22 Apr 2005 16:01:29
Mike Sullivan
Engineering project - weight of the eight being carried

Every once in a while someone comes on RSR
looking for ideas for a school engineering project,
Master's degree or whatever.

If I happen not to be here, tell them to figure
out why some people seem to carry all the weight
of a carried eight, even while the eight is level.

Others seem to just hang on....

Mike




22 Apr 2005 23:45:30
Kieran
Re: Engineering project - weight of the eight being carried

Mike Sullivan wrote:
> Every once in a while someone comes on RSR
> looking for ideas for a school engineering project,
> Master's degree or whatever.
>
> If I happen not to be here, tell them to figure
> out why some people seem to carry all the weight
> of a carried eight, even while the eight is level.
>
> Others seem to just hang on....
>
> Mike
>
>

Because we're taller than you, Shorty!

-Kieran


23 Apr 2005 11:48:46
oarsman
Re: Engineering project - weight of the eight being carried

My daughter told me it's because she is the only one on the crew that
actually works. According to her, the others are there for balance,
she is carrying the entire boat.

Bob



24 Apr 2005 05:48:06
Bill Atkinson
Re: Engineering project - weight of the eight being carried

More seriously. how about:
1. Measuring the air resistance of various seated shells (singles,
pairs, fours, eights)?
2. Finding the size of the "added mass" of water laminated to the hull
of various moving shells thus increasing their virtual mass?
3. Finding the steady state lift and drag coefficients of various
available oar blade forms at various angles of attack?
4. Same as 3. but for moving (rotating) blades as the angle of attack
changes throughout the stroke?.
Should keep a bunch of grad atudents busy for a while.
Cheers,
Bill



24 Apr 2005 18:22:40
Kieran
Re: Engineering project - weight of the eight being carried

Bill Atkinson wrote:
> More seriously. how about:
> 1. Measuring the air resistance of various seated shells (singles,
> pairs, fours, eights)?
> 2. Finding the size of the "added mass" of water laminated to the hull
> of various moving shells thus increasing their virtual mass?

I've studied fluid- and aero- dynamics (granted a long time ago, and
have not every practiced it) and don't recall this ever being a part of
the equation(s) for the motion of a body through a fluid (e.g. an
aircraft or a boat). Isn't this "added virtual mass" you speak of
accounted for in the various forms of drag (pressure, surface, form,
wave, etc.)? I'm pretty sure it is. Maybe Carl knows for sure?

> 3. Finding the steady state lift and drag coefficients of various
> available oar blade forms at various angles of attack?

Yeah, that would be interesting as would #4.

> 4. Same as 3. but for moving (rotating) blades as the angle of attack
> changes throughout the stroke?.

Personally, I've given up on the kayaking project and will be doing some
sort of kinematic/kinetic analysis on rowing technique for my MS project....

-Kieran


24 Apr 2005 21:45:32
David Biddulph
Re: Engineering project - weight of the eight being carried

"Kieran" <kc_news@sonic.net > wrote in message
news:426BE3EA.8020103@sonic.net...
> Bill Atkinson wrote:
>> More seriously. how about:
...
>> 2. Finding the size of the "added mass" of water laminated to the hull
>> of various moving shells thus increasing their virtual mass?

> I've studied fluid- and aero- dynamics (granted a long time ago, and have
> not every practiced it) and don't recall this ever being a part of the
> equation(s) for the motion of a body through a fluid (e.g. an aircraft or
> a boat). Isn't this "added virtual mass" you speak of accounted for in
> the various forms of drag (pressure, surface, form, wave, etc.)? I'm
> pretty sure it is. Maybe Carl knows for sure?

