'Thunking' at the release: does it matter?

'Thunking' at the release: does it matter?

Post by Carl » Sun, 25 Nov 2012 03:13:11



Quote:

>> To be fair to Xeno, he does spend much more time on what they are doing right (IHHO), and he does say that any 'imperfections' he sees are very minor

>> and that since they won by a landslide, who's he to say it is wrong anyway.

>> TBH, the purpose of these videos isn't really to critique his subjects, but to sell his own online video analysis service, largely aimed at people who really could do with going back to 'orthodox' basics.

>> And what better way than highlighting the very best in the world.

>> Kit

> Well... Xeno accomplished great things in a boat and yes, he's marketing his online video analysis service.

> The problem with "orthodox" basics is that it results in yet another generation of rowers or scullers who are indoctrinated to believe that you have to have characteristic A B or C before you're going to be fast.

> and if you examine the people they're often using as examples of "great technique", you'll find that they don't necessarily do what is being attributed to them, and the "commentator" either overlooks what they actually are doing with "they'd be even faster if..." when, in fact, it MIGHT be that they're faster because of the "unorthodox" thing they do..

> Case in point - I provided video of a coaching session to a coaching clinic once - for candidates to use in "how would you help these athletes improve" (not "what are they doing wrong").  One candidate said something along the lines of:
> Stroke opens her back too early and leans way too far out to port. Bow shoots her bum and rushes her slide, they both break their knees too early and they're both pausing at the catch.

> Later in the coaching session (also in the video) they'd fixed the timing at the catch, but the coaching candidate said at the end of his critique "They'll never go anywhere, who are they?"

> 1991 world champion and 1992 Olympic champion W2- Heddle and McBean during a training session in April 1992.

> Drysdale - blades go too deep according to orthodoxy.  Sullivan - too short (well, he is probably a 6 sigma for height of olympic champs).  Cohen - too short (five sigma?).

> But the big question is - why ARE they fast?

Nah, Walter!

You & I know that the bigger (but unspoken) question from that part of
the orthodoxy which can actually has the eyes to see that the great
performers don't conform to style diktat is: "How DARE they go so fast?"

What we also know is that those facts which don't fit the official grand
model are aberrations, fit only to be ignored.

What passes widely as Rowing Theory thus remains largely in the
Phlogiston era, or maybe in those times when it was thought that health
could be improved by being bled & malaria was due to "bad air".

Those convinced that Mahe would have gone faster if he'd gone less deep
have only to swallow their pride, get into a boat & carefully evaluate
the effect of varying blade depth while pulling at the same intensity.
I think they'd be very surprised to discover that, for the same work
rate, they had a speed-to-depth relationship rather like this (view only
in plain text):

  |                     .    .
  |                  .            .
  |                 *                .
  |               *                    .
  |              .
S|                                        *
P|            *                               .
E|                                                .
E|          *
D|
  |        *
  |       .
  |      .
  |     .
  |    .
  |   .
  |  .
  | .
  |.
  .__________________________________________________
  ^             ^         ^          BLADE DEPTH
  |             |         |
  |             |         |< Blade going ~7cm under (say)
  |             |
  |             |< Blade top at water surface
  |
  |< Blade bottom at water surface (zero speed)

(NB - not to scale but for indicative purposes only)

It is, of course, so much easier for those so inclined simply to ignore
this, to not experiment & to keep on asserting that _any_ amount of
looming must instantly impose unacceptable drag penalty - however
irrational that might be to anyone prepared to give it a moment's thought.

But those same folk will either not understand, or choose not to do so,
that we don't mean go instantly deep but that the blade depth should
pass through a maximum around the mid-stroke stall phase.

Cheers -
Carl

--
Carl Douglas Racing Shells        -
     Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
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'Thunking' at the release: does it matter?

Post by James H » Tue, 27 Nov 2012 17:55:07

So when setting up the boat I have never understood the orthodoxy of letting the blade flat where it naturally sits - with about 2" showing!

My sculling partner is taught the square out and no blade depth, I am trying to get deeper and feather out - which leads to some interesting on water discussions!

