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 Current boats Nacra 5.8 1703 Animal Scanning Services 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 11/07/1207:41 PM11/07/1207:41 PM
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.
Using a righting pole is different as it allows you to move your weight away from the hull immediately.
Last edited by Scarecrow; 11/07/1207:43 PM.
Re: Couldn't right my cat solo. Need advice
[Re: Andinista]
#254444 11/07/1208:03 PM11/07/1208:03 PM
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 11/07/1208:47 PM11/07/1208:47 PM
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!
'Long Live the Legend of Chris Kyle'
Re: Couldn't right my cat solo. Need advice
[Re: ]
#254446 11/07/1209:45 PM11/07/1209:45 PM
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.
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 11/07/1210:07 PM11/07/1210:07 PM
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 11/08/1205:54 AM11/08/1205:54 AM
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 11/13/1203:16 AM11/13/1203:16 AM
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 11/13/1204:48 AM11/13/1204:48 AM
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; 11/13/1204:50 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 12/10/1207:29 AM12/10/1207:29 AM
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 12/15/1209:11 AM12/15/1209:11 AM
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 01/13/1305:25 PM01/13/1305:25 PM
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 01/13/1306:44 PM01/13/1306:44 PM
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 01/13/1306:53 PM01/13/1306:53 PM
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; 01/13/1306:56 PM.
Re: Couldn't right my cat solo. Need advice
[Re: Andinista]
#256247 01/14/1306:25 AM01/14/1306:25 AM
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 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: F-Max]
#256250 01/14/1309:01 AM01/14/1309:01 AM
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.