Sunday, March 27, 2011

Last race of the season - race footage.

Last race of the season - went out equipped with a camera on the bike that records in HD (1920 x 1080).

Such a great day out there - one of those rare windless and very beautiful days for racing. Had a blast ... 1st out of the water in my wave, 1st off the bike, then ran up the white flag on the run (as per usual) and finished 6th in A/G. 4th fastest A/G swim and bike - bike time was 30:28, which is probably spot on 40kmh av on the road and about 14 sec at each end mount and dismount to the timing mats.

The camera is a Contour HD which I ordered from the manufacturer in the states, but there are places in Aus you can order online at the same price. About $350. Awesome little camera records in full HD (1920 x 1080) at 30fps (which is almost too much info to process for most computers to play easily) onto a small SD memory card. At 3/4 HD size and 30 fps you can record 1 hr of footage on a 2 Gb card, will take up to 32 Gb card, which could possibly hold a full IM bike at full HD quality.

The 25 min odd recorded on Sunday was about a 1.1 gb file at 3/4 HD res. Started the camera on the bike once I had my feet in and wasn't going to be a danger to anyone. Left it running the whole race and switched off in the rack (would have auto shut off anyway).

Here's a few speed increasing tips and times from the vid you can use to hopefully ride faster as well:

0:25 - 0:50
Get aero as possible on the downhills (even slight ones) - doing so can produce a much higher speed, and by keeping up the power output you can get a good head of steam up that can carry you up the next hill, or further along the course.

1:25 - 1:44
Make sure if you do pass any packs you go over the top with sufficient speed they can't suddenly jump on (may not be that easy!). Remember to hurl appropriate abuse as you steam by.

2:12 - 3:44
Slipstream up behind people, just remember you have 15 seconds to make the pass stick and get out of their draft. Don't get too close or pass too close - a swerving cyclist is hard to miss at full tilt. Also ride in the wheel tracks where the cars have been - they are typically smoother, but may be more prone to potholes (keep an eye out!) Remember to pass only on the right, and move left as soon as you overtake and it is safe to do so. Failure to do so may incur a blocking penalty.

Take it easy on the turn arounds, particularly if it is wet. No prizes for wiping out. Don't blow a fuse building speed on the way out from the turn around - get up to full race pace again without overcooking yourself... it's usually faster than riding out too hard from the turns.

Wave to the draft busters, they are your friends.

5:08 - 5:20
Know the course, and ride the corners hard; get in the right gear beforehand and nail it in, through, and out.

Practice those dismounts and squeeze out your opposition over the timing mat! At least then if they get away on the run you can say you dismounted first.

Time to learn how to run properly over winter...

Oh and if you do end up buying your own Contour HD, you just have to put yt:stretch=16:9 into the Youtube video Tags field to tell it it should be a 16:9 widescreen movie.

Saturday, March 12, 2011

Cervelo's LSWT tests against the Big 4

As published on recently, Cervelo recently tested the big 4 TT rigs against the P4 in the San Diego LSWT wind tunnel, in a long series of pretty significant tests.

These tests are interesting because Cervelo is using their famous DZ (Dave Zabriskie) mannequin - although Dave is super good at sitting in the same position each time, wind tunnel testing is largely a repetitive chore, and I'm sure Dave has better things to do than freeze his goolies off sitting in the same position in a couple of hundred tunnel runs.

< Super Dave - the mannequin.

This means that the test results are actually representative of what we'd expect to see in real world use - ie. someone actually riding a bike round a course, rather than bike only drag figures which are often published from tunnel tests. The second reason this is so significant is because arguably the widely available current best 5 TT bike/frame combos are there being tested, and thirdly, independant observers from Slowtwitch were present during the tests (what level of exposure to tunnel testing they had is unknown however).

Cervelo has stayed quiet on the publication of this material, possibly choosing to release the info via an "independant" third party, rather than publish the test results themselves. Given how much hype surrounds tunnel tests by manufacturers this may be a smart way of releasing the results without incurring the suspicion of "manufacturer bias" prevalent when a manufacturer goes to a tunnel, particularly since their bike comes out either on top or close to the top (depending on the wind angles being tested).

So to results:

Firstly, the graph of Bikes, with Super Dave on, and trying to get the fastest possible ride - ignore-hydration-do-whatever-it-takes-to-win. This run sweeps from -20 yaw to +20 yaw, also important, because the drive train side affects the run numbers (if you look at drive side and non drive side in isolation you can get an idea, but not the full picture of what is going on.)

What does this show? Well by and large the P4 with a bottle on is certainly better than its competitors in the narrow range of -7.5 to +7.5 degrees of yaw. So if it is a low (or no wind) day, it could be hard to hang onto that guy on the P4 that just came steaming past. At 0 yaw the P4 is an average of 100 grams less drag than the average of the competitors - or around 5% better which is a significant reduction in drag. Between -15 to -7.5 and +7.5 to +15 the bikes chop and change in results, with the P4 being worse than all competitors in -10 to -15 yaw. Strangely, the P4 is again better than all competitors at less than -15 or greater +15 yaw. All competitors to the P4 test faster with a bottle OFF, making the P4 the only bike to go faster with the bottle on (whether you can actually get at that fluid while staying relatively aero is another matter - if you have a P4 you should be racing with the bottle in, regardless of what it contains).

The second part is to compare these results against the Trek Speed Concept white paper that came out last year. This is also available from Slowtwitch. In those tests, they did use a mannequin similar to super Dave, but only published limited data for tests with a mannequin. Most of their published data was without rider... which isn't a problem here as we have without rider data from the Cervelo tests too. Now this data was collected by 2 companies that have years of experience in tunnel testing, from the same tunnel (LSWT). The only apparent difference between these tests is the use of a H3 front/Hed disk rear in the Trek study, compared with Zipp 808 front/Zipp disk rear in the Cervelo study.

Cervelo results:

Trek results:

OK, so we have to confine ourselves to 0 to +20 deg yaw, but WTF? How is it possible that these results are so dramatically different between these tests? Admittedly, we only have 2 identical bikes in both tests: Trek Speed Concept and the P4 - but even these figures themselves are widely different for each set of results. If we take the data for P4 and Speed Concept from both tests and overlay it against each other we get:

The Trek data (solid line) is markedly different to the Cervelo data (dotted line), and given what I know about the 2 wheelsets (including independant tunnel tests and field tests), I'd be very surprised that either wheelset is the primary contributor to this margin of difference. Given the large (and consistent) gap between P4 and Speed Concept in the Trek data - I'd say "please explain, Mr. Trek".

Dan Empfield (Slowtwitch) does have the following conclusions:

Other bike companies might argue that the superior straight-on performance of the P4 is: 1) Somewhat due to the superior 0° yaw performance of the Ventus (the minimal drag of the pursuit position seems intuitively to be optimized for straight-ahead winds; and, 2) The most important yaw angles are those between 7.5° and 15°. As to the latter point, that's above my pay grade.

What is nevertheless undeniable, based on the results of this test, is that the P4 is the equal, or near equal, of every other bike in the test at these greater yaws, and better yet when as the bike points directly into the wind.

I'm betting the performance of the P4 in low yaw won't vary that much regardless of what bars go on that machine. As to the idea that yaw angles between 7.5 and 15 degrees are more important, that only works if you're a mere mortal spending the majority of your time racing in wind lower than about 10 kmh (6 mph). Once the wind strength goes above 10kmh (6 mph) you'll be seeing a wide range of yaw angles depending on the direction you're pointing, so you need a bike/wheelset that works well across a wide range of yaw. And if race day dawns calm and still, I hope you've got a P4 hanging on the wall of your garage!