ericM40-44 wrote:
ZackCapets wrote:
Skin friction drag is simply more important in swimming than it is in cycling due to the fluid you're moving through...
No.
Also, why not wear both?
And, PI suit is 1sec/km faster than other *speed suits* then how much faster is it than your example?
For objects having a more streamlined shape, skin friction drag will represent a larger proportion of the total drag than for a blunt body. Basically, the more you reduce pressure drag, the more the skin friction drag term starts to show up. For an object with an aerodynamically awful shape, say...a flat plate oriented normal to the wind, induced drag represents such a small fraction of the drag that it can be entirely ignored. A cyclist, even in a good TT position, is a blunt body, whereas a human swimmer is a streamlined body. The swimmer will also have a larger wetted area due to being fully stretched out whereas the cyclist is somewhat "folded up," which would also magnifying skin friction drag a bit. The cyclist also has to overcome rolling resistance whereas the swimmer does not. The list of reasons skin friction drag represents a larger proportion of the drag on the athlete in swimming than in cycling goes on and on. Since I can't prove that it's the fluid that makes the difference I'll have to stick to some tried-and-true generalities. I wish I could do better, but a cursory lit review simply reveals widespread glossing-over of the skin friction drag in cycling. Hmmm......................It's also worth mentioning that nearly all of the research in cycling pertaining to skin friction pays more attention to the impact on pressure drag (i.e flow separation delay) than it does on the skin friction drag itself. I'm all for drag reduction, trust me, but on a cyclist the apparel is not the first place I would look.
I don't think it's difficult to demonstrate that the time savings from apparel varies from athlete to athlete. For some it may "work out" that it's faster to wear the PI suit with a speedsuit over top, for others it may not. It all hinges on your individual time savings and how quickly you can get out of the speedsuit. If it takes 15 seconds, then over 40k you'd come out 25 sec ahead wearing a speedsuit + the PI suit. If the PI suit is closer to 0.5s/km, then you're barely breaking even. If it's 0.25s/km then you'd need to get out of the speed suit in 10 sec to even break even. Maybe all of these times are wrong and the PI suit is 30-45sec faster over 40k. Whether or not it's worth it is also highly individual, and that's really my whole point: at this point in time
I'm not going to spend an extra $300 (without knowing that it's on the highest end of that time savings range--it's additional complication, one more wear-item, and expensive.
Then, there's the question of opportunity cost...could you buy something else for $300 or less that would make you even faster than the PI suit?
2 months coaching?
A high quality bike fit?
45 min of tunnel time (not that you could buy time in this increment...)
Aero-optimized nutrition setup?
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