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Re: Try cantelever shroud adjusters, [Re: Andinista] #254442
11/07/12 04:38 PM
11/07/12 04:38 PM
Joined: May 2006
Posts: 1,380
Kingston SE South Australia
JeffS Offline
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I'm not good enough with computers to do a diagram, can somebody overlay andanistas drawing with somebody pulling down with their arms so all of their weight is a further 2ft out, even though their toes are balancing on the boat, like I would do if the boat wasn't coming up.


Jeff Southall
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Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Arrow 1576
-- Have You Seen This? --
Re: Couldn't right my cat solo. Need advice [Re: Andinista] #254443
11/07/12 06:41 PM
11/07/12 06:41 PM

S
Scarecrow
Unregistered
Scarecrow
Unregistered
S



Jeff,

I'm too lazy to do your sketch, but you get the same effect by just raising your arms as you do holding the rope above your head.

This is the image I've just posted over at Sailing Anarchy (for the one or two of you who don't visit both sites). As people have been trying to explain, while your feet are on the hull there is no advantage in putting the righting rope over the hull except it is easier to hold, however, at some stage you come off the hull during righting and this is when the over the hull system becomes superior.

[Linked Image]
Using a righting pole is different as it allows you to move your weight away from the hull immediately.

Attached Files
righting.jpg (10 downloads)
Last edited by Scarecrow; 11/07/12 06:43 PM.
Re: Couldn't right my cat solo. Need advice [Re: Andinista] #254444
11/07/12 07:03 PM
11/07/12 07:03 PM
Joined: May 2006
Posts: 1,380
Kingston SE South Australia
JeffS Offline
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Are you saying that if I couldn't right the cat and I put all my weight on the over the hull rope by hanging of it, no feet on the deck, it would be more beneficial


Jeff Southall
Current boats
Nacra 5.8 1703 Animal Scanning Services
Nacra 5.8 1667 Ram Raider
Nacra 18 Square
Arrow 1576
Re: Couldn't right my cat solo. Need advice [Re: Jake] #254445
11/07/12 07:47 PM
11/07/12 07:47 PM
Joined: Jul 2001
Posts: 2,844
42.904444 N; 88.008586 W
Todd_Sails Offline
Carpal Tunnel
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Originally Posted by Jake
Originally Posted by pgp
We get a debate every few months about whether a righting line must come over the top of the hull. Mine does and I have no problem but I'm a lot heavier than you.


There is no debate. From a physics standpoint, it makes no difference whether the line goes over the hull or attaches to the inside of the beams. Over the hull may make the line a little easier to hold yourself on to with your hands - but it doesn't give you any additional leverage to right the boat. None, zip, zero. You weigh what you weigh, the boat weighs what it weighs. As long as neither one of you is moving in relation to the other (i.e., you are dangling off the end of the righting line), the position or angle of that line makes absolutely no difference on righting the boat because you are connected to the boat at all points (your feet and your hands) effectively making a closed system. Any angle change that you make with the line affects the amount of pressure your feet exert on the hulls and they cancel each other out. It's only about getting your weight out further from the CG of the boat to cause the CG of you+boat to move out beyond the pivot point so it will start to rotate up.


Jake, it must have frooze over! I totally agree with you! ;-)


F-18 Infusion
#626- SOLD it!

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Re: Couldn't right my cat solo. Need advice [Re: ] #254446
11/07/12 08:45 PM
11/07/12 08:45 PM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline OP
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Andinista  Offline OP
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Originally Posted by Scarecrow
Jeff,

I'm too lazy to do your sketch, but you get the same effect by just raising your arms as you do holding the rope above your head.

This is the image I've just posted over at Sailing Anarchy (for the one or two of you who don't visit both sites). As people have been trying to explain, while your feet are on the hull there is no advantage in putting the righting rope over the hull except it is easier to hold, however, at some stage you come off the hull during righting and this is when the over the hull system becomes superior.

[Linked Image]
Using a righting pole is different as it allows you to move your weight away from the hull immediately.


