9606

I am on the fence regarding the front box.
Handy for cue sheet and easy access to items such as food. Bike handling is fine with or without the box.
Sure seems like a speed reducer because of the flat front face. Yet I have been told by people smarter than me to get everything off the back of the bike, for a tadpole or raindrop type profile. I have a nice rear saddle bag that I will use regardless, so I certainly won't be as sleek as a tadpole. Nevertheless it may be helpful to reduce my frontal surface.
In place of the front box I have been toying with two small feed bags (one on either side of the stem/headtube and a bento box on the top tube, just behind the stem, under the cue sheet.
I get cold easily and will ride mostly unsupported (two drop bags) so I need a bit more clothing than the average. 84 hour start, hope to finish in about 80.
What will the Seattle aeronautical engineer randonneurs do?
Or what will you do?

Many thanks -

Machka 

What is a front box? Is it a handlebar bag?

StephenH

No opinion on the question itself, but I recommend, don't experiment for PBP- if you're going to use it, put it on now and get used to it.
I take "front box" to be big handlebar bag.

clasher

I compromised and got something a lot more modern, I've been satisfied with using the Dill Pickle Gear Handlebar bag. I like it because it doesn't need a decaleur or any other rack. If you have a narrow fork crown and fenders right tight you might have a hard time getting the straps to work, but they can fit other places. I find it holds enough food for 8+ hours of riding. I also ordered the large saddlebag so I can use it on longer brevets and even overnight tours to a B&B or such thing. I also like that they're made out of modern materials instead of canvas and leather, so they aren't as heavy. Since they are handmade to order it might be a bit of wait for one though.

unterhausen

if you don't need it for a 600k, you don't need it for pbp. I don't think aero is really an issue. The Bike Quarterly guys say it's not

joewein

As @unterhausen mentioned, Jan Heine of Bicycle Quarterly studied the subject in a wind tunnel and found as follows:
If you think about it, when you look at a cyclist from the front, no part of the handlebar bag extends beyond the silhouette of the cyclist. The bag hits the oncoming air, but its resistance is partly cancelled out by reduced air pressure on the cyclist's body who effectively rides in the draft of the bag. A wide saddle bag that extends beyond the hips or rear panniers have no such cancelling effects because no part of the bike drafts behind wide edge of the saddle bag or behind the panniers.

Personally I switched from a Carradice saddle bag to a much more narrow but longer Ortlieb seatpost bag for improved aerodynamics. For maps I use my GPS or my android phone on holders on the handle bar.

Like the other posters I would also not recommend trying anything at PBP that you haven't tested in at least a 600 km brevet.

RR3

Heine did not say a handlebar bag does not create any additional aero drag. He said it was less drag than saddle bags.

My handlebarbar is well below my silhouette and certainly adds some drag. We don't know what bags Heine compared and his data is his data based upon his position, his bike, and his speed (around 20 mph).

If I were doing the 84H start again like the OP and planned to get to Loudeac at say 10 or 11 on Monday night, I'd just use a saddle bag and leave my warm clothes in a drop bag since that is only like an hour or so after last light. If on the other hand, OP's arrival to Loudeach will be more like 3-4 am (probably should be in the 90H group if that slow) and since he or she gets cold, I would mount the box and stuff it to the gills with wool arm and leg warmers, wool tee shirt, goretex jacket top, and maybe a fresh paire of socks.

I anticipate starting in the early evening and will leave additional warm clothes and fresh shorts at Loudeac but may mount the handlebar bag from the start depending upon the weather.....I know not smart. Probably just wool leg warmers, goretex jacket, and rain cover for helmet in the saddle bag. I can do hardcore rain into the high 40's with that setup and this is my standard gear for everything from 200 to 600k.

Not to be too obvious to the OP but please realise Brittany can be in the low 40's and damp. Chilling to the bone. Probably high 40's or maybe low 50's is as warm as the nights will probably be from Loudeac to Brest unless there is a heat wave. I could be wrong since I have only cycled twice in that region and found the dampness quite chilling especially after quite a few hundred KM riding. Coming from a warm climate, you might consider warm gloves and other accoutrements. I usually have a lot less clothing on than other riders.....at least one layer less. I usually only have a merino tee shirt and merino jersey on with bib shorts and wool leg warmers , a helmet cover, wool gloves on cold rides (say in the 30's...if windy or colder, I add a vest). I am a weight weenie and aero nut; HOWEVER, it would be a mistake not to have access immediately to warm and waterproof gear and even bigger mistake to have it 447 KM up the road.. I am convinced a HB bag is the best for quick access although plenty use just a simple Orlieb saddle bag and maybe a small Bento bag for Vitamin M and some food. If you have to stop to get out a pair of arm warmers from you saddle bag, you just absolutely lost any trivial aero gains. If you need proof, leave a control 5 minutes after an equally matched buddy. You may well not see your friend until the next control. I don't think aerodynamics are important unless the OP is really fast. Aero is towards the bottom of my list....my last 400k was around 17 hours, so, I am not real fast but quick enough that I make sure my clothing is tight.....that is the real drag. A HB bag drag? Not such a big deal in my opinion. Not having wool jersey when cold.....not good. Just figure out what you need and then pick your bags based upon that. Just using a saddle bag and bento bag is tight but it can work. I think I just convinced myself to mount "The Box"....thanks, I needed that.

fietsbob

Zzipper fairings are aerodynamic, not Flat , you can Hide your Box behind them .
Its Not a UCI sanctioned thing so why not?

Machka 

I used a handlebar bag and a trunk bag on the PBP. That seemed to work for me.