Go back to your Fluid Mechanics textbook and look for "Lamb's coefficients".
--
David Biddulph
Rowing web pages at http://www.biddulph.org.uk/
and http://ourworld.compuserve.com/homepages/david_biddulph/




24 Apr 2005 23:22:40
Carl Douglas
Re: Engineering project - weight of the eight being carried

Kieran <kc_news@sonic.net > writes
>Bill Atkinson wrote:
>> More seriously. how about:
>> 1. Measuring the air resistance of various seated shells (singles,
>> pairs, fours, eights)?
>> 2. Finding the size of the "added mass" of water laminated to the hull
>> of various moving shells thus increasing their virtual mass?
>
>I've studied fluid- and aero- dynamics (granted a long time ago, and
>have not every practiced it) and don't recall this ever being a part of
>the equation(s) for the motion of a body through a fluid (e.g. an
>aircraft or a boat). Isn't this "added virtual mass" you speak of
>accounted for in the various forms of drag (pressure, surface, form,
>wave, etc.)? I'm pretty sure it is. Maybe Carl knows for sure?


I would defer to Leo Lazauskas as the real expert, on this particular
topic as on Australian Rules football.

However, when analysing the implications of boat speed cycling, I would
consider the mass of water within the boundary layers to be but weakly
coupled to the boat at typical stroke rates.

[For the lay reader: the boat drags along a cross-section of water, the
larger in volume the further you move to the stern, whose velocity is
distributed between zero & that of the boat. This volume of flowing
fluid affects the flow & pressure distribution in the surrounding water,
but IMHO it cannot be considered (in any way which would affect boat
velocity cycling) to be tied as a lump to the boat]
>
>> 3. Finding the steady state lift and drag coefficients of various
>> available oar blade forms at various angles of attack?
>
>Yeah, that would be interesting as would #4.
>
>> 4. Same as 3. but for moving (rotating) blades as the angle of attack
>> changes throughout the stroke?.


Couldn't agree more. I've been saying so for a long time, & noting that
we are dealing (as with kayaking) with a situation utterly different
from the normal fully-developed flow regimes for which lift & drag data
are well correlated. Nor is the evolving flow system surrounding an
oarblade throughout its stroke in any way simple to analyse. Nor,
indeed, have even steady-state lift & drag data been published (AFAIK)
for oar-like shapes operating at typical loadings & in that particularly
intractable (in analytical terms) zone at the free surface between air &
water.

That does not mean that analysis should not be attempted. But it does
mean that one should hesitate to draw firm numerical conclusions from
any analysis which makes convenient, but as yet untested, assumptions
regarding the flow, drag & lift interactions between an oar & water in
such circumstances.

None of which says that we should not seek to generate meaningful
experimental data & basic analyses for the peculiar regime in which we
choose to operate our oars. Indeed, I have on many occasions drawn
attention to the apparent folly of this being a highly-mechanical sport,
involving large energy losses in it generation of propulsive reactions
between oarblade & water, & yet coaches at large really don't have a
clue as to how an oarblade really works in the water, or how it might be
made to yield better results.

Funny old sport!

>
>Personally, I've given up on the kayaking project and will be doing
>some sort of kinematic/kinetic analysis on rowing technique for my MS
>project....


Then perhaps I have defined a profitable field for your new studies? ;^)

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)



25 Apr 2005 02:03:54
Kieran
Re: Engineering project - weight of the eight being carried

Carl Douglas wrote:
> Kieran <kc_news@sonic.net> writes
>
snip
>
>
> Then perhaps I have defined a profitable field for your new studies? ;^)
>
> Cheers -
> Carl

I'm not saying it wouldn't be profitable, but it's not really in my area
of study. I've moved from pure mechanical engineering to biomechanics
(e.g. kinesiology - kinematics/kinetics of human motion, muscle
physiology, etc.). While the hydrodynamics of an oar (or kayak paddle)
are important for what I do, they are only so in a related sense. Just
the force at the handle is more useful/interesting/important to
biomechanical problems than the actual hydrodynamics that account for
the force (although I am interested in it and would love to do such a
project, but I need to focus my efforts elsewhere for the time being).

I bet if you dug around some of the journal databases, you could find
some research done on the lift of kayak paddles. Too much specific
design has gone into those "wing" sprint kayak blades, to not have some
research behind their design (I would *think*... I suppose it could just
be a trial/error design process for them, too.)

