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Fairings for an Upright Hybrid Bicycle?


Thinking about real reinventing bicycle - in my opinion both upright and recumbents are very old and bad concepts, but I realized there are people who love to ban me for that ;-( Cui bono ;-) ?

My best next bike would be kind of rowbike, birdofprey. Love "SUV" bikes - sport, utility & excercise HPV. And as I have option to ride on bike 1/3 of way to work whole year unless switching to 1-2 car(s) or motorbike(s) - no more alternatives there...

My plan or dream was low head first bike similar to "teoretical" Superman position on upright, but during winter it would be nice to have kind of tent around also against cold, wind, rain, snow...

Tested few prototypes yet, now planning to sew a tent like box from nonwoven and hazel branches (light, cheap "green" materials), but not sure about, shape, size, etc.

Would it be better to close torso by a streamlined(?) shape and left hands out, put them inside that "tent", close upper part of wheels or not. Is it worth to use only 4th fairing below or close it a bit more, would it be good to create few streamlined shapes around particulars - torso, hands, wheels, legs, etc.

Would it be better to fix comfortable box to bike or to clothes like jacket where I started my attempts ?

Only clear now even supported by serious study is there is quite simple big fairing that can decrease drag coeficient say 4x...

In case of build new bike concept from scratch, me I would start with a volume, front area, weight and shape variables. And then imagine or model how to ride with smallest energy consumption Car top carrier and attach 3-4 wheels could probably be unbeatable start, then optimise shape of the box, etc.


Are there velomobile alternatives, something closer to, but build on up-right or similar cheap old school base or something modern like https://www.rowbike.com/, https://birdofpreybicycle.bigcartel.com/, etc. ? Lighter then velo and better than classic, recumbent or even race bike ?

Something inspired by Graeme Obree's The Beastie (56.62mph record) ? Beastie

or

Lightning F-40 ? F-40 Is there something similar for simple mass-produce bikes?


https://www.rei.com/product/212790/thule-courier-bike-trailer

Maybe good inspiration(-s) for such light foldable velo concepts ?

Having something like this instead of fairing should improve both drag (similar like mentioned fairing) and comfort (rain, wind, cold), maybe easiest as kind of jacket to be easily attachable ? From my tests it seems back jacket extension do not have much sense - there is teoretical limit 10% improvement comparing to 4,5x lower drag of best front fairing.

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    Your jacket seems to have a lot of floppy areas where the skin is free to flap with the wind. This produces an enormous amount of drag! There's a reason why pro riders use skin tight clothes, only. If you want to improve over your bare skin, your fairing must have a hard surface. Aug 26, 2022 at 15:38
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    Of course shape is important. It's just that you cannot expect to see any benefit from shape if you coat that shape with flappy fabric. The drag from the flapping will outweigh any benefits from shape. And yes, accidents happen. And yes, not having the tail fixed to the bike helps reduce side kicks from the wind. I'm just saying that you want to be careful and wary of this effect. I've had many accidents, considering one accident per winter to be perfectly normal. However, those winter accidents are orders of magnitude less dangerous than any high speed accident in summer. You have been warned Aug 26, 2022 at 18:59
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    I feel like the section below the break that contains test results should be removed from the question and written as an answer
    – Andy P
    Aug 28, 2022 at 12:34
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    Please don't rewrite existing questions, this invalidates the entire Q&A format and makes the existing answers nonsensical. I will revert the last edit, if you could please ask a new question and link back to this one as supporting information. I have both and will provide an answer.
    – Criggie
    Oct 26, 2022 at 6:36
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    @Tom Mods work to make the site more useful. This question lacks focus, which decreases its usefulness in a Q&A format. Both Criggie and I, as well as several non-mods, have given you some constructive feedback about how to write a good question. Your subsequent edits have flagged the question for reopening. However, the community has opted not to reopen it, indicating that it has not been improved. I recommend that you consider all of the feedback that you have been given, as well as reading our help pages on how to write a good question.
    – jimchristie
    Feb 1, 2023 at 15:34

3 Answers 3

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If you have a 50 km/h downhill section, that would be a good place to measure. Aero resistance roughly quadruples with speed. Ted Hohls comment below is better formulated. At 50 km/h you can be sure the major resistance is wind. At 25 km/h rolling resistance still plays a major part. As a % of total it gets less important as speed rises.

Simply rolling down that hill, starting from 0 speed or a fixed speed of the speedo, would give you an idea. It is important to realise that other factors like wind and temperature can mess up the results. If you measure on different dates, it's good to have 1-2 control runs with a setup you know. If setup x does 0-40 km/h and setup Y does 0-50, the later is best.

There are 3 things that factor in on overall aero resistance.

  1. Frontal surface. Less is mostly better. On your upright you are about 180 high, perhaps even 190 from the ground, and about 50 cm wide.

  2. The smoothness of the shape. Even a small edge can cause a disturbance, and vortexes. A Vortex causes more drag. As an example the difference between a modern glued in car windshield or a 1970 one with a rubber strip and chrome trim.

