Sculling

[caustic]

Squaring early or late is not really an issue. An easy, more gradual roll up can help with being more relaxed at the entry position, but in a head wind it is better to hold the feather longer.

We now know that during the early phase of the stroke, lift makes the blades most efficient: no slip and maybe some positive pull towards the finish. You need the blades square and in the water to get max lift. It is, of course, not possible to instantly cover the blade, but the most effective catch is quick, even if the application of power to the covered blade can be momentarily delayed.

No, we don't. Lift is, at best, a minor effect on the blade. How, exactly, can lift provide any kind of force when at the instant of the catch, the blade is not moving. Answer, it can't, because when the blade is not moving, lift cannot exist.

If lift was truly pulling the blade ahead during hte drive, then if you drop your blades straight into the water, the boat would be pulled forward. This does not happen. What happens is that you eat your handles.

The best way to see this is in frame-by-frame video of your entry. How far into the drive does it take you to cover your squared blade? If you are already at ¾ by the time you’ve fully engaged you’ve lost much efficiency. One reason it is a good idea to set the blades with small movements of the shoulders and arms is that it means you can start the leg drive with a fully engaged blade.

So a quick, squared entry taken at the last moment of the recovery is “longer” and takes advantage of lift forces.

[/quote][/quote]

A quick entry is better because the sooner you have it buried, the less it will slip. Water is heavy - and your blade is pushing against a LOT of water. Volumetrically, at least 10 gallons per blade are affected by the blade; and one gallon weighs 7lbs. the lion's share of work is literally leverage. More length prying means more acceleration each stroke.

[Steven M-M]

Caustic is right that lift requires pressure on the handles. There is also some uncertainty as to the extent that lift forces contribute to blade efficiency and room for analysis in how technique can best take advantage of lift. But lift forces are a meaningful part of the equation and describing the work of the blade as only “pushing” against the water—drag—is incomplete. If Caustic’s blades are covered and square, like Xeno’s, while still fully compressed then he has achieved the same ends by different means. He will get the benefits of lift, even if he doesn’t believe in it.

[Guy Noir]

Volumetrically, at least 10 gallons per blade are affected by the blade; and one gallon weighs 7lbs.

I know I'm being somewhat anal here...but a US gallon weighs 8 lbs and an Imperial gallon weighs 10 lbs

[caustic]

Volumetrically, at least 10 gallons per blade are affected by the blade; and one gallon weighs 7lbs.

I know I'm being somewhat anal here...but a US gallon weighs 8 lbs and an Imperial gallon weighs 10 lbs

It's the rare tare-bushel gallon .

[caustic]

Caustic is right that lift requires pressure on the handles. There is also some uncertainty as to the extent that lift forces contribute to blade efficiency and room for analysis in how technique can best take advantage of lift. But lift forces are a meaningful part of the equation and describing the work of the blade as only “pushing” against the water—drag—is incomplete. If Caustic’s blades are covered and square, like Xeno’s, while still fully compressed then he has achieved the same ends by different means. He will get the benefits of lift, even if he doesn’t believe in it.

ultimately, the lifting force is minimal when the blade velocity with relation to the water is minimal. No matter how fast you catch, the whole purpose of the catch is to accelerate the blade in the opposite direction of the velocity of that boat. If you pause at the catch - the blades are moving forward at, say, 3 m/s. When you catch, they are travelling at 0m/s. When you pull through, because the boat is being accelerated, they will, at best, be moving sternward at some velocity very much less than even a 10th of 3m/s.

A good catch is easy to spot, just looks (and hear) for three things - firstly, a symmetrical entry splash, and secondly a dark puddle, and thirdly a quiet entry.

A lot of folks mistakenly assume that rotational velocity can be used in a lift equation without any kind of detriment - but this is not the case. Just because the blade is transcribing an arc at a particular rotational velocity, that velocity is not directly equivalent to a linear velocity. As an example, think of a rolling tire, and then a point fixed on that rolling tire. The tire itself will have a linear velocity in a particular direction. But the point on that tire is actually constantly changing its linear velocity - from 2x the tire's forward velocity to 0x. If we were to affix a wing on that point on the tire, would we then logically conclude that obviously it's the lift on the wing that is propelling the tire, even somewhat? Of course not.