-Kieran


25 Apr 2005 05:26:01
Bill Atkinson
Re: Engineering project - weight of the eight being carried

Carl:
Your usual thoughtful reply.
Good description of the phenomenon of "added mass".
I think in the case of the shell speed curve (not the steady sate
average) that the added mass may be significant in making calculations
on the boat's instantaneous accelerations as the augmented shell mass
is urged forcefully back and forth by the rower's feet.
I was warned of the effect of added mass by Prof. Douglas Carmichael of
MIT several years ago. I believe it is taken into account in the
acceleration and deceleration of large ships.
Best regards,
Bill



25 Apr 2005 05:46:30
Bill Atkinson
Re: Engineering project - weight of the eight being carried

David:
I have Lamb's "Hydrodynamics" (6th Ed., 1932) and can make no sense
whatever of his mathematics on inertial effects; the wages of not
having passed beyond differential equations at university years ago.
Of course, in his own text, Lamb's coefficient is not in the index as
such.
Perhaps a brief description of Lamb's coefficientss?
Bill



25 Apr 2005 14:36:08
Carl Douglas
Re: Engineering project - weight of the eight being carried

Bill Atkinson <watkinson@compuserve.com > writes
>Carl:
>Your usual thoughtful reply.
>Good description of the phenomenon of "added mass".
>I think in the case of the shell speed curve (not the steady sate
>average) that the added mass may be significant in making calculations
>on the boat's instantaneous accelerations as the augmented shell mass
>is urged forcefully back and forth by the rower's feet.
>I was warned of the effect of added mass by Prof. Douglas Carmichael of
>MIT several years ago. I believe it is taken into account in the
>acceleration and deceleration of large ships.
>Best regards,
>Bill
>
Bill -
I suspect that for large vessels with slow accelerations this "added
mass" effect will be quite significant. My feeling is that for the kind
of velocity fluctuations involved with a rowing shell that would not be
so important, But I really would welcome Leo's more expert thoughts.

As for Lamb's coefficients, aren't these of more relevance to very low
Reynolds number situations (e.g. slow, viscous). Perhaps David can
enlighten us there?

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)



24 Apr 2005 20:38:30
Carl Douglas
Re: Engineering project - weight of the eight being carried

Kieran <kc_news@sonic.net > writes
>Bill Atkinson wrote:
>> More seriously. how about:
>> 1. Measuring the air resistance of various seated shells (singles,
>> pairs, fours, eights)?
>> 2. Finding the size of the "added mass" of water laminated to the hull
>> of various moving shells thus increasing their virtual mass?
>
>I've studied fluid- and aero- dynamics (granted a long time ago, and
>have not every practiced it) and don't recall this ever being a part of
>the equation(s) for the motion of a body through a fluid (e.g. an
>aircraft or a boat). Isn't this "added virtual mass" you speak of
>accounted for in the various forms of drag (pressure, surface, form,
>wave, etc.)? I'm pretty sure it is. Maybe Carl knows for sure?

I would defer to Leo Lazauskas as the real expert, on this particular
topic as on Australian Rules football.

However, when analysing the implications of boat speed cycling, I would
consider the mass of water within the boundary layers to be but weakly
coupled to the boat at typical stroke rates.

[For the lay reader: the boat drags along a cross-section of water, the
larger in volume the further you move to the stern, whose velocity is
distributed between zero & that of the boat. This volume of flowing
fluid affects the flow & pressure distribution in the surrounding water,
but IMHO it cannot be considered (in any way which would affect boat
velocity cycling) to be tied as a lump to the boat]

>
>> 3. Finding the steady state lift and drag coefficients of various
>> available oar blade forms at various angles of attack?
>
>Yeah, that would be interesting as would #4.
>
>> 4. Same as 3. but for moving (rotating) blades as the angle of attack
>> changes throughout the stroke?.

Couldn't agree more. I've been saying so for a long time, & noting that
we are dealing (as with kayaking) with a situation utterly different
from the normal fully-developed flow regimes for which lift & drag data
are well correlated. Nor is the evolving flow system surrounding an
oarblade throughout its stroke in any way simple to analyse. Nor,
indeed, have even steady-state lift & drag data been published (AFAIK)
for oar-like shapes operating at typical loadings & in that particularly
intractable (in analytical terms) zone at the free surface between air &
water.

