Rowing questions

While watching olympic rowing events I made some observations about which I am puzzled.

Everyone is using offset blades. The blades seem to have little or no camber in either direction and they all appear to have square tips.

The pairs boats pitch noticeably at each stroke. Seems to me that pitching motion would cause some unwanted drag. I suppose that we have to live with that on account of the needle like boats with so little forward bearing.

Most of the crews are using an elongated catch where the blade is very far forward of the outrigger pivot, maybe 45 degrees or more. At large angles like that there is a sideways force component that does not contribute much to forward motion. I did notice that when the boat went into sprint mode the cadence increased and the catch was shortened.

Any oarsmen or oarswomen out there who will comment on these curiosities?

One other observation is that the oarspersons are clearly superbly conditioned and skillful athletes. WOW!

 

I rowed quite a bit in my youth.

Your observations are spot on.

The only thing I can tell you is a race start is something I will never forget.

Things become more than silent, time hangs, the gun goes off and the sound level goes off the scale.

All hell breaks loose and the adrenaline levels explode.

The rest is shear torture that lasts for what seems like forever.

Enjoy the show.

 

You are correct that pitching of the boats is an issue.

First, there is the pitch induced by the movement of the rowers as
they slide forwards and backwards on their seats.
Then, there is the issue of squat which acts to sometimes increase
the pitching, and to reduce it during other parts of the stroke.

For example, at the start of the stroke rowers are farthest towards
the stern. That tends to lift the bow and drop the stern.
It is also the part of the stroke when speed is lowest, so dynamic
forces and moments are low.

Towards the end of the pull phase, the rowers are closer to the bow,
which tends to push the bow down and lift the stern.
But speed is higher than at the start of the stroke, so dynamic
forces tend to raise the bow back into a level position.

The boat moves fastest when rowers slide back towards the stern with
their oars out of the water. When they are sitting upright, the boat
is relatively level, but dynamic forces are highest and tend to raise
the bow a bit.

So, yes, it is important to balance the boat in the right way to
account for this.

There are a couple of short notes that I have put up that might be
of interest. See "Rowing Science Notes at:
http://www.cyberiad.net/rowing.htm

I have put up a short report on the effect of seat location in kayaks
(which also need to be "balanced") at:
http://www.cyberiad.net/kayak.htm
Getting it "wrong" might only cost a tiny amount in time, but in the
Olympics these are important.

And you are right about them being superb looking athletes. When I look
at the shoulders of some of the women rowers, my immediate thought is:
"Now there's a girl who could help a farmer bring in the harvest and
pull a tractor out of the mud."

Leo.

 

Thanks for the comments Leo. I notice that the Aussies are not doing too badly at this game. Perchance you had some input for the OZ boat intricacies and excellences.

 

Asymmetrical blades, compared to the older Macon style, are much easier to row with. One advantage is that they tend to set vertically naturally when you pull. Also, they oars need to be lifted less.

 

I had a minor involvement, but they were doing very well without me!

As for improvements to boats, well, there are no magic bullets that
will give athletes a great edge over their competitors. Knowing the
forces and moments that act on the various boat is just as important.

I'll probably sound very corny when I say that elite rowers get to
the Olympics through great determination and dedication, good parents
who got them to training when they were young, and a lot of luck in
avoiding injury.
If nerds like me save them 1/100th of a second, that must be balanced
against the thousands of hours of sweat and toil the athletes put in
during the 4 years prior to the event.

 

The blade designs have been developed with detailed analysis to give the maximum thrust. A flat blade is more efficient, and I have always wondered why they were curved in the first place, likely a marketing or styled design that gives the impression of better performance. Fluid mechanics over a paddle or or oar blade are not intuitively obvious. Most of the commercially available paddles for example are garbage, I even had a polite discussions with the founder of one of the largest kayak paddle makers about how they develop their blade design, without saying so, I realized they were completely clueless as to the reason paddle blades generate thrust. I saw no reason to explain to them the physics of fluid mechanics; no point in trying to teach a pig to sing, it will only frustrate you and annoy the pig.

Usually the most advanced levels of the sport however, there are a small group of people that know what they are doing when it comes to design. That is usually why what you see used in the Olympics are very different than what you can buy in sporting goods stores.

 

I can't argue with that!
Of all the areas of rowing I have looked at, oar analysis is the one where
outright ignorance and bs flies thickest and fastest.

Interestingly, there will be a paper presented at the 28th Symposium on
Naval Hydrodynamics in Sept. this year. Perhaps the French are contemplating a return to war galleys

 

Methinks that Leo is a bit modest. I agree that athletic dedication, plain old sweat, is the more decisive factor in contests involving strength and endurance. It can't hurt that the boat and its oars are optimized however.

I have wondered about my high zoot kayak paddle with all its sexy curves. My frequent paddling buddy is a scrawny woman. She insists that her Greenland style paddle is better than my CF beauty. Though I am twice as strong, she can stay with me while using that flat piece of ugly lumber. Damn, I'd hate to admit that she might be right about the paddle. (No man could entertain the thought that she might be the more skilled paddler.)

 

Help me to keep up here. By curved do you mean spooned (lengthwise curve), dihedral or asymetryical??

 

FWIW I carved a Greenland style paddle from a Western Red Cedar 2X4 that I like as much my carbon fiber ONNO paddle.

 

My guess is the rowlocks used on shells only allow 90 degree so rotation along the axis of the shaft of the shaft/blade. The blade can only rotate between vertical and feathered positions; and the rowlock takes the moment of the offset blade trying to twist the shaft. The offset blade keep the shaft mostly out of the water.

Interesting difference between these oars and Greenland style paddles. The oars have short wide blades while Greenland style paddles have long, very narrow blades.

 

Amen to that.

Just as the Aussie coach pointed out at Ye Shiwen winning in such fashion over everyone else. Despite creis of fowl from the US coaches.

Good technique and working hard to focus upon maintaining it...through hard work and dedication, gets the results.

Although I'm sure they would be grateful of your 1/100th second at the photo finish

 

Considering the geometry, I estimate the forward propulsion at 45 degrees would, at worst, be about 50% of the force at 90 degrees. This is based on the lever arm of the rower being reduced by cos45 and the forward component of the blade also reduced by cos45.

50% is much better than nothing and you can't sprint for 2000m.

 

While watching the double canoe whitewater paddlers, I notice that their blades are also flat, as they would be for such a purpose. I mostly noticed that they are terrific paddlers that do a sort of mad ballet between and through all those gates. For Americans, the boats would be called kayaks but the Brits call 'em canoes. In either case they are fast and maneuverable. (The UK paddlers won both gold and silver. Good on them.)