faired or un-faired

 CervelowRAAMfairing2        The human body and the up-right bicycle are both aerodynamic disasters.

Yes – for this up-right rider – this is improvement – but there are better ways. I have come to realized there are two camps regarding the recumbent bicycle. Even major racing events now separate faired and un-faired bikes because faired bikes are aerodynamically more efficient.

Here is an example of the two categories.

Both of these bikes are of the same manufacture. The un-faired bike relies on high output  wattage for speed while the faired bike can hold the same speed on less wattage.

164088_129687543760263_100001570540123_218827_2010437_n

So why isn’t there more recumbent riders using fairings ? ?

Mostly because of the left over mind-set from the up-right bike whence we all grew up with. It also has to do with “the flock” the rider chooses to ride and race with.

Even though the faired bikes give more performance with less energy – your performance window could be a mis-match with the groupie your riding with.

Easy Racers recumbent bikes basically started the fairing movement years ago. The addition of a front fairing on a long wheel base “LWB” bike with low bottom bracket “BB”became a natural for noticeable improvement. It is now rare not to see a Tour Easy, Gold Rush, ti-Rush without a fairing or body sock.

Stars and Stripes 2

Here in the Great NW – the Oregon Human Powered Vehicles “OHPV”  have had faired recreational riders for years. We fair our bikes not to go faster – but to ride a preferred speed easier.

Fairings Cookie Monster

To better understand aerodynamics “in layman’s terms” lets take a look at a few pictures that perhaps will make it easier to understand the fundamentals of aerodynamics. One doesn’t have to be an expert in aero physics to understand that nature has already sorted it out for us.

Dolphin 3-1 aspect ratioDolphin aspect ratio

Notice that both – marine and air animals have one thing in common – Their body mass has a “the tear drop shape”

seagull aspect 1seagull aspect side

From all dimensions – the tear drop shape is natures aero dynamic shape for high performance animals/mammals.

OWL aerodynamics

This OWL is one of my favorite pictures of all time.

Now – lets take a look at some easy to understand illustrations.

Aero1

Notice when messing with natures shape the aerodynamic coefficient diminishes – or does it ? ? ?

aero_1

Even Moche knew how beneficial streamlining was back in the 1933

mochet-super-velocar-1933-

Up-right bike aero dynamics most riders don’t know about. Think about wattage as horsepower.  746 watts = 1 horse power.

Aero Drag Power for HPVs

Here is another chart that helps with understanding how much power = km/h for un-faired recumbents at race speeds.  The speedo should help with conversion.

Wattage comparison chart1 - A speedometer km vs mph

One can only imagine  what speeds could be obtained if fairings were used with these wattage outputs. Of course the amount of improvement would be in accordance to the application.

Notice the different Bottom Bracket “BB” heights in the pictures below. The lower the BB – the more need there is for a fairing.

BB position on bents

The higher the BB – riders tend to not use fairings because of the near horizontal body position.

Long wheel base liner

Here are some examples of fairings that have varied from mother natures tear drop shape. What is learned ? ? any fairing close to the aero shape of nature is better than nothing at all.

A closer look at the “aspect ratio”. Notice the first third of the shape is the nose cone.

profile of a tear drop

Below we can see a 3.5 – 1 aspect ratio. Meaning the widest part of the tear drop is approx. 1/3 the length of the shape. This is where the front wheels are on Velomobiles.

milan wind tunnel top

The infamous Milan Velomobile that holds the “distance” world record 757.451 miles – 24 hours.  Average speed 34 mph.  I would say that is one refined tear drop.

Milan_in wind tunnel

Ironically – the tear drop shape disappears when looking at from different angles. It is still there – but hard to see.

medium_quest-017

The Quest is another record holding Velomobile. No doubt natures tear drop is working very well with a 3-1 aspect ratio.

For those of you that are thinking – what happens with the toe/knee box bumps on the Milan and WAW – if the body shape is reduced – the humps and bumps are minor influences. However, there is significant known drag when the wheels are exposed to the laminar flow.

Tear Drop velos

The WAW is almost 4-1 aspect ratio where as the blue Birk is example of a 3 – 1 aspect ratio tear drop. Notice the wheel fairings, which are 4-1.

Single Track Streamliner

Canadian rider Sam Whittingham rides the Varna Diablo III to a world record speed of 82.3 mph (132.5 km/h …

Varna profile

Current World Record: September 18, 2009, 82.819 MPH

Varna top

Both of these World record holder share a similar feature – they both are of a narrower 5-1 aspect ratio.

