1. On The Waterfront John D Barrow ***

2. Swimmers Improved Much Faster Than Runners Men’s 400m run: 43.8 (1968) to 43.18 (2011) Men’s 100m swim: 52.2 (1968) to 46.91 (2011) V(run)  5V(swim)

3. English Channel Swim Approximately 21 miles Men’s record of 6hr 57m by Peter Stoychev is 3mph Women’s record of 7hr 25m by Yvetta Hlavacova is 2.8mph Sprint swim 100m in 50s is 2 m/s

4. Record Speeds over 50m StrokeMen(sec)Women(sec) Crawl >1904 Olympics 20.9123.73 Butterfly >1952 Olympics 22.4325.07 Backstroke >1904 Olympics 24.0427.06 Breaststroke 26.6729.80 Men – Women  3 sec

5. Arms or Legs? Legs only 100m in 80s  V = 1.25 m/s Arms only 100m in 60s  V = 1.67 m/s. All freestyle All freestyle Arms + legs 100m in 50s  V = 2 m/s The ratio of arm pull to leg kick is 1.3 The kick also plays a stabilising role in backstroke and freestyle

6. Symmetries Butterfly and breaststroke are laterally symmetric Crawl and backstroke are laterally asymmetric Other recreational strokes Trudgeon = crawl arms + breaststroke legs Inverted breaststroke Slow butterfly = butterfly arms + breaststroke legs Fast breastroke = breaststroke arms + butterfly legs sidestroke

7. Breaststroke Swimming is Different Speed is not constant Arm recovery must be underwater Part of head above water surface Drag force  V always decelerates Accel n by moving water backwards Deccel n by moving water forwards with knees Max speed of  2 m/s Min speed  0 m/s Created by periodic variation of net force on the body

8. Hydrophobic Polyurethane Swimsuits Banned by FINA in 2010 Past records ‘starred’ Increase buoyancy by trapping air  reduce water drag Drag on body in water  780  Drag on body in air Seamless, wrinkle-free, fibred texture, Up to 8% drag reduction (20 world records at July 2009 Champs 30 mins to put on, $500 each, last 1-2 races !

9. Water Temperature FINA Rules for Swimming competition specify 25-28C (77-82F) Drag = ½  AV 2  viscosity of water Density fall with T is a much smaller effect than water viscosity change  as T up to about 15% on range allowed

10. Drag Force = ½ c  AV 2 Body Shape Matters

11. Inge De Bruin’s Drag Effect Compared With Many Other Swimmers With Many Other Swimmers A significantly smaller c  A factor at all speeds …. De Bruin former World records 50 &100m free 100m fly

12. Friction drag cAV 2 Friction drag: in the thin layer of water near the body  cAV 2 It is higher if flow is turbulent (c  ) rather than smooth (c  ) Pressure drag Pressure drag: fast swimmers create high pressure in front AV 2  [p(high) – p(low)] and low pressure behind  AV 2  [p(high) – p(low)] Wave drag Wave drag: energy lost making surface waves. As V  the wavelength  and amplitude . Wavelength a bit longer than swimmer Swim more underwater! puts him in a speed-limiting wave trough. Swim more underwater! 15m is the max allowed at the start and from each turn The Three Main Drag Forces

13. Turbulence The Onset of turbulence occurs when Reynolds Number = VL/  500,000 Average Speed V = 2 m/s Body surface size L = 2m Water density  = 1.00 kg/m 3 Water dynamic viscosity  = 0.9  10 -3 Ns/m 2  = / Reynolds Number  450,000  Reynolds Number  450,000 Small variations in L and V will produce turbulence

14. Wavelength L= 2V 2 /g = 2m  (V/1.8 m/s ) 2 Wave Drag

15. Speed Frictional drag The Dominant Drag Depends on Your Speed 1.5-2m/s Pressure dragwave drag Pressure drag and wave drag (56%) Dominate F drag = 40(V/1.3m/s) 2 N Dominant Drag Effect Recreational Swimming speeds Length L = 2V 2 /g = 2m  (V/1.8m/s) 2 World class

16. Hand supplies energy for moving waterHand supplies energy for moving water Don’t push water back in a straight lineDon’t push water back in a straight line Follow a curvilinear path so as to keep on findingFollow a curvilinear path so as to keep on finding still water to push against so as to gain larger still water to push against so as to gain larger resistance and reaction resistance and reaction Moving The Right Sort of Water

17. Use Hands to Pull Still Water ‘S’ or ‘inverted question mark’ paths Flow Lift Drag  hand Make resultant force always forwards

18. Optimal is about 12 deg (usual rest spacing) It has about 8.8% greater drag than wide open or closed hand Minetti et al

19. Optimal Finger Spacing AE Minetti et al

20. Rowing and Paddling in Numbers How does the speed of the boat depend on the number of rowers? Drag on boat  V 2  wetted surface area of boat  V 2  L 2 Volume of boat  L 3  N – the number of crew Drag  V 2 N 2/3 Crew Power overcoming drag = N  P = V  Drag  V 3 N 2/3 P is the constant power exerted by each (identical) rower V  N 1/9 With a cox V  N 1/3 /[N + 1/3 ] 2/9 if cox is third the weight of a rower

21. Moscow Olympic Kayak Times Are race times T  1/N 1/9 ? Race times in the 1-person and 2-person and in the 2-person and 4-person races should be in the ratio of 2 1/9 = 1.08 Men’s 1000m events: Women’s 500m events:

22. Results of 1980 Olympic coxless races (N = 1, 2, 4) + coxed N = 8 Distance is 2000 metres N Time, T(sec) 1429.6 2408.0 4368.2 8349.1 T = (2000)/V  N -0.11 V  N 0.11  N 1/9 But with a cox N = 2: T = 422.5 s N = 2: T = 422.5 s N = 4: T = 374.5 s N = 4: T = 374.5 s Better without one!

23. The Impact of A Cox Adds weight to the crew but not to power Lightweight cox is N  N + ½ effect T(with cox)/T(coxless) = [(N + ½)/N] 2/9 = (25/16) 1/9 = 1.05 for N = 2 = (81/64) 1/9 = 1.03 for N = 4 1980 Olympics

24. Rigging Rowing Eights

25. Rowing Has Its Moments +N -N F F and

26. Moment on boat  = -Ns + N(s+r) - N(s+2r) + N(s+3r) = +2Nr Then, half a stroke later…N reverses to –N and.. Moment on boat = -2Nr The Wiggling Boat s

27. Size of the Yaw Pair: 0.37 deg per stroke Four: 0.77 deg per stroke Eight: 0.015 deg per stroke

28. Moment = -Ns + N(s+r) + N(s+2r) - N(s+3r) = 0 The Italian Rig No wiggle!

29. Four no-wiggle rigs for eights Italian tandem Rig ‘Italian tandem Rig ’ ‘German Rig’ Moment = 1-2-3+4+5-6-7+8 = 0 Moment = 1-2-3+4-5+6+7-8 = 0 Moment = 1-2+3-4-5+6-7+8 = 0 Moment = 1+2-3-4-5-6+7+8 = 0 New* New*

30. Women’s European Championships 1963, Moscow Albanian stamp

31. Canada used the German rig to win 2008 Olympics ! 1-2+3-4-5+6-7+8 = 0

32. Oxford Use a German Rig to Win 2011 Boat Race to Win 2011 Boat Race 1-2+3-4-5+6-7+8 = 0

33. The Imperial College 2010 Trial 1 + 2 – 3 – 4 – 5 – 6 + 7 + 8 = 0