That's true. But when you come off the hull I suspect that you are already done and it might even be better to have less lever arm, so that the boat comes out slowly

Re: Couldn't right my cat solo. Need advice [Re: JeffS] #254447
11/07/12 09:07 PM
11/07/12 09:07 PM

S
Scarecrow
Unregistered
Scarecrow
Unregistered
S



Originally Posted by JeffS
Are you saying that if I couldn't right the cat and I put all my weight on the over the hull rope by hanging of it, no feet on the deck, it would be more beneficial


no because you would have a very small lever (about 300mm as against the 1200mm shown above)

Re: Couldn't right my cat solo. Need advice [Re: Andinista] #254450
11/08/12 04:54 AM
11/08/12 04:54 AM
Joined: Nov 2011
Posts: 381
SE MI / NE IN
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By the time the boat get's to the 3rd position, I'm usually heading for the dolphin striker brace to keep it from going over the other way.


Jeff R

H18, C2 USA1193
cramsailing.com
crescentsail.com
Re: Couldn't right my cat solo. Need advice [Re: TeamChums] #254466
11/08/12 12:47 PM
11/08/12 12:47 PM
Joined: Jul 2004
Posts: 125
Clinton, Mississippi
rattlenhum Offline
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Clinton, Mississippi
This guy's system looks promising.....a lot like Hobie Gary's:

http://tinyurl.com/au5w2ka


http://tinyurl.com/a2lu356


Jerome Vaughan
Hobie 16
Clinton, Mississippi
Re: Couldn't right my cat solo. Need advice [Re: northsea junkie] #254467
11/08/12 02:16 PM
11/08/12 02:16 PM
Joined: Dec 2001
Posts: 5,590
Naples, FL
waterbug_wpb Offline
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Originally Posted by northsea junkie
I totally agree with that, Jake.
And getting your weight more outboard can only be done with a pole.



well, I guess you could wear heels or platform shoes, too...


Jay

Re: Couldn't right my cat solo. Need advice [Re: Andinista] #254471
11/08/12 02:51 PM
11/08/12 02:51 PM
Joined: Jun 2009
Posts: 519
Petten Netherlands
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northsea junkie Offline
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Petten Netherlands
Yes Jay, and you could also wear a nice dress too.

But you brought me on a new idea: You can also hang yourself with your harness on the uphaulline (which is hanging over the tophull) and push your self outside with a pole against frontbeam/hull ......

ronald


ronald
RAIDER-15 (homebuilt)

hey boy, what did you do over there, alone far out at sea?..
"huh....., that's the only place where I'm happy, sir.
Re: Couldn't right my cat solo. Need advice [Re: Andinista] #254668
11/13/12 02:16 AM
11/13/12 02:16 AM
Joined: Jun 2006
Posts: 431
Netherlands
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Netherlands
Ronald, I'd try a diagram first. I used to do hang gliding and the steering on those is exactly like righting a cat (but easier). Its a weight-shift system.

The problem with hanging your weight off the higher hull (once its past vertical) is that your CG probably doesn't change much, your legs are further from the rotational center of the boat but your arms and head are closer.

In hang-gliding its called cross-correction which translates to ineffective steering due to minimal net change in the CG of the pilot.

You may need to "walk tall and carry a big stick" like Churchill once advised ;-)

Anyhow, in my experience the hardest part is lengthwise stability, you tend to sway from bow to stern while balancing in any waves. Makes it really hard to keep your weight out where it counts. Maybe some kind of Hawaiian righting line and a pole combination would work best?

Re: Couldn't right my cat solo. Need advice [Re: Andinista] #254670
11/13/12 03:48 AM
11/13/12 03:48 AM
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Petten Netherlands
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Yes Dennis, I agree with you.

After one night sleep, my idea was already vanished.

Problem is that I sail only with wind mostly more then 15 knots. Therefor after the righting itself, there is always this risk on flipping through to the other side.
This is especially true for a single-handed sailer who tends to swim his sails more off the wind for support.

