Jump to content
Peter

So Ali Brownlee said re Swimming

Recommended Posts

The difference between Ali Brownlee and Kye Hurst wouldnt be that different. 

Me swimming at 104kgs at 1.30 pace would displace way less water then Brownlee at 65kg at 1 min pace. Less friction from my big frame at a slower pace. Way more friction at the higher speed. 

Share this post


Link to post
Share on other sites
15 hours ago, Greyman said:

In the big scheme of things it's a minuscule difference. Most pro triathletes are so thin they don't displace enough water to make it worth worrying about this in a triathlon.

Then using that same argument, a 60kg pro cyclist shouldn't bother trying to draft behind another pro cyclist, as they are far too skinny.

Share this post


Link to post
Share on other sites
19 minutes ago, Ex-Hasbeen said:

Then using that same argument, a 60kg pro cyclist shouldn't bother trying to draft behind another pro cyclist, as they are far too skinny.

Ex, same argument doesn't apply. Different matter (air) to water plus the environmental factors of gravity, wind and rolling resistance come into play. There will always be an advantage for a cyclist to draft another cyclist when the speed travelled is above approx 15 kph. 

Willie, the displacement factor is relevant to speed of the swimmer. We were talking about a group of skinny pro triathletes all swimming at similar fast speed. The disparity between their water displacement would be of a similar value. Ky Hurst on the other hand, competes against swimmers of a variety of size hence my comment. You at 104 kg swimming at a slower speed and displacing less water has no relevance to he discussion. 

The real thing thing Brownlee missed, is that if you are the front swimmer and someone is swimming on your hip and you want to get rid of them, just roll to your side and give them a kick in the guts. Brownlee obviously hasn't competed in a surf carnival swim race.

Share this post


Link to post
Share on other sites

We'll have to agree to disagree. My last OW race, I swam like buggery to catch a tiny 14yr old kid that wouldn't have been half my size, but once I had him, it was an easy sit for the next 1000m. It makes a big difference in the swim.

 

And if an n=1 case isn't good enough, try this published study.

https://www.ncbi.nlm.nih.gov/pubmed/9710869

This is the last sentence of the Results Abstract: 

Quote

In drafting position, the performance gain was related to the 400-m time (r = 0.80, P < 0.01) and to the skinfold thickness (r = 0.94, P < 0.01), with faster and leaner swimmers having greater gains of performance.

 

Share this post


Link to post
Share on other sites

Sit on someone where you feel comfortable - or sit by yourself if you prefer that. Personally, I prefer to ride someone's hip - always hated sitting on feet.

As for advice on what's 'better', the advice doesn't matter if you're not going to follow it because you're uncomfortable. The best advice would be learn to swim better.

Share this post


Link to post
Share on other sites
2 hours ago, trinube said:

As for advice on what's 'better', the advice doesn't matter if you're not going to follow it because you're uncomfortable. The best advice would be learn to swim bette

Good common sense here - I still cannot believe that a swimmer swimming on your hip can slow you down - I am fully aware of the advantages to swimming on the feet or on the hip of the swimmer in front of you - just can't accept that the "drafter" can affect the leader (apart from giving him the shits) - I believe the "drafter" can affect the leader psychologically - but not physically :huh:

But I don't have an Olympic gold medal - I'd just like someone who has one explain how this is possible :mellow: 

Share this post


Link to post
Share on other sites

While I've not seen anything on swimming, it's well established that drafting in cycling actually reduces drag for the rider in front as well. Effectively they get a little 'push' from the bunch behind.

With water being a couple of orders of magnitude denser it's possible that a similar effect might exist...as long as propulsion is not disturbed

Share this post


Link to post
Share on other sites
1 hour ago, BarryBevan said:

turbulent water flow, drag

That's what I was kinda thinking, having the person at your side is affecting the water beside you etc, maybe affecting the flow at the back half of your pull? Maybe the fact they're there creates a little hollow in the water beside you?

Share this post


Link to post
Share on other sites
1 hour ago, AP said:

But I don't have an Olympic gold medal - I'd just like someone who has one explain

Probly gud to ask someone with physics qualifications rather than a swimmer., if you want an explanation of the physics involved. 

Share this post


Link to post
Share on other sites

The customer is on to it, it effectively widens the vessel sitting on a hip and changes the bow wave making it wider. 

The tactics all depend on whether you wish to slow them or instead get away with them. Brownlee would be trying to get away and put mola and Murray out the arse. 

Share this post


Link to post
Share on other sites

Yeah but as soon as you turn around and walk away we're swearing our guts out about ya ;);) 

  • Like 1
  • Haha 1

Share this post


Link to post
Share on other sites

Aerodynamics and hydrodynamics are just subsets of fluid dynamics. Many of the same principles apply to each. When an object displaces a body of gas or liquid that fluid has to first push out against other fluid particles (hence why frontal cross section and the 'shape' of the object are important considerations in determining the amount of force required for the initial displacement). 

However the the biggest factor in determining the overall drag is how those fluid particles come back together after the object moves through. There is a 'suction' effect as the fluid becomes turbulent as it rushes to replace the space occupied by that body - a low pressure system forms. In order to compensate for turbulence the shape of the object at the rear becomes very important. There are lots of different designs (golf ball dimples, long tails, medium tails etc) all hoping to create the opposite of turbulence - liminar. In cycling the head of the peloton definitely gets an advantage from the riders behind because the 'tail' is longer. Also a bunch as big as the TDF also has a massive advantage - not just because of the extra legs to take turns driving but because of the overall size and shape of the pack.

In an open water swimming bunch context the leader having done most of the hard work in displacing the water at the front also creates a sweet spot eddy alongside his/her body at a point (ie the hip) before the water comes back into the area displaced by the front swimmer. If you swim there it's possible that there is a mutual advantage for both swimmers ...

That said, amongst the turbulence at the back of that swimmer there is also a significant current that has an advantage for a following swimmer. In my experience that point is achieved by placing your hand in the catch position about 6-12 inches behind the feet. Personally I prefer to swim behind because I don't trust someone (who I don't know) not to do something kooky - like change direction erratically, lash out with an arm or leg - if I was swimming at the hip in a triathlon. I'm guessing it's a bit different in the lead pack in an ITU race where everbody's strengths, weaknesses and eccentricities are well known. ...

 

 

Edited by Andrew #1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×