? (it's the size of the space I have to store them under the sole)

 

[Catalina36]

Thanks for the reply Catalina36. I think I'll go ahead and make some then. Do you think 52cm square would be big enough? (it's the size of the space I have to store them under the sole)

Hard to tell without doing some sums, obviously the larger the better but a thing to bear in mind is that they're more effective the quicker they "take up". Thus the conventional triangle with a lead weight on one corner which dives vertically then has to pull horizontal before it brakes the boat has more travel and is less effective than types which have slats like louvre blinds which open and close rapidly. Bear in mind that you can get double the area if you use two boards hinged with stainless piano hinge, weighted so it drops hinge side first then opens like a V as it starts to rise. It's all a bit of trial and error but that's part of the fun.

 

[Simon F]

Yes, I see what you mean about the take up time. I like the hinge idea. It would have the benefit of folding for storage. Or a stack of boards maybe?

 

[Catalina36]

A stack of boards like a W would suffer from the bottoms opening on the downward plunge which would slow it down. It needs to go down fast on a tight line as the boat rolls that way, then open the moment the boat rolls back, like a non-return valve. Restraint lines stop the V from opening beyond say 120 degrees and the hauling lines go down to the bottom of the V, through holes on both sides and round the hinge.

 

[Simon F]

Yes, I see. I guess that, as well as the weights near the hinge, the boards would need to have a bit of weight added at the top edge, to keep the v open in the ready position, or their positive buoyancy would cause it to float shut.

 

[RupertW]

I’m thinking of making some myself so good suggestions thanks. Mostly though I just make sure the bow is pointing into the swell but a floppper stopper could be great if I’m on long lines back to shore.

 

[Catalina36]

Yes, I see. I guess that, as well as the weights near the hinge, the boards would need to have a bit of weight added at the top edge, to keep the v open in the ready position, or their positive buoyancy would cause it to float shut.

Yes, good idea too. Alternatively a couple of wooden blocks on the top edges to stop them closing completely would keep them ready for opening.