Chris Pringle

I agree that the 600K will give you a really good idea of what you'll need to carry for PBP. This is what my bike looked like for my 600 Km brevet two weeks ago. It got really hot the second day of the ride (the photo is from the first day). Glad I had the three water bottles. I plan to use the same set-up.

My plan for the PBP is to do the 90-hour start (i.e., Sunday late afternoon/evening) and finish somewhere between 75-80 hours.

dwmckee

I am an east coast aerospace engineer. Your basic comfort is going to matter a whole lot more than this little bit of drag, but in principle:
- Jowein is correct that as long as it does not increase your front profile view it does not increase your parasitic drag.
- The tadpole shape you mention, remember is a blunt and rounded front with a pointy back end to slowly bring the air back together smoothly behind (think of an airplane wing cross section), not the other way around.
- Neither front or rear bag is anywhere close to a good aerodynamic profile so unless you are getting close to a true faired shape it is not going to matter enough to compromise your overall comfort or convenience while riding.

Steamer

Quibble: That assumes Cd doesn't change, which is not true if the shape of the object changes. A handlebar bag does change the shape of the bike-rider system.

unterhausen

it's really hard to be definitive without wind tunnel testing, but there is a huge pillow of air in front of a rider's body. And the air entrained by the front wheel is also quite substantial. The advantage of PBP is that you can ride in a pack almost the whole way if you want.

RR3

Most randonneurs can improve their overall time by lightening the load (on their body), wearing tighter fitting clothing, and minimizing time at controls. Minimizing luggage (and warm clothing) is false economy.

Cervelo and Felt share a lot of wind tunnel data and although not entirely applicable to most randonneurs, some might benefit or just find it interesting. There is another Forum where Felt (Dave) and Cervelo Engineers banter while trying to win the fickle hearts of moneyed Tri Guys. Nonetheless, who wants to waste 6 watts on something simple or 25 watts with a floppy jacket.


Cervelo found that water bottles behind the saddle reduced drag compared to no bottles or cages behind the seat and was a preferred location rather than on the downtube or seat tube. This data would seem to support certain saddle bag designs like the Revelate Versace or maybe Ortlieb if the OP really wants the best aerodynamics.

Hydration and Aerodynamics - Cervélo

Steamer

Or R. Chung style virtual elevation type testing, which is very nearly as good. (at least for zero yaw)

RR3

Do you know if anyone has a spreadsheet for these calculations? Or if model/protocol exists? I googled but did not find anything

I have a perfect hill that we use for soap box derby type competitions the wind is often calm there in the early am.

I want to run tests on the Compass EL vs Continental 4000 sii in 28mm. I also want to look at luggage.

Steamer

If you don't have a power meter, you can do coastdowns where you record speed at one second intervals with something like a Garmin with an aux. speed sensor. Here: BentRider Online Forums - View Single Post - Something remarkable is happening

this might help too: https://www.bentrideronline.com/messa...d.php?t=116547


If you have a power meter, then you might do best to start here (at the 'source'): https://anonymous.coward.free.fr/watt...direct-cda.pdf You could also read my synopsis: https://rothrockcyrcle.wordpress.com...-my-aerolab-2/
and: https://rothrockcyrcle.wordpress.com...ion-revisited/

I should also point out that the 'aerolab' feature of golden cheetah IS Robert's VE method.

RChung

Soap box derby type hills might be too steep and featureless. A slightly shallower hill with a change in slope (like a flattening or a dip and recovery) can be better -- but calm conditions trump that so if that's all you have then use that.

StephenH

I would like to point out that this assumes you're riding in a similar climate. Here in Texas in the warmer months, you don't need ANY extra clothing of any kind on a 600k. Spare tube or two, some way to inflate it, reflective gear, and a Camelbak, and you're off.

prathmann

Not a very rigorous test, but comparison of my downhill coasting speed relative to other people in my club with and without my handlebar bag seemed to indicate a slight aerodynamic advantage to having the bag. OTOH, the bag results in a minor reduction in the cooling wind on my body.

RR3

The hill is 11 % and it is flat at the finish line with about a 500m runout afterwards. Starting halfway up, I hit 22 mph at the finish line and then coasted to about 13 MPH. Starting at the official start line, I hit 33 mph at the finish line. Probably better to use the half way point...?

I will check out the links. Thanks

Steamer

sounds too steep.

A good venue is:

- free of large amounts of traffic

- not completely exposed - some wind buffers (hills, trees, etc.) is a good thing.

- has a reasonably uniform surface over the test section (you don't want to go from chipseal to fresh blacktop halfway through the test run area).

- has a flat top and a flat bottom

- is not so steep or so long that you have very similar ending velocities (at the finish line) regardless of how slow or fast you were going when you passed through the start line. A quarter mile (or even a little less), at a 2-3 percent grade would probably do. The key is that the finish speeds are significantly lower for the slow speed start than they are for the high speed start. OR if the two ending speeds are kinda similar, at least not till very close to the end of the run.

- is reasonably close to home

- has some features to it that help you snip out and align the correct speed vs. time data for each run.

HOWEVER, none of this applies if you have a power meter. do you have a power meter?

RChung

That's pretty steep. When the hill is steep you attain terminal velocity pretty quickly, no matter what your initial velocity is. Shallower hills let you get good separation between runs with a low initial speed and those with high initial speed.

But, if the hill is well-sheltered from the wind, that trumps everything else so use what you have.

RR3

I have a power tap G3.

The hill is next to my home.....1/2 mile away. The runout is flat. I assumed that starting part of the way up and entering "my" starting line at 20 mph and then beginning my timer on a flat spot until the finish line and then it is totally flat

RChung

Oh, if you have a PT then do powered runs.