When taking this parallel over to a rowing arc, we can think of the boat+ oar itself transcribing the linear line of velocity, and the oar blade being a fixed point on part of an arc (a "virtual" tire). The rower takes the blade going at 1x forward speed, and accelerates it in the opposite direction to 0x speed, and then tries to accelerate it to the stern. In reality, the oar doesn't move too much - you can see it displaces from it's entry by about a foot - and the boat benefits from increased velocity.

But nowhere in that situation is lift a major contributing factor; the initial, primary condition required to generate lift - i.e. a linear velocity element of appreciable magnitude - is never satisfied.

As another analogy, if I throw a brick, is the lift generated from it being thrown keeping it aloft, of the fact that I imparted a very large initial force on it, accelerating it to a high velocity, and that it is taking much longer for gravity to pull it back down? I think that anyone would agree that in that scenario, the effect lift is having on the brick is essentially nil. If I were to throw the same brick in a perfect vacuum and with the same force, it would not travel appreciably farther.

The whole lift thing started out as a pseudo-scientific marketing dribble by oar manufacturers. While they like to use "lift" to determine how come a bigger blade slips less, they ignore the very glaring fact that, surprise suprise, a bigger blade face is harder to push through water.


finally, the very large, glaring hole in the whole lift theory is that it is not universal. Lift is a universal force, and that means that if I can find even one stroke out there that defies the lift theory, the lift theory is not correct. There exists one such stroke. your first one from a dead stop.

[1xsculler]

This is just the discussion between SMM and Caustic I was hoping for. It saves me PMing each of them seperately.

[Steven M-M]

Caustic – I cannot follow your argument, and, unfortunately, haven’t saved up enough box-tops for my decoder ring.

Look at the C2 website: http://www.concept2.com/us/oars/pursuit/blade_path.asp Lift forms in Phase 1 as the water flows from the tip of the blade towards the shaft. All it takes for lift is for the rate of flow to be different on the bow-side and stern-side face. It doesn’t take much to create lift. Somewhere in the middle of Phase 2 there is no differential flow, lift dissipates, and the blade starts slipping backward toward the start line, forming a puddle behind the blade.

[caustic]

Caustic – I cannot follow your argument, and, unfortunately, haven’t saved up enough box-tops for my decoder ring.

Look at the C2 website: http://www.concept2.com/us/oars/pursuit/blade_path.asp Lift forms in Phase 1 as the water flows from the tip of the blade towards the shaft. All it takes for lift is for the rate of flow to be different on the bow-side and stern-side face. It doesn’t take much to create lift. Somewhere in the middle of Phase 2 there is no differential flow, lift dissipates, and the blade starts slipping backward toward the start line, forming a puddle behind the blade.

Well, does lift keep a brick in the air for a longer appreciable time? Would you say that lift is the defining force in keeping that brick aloft?

As I said - oar manufacturers use it as marketing dribble. Using their animation, the blade enters the water at zero velocity, moves out, stops (stall phase), moves back, and is again at zero velocity with it leaves the water. The slippage will have water flow around both ends So, that means that, at best, maximal lift is generated at two points - neither of which are at the instant of the catch. So, lift cannot be a determining factor in establishing a good catch, because by the time it's at its maximal amount - i.e. at the midpoint between the catch and the stall, you should already have been fully caught and buried in the water. But we do need to pull hard, because we have to preserve our force equation. If we have to propel 200lbs of rower and boat in one direction at a certain speed, we need to move an equivalent mass sternward at a proportional speed.


Secondly, the pocket. Yet another thing that shows good rowing is not lift based. A well pulled oar will always form a depression on the convex side of the blade - the very same side that is supposedly also being pulled forward by lift. That depression will expose the blade to air, and thus means no water is flowing across it. No water flow across it = no lift on that area. So, how can a blade supposedly designed for lift be in any way using it when up to half the blade surface on that side is not even wet?

Another interesting thing when you pull - look at the concave side. You'll see a pile of water build up. That's a LOT of water. water's dense. When you try to move it, there's a force required to do so, and when you try to move a LOT of it, it requires a LOT of force. If lift were the primary force moving the boat, we'd not need to pull very hard to really get it moving.

[Steven M-M]

Brick - no; Frisbee - yes. I'll pass on the rest. Anyone else want to comment?