So when the mast comes up, I'm used to dive to the leeward hull in order to keep it down.
Hanging with my hook on a uphaulline is working contra.

ronald

Last edited by northsea junkie; 11/13/12 03:50 AM.

ronald
RAIDER-15 (homebuilt)

hey boy, what did you do over there, alone far out at sea?..
"huh....., that's the only place where I'm happy, sir.
Re: Couldn't right my cat solo. Need advice [Re: Andinista] #255616
12/10/12 06:29 AM
12/10/12 06:29 AM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline OP
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Problem solved! I took a windsurf mast and made a righting pole. Instead of inserting some sort of spatula into the daggerboard trunk, I attached a loop of strap at the end of the pole and the daggerboard goes through this loop. The loop is long enough so that the pole doesn't bite the hull. It worked great. I didn't cut the pole, I just store it under the tramp, along one hull. At the front beam it goes between the dolphin striker strap and the beam, so it doesn't touch the hull. I used a unique line that starts at one end of the rear beam , goes forward to a fixed loop at the forward beam (same side), then along the front beam to a loop at the other end and then back to the rear beam. I take the extra length of line to either side depending on which side the boat capsized. There's a knot with a little loop at the right position on each side, that attaches to a carabiner at the pole. I also set a second line for support at the middle of the pole (between the carabiner in one end and the daggerboard in the other). The line for this one goes from the middle of one beam through a fairlead at the pole (running free, not tied in) to the middle of the other beam. I intend to manage the excess of line length with bungies and a couple carabiners, to minimize the set up and the storage time. I'm not quite there yet but almost..

Re: Couldn't right my cat solo. Need advice [Re: Andinista] #255722
12/15/12 08:11 AM
12/15/12 08:11 AM
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Santiago, Chile
Andinista Offline OP
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Re: Couldn't right my cat solo. Need advice [Re: srm] #256236
01/13/13 03:47 PM
01/13/13 03:47 PM
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Originally Posted by srm
Originally Posted by pgp
Speak for yourself. There's more to the problem than physics, like balance, but I'm not even sure your analysis is valid.


Ummm, no. It actually is ALL about physics.

Jake's explanation entirely valid and correct. The position of the rope has absolutely no bearing on whether or not you are able to right the boat, it only affects the forces felt by your body and the reactionary forces on the hull. All that matters is the location of your body's CG in relation to the CG of the boat, the pivot point of the system (lower hull), and any external forces acting on the system (wind & wave forces).

sm


At the risk of resurrecting a lengthy debate I have to comment and solicit further response. I agree it is all about the physics. As a chemical engineer, I am familiar with the concepts dicussed but not an expert in this area. But I think one aspect of the physics may be missing here. By saying that the angle of the righting line does not matter, I think you are assuming that the feet of the sailor can put torgue on the lower hull. This is not the case since the sailer's feet are not rigidly attached to the hull. For example if there was a rigid rod extending from the bottom hull through the sailer's body then there would be no need for a righting line as the sailor's weight would be transfed as torque directlyon the bottom hull. Since the feet aren't rigidly attached they can't apply force to right the cat, all the righting force mush come via the righting line. So, if it were true that the righting line angle did not matter then you should be able to tie the righting line to the lower beam right next to the bottom hull and still be able right the boat. In a less extreme case, it should be equally as easy to right the boat if you tied off to the mast base? In other words I'm suggesting that the lower you tie the rope the more difficult it would be to right the boat. I haven't tried either approach so please correct me if you have experience that says otherwise. So, my contention is that while there may be only a slight or negligble differnce going over the hull or diretly to the upper beam, the angle of the rope does matter and as you approach the extreme positions it's impact becomes greater.


Steve
Texas Gulf Coast
91 Mystere 5.0
04 Nacra 570
Re: Couldn't right my cat solo. Need advice [Re: srm] #256238
01/13/13 04:25 PM
01/13/13 04:25 PM
Joined: Jul 2011
Posts: 5
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F-Max Offline
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Originally Posted by srm
Originally Posted by pgp
Speak for yourself. There's more to the problem than physics, like balance, but I'm not even sure your analysis is valid.


Ummm, no. It actually is ALL about physics.

