ROWING
Popular fluid dynamic fallacies
1. Big puddles are good. No, they contain that part of your work
which did nothing to move the boat.
2. Oar-blades ‘push water’. No, that’s their least efficient mode
of operation.
pseudo-science theories on technique and boat design. What at that time seemed to make sense has ever since held back development, while the more recent emphasis on using ergs as selec- tion tools has not always been helpful. Part of crew coaching is devoted to getting a bunch of athletes to make the same mistakes together, which makes the boat faster than if everyone rows differently. So it can be hard to see why you should engage with a tricky branch of science. But fluid dynamics became a science over 150 years ago and today permits the design performance predic- tion of entire aircraft and engines – we no longer take new planes to the end of the runway to see if they’ll fly! Fluid dynamics’ sometimes coun-
ter-intuitive insights can help us replace guess and dogma with demonstrable facts. It can show that what we’ve always believed may not be true. High-performance sailors do appreciate fluid dynamics. I’ve been involved in that area as builder and designer, and it is hard to answer sailing friends who ask, “You rowers work so much harder than us, so why not apply real science to rowing?” It’s a good question, and an informed debate can only help us to row faster.
We think of sailing as wholly depend- ent on the elements, yet forget how they can affect rowing performance. Often we hear “It’s the same for everyone”, even when lane advantage is so obvious that “fast” crews are seeded into “fast” lanes. For intelligent rowers there are ways to reduce such disadvantages and, whether conditions are fair or not, to en- hance technique and to change equip- ment to waste less energy and thus to go faster. The science makes this entirely feasible, but not if we remain weak on fluid dynamics and fail to engage with it. A future article will explain how shells
cut through water, how water responds, how those responses create the total liq- uid drag on the boat and how a nearby boat or bank increases that drag. Anoth- er explores the interaction between oars and water, how so much energy is wast- ed in that process and how to reduce that loss. I will also examine how wind affects performance and how to reduce that deficit. Then there is steering, and how hard it is to cox, how shells respond and how tough we are on coxes – it will empower coxes and steerspersons, but also help the crew. And we will discuss how boat weight does, and does not, affect performance – it’s not as simple as it might seem. ROW360
3. Reduced wetted surface makes a faster boat. Not so – fast
shells must be long and narrow, and high wetted area is a price worth paying.
4. You need to accelerate the boat. No – hull drag is lowest at
the most constant boat speed.
5. Aerodynamic drag is unimportant, or the same for
all. No, and No! (But it is easily reduced).
6. Blade slip is another kind of gearing. No, it is always a dead
loss, like wheel spin on a car.
7. You should drop the blade in, feel for the grip and only then
apply load. Errr, no!
8. The middle is the most efficient part of the stroke. No it isn’t!
9. A more efficient blade should feel the same as the blade
you’re used to. Unlikely – a more efficient blade will always feel “heavier”.
ROW360 // Issue 001
95
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