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aero - let's have some realistic thoughts
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tuckandgo




Joined: 03 Sep 2012
Posts: 455

PostPosted: Thu Feb 14, 2019 7:27 am    Post subject: aero - let's have some realistic thoughts Reply with quote

Soooo.... I normally race hillier courses where aero is less important.
I did a faster flatter half last year and I'm doing a faster (in theory Smile ) flatter full this summer.

Over on the 'other site' there is a bit of an obsession with looking like you're ready to do your no (aero) holds bar fastest 10 even if it's a full tri.

Back in the day, ooohhhh 6 or 7 years ago, there seemed to be a view that if you were on the aerobars and comfortable then that was all that mattered, if you could stay in the aero position and run off the bike then job done.

What do guys think is really going on. How much difference does changing your CDA (so you can still stay aero and run) really make. If at 35kmh I can really save 5W on the helmet, 5W on shaving the hairy legs and 5W by jamming my elbows together then that is 15W which is huge.

But a lot of the 'good aero' positions look awfully uncomfortable for 5 hours.

Having said that have you seen the testers who do the 12hour Shocked
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stenard




Joined: 04 Sep 2013
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PostPosted: Thu Feb 14, 2019 9:55 am    Post subject: Reply with quote

I think 70.3 is where it crosses over for me.

For an olympic, not that I've done many of those recently, I'd try and be as aero as possible. For a 70.3, I'm similar but comfort plays more of a factor.

One thing I blogged about last year was the difference triathlon naturally makes to comfort. I did my first 50 mile TT, and I could hardly walk afterwards, let alone run, and I was in my "70.3 position". The thing I identified was how much a difference micro-breaks from the aero position make. On a dual carriageway TT, in >2hrs I broke aero three times I think it was, twice for a compulsory basebar roundabout and once for a gel. The lack of any kind of movement destroyed me. Yet in a tri, you are constantly getting little breaks as you go through sharp corners, junctions, over climbs, etc.

Your point about "free watts" was definitely something I bought into last year though. I just don't see why you wouldnt do it (if you can buy the stuff). Cycling is my weakest discipline relatively, and so over the longest leg of an ironman, I wanted as much free watts as I could manage. I got a waxed chain, I bought trip socks (the calf guard only version), I got the velotoze toe covers... I already had aero helmet and disc, and I made a real focus on tidying up the frame as much as possible.

I did also have a refit before and managed to (comfortably) get a tiny bit lower, which surely helped. I'm still not the lowest though. As you say, for 5+ hours, comfort has to be the key priority. I went past a number of people in the last hour who were sat up. I may have only put out 167W average, but I held aero the entire ride, except for eating.

But the waxed chain, trip socks, and toe covers, apparently could have equated to roughly 10w. After Copenhagen I did a fresh best bike split simulation to try and replicate my time off the watts I actually put out, and got it within a few minutes of my actual time. If I knock 10w off my power output my ride time increases by 7 minutes.

That's possibly the wrong way round to analyse it, as really it would be an increase in cda. But I don't know what all the stated "watt savings" really equate to in cda terms. But for ref, to get a similar 7min increase in ride time, I have to bump up average cda by 8% (from 0.235 to 0.254).
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tuckandgo




Joined: 03 Sep 2012
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PostPosted: Thu Feb 14, 2019 10:08 am    Post subject: Reply with quote

Interesting, thank you.

I'll have a look at your blog.
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stenard




Joined: 04 Sep 2013
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PostPosted: Thu Feb 14, 2019 10:27 am    Post subject: Reply with quote

tuckandgo wrote:
Interesting, thank you.

I'll have a look at your blog.

It was just some random pondering in the 50 mile TT report ... so don't expect anything hugely insightful! Pretty much captured the main points above! Laughing
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kevb




Joined: 11 Aug 2010
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PostPosted: Thu Feb 14, 2019 12:40 pm    Post subject: Reply with quote

If you have five minutes to spare, this might help; http://olivernash.org/2014/05/25/mining-the-strava-data/cycling_drag_force.pdf
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Chrace




Joined: 28 Apr 2010
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PostPosted: Thu Feb 14, 2019 1:37 pm    Post subject: Reply with quote

kevb wrote:
If you have five minutes to spare, this might help; http://olivernash.org/2014/05/25/mining-the-strava-data/cycling_drag_force.pdf

Oh goodie, I'm saved. I don't ride at 50 kph. Smile
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stenard




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PostPosted: Thu Feb 14, 2019 2:31 pm    Post subject: Reply with quote

Haha, yeah. 14m/s is a seriously fast speed with which to analyse. Maybe relevant for the pros, but not much else. Even general watt saving numbers tend to be at 40kph, which is still a bit punchy for most amateurs!
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JaRok2300




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PostPosted: Thu Feb 14, 2019 3:03 pm    Post subject: Reply with quote

One of my favourite pieces of information I've gleaned from reading all the aero discussions over the years is that the time saving is broadly the same irrespective of how fast you go.

So an aero saving worth 5mins to a 5 hour rider will also be worth @5mins to a 6, 7 or 8 hour rider. Obviously less significant as a percentage (and we can debate the significance of 5mins at that end of the field) but if it's free speed why not take it.

