Scissor Keel

[Guillermo]

What do you think of this Rob Humphreys' "Scissor Keel"?
http://www.yachtforums.com/forums/ne...ssor-keel.html

[Vega]

Great idea!

But this doesn't serve the same purposes of a canting keel, because it doesn’t add much to the initial stability of the boat. Just a smart and simpler way of diminishing the draft of a boat (by opposition to a retractable keel without a bulb).... and draft is a big problem in big sailboats.

The added bonus of the roll-damping when moored is also interesting.

[MikeJohns]

I wonder what they are basing their patent on? I have seen side folding fins proposed before (like all the carrier based aircraft wings). Scissor is perhaps not an accurate description of the movement ....it simply folds.


Having had a bit of input to ride level control device design I am a little skeptical about the reliability of such complexity in pleasure craft. To me there are much better ways ways of getting the desired immersed lateral plane. I hope it is all strong enough for a good grounding (including the moment on the keel root).

Vega
Roll damping at anchor is an interesting one certainly it will reduce the roll but so would some small end plates. I was wondering if it would roll in an uneven manner.

You would get better antiroll with the keel down if there was a tide running.
Marchaj reported that the damping of a fin keel at rest is lower than that achieved from a horizontal keel of the same area, (but it is higher underway).. all got to do with turbulence. At rest the fin creates more turbulence as it rolls back and forth and then is stuck operating in the high turbulent zone. Underway the turbulence is left behind

[Vega]

Originally Posted by MikeJohns

Vega
Roll damping at anchor is an interesting one certainly it will reduce the roll but so would some small end plates. I was wondering in it would roll in an uneven manner.

MikeJohns, a larger surface will be a lot more effective (meaning the small end plates against the big tilted keel).

About the "roll in an uneven manner", I guess you say that because the keel is tilted to one side giving an unsymmetrical profile to the boat?

As you know there are on the market several devices to damp the roll (at anchor) on small yachts. The ones I know are deployed on the side of the boat, some using the spinnaker pool to be more distant (and effective). I have read some tests about their efficiency (they all reduce roll to some extend) and they didn't report an uneven roll as a side effect. So I guess that in the case of the scissor keel (stupid name) you will also not get a noticeable uneven roll.

[tom28571]

If you are willing to spend enough money, all kinds of esoteric stuff is possible. I wonder what advantage this has over a conventional keel CB of the same depth, dimensions and greater simplicity. If you hit something with this thing, it is not going to pop up and let you keep going. More lost time, lost dignity and more money

[SeaSpark]

Would never want one on my boat, but looks a bit like scissor.

http://www.jongert.com/index2.html

Under technics, foldingkeel there is a small animation, could not find any better pictures.

[jehardiman]

I'd like to see how they are working the hydraulics and/or mechanics. Having built large structures that move and live in salt water, in these pictures I"m not seeing what I expect to see for operationability and reliability.

[Windvang]

I don't see any advantage over a keel/lifting-cb configuration. That cb would stay easely under the cabin floor, when lifted inside the keel. That way you can also add some valuable ballast inside the centerboard.

sailing in shallow water will be impossible on sb side (unless it folds both ways) and when motoring in shallow water the centerboard will be sucked down, severely slowing progress.

I don't think you would like to be aboard when than girl starts rolling under anchor. When that happens, the owner most likely will be air lifted to the nearest Hilton anyway.

[Guillermo]

Originally Posted by SeaSpark

Would never want one on my boat, but looks a bit like scissor.

http://www.jongert.com/index2.html

Under technics, foldingkeel there is a small animation, could not find any better pictures.

My Goodness! Didn't know that one either.
I think there is people around with too much money to spend...

[Vega]

Quote: Originally Posted by SeaSpark
Would never want one on my boat, but looks a bit like scissor.

http://www.jongert.com/index2.html

Originally Posted by Guillermo

My Goodness! Didn't know that one either.
I think there is people around with too much money to spend...

It looks alright to me.

That would not be a problem to people that have money to have (and maintain) a 100ft sailboat.
Big sail boats need a big draft, not on account of the ballast, but to sail well.
This system provides also a damp roll action while on anchor and is mechanically simple with the advantage of having all the hydraulics and electrical motors over the waterline.

Originally Posted by Guillermo

What do you think of this Rob Humphreys' "Scissor Keel"?
http://www.yachtforums.com/forums/ne...ssor-keel.html

======================
One of the more or less regular posters here-Stephen Ditmore has a patent on a high aspect foil that rotates on the same axis as this one but is located-more or less- at the back of a short fin keel. It can be rotated to either side or "stowed" with the foil vertical ,behind and directly parallel to the trailing edge of the fin. The two concepts are so very similar in their essential princibles that I would think Stephen's might preclude the new one shown by Guillermo...

[Islandboy]

what software did u use to design your boat with the scissor keel?