Re: Amount of span


<paul_v_smith@xxxxxxxxxxx> wrote in message
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On Mar 11, 11:19 am, "Mike Sullivan" <s...@xxxxxxxxxxxxxxxxxxxxx>
wrote:
<paul_v_sm...@xxxxxxxxxxx> wrote in message

news:251280f4-2cd4-4145-ab01-3e3715d0850d@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
On Mar 10, 8:06 pm, wmart...@xxxxxxxxx wrote:


snip

The adaptive rowers you have worked with, amputees or
paraplegic?

Paraplegic, i.e. a genuine "Arms Only", rather than the type that can
stand with crutches.

Does he/she have to be strapped on a backed chair, or can he/she
sit up by themselves.? A guy that wanted to try rowing said he
couldn't kayak because he couldn't really sit up easily.

I have an old catamaran type single that is very stable but makes
me nervous to seat belt someone into a boat.


6:42 at 60+, you should get the guy to an Indoor regatta, sounds like
just his type of thing.
I recognize the story I think. This is the guy that also puts the oar
on the other side of the pin for his backing session?

Yes, and he's gotten funded to Boston a few times, done well there.

When I stuck him in a properly rigged wherry one time, he thought
it was too difficult, though.


I need clarification on some points of your conclusion for the extreme
example.

I don't follow that the arc would decrease, why would that be?
And what do you mean by "flattening"? (Relative to the angle the the
water?)

This has been brutal. I drew a color pic then couldn't make my scanner
work or find the cable for my camera.... damn. It's easier to see than
for me to describe.

geometrically, the length of the arc is the circumference of the circle
described by a particular radius. The length of the pull in the center
of the boat is fixed, from full reach to finish. As you push the radius
away from this straight line, the angles decrease and the catch goes
in the water at a shorter relative distance to the boat (slightly closer
to the middle) and exits a bit shorter.

What is a "Standard sized athletic rowing body"?

5 ft 9to 6 ft 3.

What is "working way through the pin"? That is something that changes
dramatically with different body type alone, doesn't it? It's usually
described as where the hips are in relation to the pins, but would
seem to be more related to the catch angle achieved based on a
combination of variables. I've seen many rowers try to get their seat
"through the pin" and then end up with no room at the finish with
standard rigging (160/88), it doesn't do much for their performance.

right, but with the second rig, the handles are finishing farther from the
body.
If you shift the footboards to stern to have the handles finish closer to
the
body, you now move your whole drive through the pin.

What if the span were only increased to 165cm instead of 180cm. Or
even 170cm. Neither of those would alter the finish position much, or
at all with a small change in stretcher position, and both would allow
more catch angle.

It affects the finish position more critically than the catch. Everything
starts at the finish as far as body and rig. There is an ideal mechanical
advantage for each body that starts at full extension, and ends with
the the oar handles close to the tits.

The basic problem with the additional outboard with no other change is that
your
leverage point is very slightly not as far down the course. there is an
advantage
I believe in flatter arc, but the shorter arc is a bigger disadvantage.

I'm not doing well at this, I need to draw a pic.

By trying out some very different rigging dimensions, I'm finding that
what seems to be the "common understanding" (conventional wisdom)
doesn't really hold up all that well. i.e. narrow spans increasing
arc length Vs Wide spans decreasing it. The specific cases had to do
with maintaining overlap with a narrow span Vs Maintaining inboard
with a wider span, actual results were nearly opposite of what is
often cited.

I find it helpful to have a large sheet of paper and a straw. Draw out
the dimensions of the riggers and boat on the paper, with differing
placements
of the pin. The straw is the oar. draw the collar on the straw at
approximate dimensions then play with the arcs and you can see that
with a wider spread with same reach, your catch goes in the water closer
to the middle of the shell. This is borne out by the feel of the stroke
which will be lighter on the drive.



.

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