I'm definitely nearer the slower end of that scale but love the tech. and have dabbled with some very basic aero testing of my own. I'd love to have a proper go at the Chung method if I could sort out a suitable location near by but struggling to nail anywhere down.
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jibberjim




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PostPosted: Thu Feb 14, 2019 3:08 pm    Post subject: Reply with quote

stenard wrote:
Haha, yeah. 14m/s is a seriously fast speed with which to analyse. Maybe relevant for the pros, but not much else. Even general watt saving numbers tend to be at 40kph, which is still a bit punchy for most amateurs!


Sure, but just because it's 10w at 40kph, doesn't mean it's 0 at 35 ?
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stenard




Joined: 04 Sep 2013
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PostPosted: Thu Feb 14, 2019 3:29 pm    Post subject: Reply with quote

jibberjim wrote:
stenard wrote:
Haha, yeah. 14m/s is a seriously fast speed with which to analyse. Maybe relevant for the pros, but not much else. Even general watt saving numbers tend to be at 40kph, which is still a bit punchy for most amateurs!


Sure, but just because it's 10w at 40kph, doesn't mean it's 0 at 35 ?

Oh, I agree. I havent actually read that paper linked (no time currently), but I did open it up and just found it surprising they'd gone with a stated "standard" for the analysis that would apparently follow of >50kph. When from a lot of other things I've read, 40kph seems to be used widely. I guess I was just expecting a paper like this would have used that same speed to make any outputs comparable with other data/numbers that is already out there.
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Last edited by stenard on Thu Feb 14, 2019 3:30 pm; edited 1 time in total
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Wheezy




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PostPosted: Thu Feb 14, 2019 3:30 pm    Post subject: Reply with quote

Like's been said, further up the thread, I think if you can tinker with kit and optimise what you've got, that can only be a good thing. As I have done a lot more TTing over the past 5 years than triathlons, I've tinkered quite a lot, but I haven't really used any hard data, so what I have done has been much more by feel and therefore probably wrong. As I've now bought some P1s I'm hoping to do a bit of my own testing this summer and I would happily change my position to get more aero. The set-up I currently have I use for everything, from 10m up to 12 hours and I'm pretty comfortable, but I am sure that I could get a lot more aero.

I did the Outlaw in this position and I was absolutely fine running off the bike (for the first 3 hours anyway; my deterioration was more to do with only doing 4 runs in the preceding 3 months of the event). Personally, I don't think the position has quite as much to do with it as some people think; my thinking is that one's ability to run off the bike has more to do with how hard you've hit the bike and therefore how much you have left in the tank. I'd rather try to keep as aero as possible at as low a power as possible. I'm not a biker with a very high ftp anyway, so it's best that I aim to say aero as much as possible.

My main issue at the moment is that I've got an old frame (Argon e-80) which by modern standards is probably a brick. If I had the cash to invest in a new frame and a fit I would, but I don't, so I won't. I quite like the idea of getting the most I can out of my old clunker.
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Tri'ing Swimmer




Joined: 15 Nov 2016
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PostPosted: Thu Feb 14, 2019 4:37 pm    Post subject: Reply with quote

My first yet of Tri I just stuck some bars on for comfort. This year going to get a fit probably next month. My outdoor riding is a lot worse than indoor wattbike suggests should be so wonder if drag might be a factor with typical swimmer shoulders.
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Jorgan




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PostPosted: Fri Feb 15, 2019 10:20 am    Post subject: Reply with quote

When people quote the various Watt savings adding up, I think it's misleading. In that you don't actually get the sum of those savings, it's somewhere between your old & new drag number i.e. if you make 4 x 5w changes, you are unlikely to get a full 20w saving in real terms.

Some of the easiest savings that involve no physical changes is clothing. Return on investment with frames diminishes pretty fast.
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JaRok2300




Joined: 01 May 2014
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PostPosted: Fri Feb 15, 2019 10:30 am    Post subject: Reply with quote

The Aero Assistant on Aeroweenie gives 3 position options of Typical, Good & Excellent with 90 & 150 seconds (40km) between them based on my other parameters.

Not sure how accurate it is but it's interesting to play with different equipment configurations and weigh up the cost/benefit ratio.

I've never really played with the other calculator on there before but by messing with the CdA to get the power & speed I see on the 2km stretch of road I use for testing I get 0.27 for the TT bike & 0.37 for the road bike.
Again, not sure how accurate that is but I'm never going to be in the 0.20 region at my size so seems plausible.
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stenard




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PostPosted: Fri Feb 15, 2019 10:53 am    Post subject: Reply with quote

Jorgan wrote:
When people quote the various Watt savings adding up, I think it's misleading. In that you don't actually get the sum of those savings, it's somewhere between your old & new drag number i.e. if you make 4 x 5w changes, you are unlikely to get a full 20w saving in real terms.

Some of the easiest savings that involve no physical changes is clothing. Return on investment with frames diminishes pretty fast.

I get your general point, and it's of course true for certain changes where the same wind is impacted, but of the three main things I changed last year, I think they could compound.

The trip socks and aero toe covers are in different bits of the body, albeit very close, and the wind around each should not impact the wind around the other significantly, so if you're reducing drag in both places that could add up.

And the waxed chain is a totally different type of "watt saving", being drive chain efficiency, meaning more of the Watts that are reported as being generated by me at the crank actually make it to the rear hub.

Agree with the point on the frame. From what I've seen, it's one of the worst "returns on investment" in terms of time saving. But of course, we all love a new bike!
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