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fishboy

Getting aero and pacing for TristanP

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Well after 6-8 months of testing on TristanP we've managed to get his drag down a heap ... to the point he's added about 2.5 kmh of speed at 40 km/hr running on the same input power.

This is in a position that we know he can sustain for IM, which is quite impressive, and bodes well for Port this year.

 

It's been a bit of an eye opener for Tristan, to the point he's been total believer in the whole aero thing for some time, and has now started doing aero testing through his shop in addition to the bike fitout. (You need to BYO power meter at the moment, more details here).

 

Here's the graph, you can see each subsequent test shifting the data curve further and further to the right. The tests were pretty much in sequence from left to right - we kept getting slightly better and better as we worked out things to improve on, with a big jump at the end.

 

The last thing we tried, which delivered the absolute best aero, was some tricko stuff I developed over a couple of years R&D ... it seems it works on other people too, which is cool.

 

NB. At the moment we've left the actual watts off the Y axis (and shifted the zero point a bit), after Port Tristan plans to post the full data.

 

tristanP.gif

 

The other thing I managed to do this weekend was upgrade my power calculator so that it can back calculate speed, Crr, CdA, and slope in addition to watts (it used to just be able to calculate watts). So basically now you can use a Crr of 0.005 which is typical for normal road conditions and if you know your watts and speed you can work out your own CdA (drag) quite easily.

 

To do this:

 

Use the default air density (it's a rough guide).

Enter the mass of you and your bike and all your gear (closest kilo or two is OK, this affects rolling resistance mostly so doesn't affect CdA too much)

Enter 0.005 for the Crr (Rolling resistance).

Enter 0 for the slope.

Enter the speed (use the convertor to get speed to metres/sec).

Leave the CdA blank.

Enter the watts.

Press calculate.

 

It'll spit out a table of watts, split times and a graph for you, as well as the all important CdA.

 

For those people doing Port with power, it may assist in being able to predict a split time based on your input power you're hoping to maintain. I've found it to be accurate over shorter distances (up to 40km) to within a few seconds, but I'd be interested hear from anyone as to how their prediction stacked up vs their actual.

 

Enjoy.

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Hi Fishboy,

 

Like your work. Had a go on your calculator with some race data from Shepp, Busso and Torquay. Shepp and Busso line up pretty well (dead flat courses) and give me a cda in the 0.23-0.24 range. Torquay gives me 0.277. From the SRM it measured the change in elevation at Torquay at 114m so that must have an effect. Similarly I would have stood out of the saddle more at Torquay due to the nature of the course compared with the other two. Bike set up was exactly the same for all three rides, power level at Torquay was ~8% higher than Shepp and 14% higher than I rode at Busso. Got a power range I'm looking to ride at Port but not sure how I could use your calculator to estimate a bike split with the 600m or so of altitude gain that will go on at the same time?

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Hi Fishboy,

 

Like your work. Had a go on your calculator with some race data from Shepp, Busso and Torquay. Shepp and Busso line up pretty well (dead flat courses) and give me a cda in the 0.23-0.24 range. Torquay gives me 0.277. From the SRM it measured the change in elevation at Torquay at 114m so that must have an effect. Similarly I would have stood out of the saddle more at Torquay due to the nature of the course compared with the other two. Bike set up was exactly the same for all three rides, power level at Torquay was ~8% higher than Shepp and 14% higher than I rode at Busso. Got a power range I'm looking to ride at Port but not sure how I could use your calculator to estimate a bike split with the 600m or so of altitude gain that will go on at the same time?

I would be careful using the power data from Torquay due to the wind as well as the crap road conditions. I know that my power to speed output there was not directly in line with expectations based on known drag data.

 

The 600m of gain at Port will put things out a little on the calculator I am sure, but it is relatively flat still. I actually didnt think its was 600m on the new course anyway, but not too much less.

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I would be careful using the power data from Torquay due to the wind as well as the crap road conditions. I know that my power to speed output there was not directly in line with expectations based on known drag data.

 

The 600m of gain at Port will put things out a little on the calculator I am sure, but it is relatively flat still. I actually didnt think its was 600m on the new course anyway, but not too much less.

I think you're right with the comparison - there was little in the way of wind impact at Shepp and Busso whereas Torquay was all over the place.

 

I was using the 600m from somewhere else on here (so it must be true!). Assuming that it is, then that equates to a slope across the course of ~0.003% which, in my case, increases my predicted bike time under perfect conditions by around 17mins. Without putting the time out there its about 5mins quicker than I was thinking it should be.

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The man was already motoring - so what did you change to get him 2.5km/hr quicker?

 

4 sets of wheels, 3 helmets, seat/arm height ratio changes, forearm angle changes, elbow width changes and special fishboy add on at the end.

 

Helps if you own a bike shop and you can afford to swap that stuff over quickly!

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I think you're right with the comparison - there was little in the way of wind impact at Shepp and Busso whereas Torquay was all over the place.

 

I was using the 600m from somewhere else on here (so it must be true!). Assuming that it is, then that equates to a slope across the course of ~0.003% which, in my case, increases my predicted bike time under perfect conditions by around 17mins. Without putting the time out there its about 5mins quicker than I was thinking it should be.

 

Yeah if there is a lot of elevation change, and you are out of the saddle a lot, the CdA will be comparatively higher...

 

You can take a small chunk of data eg around 1 min with constant speed and watts on level ground and see what that throws out.

 

IM times are a bit hard to predict really accurately, any time you are out of aero, sitting up, stretching etc it can affect your CdA and the "likely" time based on the estimate of your drag.

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Yeah if there is a lot of elevation change, and you are out of the saddle a lot, the CdA will be comparatively higher...

