You could choose as lever arm the body of the sailor instead of the horizontal. Then you'd have to calculate force component perpendicular to that lever arm.
The result would be the same as using the full weight and calculating the horizontal lever arm, that is perpendicular to it.
Again I agree with you as stated above, it seems like you disagree, that I agreed with you above. Again, I am NOT disagreeing with Mrig =< Mrighting, as Jake drew above.
Simply, as drawn the FBD appears to show the location of tension members with Fy(b) and Fy(c) are on opposite sides of the C.B. Can you edit the FBD of the tension member(s) whose vertical component(s) are on the same side of the C.B.? (not sys diag as Jake drew)
I disagree that I disagree that you agreed with me above...
I also agree that the vertical component that you mention does act in the opposite way. But there is also a bigger horizontal component that compensates it. I think we would bore the audience if we try to draw it..
By the way, if you want to consider the sailor external to the system, you should also include the force that she applies with her feet. As it doesn't produce much torque, no problem here.
The CG location of the boat (somewhere to the left of the hulls) The CB location of the boat (also somewhere to the left of the hulls since the mast in the water contributes to it) The CG location of the person righting (approximately lower chest)
As soon as the location of the combined CG(boat)+CG(person) is to the right of the CB(boat), the boat will start to rotate clockwise. Moving the combined CG out further will just increase the rotational speed / and counteract the movement of the CB to the right (when the mast clears the water).
The only thing that pulling the line from the top of the hull does is make it easier for the person to hold on to. Makes no difference in righting force or leverage.
Ok that's solved, now... which came first the chicken or the egg?
"I said, now, I said ,pay attention boy!"
The cure for anything is salt water - sweat, tears, or the sea Isak Dinesen If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most. E. B. White
I'm still not really convinced, but I'm ignorant and prone to stubbornness. Damn that 10th grade education.
I'm with ya, but I think this is like politics,Chevy vs. Ford, and which boat is best. No winners.
"I said, now, I said ,pay attention boy!"
The cure for anything is salt water - sweat, tears, or the sea Isak Dinesen If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most. E. B. White
Re: righting line position, engineering/physics needed
[Re: mbounds]
#239304 10/25/1105:27 AM10/25/1105:27 AM
The CB location of the boat (also somewhere to the left of the hulls since the mast in the water contributes to it)
Disagree. What center of balance you mean? There is an axis of rotation that is on the hull, it changes somehow as the boat rotates but is always on the hull. The center of balance that you are probably referring is what you then call the combined CG of the boat plus the person which will never be to the right or to the left because it´s the same thing..
Re: righting line position, engineering/physics needed
[Re: Team_Cat_Fever]
#239305 10/25/1105:44 AM10/25/1105:44 AM
CB= Center of Buoyancy. It's the force counteracting gravity.
In a stable configuration, the horizontal position of the CB = horizontal position of the CG, otherwise the boat will shift until they do.
As the person leans out (to the right), the combined CG shifts to the right, as does the CB as the mast comes out of the water. The further the CG moves away from the CB, the faster the boat will move in an attempt to restore equilibrium.
The bottom line is that only the horizontal positions of the Center of Buoyancy and Center of Gravity matter. How they get to where they are makes no difference at all.
Re: righting line position, engineering/physics needed
[Re: mbounds]
#239307 10/25/1106:01 AM10/25/1106:01 AM
And I would venture that the boat is not perpendicular to the horizontal plane when you are attempting to right the boat. When you are at that point (trampoline is vertical), you've already cleared most of the main from the water, and righting should be almost automatic at that point (if the boat is facing somewhat windward)
Last edited by waterbug_wpb; 10/25/1107:37 AM.
Jay
Re: righting line position, engineering/physics needed
[Re: waterbug_wpb]
#239313 10/25/1108:11 AM10/25/1108:11 AM
And I would venture that the boat is not perpendicular to the horizontal plane when you are attempting to right the boat. When you are at that point (trampoline is vertical), you've already cleared most of the main from the water, and righting should be almost automatic at that point (if the boat is facing somewhat windward)
Actually, that's at it's worst point from a pure weight balancing perspective. The center of weight for the boat extends further away from the center of rotation when the mast is horizontal. In the real world scenario, however, wind is starting to get under the sail, providing lift, and helping move the combined weight center move further toward the sailor side of the equation.
Jake Kohl
Re: righting line position, engineering/physics needed
[Re: Jake]
#239327 10/25/1111:59 AM10/25/1111:59 AM
Come on, don't make me disagree everytime... I think the the weight of the upper hulls are a significant factor and it's not the same whether they are in one side or the other of the vertical. The worst point to me is just when the mast left the water and none of it is floating. If you can move it up from there you are fine.
