Re: Technical: heels on foot plate?


KC wrote:
paul_v_smith@xxxxxxxxxxx wrote:

I think that Mikes example of just sitting and rolling back and forth
on the seat explains that nicely. As you draw yourself toward the
catch, which happens very shortly after the release the hull
accelerates forward relative to our body mass, since the hull + drag is
a fraction of our body mass.

Careful, don't go adding force and mass. Can't be done. ;^)


Here is where Mikes exercise gets tricky, since the hull drag is not
fixed, the direction which we move our body mass the most quickly
realtive to the hull, will be the direction the COM of the system
begins to move. i.e. move through the recovery very quickly and then
the "oarless drive" slowly, the system will be moving slowly
sternwards.

I think you have that backwards. Oars out and above the water, quick

I know you think that, due to your earlier answer to Mikes question.
Think about it some more, and I'm sure Mike will tell us what he
thinks/knows eventually. [;o)

recovery, slow "drive" and you'll inch your way in the direction the bow
points, not sternward. On the quick "recovery" you surged the hull
forward. Then, you ease to a stop at the sternstops, and at the same
time stop some/all forward movement of the hull. Then, ever so
slightly, you slowly extend the legs. With almost zero acceleration of
your body as you move toward bow, there is almost zero force applied to
the boat, so the friction between boat and water is enough to keep the
hull almost stationary, it's enough to counter the small force you're
applying to the foot stretchers. So, the boat moved forward on your
"recovery" and didn't move (not much anyway) on the "drive", so you've
got a net displacement in the bow-ward direction.

We'll have to see I guess. The reason for this counter-intuitive
result is that with the rapid recovery there was a greater drag on the
hull than on the slow drive, since the forces must be equal during each
phase there was more force produced in the sternward direction causing
sternward momentum to be established that will exceed what will be
established in the slow drive bow-ward direction. Netting sternward
system velocity.

- Paul Smith

Do both equally and the system will be stationary.

If you're perfect. ;^)

-Kieran

.

Relevant Pages

  • Re: Technical: heels on foot plate?
    ... I did the "no oar, sliding" exercise today and advanced the ... exactly as I had described (opposite the direction of the rapid hull ... the stern (rushing the body sternward) and then 3 feet back to the bow ...
    (rec.sport.rowing)
  • Re: Technical: heels on foot plate?
    ... I did the "no oar, sliding" exercise today and advanced the ... exactly as I had described (opposite the direction of the rapid hull ... the stern (rushing the body sternward) and then 3 feet back to the bow ...
    (rec.sport.rowing)
  • Re: Technical: heels on foot plate?
    ... I did the "no oar, sliding" exercise today and advanced the ... exactly as I had described (opposite the direction of the rapid hull ... the stern (rushing the body sternward) and then 3 feet back to the bow ...
    (rec.sport.rowing)
  • Re: Technical: heels on foot plate?
    ... So explain again how if the hull is still accelerating after a good ... a fraction of our body mass. ... Perhaps an example from another water sport will serve to help. ...
    (rec.sport.rowing)
  • Re: Technical: heels on foot plate?
    ... accelerates forward relative to our body mass, since the hull + drag is ... a fraction of our body mass. ... Oars out and above the water, quick recovery, slow "drive" and you'll inch your way in the direction the bow points, not sternward. ...
    (rec.sport.rowing)