  3. Wetted surface. The surface of the object that is "wetted" by the air. You can get a very elongated shape, that is smoother to the air. But that same longer shape, can create more surface friction, of the air flowing past it. This works together with the previous point. A cylinder upright, has less wetted surface than an aero, symmetrical wing shaped profile around that cylinder. If you elongate that wingshape even more, eventually you will reach a point where the total drag does not go down, but starts going up.

A good place to start with aerodynamics is Julian Edgar, he had several youtube video's on car aerodynamics.

With your upright, you are roughly putting 50x180cm in the wind. That is 9000 square cm. A Snoek velomobile is 80 cm high and 70 cm wide at the bottom, but only about 30 at the headfairing. I would estimate that to have roughly half the frontal surface.

If you want to improve your upright, first look at how they improve UCI approved racing bikes. That is where the money is, and where most research is done.

Mochet experimented with tailfairings on upright racing bikes in the 1930ies, Then went for the recumbent position and eventually came to fully faired recumbents.

This is also a very good tread. https://www.bicycles.net.au/forums/viewtopic.php?t=99693

Fairing an upright is basically like fitting a spoiler on a VW bus to make it faster. It can be done, but there are more efficient vehicles to be found if you want to get the most speed out of limited horsepower.


When racing lowracers, the common experience when adding a lowracer tailfairing out of Fibreglass or Carbon Fibre, was a speed increase of about 10% at speeds over 30 km/h. Those fairings fit very nicely to the riders profile. http://www.m5-ligfietsen.nl/site/EN/Models/CrMo_Low_Racer

I am pretty sure anything shaped less perfectly, and less smooth will provide less performance gain.

If you want to improve speed on an upright bike here are my tips;

  • Drop the touring tyres and mount some fast racing tyres decrease rolling resistance from 50 to 20 watt
  • Fit an Aerobar
  • Wear a onepiece TT suit

https://cyclingtips.com/2010/04/biggest-bang-for-your-buck-in-time-trial-equipment/

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    You might want to clarify your quadruple statement. Aerodynamic drag quadruples with a DOUBLING of speed. Stated another way, doubling the speed increases drag by a factor of four. Another way is that aerodynamic drag is relative to the square of the speed. Good stuff though.
    – Ted Hohl
    Aug 14, 2022 at 15:16
  • UCI is very old school - it bans all best innovations like velos, etc. probably to keep fair competition. I also played with frame or wheels, but front area is probably not significant - maybe more relation or flow between particular parts, that is wind tunnel only(?) And even some cars have excellent coefficient despite they are far from streamlined, etc. But it is complex science/CFD optimisation then...
    – Jan
    Aug 14, 2022 at 19:07
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    IHPVA arranges competitions for many things that are banned from UCI events. If you don't know about IHPVA, it probably shows how well they worked out.
    – ojs
    Aug 15, 2022 at 12:25
  • web.archive.org/web/20110121095730/http://www.hedcycling.com:80/… Lost link mentioned at the end of last URL.
    – Jan
    Dec 29, 2022 at 7:39
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Adding extra shapes to your body to streamline yourself can certainly help, but its also more mass to move, can catch side and buffetting winds, and could do you a lot of damage/injury in the event of an accident.

In my experience, the quickest aero gain comes from getting your head lower and your hands closer to centerline, and trying to be "small"

A well-sized backpack can help fill in the void behind you when in the upright position on your flatbar bike, but bending down mostly eliminates the area. Hunched-over road bike riders tend to put items in special jersey pockets that hang at the back , also giving a subtle aero gain.

Sadly I don't have numbers for these.


Based on your bike link you're currently riding a hard tail MTB thus:

enter image description here

The first thing to do is swap out any knobby tires for smooth tyres. But given the bike's shape, there's a lot limiting your potential improvements.

You might be best off forgoing tyres, and buy or borrow a drop-bar road bike. Even a steel 80's bike will be more aerodynamic than you current bike could ever be, regardless of how many modifications you make.

The other item you need is accurate timing - a way to measure performance changes. That might be a simple stopwatch, though these days running Strava's app on a modern smart phone will give you a heap of useful data and make it easier to see your best 10 results on a segment for free. No need for an expensive head unit or power meter.

Otherwise committing to riding on the drops will show you the difference between the two styles of bike.

Later on you can invest in a lighter road bike and aero clothes and aerobars, but at this point developing your own power output, endurance, and position are probably the keys to speed.