 
 
 

'Thunking' at the release: does it matter?

Post by s.. » Tue, 27 Nov 2012 22:53:23

Quote:

> So when setting up the boat I have never understood the orthodoxy of letting the blade flat where it naturally sits - with about 2" showing!

> My sculling partner is taught the square out and no blade depth, I am trying to get deeper and feather out - which leads to some interesting on water discussions!

James,

Based on personal experience alone, I "think" blades just below the surface and a straight pull. During easy SS rowing, they stay there.  But if my upper body is relaxed and I put some pressure on the blades, they sink to the level Carl recommends.

Steven M-M

 
 
 

'Thunking' at the release: does it matter?

Post by Rebecca Caro » Fri, 04 Jan 2013 11:38:34

Quote:

> So when setting up the boat I have never understood the orthodoxy of letting the blade flat where it naturally sits - with about 2" showing!

James

I used to sell Dreher oars and sculls.  They are the ONLY oars that sit naturally in the water with the top edge of the spoon at the water's surface when stationery.
IMO this is the correct place.
Think about the additional effort needed to hold the oars under the water during the stroke.

Could that energy be better used elsewhere e.g. making more power?

 
 
 

'Thunking' at the release: does it matter?

Post by davies... » Fri, 04 Jan 2013 18:51:01

Quote:

> I used to sell Dreher oars and sculls.  They are the ONLY oars that sit naturally in the water with the top edge of the spoon at the water's surface when stationery.

> IMO this is the correct place.

> Think about the additional effort needed to hold the oars under the water during the stroke.

> Could that energy be better used elsewhere e.g. making more power?

Would it not be better if they sat naturally below the surface so that you got the benefit of more efficiency without having to hold them down?
 
 
 

'Thunking' at the release: does it matter?

Post by Carl » Fri, 04 Jan 2013 21:55:56


Quote:

>> So when setting up the boat I have never understood the orthodoxy of letting the blade flat where it naturally sits - with about 2" showing!

> James

> I used to sell Dreher oars and sculls.  They are the ONLY oars that sit naturally in the water with the top edge of the spoon at the water's surface when stationery.
> IMO this is the correct place.
> Think about the additional effort needed to hold the oars under the water during the stroke.

> Could that energy be better used elsewhere e.g. making more power?

Rebecca -

You presuppose that "level with the surface" is for some unknowable
reason the ideal depth of immersion.  Yet every top sculler digs deeper
than that, & fluid dynamics (if we care to listen to real science) tells
us that going deeper has to be more efficient for boat propulsion.

We didn't have this particular branch of orthodoxy before the
Dreissigacker brothers introduced cleavers whose top edge lies roughly
parallel with the water surface when the blade is just immersed.  Only
then did we start to hear coaches presuming aloud that this had to be
the correct depth, whereat it morphed into tablets of stone.  Now we
have good rowers who go deeper being told that this is making them
slower - unscientific balderdash from folk who have never actually tried
to evaluate the effect of blade depth on propulsion & performance.

So what do we know about the effect of blade depth?  Well I covered this
in graphical form with a bit of ASCII art a few weeks back, & someone
will dig that out for us, no doubt.

1.  If we barely scrape the water surface we get no load & no propulsion.
2.  If we take a shallow stroke it is easy on us, washy & doesn't move
the boat very well.  And we've all done that at the end of a
particularly arduous (for us) crew outing I'm sure.
3.  If we go to your preferred depth the stroke is more effective but
feels heavier/harder - because there's more resistance from the water to
our attempt to push blade through water.
4.  But for some unfathomable reason we are then told, wholly without
scientific proof or experimental evidence, & in conflict with the
evidence of some great scullers, that if we were to go any deeper we
would immediately be incurring penal losses in performance.  Apparently
this will be due to the deadly "looming" - due to drag of oar-shaft in
the water.

No, oarmakers do not have some magical insights denied to the rest of
rowing which lead them to make oars which float just near the surface
when immersed square.  What they hear is that rowers believe oars should
not go deeper than this, so they make us oars which satisfy that desire
- no point in arguing with the market.