That does not mean that analysis should not be attempted. But it does
mean that one should hesitate to draw firm numerical conclusions from
any analysis which makes convenient, but as yet untested, assumptions
regarding the flow, drag & lift interactions between an oar & water in
such circumstances.

None of which says that we should not seek to generate meaningful
experimental data & basic analyses for the peculiar regime in which we
choose to operate our oars. Indeed, I have on many occasions drawn
attention to the apparent folly of this being a highly-mechanical sport,
involving large energy losses in it generation of propulsive reactions
between oarblade & water, & yet coaches at large really don't have a
clue as to how an oarblade really works in the water, or how it might be
made to yield better results.

Funny old sport!

>
>Personally, I've given up on the kayaking project and will be doing
>some sort of kinematic/kinetic analysis on rowing technique for my MS
>project....

Then perhaps I have defined a profitable field for your new studies?
;^)

Cheers -
Carl
--
Carl Douglas Racing Shells -
Fine Small-Boats/AeRoWing low-drag Riggers/Advanced Accessories
Write: The Boathouse, Timsway, Chertsey Lane, Staines TW18 3JY, UK
Email: carl@carldouglas.co.uk Tel: +44(0)1784-456344 Fax: -466550
URLs: www.carldouglas.co.uk (boats) & www.aerowing.co.uk (riggers)



26 Apr 2005 15:27:55
Walter Martindale
Re: Engineering project - weight of the eight being carried



Mike Sullivan wrote:
> Every once in a while someone comes on RSR
> looking for ideas for a school engineering project,
> Master's degree or whatever.
>
> If I happen not to be here, tell them to figure
> out why some people seem to carry all the weight
> of a carried eight, even while the eight is level.
>
> Others seem to just hang on....
>
> Mike
>
>
How can so many people misread the question? Or do "we" all just go off
on our favourite tangents by default?
Mike's asking about the 8+ on shoulders being carried about....
W



26 Apr 2005 13:41:29
Re: Engineering project - weight of the eight being carried


Kieran wrote:
> paul_v_smith@hotmail.com wrote:
> > Walter Martindale wrote:
> >
> >>Mike Sullivan wrote:
> >>
> >>>Every once in a while someone comes on RSR
> >>>looking for ideas for a school engineering project,
> >>>Master's degree or whatever.
> >>>
> >>>If I happen not to be here, tell them to figure
> >>>out why some people seem to carry all the weight
> >>>of a carried eight, even while the eight is level.
> >>>
> >>>Others seem to just hang on....
> >>>
> >>>Mike
> >>>
> >>>
> >>
> >>How can so many people misread the question? Or do "we" all just go
> >
> > off
> >
> >>on our favourite tangents by default?
> >>Mike's asking about the 8+ on shoulders being carried about....
> >>W
> >
> >
> > Kiernan and Oarsman gave adequate answers up front, and since
> > "engineering project" was mentioned it seemed to lend free reign to
> > topic expansion. [:o)
> >
> > Here is another: Why can two people take a quad off the rack
easier
> > than 4?
> >
> > - Paul Smith
> >
>
> Here's another project (maybe sociology, not engineering)...
>
> Why do *so* many people mistake my name for Kiernan, when it's just
> Kieran? (I'm not offended Paul, it happens way too often for that).
I
> mean here, it's even spelled out for you... no mis-pronouncing or
"oops
> I didn't hear you right".
>
> Even relatives of mine (granted through marriage) say Kiernan instead
of
> Kieran. :-( Just ONE 'n' thanks! ;^)
>
> Honestly, I've never met anyone with the first name of Kiernan...
EVER.
> Further, I've only *heard* of people with the LAST name of Kiernan.
I
> have, however, met people with either their first or last name as
Kieran.
>
> Maybe I should just go with the Gaelic spelling...
>
> -Ciar=E1n
> (a much prettier word to look at, IMO) :^)

Well, it's probably a good thing I didn't try to pronounce it in front
of you... [;o)

My excuse? I'm jsut a terrible typsit! Darnnit, or is that Damnit!

