Me and members of my swim club have been having a debate over if drafting effects the leader in that it slows them down. I am usually the one leading and I feel that it slows you and I know it is very annoying. They claim that the added speed they get would normally just be lost as waste by just moving water. Can anyone help clear this up?
Thanks all
Not sure about drafting in the water but if hydrodynamics and aerodynamics are even closely related I would think that the person in front does get a nominal benefit form being drafted. Since I’m not even close to being qualified to quantify the effect I’ll defer to the experts. But if in cycling the lead cyclist gets some benefit from being drafted I see no real reason why a lead swimmer should not also benefit from a similar principle. How’s that for vague.
100% unqualified guess: it doesn’t slow the leader. I don’t think it’s like car racing at a couple-hundred miles per hour…even though I wouldn’t be surprised if it would take extreme speeds like this in air to approximate hydrodynamics. In car racing, they are getting right up close to the leader in a near-constant position with the following car’s nose closely approximating the area of the leader’s rear end. In swimming, when following from behind, there’s an alternating close-not so close-close relationship going on between the leader’s feet and the drafter’s alternating arms, and the hand is so small compared to the hole the leader is pushing in the water, I find it hard to imagine that it makes a difference to the leader. BUT, if you were drafting off the hip…I think that may slow the leader…because the drafter is forcing water back towards the leader, this water wouldn’t normally be forced back towards the leader. Just guesses…
If the follower is close enough it actually helps the leader. It decreases the tail of turbulence that streams out behind him, which is his main source of drag.
you notice in NASCAR racing both the leader and follower(s) go faster than lone cars.
In the swim drafting behing doesn’t slow the leader. You can slow the guy down in front if you move off his upper hip. Put your head somewhere between the bottom of his ribcage and the top of his hips.
“If the follower is close enough it actually helps the leader. It decreases the tail of turbulence that streams out behind him, which is his main source of drag.”
Why do you say this. What is the Reynolds number for a NASCAR racer? a cyclist? a swimmer?
Why not see the thread “First Time Drafting …”
http://forum.slowtwitch.com/gforum.cgi?do=post_view_flat;post=194006;page=1;sb=post_latest_reply;so=ASC;mh=25;
I’m also told its does assist the leading rider to some degree. No quantification though. If it does, it must be very minor.
As for swimming, I don;t know. The only thing that would draft of of me is a cinder block.
In the swim drafting behing doesn’t slow the leader. You can slow the guy down in front if you move off his upper hip. Put your head somewhere between the bottom of his ribcage and the top of his hips.
Hmmmm…Interesting. Why?
Psychologically most leaders are slowed by drafters because they know the suckers are saving energy that will be used against them later. More than enough to overcome the slight benefit of having someone draft you in most cases.
B/c of the turbulence coming from the side. Try swimming in a lap pool without lane lines and somebody swimming 'fly next to you.
Been a while since my last thermofluid dynamics class; here goes:
The benefit of the draft in terms of the leader is also a function of speed and efficiency. Obviously the NASCAR is a bit more efficient ~99+% given tire slip against the pavement and mechanical energy transfer from the engine to the wheels if you are looking at the whole system. At speeds north of 175 mph the car behind can make the air coming off the rear spoiler more smooth and thus reduce drag by a tiny bit. But this is enough to add enough speed on a % basis to pull slightly ahead of cars going a similar speed.
– The typical olympic type swimmer is 6% efficient (94% of the energy just makes waves). The average chucklehead age grouper (65 min IM swim) like me is 5% efficient, which is 20% less efficient than Ian Thorpe. The propeller heads that do the America’s Cup Hull design proved that the top speed in water is a function of length when you get more efficient so short swimmers are screwed from the get go. 
Then the ability for the lead swimmer to gain from the rear draft would be a function of his ability to efficiently benefit from the reduced turbulence from his rear spoiler (feet) which are moving and inefficient (if you kick). The rear swimmer can get a benefit from the draft at much lower speeds than the NASCAR due to the viscosity of what is being moved through (air vs water)
So until you can pull a water skier, I don’t think that the guy (gal) tickling your feet will slow you down – or speed you up.
Or, I could be wrong - I got a B in thermo…
It’s more like this: The back swimmer slows the front swimmer but the two of them move faster than if it was only one 
Bottom line, no, the back swimmer doesn’t slow the leader.
Believe the current issue of Outside magazine has a question/answer column which discusses this and their answer is that a lead cyclist does benefit from a close drafter by the “smoothing out” of the trailing vortices by the drafter(s).