Kick-up rope fuse

Somewhere out there exists a rope fuse that will 'blow' when one of my kick-up rudders hits something, then allow me to reset the device and carry on sailing. I heard rumours of it being used on Ellen Mcarthurs tri, saw a pixelly picture of one in an archived forum post that has since disappeared...

Anyone know anything?

 

http://www.cruisersforum.com/forums/f48/catamaran-retractable-rudders-16734.html

 

Are you asking how to hang the rudders, or how to allow them to be released. On my small tri the cassettes are a tight fit so that the rudder work pretty well with nothing other than the pressure in the slot. Over time the slot has tightened due to very slight movement of the transom halves. This means that I can't just tug rudders down any more, I have to push them, but it is easy enough to do. If you just want something to break, there are lots of options. You can drill a hole in the bottom of a plastic cleat so that the retaining lines gives when the pull forces it deeper, but that would be too much force on my arrangement. There is an exposed section of my hold down line, and I can prusik knot a second small line into the first so that there is a segment of rope supported by a much smaller line that will break when there is an impact.

 

A couple of wrinkles from my point of view

The fuse can be used on a daggerboard too. John Shuttleworth writes about using a fuse to hold the board down and then winching it back against the fuse so that any touching breaks the fuse and the board gets pulled up.

Personally I use a piece of plastic pipe. I replace it often as it can get flexible. I have had mine pop up three times. Twice I saw the fish float too late and then I thought I had missed it but looking back one rudder was up and the other was used to keep the boat straight until the released one was pushed back down.

I prefer not to use the typical arrangement. Parallel sides to the cassette can lead to stuck cassettes or wobbles. Use a tapered slot and mold the cassette out of the slot. Also I got rid of my strong hinge. We usually go aground inadvertently sideways or backwards and then the hinge does not work. I have a lashing around the rudder post that allows the rudder to come up vertically as well as pivot. I did this after I went up on a sandbank in a squall sideways and the hinge point did not like it.

I prefer the cassettes and have just had my rudders at home giving them an antifoul whilst the boat swung on the mooring. The boards came home too. Weight would be neutral as the rudders can be made strong enough only for hydrodynamic loads. If you are a gunk holer then kick ups are great - I have a singly outboard too.

cheers

Phil

 

"I have a singly outboard too."

pics or info?

 

One arrangement I've seen is a cam cleat mounted with a hinge to a wedge, with the thick edge of the wedge (and the hinge) in the direction of pull. The cleat sort of leans back from the pull.

A sudden load will pull the cleat up, and the changed angle of the line to the cleat will pull it out of the jaws. Flip the cleat back down to reset it, pull in the line to drop the rudder back down and you're good to go.

If the cleat is prone to releasing under normal loads, you might try putting velcro between the cleat and the wedge. The area of the velcro could be varied to get just the right amount of resistance before the cleat flips up.

I experienced an unintended fuse on my boat earlier this summer. The centerboard pendants on my boat are double braid. When I touched ground with my centerboard, the cover of the down-pendant broke where it was gripped by the cam cleat. But the core was OK. I was able to pull the board back down by the core.

Afterward, whipped and stitched the cover of the standing part to the core and milked the cover of the tail over the cover of the standing part. Then I whipped and stitched the tail cover above and below the break to restore the line to near its original strength. I suppose I might have been able to stitch the covers together so that the stitching would serve as a fuse.

 

Slider has a system for handling the kickup rudders that looks a little complicated, but is dead easy in practice, and very cheap. The rudders are pulled up and down by a continuous line that attaches to deck loops on the front and back of the rudder blade above the water line. This line is long enough that it goes up from the leading edge to a heavy stainless loop on the stock (a fairlead or block would work even better) forward along the tiller and then back to the stock, through another loop and down to its attachment point on the trailing edge. At the forward end, this loop is threaded through a wooden block that is sort of like a euphroe on a junk rig, except that the holes drilled through it are designed to resist the movement of the line. This block has another short line attached to it, and this line is cleated to a cleat set on the tiller. The tension you put on this cleated line determines the force that holds the blade down-- lees tension on the line to the euphroe, the easier the blade kicks up. There are also loops on the main control line so that a toggled line can be passed through them to give a 2 to 1 mechanical advantage when time to haul the blade up or down.

There's a video explanation here.

 

See
http://www.duckworksbbs.com/hardware/cleats/sd002570/index.htm
They work

 

Correction

Thom D

A single outboard - mispelt as singly. I should get some photos I guess. It is on a pivoting nacelle to get it clear of the water by about 25cm sailing. It works well. Hint - Don't make it too high. My last nacelle was taken by thieves who slid their boat under the 500mm gap between it and the water. They didn't want the nacelle I am sure but it was attached to the outboard they desired.

cheers

Phil

 

I found this in Brian Eiland's gallery in this forum-pretty cool:

(click on image and then again on resulting image for best clarity)

 

There were home made versions of that in various older texts, to release sheets. A cleat was mounted on a hinged flap that was held down somehow. When it broke upwards it would spill the lines.

For the rudder I like just breaking little stuff. Or a little friction block. Relative to the jib sheets, it doesn't take much to hold a rudder in place, so I just tie off to something that will break, though I suppose one's patience would depend on how often it happened. My dagger does a Poseidon missile long before the rudder hits, sorta an early warning.

 

The german company Pfeiffer Marine invented this cleat in the 80s, gave it no name. I named it "Drehmoment-Curryklemme"--torque-cleat.
Since about 1990 is out of production .
Many people in Germany are asking for a Drehmoment-Curryklemme.
Is it in production somewhere ?

pogo