Cheers, Kieran!

- Paul (really easy name) Smith



26 Apr 2005 15:37:00
Re: Engineering project - weight of the eight being carried


Mike Sullivan wrote:
> <paul_v_smith@hotmail.com> wrote in message
>
> >
> > Here is another: Why can two people take a quad off the rack
easier
> > than 4?
>
> Good one, or 2 people can roll an eight over in slings easier than 8!
>
> Mike

Maybe this is part of the issue when it comes to why it is so difficult
to get an 8+ to go as fast as is should, compared to a 2x. [;o)

Surely one of the engineers of the group should have the factors for
"individual share of drag" differences between boats. It would be okay
to consider all boats "optimized" in this case.

- Paul



26 Apr 2005 22:07:39
Leo Lazauskas
Re: Engineering project - weight of the eight being carried

Carl Douglas <Carl@carldouglas.co.uk > wrote in message news:<fPp1TdG2W$aCFwQh@rowing-cdrs.demon.co.uk>...
> Kieran <kc_news@sonic.net> writes
> >Bill Atkinson wrote:
> >> More seriously. how about:
> >> 1. Measuring the air resistance of various seated shells (singles,
> >> pairs, fours, eights)?
> >> 2. Finding the size of the "added mass" of water laminated to the hull
> >> of various moving shells thus increasing their virtual mass?
> >
> >I've studied fluid- and aero- dynamics (granted a long time ago, and
> >have not every practiced it) and don't recall this ever being a part of
> >the equation(s) for the motion of a body through a fluid (e.g. an
> >aircraft or a boat). Isn't this "added virtual mass" you speak of
> >accounted for in the various forms of drag (pressure, surface, form,
> >wave, etc.)? I'm pretty sure it is. Maybe Carl knows for sure?
>
> I would defer to Leo Lazauskas as the real expert, on this particular
> topic as on Australian Rules football.

Forget my expertise on Aussie Rules! This season has been a disaster
for all so-called experts.

I had a look at including added mass after seeing that Bill Atksinson
was using it in his model, but it turned out that the contribution to
the drag is very small - under 1/2%. I haven't got my books with me at
the moment, but I think there is something in Newman's
"Hydrodynamics". The effect is important for slow, bluff full-bodied
shapes like myself and some cargo vessels, but is very small for
slender bodies such as rowing shells and Ally McBeal.

Leo.


27 Apr 2005 05:05:35
Bill Atkinson
Re: Engineering project - weight of the eight being carried

Thanks Leo.
I'll stop worrying about added mass in shells.
Having the capability in the model (layer thickness x wetted surface x
density) allowed me easily to solve the asynchronous rowing problem.
Increasing the added mass essentially to infinity (without altering the
displacement) effectively fixes the footboard and reduces the shell
speed curve to a horizontal line.
Asynchronous rowing turned out not to be a good thing.
Bill



27 Apr 2005 14:45:44
Jon Anderson
Re: Engineering project - weight of the eight being carried

Bill Atkinson wrote:
> Asynchronous rowing turned out not to be a good thing.

You're stating once and for all that caterpillar-style rowing is no good?
This may help win some arguments at the bar.

Jon
--
Durge: jon@durge.org http://users.durge.org/~jon/
OnStream: accounts@rowing.org.uk http://www.rowing.org.uk/

[ All views expressed are personal unless otherwise stated ]


27 Apr 2005 15:54:34
Ewoud Dronkert
Re: Engineering project - weight of the eight being carried

"Jon Anderson" <jon@durge.org > wrote:
> Bill Atkinson wrote:
>> Asynchronous rowing turned out not to be a good thing.
>
> You're stating once and for all that caterpillar-style rowing is no good?
> This may help win some arguments at the bar.

But how?

"Hey man, Bill Atkinson says so!"
-"Right. Your turn to get beer, mate."