[lt.wolf]

You guys think far to much about it for me to get invloved..

[NashvilleSculler]

the blade enters the water at zero velocity, moves out, stops (stall phase), moves back, and is again at zero velocity with it leaves the water.

The oars do not enter the water at zero velocity; they enter the water at the velocity of the entire system (boat, oars and rower). If oars were to enter at zero velocity then the whole system would be at zero velocity (boat and rower) which we all know is not the case. The boat, oar and rower continue to move forward at the entry and the finish. Take a few strokes and hold the blades in the water at the catch or at the finish and you will see the system continues to move through the water even though the blades are not moving. A simple concept is when we hold water to stop the boat; we all know it continues to move through the water even though the oars are not moving in relation the boat. Just because the oars are not moving inside the system does not mean they are no moving in relation the earth (water). It is that movement of the entire system as a whole that causes water to move across the blade creating lift. That is the piece of this concept of lift that is missed, the blades enter the water with forward movement because the entire system in moving through the water.

[caustic]

the blades can move at just about any speed you can make them, because they are freely moving around hte pin. Were they fixed, you'd be absolutely correct. But the fact is that I can change the speed of my blades, and of myself, and of the boat.


Here's a simple and very easy experiment. Bring the boat up to speed. Pause at the catch, blades squared. Drop the blades into the water. What happens? you cannot have the blade, when buried, moving forward AND accelerating the boat at the same time. This defies physics. Give it a try. Get your boat up to speed, and have your athletes drop their blades in the water and hold them there. Does the boat accelerate? No. It comes to a screeching halt. Lift is not pulling it forward.

Ask what they feel when they drop their blades in - they do not feel their handles being pulled away from them, but instead being slammed back into them.

I'm always flabberghasted that lift proponents seem to ignore this very obvious, and easily verifiable fact.

This is why a symmetrical splash around a catch even exists - because the blade as it enters the water is not traveling at any speed with relation to the water. Just like that point on a rolling tire - even though the tire is traveling forward at a particular speed, every revolution, that point comes to a stop with relation to the ground. That's how rotational velocity is translated into linear velocity.


http://riversportokc.org/row/about/rowing-terms

conveniently, this shows a great photo of an oar patently showing a lack of directional flow across it's convex surface. No linear flow = no lift. You'll notice that you can see that not only is water moving around each side, but also over the top! And although we can't see it, it is also flowing up from the bottom. Flow that is conducive towards a lifting force cannot all move together from all the edges like that.

[abr]

http://riversportokc.org/row/about/rowing-terms

conveniently, this shows a great photo of an oar patently showing a lack of directional flow across it's convex surface. No linear flow = no lift. You'll notice that you can see that not only is water moving around each side, but also over the top! And although we can't see it, it is also flowing up from the bottom. Flow that is conducive towards a lifting force cannot all move together from all the edges like that.

Dude:

I'm not going to try to get at all the different things you've said that don't make any sense, but how can you possibly think it helps your case to get people to look at a photo of an oar that appears to be exactly perpendicular to the direction of travel, at the precise place where the proponents of lift agree that there is no lift?!

Try to find the same kind of shot, but near the catch or finish.

[Long'n Strong]

There is an excuse: ANOSOGNOSIA

http://pervegalit.wordpress.com/2010/06 ... re-stupid/

[John Ewans]

I have always been intrigued by this.

While wing paddles appear to be well established in the kayak world
they apparently need a significant change of technique (more
exaggerated vertical movements) in order to generate sufficient flow
across their, quite radical, aerofoil sections.

My questioning of whether there is a measurable similar effect in
rowing centre around the low speed the water must flow at over the
length of the blade and the fact that modern rowing blades are really
curved plates, rather than aerofoil sections. While I know that true
aerofoil sections are not necessary to generate lift if they are set
at an angle of attack to the fluid, this doesn't seem to the
mechanical system we have in rowing.

My doubts were really crystallised though when my crew mate Charlie
Hamlin held a blade in his hand and floated the head perpendicular to
a landing stage. He then vigorously pulled and pushed it away from and
towards himself with no sign of any sideways movement. If lift is not
discernable in that situation why would there be any measurable lift
generated during the rowing stroke?

I (genuinely) await enlightenment!


John Ewans