Now the reasons we coach crews to row to a certain depths are:
1.  The need to have some reference point when getting a crew of
disparate folk to do at least the same thing - doing the wrong thing but
doing it all together always brings better crew coordination & a better
immediate result than some of the crew doing the "right" thing & others
doing something else.
2.  Most rowers don't know what's going on in the water around the
blade, won't examine the evidence before them & cling instead to
frequently parroted fictions.

The most common reason offered, other than "that's where they float so
that's where we should row them", is that some have a dread of the oar
shaft getting wet.  Somehow they suppose that immersion of a few
centimetres of this thin carbon tube must be imposing a large &
immediate drag penalty, whereas at the same time they presume that the
most inboard bit of the blade is valuable & necessary - even though
these 2 will be moving at much the same speed in the water, & probably
moving _astern_ too, certainly during the mid-stroke stall.

Until we are prepared to deal with blade dynamics in a less fluffy &
irrational manner, & actually start to ask serious questions about "why
do you tell me this" & "what's really happening there" we are never
going to get full value out of each stroke.

Clearly it is irrational to suppose, & even more so to assert, that the
steady increase in propulsive efficiency which we all observe as we go
from barely scraping the water to just fully immersed does not, &
cannot, suddenly go into reverse if we go a few millimetres deeper
still.  All the evidence of reduced puddle frothiness & the sense of
increased resistance ought to tell us that deeper, up to some as yet
undefined point, has to be more efficient.

So let's be bolder this New Year & experiment with blade depth but, if
in a crew, please do it all together.  And remember that rowing is not
about "getting the blade through".  The art & science of boat propulsion
is to row in such a way that we move the blade past the water, not use
the blade to move water past the boat.  In this we should be honest in
recognising that when we move the boat with oars we will also move water
the other way, but let's also be intelligent & understand that the most
efficient way of doing this is to move the largest possible amount of
water by the smallest possible amount, not to create puddles which
comprise compact zones of ***, fast-moving & highly-aerated
turbulence.  Remember - your puddle contains all the work you did which
did _not_ move the boat.

Cheers -
Carl

--
Carl Douglas Racing Shells        -
     Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write:   Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find:    tinyurl.com/2tqujf


 
 
 

'Thunking' at the release: does it matter?

Post by Carl » Sat, 05 Jan 2013 21:59:15


I managed to make a bit of a confusing mess in failing to properly edit
my own words before pressing "send":

Quote:
> Clearly it is irrational to suppose, & even more so to assert, that the
> steady increase in propulsive efficiency which we all observe as we go
> from barely scraping the water to just fully immersed

please delete this:

Quote:
> does not, &
> cannot,  suddenly go

& replace by this:

    goes

Quote:
> into reverse if we go a few millimetres deeper
> still.  All the evidence of reduced puddle frothiness & the sense of
> increased resistance ought to tell us that deeper, up to some as yet
> undefined point, has to be more efficient.

> So let's be bolder this New Year & experiment with blade depth but, if
> in a crew, please do it all together.  And remember that rowing is not
> about "getting the blade through".  The art & science of boat propulsion
> is to row in such a way that we move the

2nd correction:

    boat (not the blade)

Quote:
> past the water, not use
> the blade to move water past the boat.  In this we should be honest in
> recognising that when we move the boat with oars we will also move water
> the other way, but let's also be intelligent & understand that the most
> efficient way of doing this is to move the largest possible amount of
> water by the smallest possible amount, not to create puddles which
> comprise compact zones of ***, fast-moving & highly-aerated
> turbulence.  Remember - your puddle contains all the work you did which
> did _not_ move the boat.

Sorry about hasty proof-reading :(

Carl

--
Carl Douglas Racing Shells        -
     Fine Small-Boats/AeRoWing Low-drag Riggers/Advanced Accessories
Write:   Harris Boatyard, Laleham Reach, Chertsey KT16 8RP, UK
Find:    tinyurl.com/2tqujf