Jake's explanation entirely valid and correct. The position of the rope has absolutely no bearing on whether or not you are able to right the boat, it only affects the forces felt by your body and the reactionary forces on the hull. All that matters is the location of your body's CG in relation to the CG of the boat, the pivot point of the system (lower hull), and any external forces acting on the system (wind & wave forces).

sm



At the risk of rekindling this lengthy debate I have to comment and solicit further response. I agree it is all about the physics. As a chemical engineer, I am familiar with the concepts dicussed but not an expert in this area. But I think one aspect of the physics may be missing here. By saying that the angle of the righting line does not matter, I think you are assuming that the feet of the sailor can put torgue on the lower hull. This is not the case since the sailer's feet are not rigidly attached to the hull. For example if there was a rigid rod extending from the bottom hull through the sailer's body then there would be no need for a righting line as the sailor's weight would be transfed as torque directlyon the bottom hull. Since the feet aren't rigidly attached they can't apply force to right the cat, all the righting force must come via the righting line. So, if it were true that the righting line angle did not matter then you should be able to tie the righting line to the lower beam right next to the bottom hull and still be able right the boat?? In a less extreme case, per ur assumptions it should be equally as easy to right the boat if you tied off to the mast base? I don't think this is the case for either of these examples and I'm suggesting that the lower you tie the rope the more wieght it would take to right the boat and not sure you could right it tied of at the bottom hull?? I haven't tried either approach so please correct me if you have experience that says otherwise. So, my contention is that while it may be true that there is only a slight or negligble differnce going over the hull or diretly to the upper beam, the angle of the rope does matter and as you approach the extreme positions it's impact becomes greater.


Steve
Texas Gulf Coast
91 Mystere 5.0
04 Nacra 570
Re: Couldn't right my cat solo. Need advice [Re: F-Max] #256239
01/13/13 05:44 PM
01/13/13 05:44 PM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline OP
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Originally Posted by F-Max
all the righting force mush come via the righting line. So, if it were true that the righting line angle did not matter then you should be able to tie the righting line to the lower beam right next to the bottom hull and still be able right the boat.

No.. All the righting force comes from the sailor weight. The line and his feet only help him keep his position, as far out as possible. If the line is attached lower, near the bottom hull it turns harder and harder for him to keep in place, that's all. The righting moment doesn't change as long as he's able to hold on

Re: Couldn't right my cat solo. Need advice [Re: Andinista] #256240
01/13/13 05:53 PM
01/13/13 05:53 PM
Joined: Aug 2003
Posts: 351
Santiago, Chile
Andinista Offline OP
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You could also take the guy out of the analysis and think of line tension and his feets force against the hulls. In that case, as the attachment point goes down, the line tension increases, but the distance that make the torque (or the cosine of the angle) decreases in the same measure.

Under your same logic you could conclude that it's better to attach the trap wire at the top of the mast. In terms of righting moment it's not. In terms of wire tension yes, a little bit but it doesn't hurt the final goal which is producing torque.

It's a funny discussion, but as somebody said previously, there's no discusion...

Last edited by Andinista; 01/13/13 05:56 PM.
Re: Couldn't right my cat solo. Need advice [Re: Andinista] #256247
01/14/13 05:25 AM
01/14/13 05:25 AM
Joined: May 2006
Posts: 1,380
Kingston SE South Australia
JeffS Offline
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There's no discussion because people have already made up their minds but there is more righting moment in over the hull than under. In all of scarecrows pictures there is no righting moment because the person is lying in the water if you drew a picture comparing the proper stance it may become more obvious


Jeff Southall
Current boats
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Nacra 5.8 1667 Ram Raider
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Re: Couldn't right my cat solo. Need advice [Re: F-Max] #256250
01/14/13 08:01 AM
01/14/13 08:01 AM
Joined: Jun 2001
Posts: 12,310
South Carolina
Jake Offline
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Jake  Offline
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The lower the line, the harder it is to hold on to - but it doesn't change the static equation. If the sailor, the line, and and the boat are not moving in relationship to each other, no change in the position angle, length of the line will affect the amount of righting force being applied. The line weight is negligible and the center of the weight doesn't change either. Only the sailors weight and position is important - not how he's braced there.


Jake Kohl
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