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FatPom

Eyeball aero test

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Could do with your advice (again).  I've been running my P3 with a spares bottle BTS as you can see in this pic.  I've never really liked it there due to hassles fixing race numbers and rear lights for TTs, as I have little post showing.  Couple of weeks ago I bought an X-Lab carbon aero pouch thingy and fixed it on to the top tube with the bosses that come with the P3. I use this for my spares now. (I use liquid nutrition so don't really need it for food).  I took the BTS bottle off for now.

Which set up should be more aero?  (in theory).

https://www.xlab-usa.com/stealth-pocket-500c.html

 

IMG_0332.thumb.JPG.549cbf4942401b4e6a0fa96cc5d0b5d6.jpg

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If you really want our opinion, I think you should follow these guide lines for an inside aero test.

Get yourself a really big fan and set it up in front of your bike which is on the trainer, maybe a few metres in front.  Then find a big 44 gallon plastic drum and fill it full of those little tinsel/confetti like gold stars. Set up a video camera across the room, sideways from you, and run it recording on a high speed (so we get a slow mo vid), and start it running.  Stand the drum on top of a ladder beside the fan and attach a rope to the top lip, and then run the rope to a pulley your screwed into the side wall and then back to yourself as you gently spin on the bike.  Make sure the fan is blowing, ramp things up, get aero, and then pull the rope, tipping the drum over and all the tinsel/confetti stuff falls into the airflow of the fan.  Then we can see, via the confetti, how the air flows around you!  Do this test twice, with each different setup.  I'd suggest you do this test in your lounge or bedroom.

Most importantly, keep the camera running so when Mrs FP comes home and sees the mess we can see her reaction!

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32 minutes ago, Alex Simmons said:

The eye ball is a crappy aerometer.

In this case there is no "in theory" answer.

After watching Alex do his thing with AshleyS at the velodrome, I can confirm this is true. 

After getting Ashley as aero as possible they tested a behind the seat bottle holder and it showed no discernible penalty, which would be contrary to the "eyeball" test. 

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7 hours ago, goughy said:

If you really want our opinion, I think you should follow these guide lines for an inside aero test.

Get yourself a really big fan and set it up in front of your bike which is on the trainer, maybe a few metres in front.  Then find a big 44 gallon plastic drum and fill it full of those little tinsel/confetti like gold stars. Set up a video camera across the room, sideways from you, and run it recording on a high speed (so we get a slow mo vid), and start it running.  Stand the drum on top of a ladder beside the fan and attach a rope to the top lip, and then run the rope to a pulley your screwed into the side wall and then back to yourself as you gently spin on the bike.  Make sure the fan is blowing, ramp things up, get aero, and then pull the rope, tipping the drum over and all the tinsel/confetti stuff falls into the airflow of the fan.  Then we can see, via the confetti, how the air flows around you!  Do this test twice, with each different setup.  I'd suggest you do this test in your lounge or bedroom.

Most importantly, keep the camera running so when Mrs FP comes home and sees the mess we can see her reaction!

I have a 4yr old daughter running around, trust me, you wouldn’t be able to tell the difference:lol:

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The answer to all your issues is fake tan. Definitely faster.

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Legs too white. 

Can't make out the bike in the picture mate. Fake tanning is your best friend.... LOL 

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5 minutes ago, Naut said:

The answer to all your issues is fake tan. Definitely faster.

 

5 minutes ago, FFF1077 said:

Legs too white. 

Can't make out the bike in the picture mate. Fake tanning is your best friend.... LOL 

Fake tan is useless in a Welsh summer, the rain washes it off and then the ice freezes the stains. :lol:

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There's an article showing the side view of the top ten bike riders in last years Hawaii Ironman - every one of them has a rear mounted bottle holder - tucked up close under the seat - so it can't be too bad 

And those legs are incredibly white 

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21 minutes ago, AP said:

There's an article showing the side view of the top ten bike riders in last years Hawaii Ironman - every one of them has a rear mounted bottle holder - tucked up close under the seat - so it can't be too bad 

And those legs are incredibly white 

Thanks AP. Yeah I've tried a couple of TTs with the bento box and didn't notice much difference except when climbing as it slightly touched my legs (it's a tiny bit wider than the top tube). What I found surprising is how much I didn't like the look of the aero pouch there.  I figure if I can't see something, then it's not slowing me down 😁

I use the whiteness of my legs to blind the competition!  (it didn't work :lol:)

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FP, I like the level of whiteness you are achieving. 

With your Bentobox, if you don't like how it looks or sits at the front of your top tube, try it at the other end of you top tube up against your seat post. I've seen quite a few people do this. Aero wise it would be slightly better as your knees and thighs are disturbing whatever aero drag the Bentobox may catch. Functionally, I think it's not a good spot. But try it if you like, just to see. 

Honestly, the speeds us age groupers are doing on our Tri bikes, the position of biddons and Bentobox's is negligible in the overall drag coefficient of our bikes. The biggest gains to be made are with the human riding the bike and the position the human is in whilst riding.  That's worth a thread on its own. 

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5 minutes ago, Greyman said:

FP, I like the level of whiteness you are achieving. 

With your Bentobox, if you don't like how it looks or sits at the front of your top tube, try it at the other end of you top tube up against your seat post. I've seen quite a few people do this. Aero wise it would be slightly better as your knees and thighs are disturbing whatever aero drag the Bentobox may catch. Functionally, I think it's not a good spot. But try it if you like, just to see. 

Honestly, the speeds us age groupers are doing on our Tri bikes, the position of biddons and Bentobox's is negligible in the overall drag coefficient of our bikes. The biggest gains to be made are with the human riding the bike and the position the human is in whilst riding.  That's worth a thread on its own. 

Cheers Greyman, good point.  I do quite a few TTs as well, so outright speed can be a consideration. For the short TTs, I'd love to be able to stash the spare tube and bottle under the saddle but there just isn't room.  The BTS bracket is a bit of a PITA to take on and off, so would like something I can live with.

My aero pouch is the bolt on type so I don't think I could fix it any other way.  Of course, using the BTS does give me the room to carry solid food if I ever needed to. It just seems like quite a lot of structure for what is essentially spare tubes and CO2.

Perhaps I should have got that Canyon! :)

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Down in the aero position, how much drag could a bento box actually be generating???

I think it all looks quite clean - wouldn't worry about it.  You could try a mini bad tucked right up under the seat if you wanted to, but don't think that'll really make much difference.

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26 minutes ago, goughy said:

Down in the aero position, how much drag could a bento box actually be generating???

I think it all looks quite clean - wouldn't worry about it.  You could try a mini bad tucked right up under the seat if you wanted to, but don't think that'll really make much difference.

I can't, there is absolutely no room due to the position of the saddle and the edge of the post :(

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