Lower hand versus upper hand

Bernd · Post by **Bernd** » Mon Dec 26, 2011 2:34 pm

sms wrote:Maybe something like: "Empasize the movement of your bottom hand."

Student: "You want me to be more dominant with my bottom hand, using more force here?"

Magnus · Post by **Magnus** » Mon Dec 26, 2011 3:39 pm

Hi Bernd

Start by telling him "The force is not with you, my student."

(mühe, anstrengung, bemühung, kraftaufwand ? best google translate can do.)

sms · Post by **sms** » Mon Dec 26, 2011 3:53 pm

Do not use the force Bernd. I am not you father. :p

Magnus · Post by **Magnus** » Mon Dec 26, 2011 4:57 pm

If I take my bottom hand off the rod and stick in in my pocket, I can still cast. Conversely, with shorter rods and using two hands, I can stick my top hand in my pocket.

Why do I have to have a relationship fixed to 60/40, when I can very obviously make it 100/0?

Paul

The lengths and proportions have changed a lot there when you go from two to one hand. Not sure where you're getting 60/40 from? If the hands or points of contact move closer together the percentages change. ( - a lot when very close.)

Paul this is like a see-saw - forces at both ends and we usually ignore the forces at the fulcrum.
Say you and Lasse were on the seesaw - to get you to balance you would be closer to the pivot than Lasse. And with the two of you on the beam the forces at the pivot would be far higher.

I think I'm right in saying that this approach assumes an equilibrium thanks to the forces applied at those three points. The bend in the rod varies with the forces. The length of the 'rod' varies with the bend.

Sakari set up some conditions - load angles mainly. But as far as I can see it works.

Marc LaMouche · Post by **Marc LaMouche** » Mon Dec 26, 2011 5:15 pm

i'm pretty sure Lasse would fly away no matter where you placed your fulcrum...

Magnus · Post by **Magnus** » Mon Dec 26, 2011 5:22 pm

Say you and Lasse were on the seesaw - to get you to balance you would be closer to the pivot than Lasse.

....a lot closer to the pivot and Lasse would be in, say, France perhaps?

Paul Arden · Post by **Paul Arden** » Mon Dec 26, 2011 7:29 pm

sms wrote:Well no, I was referring to a case where the grip with one hand is on the grip. If you tuck the butt to the forearm, you are widening the grip vs. finger grip.

I think we're on crossed communications here. I mean cast 1; the rod is rotated by closing the fingers. Cast 2; the rod is simply held in the hand with the rotation point around the elbow. In these cases the torque proportion between top and bottom of the hand is the same?

Cheers, paul

sms · Post by **sms** » Mon Dec 26, 2011 8:17 pm

Yes, misunderstanding there definately! I do get you now. For massless rod, the answer is yes. It does not matter where the rotation is generated or where the ICR is (for same grip points, so you need to hold the rod in finger grip, but cast with elbow rotation).

Paul Arden · Post by **Paul Arden** » Tue Dec 27, 2011 1:52 am

OK thanks. I don't know where the hell it is now, but can you give me the equation again please?

Cheers, Paul

sms · Post by **sms** » Tue Dec 27, 2011 8:20 am

http://www.sexyloops.co.uk/cgi-bin....y254031

Paul Arden · Post by **Paul Arden** » Tue Dec 27, 2011 11:49 am

Got it - thanks Sakari.

Tell me, would there be a significant difference in air resistance upon the rod between the two (top vs bottom).

Thanks, Paul

Magnus · Post by **Magnus** » Tue Dec 27, 2011 12:29 pm

why would there be Paul? Rod has to be moving to create the load at the tip. Bottom hand applies a shorter lever - meets a smaller resistance - so might be easier to move it faster? better acceleration perhaps? But it has to move through a larger change of angle (greater distance.)

sms · Post by **sms** » Tue Dec 27, 2011 12:48 pm

The air resistance depends on rotation velocity and rotation center (which includes translation as long as rotational velocity is not zero).

With top hand still, bottom moving (compared to other way round)
case 1, set tip velocity: lower air resistance as the lever is essentially shorter so the moving hand must travel faster
case 2, set hand velocity for the moving hand: lower air resistance and lower tip velocity
case 3, set forces on hands: slightly more tip speed as the air resistance is smaller, but the hand is also moving considerably faster too

Paul Arden · Post by **Paul Arden** » Tue Dec 27, 2011 1:27 pm

So case 1. Same tip velocity, but the lower hand has to move faster. How would that feel? Lighter? How significant is air resistance on the rod during casting?

Cheers, Paul

sms · Post by **sms** » Tue Dec 27, 2011 2:05 pm

It would probably feel lighter as the force needed to overcome the air resistance is smaller. Unless our perception is fooled of the movement velocity, of course.

I would say rod's air resistance is not very significant in normal conditions (in high winds it feels like there is but I do not know). And the change from bottom hand to top hand is not much in terms of air resistance.

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