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    Well, on the downhill, extra mass is a bonus. "Free" extra Watts. Until you try to get back up the hill, that is. Aug 26, 2022 at 15:50
  • Probably 1st upgrade were Schwalbe and Conti Ultra Sport 23mm tyres, great resistance at 6-9bars and bike has Al frame; 13-14kg is comparable or even less than some road bikes... And do not care about top speeds, but low power requirements - commuting 15km and 190m up/down in 45-50 minutes (16-20 average).
    – Jan
    Aug 28, 2022 at 19:19
  • @Tom I suggest you find a road bike and try it out. Borrow one if you can.
    – Criggie
    Aug 28, 2022 at 19:31
  • Maybe easiest way to optimize fairing would be small model from plasticine(?), rotate it in air or water and compare power consumption or attach far to motor vehicle and compare different setups/speeds by thrust force. Also smoke or water can show wind flow - saw triangle next to truck on rainy highway slowly sucking water back to its top edge...
    – Jan
    Nov 4, 2022 at 5:41
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    On backpacks, my understanding is that Camelbak type gear generally increases the rider's drag. Part of it has to be the straps generating some additional turbulence, but I'm not sure if there's anything else to it. So, I'm not sure if any wearables will reduce drag. You can come out aerodynamically neutral with behind the saddle mounts is what I recall.
    – Weiwen Ng
    Feb 6, 2023 at 19:47
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Found interesting simple CFD simulation, improved it to be able to copy/paste canvas's content from/to graphic editor and created 5 simple Cyclist 2D planes, looks like interesting starting point to get basic idea how should some shape work in theory... https://eltomjan.github.io/JStoolsSPAdemos/fluids.htm also added new binary format to get rid of frequent coordinates and better human readability (https://eltomjan.github.io/JStoolsSPAdemos/barrierdata.js), page works also offline in case you have both files on same place.

There is also link to original page on top, you can copy current shape by mouse over, right click/copy and just paste when page is active to update it, but mind resolution is different and only top left pixel is read for easier processing and there were some issues with resize/resolution switch; still unresolved.

https://lonniemorse.wordpress.com/tag/body-sock/

http://recumbents.com/wisil/whatsup.htm

http://recumbents.com/wisil/copeland/stevecopeland.htm this model seems to be quite close answer to my question...

Interesting info we fight about in long opinion based flames here...
Recumbent Bikes Are Not Faster http://recumbents.com/wisil/misc/notfaster.htm Great Human Power Ideas ... don't work so well.
http://recumbents.com/wisil/misc/great_ideas.htm


http://diginfo.ru/en/cycling_en/road-bike-aerodynamics-improvement/

Sad it is in terrorist country, but quite interesting and valuable content. "Glory to Ukraine!" (Слава Україні!, Sláva Ukrayíni!)


3 fairings Results Source INTERNATIONAL JOURNAL OF INNOVATIVE RESEARCH IN TECHNOLOGY https://ijirt.org/master/publishedpaper/IJIRT152797_PAPER.pdf


My downhill test show it may have tiny effect above 25km/h:

1st T shirt - quickest speed increase, then slows down

2nd this jacket (quite big size, wide sleeves), speed increase seems to be linear, but acceleration maybe slower

3rd 1/2 (only bottom hazel branches left) of back extension next day, same place

4 tests Data collected by BikeTracker apk's SQL export, time converted to seconds and speed to km/h, had to stop under hill to give way.

Mind extension was temporary test setup made from nonwoven (17g/m2, 2 layers), aprox. 1m long side after my back; not smooth, wind resistant nor perfect stable, anyway it looks like this part is not worth it...


Another day full 2 results seems to be similar, inflated, even more broken structure (wider front part), altitude difference during test by GPS aprox. 11,8 meters.

4th umbrella + jacket + new speed from distance chart

It seems to be clear proven you should not increase front area unless you create excellent shape to compensate that.

Found also interesting mail discussion www.ihpva.org ... fairings_rear.txt:

„Note that the tail fairing changes the drag by .1 no matter
what the rest of the vehicle looks like, but depending on what you compare
it to it either looks like a %10 or a %50 difference.  The upshot of it
is that you should streamline the nose first if you want really noticeable
drag improvement, streamlining the tail is only worth doing after 
everything else has been treated.  Hope this helps.  Nick.“ / Boeing Commercial Airplane

Till now best results were just forward bend without extensions.

Switching to smaller detachable front version test now...


Are there any occasion worth switching to road bike if someone has both or do you ride Velomobile only now?

https://www.renehersecycles.com/super-tuck-vs-aero-tuck/

https://roadbikeaction.com/chris-carmichael-explains.../amp/

Realized and found some support good position on upright can add few hundred watts (realized 50->62km/h short downhill max)

S. A. M.: To give you an idea of the aerodynamic efficiency of a true velomobile (WAW), I reach 62 kph downhill without pedaling on a moderate slope of 2.4%. I achieved my highest top speed of 93 kph on a longer 5.6% slope. But riding uphill is another story....

Chart

Each bike has its own playground. I switch between velomobile, mid racer recumbent bike and high wheel! A velomobile has other advantages than its top speed: comfort, weather protection, ability to take luggages,...

N. K.: No, and if I switch it's to another recumbent, I need my ass, back, shoulders, arms ... to work a few more years.


Here charts of fairing and Tuck records Fairing vs Tuck X/Y axes should be same in each pair.

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  • engineeringsport.co.uk/2016/09/04/… interesting tables here...
    – Jan
    Aug 28, 2022 at 21:11
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    First, you link a paper discussing 3 fairings that can be attached to a standard bike. Then you discuss your own roll-down tests using items of clothing (I think?). Those are not fairings as far as I can tell. Then you discuss different body positions on the bike. Those are definitely not fairings. As previously commented, I’m not clear what the main question is asking, but this answer seems like it’s not closely related to the question.
    – Weiwen Ng
    Jan 31, 2023 at 17:21

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