 

You can take a small chunk of data eg around 1 min with constant speed and watts on level ground and see what that throws out.

 

IM times are a bit hard to predict really accurately, any time you are out of aero, sitting up, stretching etc it can affect your CdA and the "likely" time based on the estimate of your drag.

Always going to be harder, but from memory we were within 5 min from my Port time last year... In the grand scheme of things thats pretty bloody close

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Given my newfound interest in power and all things bike speed I thought I'd do a bit of malicious (not really! :lol: ) stalking and came up with a few questions.

 

Tristan's sprint distance bike improved by a whopping 2 minutes over 20km from GTS Race 2 to GTS Race 6.

Did you record the data for that? How much of that was due to improved cda, improved fitness or other factors (eg was course more technical/winds etc)

 

A bonus question. On the the final race Tristan was 2 minutes faster than Fishy on the bike (Fishy's ride was still pretty impressive!) - what can you attributed this to in terms of power, cda and fitness?

 

Anyway, love your work guys - great to see some real objectivity into the black art of TT'ing. :lol:

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Given my newfound interest in power and all things bike speed I thought I'd do a bit of malicious (not really! :lol: ) stalking and came up with a few questions.

 

Tristan's sprint distance bike improved by a whopping 2 minutes over 20km from GTS Race 2 to GTS Race 6.

Did you record the data for that? How much of that was due to improved cda, improved fitness or other factors (eg was course more technical/winds etc)

 

A bonus question. On the the final race Tristan was 2 minutes faster than Fishy on the bike (Fishy's ride was still pretty impressive!) - what can you attributed this to in terms of power, cda and fitness?

 

Anyway, love your work guys - great to see some real objectivity into the black art of TT'ing. :lol:

It is possible with careful analysis to attribute differences to each of the major things that matter in a TT:

course profile and environmental conditions

power output

CdA & Crr improvements

pacing

 

but it takes some time to pull it apart. I gave an example in this blog post.

 

I just got great news this morning that one of my clients won the Pan American TT championships overnight and is now selected to go to world championships. In his case we focused on all elements to develop the incremental gains. This included time in the wind tunnel amongst other things.

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Thanks Alex. Must be nice to know that your work is actually assisting many people to go quicker!

It's actually getting into it and doing the practical stuff that is what's so cool. You do that well.

 

You are going to love Aerostick when it comes out.

 

Once all is confirmed (I will have first unit) and I have done all the preliminaries and testing, I will look to do a session in Melbourne at some stage. Perhaps you'd like to work with me on that.

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Given my newfound interest in power and all things bike speed I thought I'd do a bit of malicious (not really! :lol: ) stalking and came up with a few questions.

 

Tristan's sprint distance bike improved by a whopping 2 minutes over 20km from GTS Race 2 to GTS Race 6.

Did you record the data for that? How much of that was due to improved cda, improved fitness or other factors (eg was course more technical/winds etc)

 

A bonus question. On the the final race Tristan was 2 minutes faster than Fishy on the bike (Fishy's ride was still pretty impressive!) - what can you attributed this to in terms of power, cda and fitness?

 

Anyway, love your work guys - great to see some real objectivity into the black art of TT'ing. :lol:

The last piece of the puzzle as far as the aero stuff goes was not on the bike for the ride at GTS race 6, so my CDA was actually less than what it is currently. I would have been about another minute or so quicker again if I had that as well at the time... The interesting bit is that that piece of the puzzle was strapped to Fishboy's bike... I will let you do the maths, but the time difference at the last race is purely due to my FTP being so much higher than his as he was a lot more aero than I was at the time.

 

As far as the difference between race 2 and 6, my position between these races didnt change a whole heap, my available power went up considerably. There was about 70 watts difference in the average power for the 2 rides.

 

Since racing Roth last year in July, my FTP has increased by about 70 watts as well, so a lot of the increase is training related. Most of the aero savings were completed before race 1 of GTS. Aero savings are still a massive piece of the TT puzzle, but most people with a power meter will still get more benefit from improved training techniques that will increase FTP. The aero stuff just gets the most out of the available power.

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Fishmonster - without getting too technical, could you give a bit of insight into how your protocol accounts for differnt yaw angles (I'm guessing the most common being around the 15-20 degree mark). Reason for the question is that I get the real world testing would be very reliable in still conditions, but not sure how you get a repeatable result when its a bit windy (which is the most common condition).

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Fishmonster - without getting too technical, could you give a bit of insight into how your protocol accounts for differnt yaw angles (I'm guessing the most common being around the 15-20 degree mark). Reason for the question is that I get the real world testing would be very reliable in still conditions, but not sure how you get a repeatable result when its a bit windy (which is the most common condition).

You are right Otter... When doing the testing we would complete the tests on days where the conditions are as still as possible. It is a restriction of the model but is a restriction that when worked around by selecting optimal times for testing is still a heap cheaper than going to a wind tunnel.

 

It would be pretty pointless to take data that you collected on Beach Rd coming back from Mordi with a 50km Southerly and expect an accurate result... You would however be very bloody aero if you did use such data ;-)

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Fishmonster - without getting too technical, could you give a bit of insight into how your protocol accounts for differnt yaw angles (I'm guessing the most common being around the 15-20 degree mark). Reason for the question is that I get the real world testing would be very reliable in still conditions, but not sure how you get a repeatable result when its a bit windy (which is the most common condition).

 

Is yaw angle how far open your mouth is while riding? :lol:

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Is yaw angle how far open your mouth is while riding? :lol:

Directly correlated to the number of bugs that you swallow... Its a means of calculating the reduction in calories that you need to consume when riding based on said bugs.

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Are there any before and after shots that you are both willing to share?

 

That is really up to TristanP.

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