See the 5-1 tear drop? This is the mpg world record holder of the World. Running on hydrogen, the PAC-Car II achieved a fuel economy of 12,665 miles per gallon gasoline equivalent (MPGe)!

pac-car-05-

As bicycle riders – we all know that we are in cross winds most of the time. The lateral roundness of the tear drop shape it preferred to the flat sided designs. Refinement studies of cross winds are now being done with success.

pac-car-cfd-

Trisleds “Completely Overzealous” World record holder for multi track Sept. 14, 2012 – Trisled’s trike powered by Gareth Hanks has set a record for three wheels of 71.79 mph.

trislede velo comparisons

Another example of tear drop refinement.

??????????

Note: – “with a bit of sarcasm” riding an up-right bicycle has the aero efficiency of a Humvee when exceeding the speed of 20 mph. It is the riders fitness that provides the horse power/wattage that make either of them go fast.

As I observe nature’s tear drop with relevance to a daily bike ride – I hopefully have illustrated the importance of aerodynamics. Human power is a fragile low power energy source when compared to our “feel the pain” of work vs performance.  Aerodynamics is the most important element for human power over anything else. A simple fairing will give back more performance per dollar spent than a $2600. set of carbon disc wheels. The tear drop shape is only the beginning of establishing a successful model of aero efficiency. The ongoing refinement by World Record setting builders that go to Battle Mountain annually are at the cutting edge of human power.

This article hopefully titillates the rider to refine their existing recumbent bike as a faired bike “to feel it’s performance enhancement”. I encourage you to think more of the fairing 1st as a more efficient component to purchase in lieu of the “more expensive – less efficient components” that bike riders usually buy.  How to set up a fairing properly with the many varied platforms of recumbents will come in a future blog.

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About Lonnie Morse

Long time recumbent bike rider - former general aviation pilot - always looking for an adventure to experience - aero dynamics fastenates me.
This entry was posted in recumbent bicycle aerodynamics and tagged , , , , , , , , , , , , , , , , , , . Bookmark the permalink.

18 Responses to faired or un-faired

  1. Great Blog. It explains well some of reasons velomobiles are shaped the way they are. I still like my Quest over the Milan, even though the Milan is more aerodynamic.

    • Lonnie Morse says:

      Thanks Kevin for the compliment.

      I too like the Quest for open road touring with it’s self-support capabilities. My choice to go Milan SL is based upon my intended uses of TT and credit card touring. I have found that a light weight aerodynamic package is a nice balance for this rider. I have since passed the desire to self-support tour any longer. Warm beds/showers after a hard days ride are more appealing for me than camping. It must be mentioned that the Quest can also provide similar choices with their new XS carbon model. I have ridden both. The Milan SL smaller size seemed to fit me like a glove. Isn’t it wonderful that we have choices of quality velomobiles with active R&D.
      Thanks for your comments.

  2. Lonnie – I have started to have fun optimizing my aero profile on my recumbents using Robert Chung’s virtual elevation approach. Have you considered doing some of these kinds of field tests yourself on your recumbents? I would be very interested to know what kind of CdA can be achieved with a socked GRR.

    • Lonnie Morse says:

      Hi Tom ~
      Good reading on the Chung site. I have found this type of data very helpful for the un-faired riders that have hit a wall with components like disc wheels, chains, bearings etc. Riding unfaired is when the combination of all the small elements pulled together to make “only” moderate difference’s at best.

      When riding faired – just one fairing component makes big differences. The difference between the two categories faired/un-faired is huge. The closest faired platform to the un-faired would be the use of a tail box. The lowracer is the platform of choice that gets the most from a tail box.

      I’m always in a testing mine set when riding my body socked Gold Rush. When I built my streamliner “Varna shell on a steel Zephyr lowracer” there was so much aerodynamic gain – (like warp speed) comparitivly. I then knew that a body sock was nothing more than a user friendly compromise of minimal aerodynamics – which equated to 30% improvement over a up-right bike. The next cd improvement step from the GR would be the F-40 – then a F-40ized lowracer – then a composite streamliner – the Battle Mountain racer would mean getting back into the Chung research mine set. All of these different platforms I mentioned have huge gains over the other. Tweaking more cd from a given platform like the GR means going out on a few rides with known friends for terrain riding comparisons. This is how I know the Aero Wing tail frame is more efficient than the other two brands on the market. It’s not that theirs isn’t working – the Aero Wing has on going changes from R&D every season.

      Thanks for your comments ~

  3. Maciej says:

    Without electric assist 3-wheel velomobiles are very slow going uphill, Your friends will wait for You one the top. Faired 2-wheel recumbents act like a sail when it’s pretty windy (wind tries to push You off the line). Being enclosed in “envelope” and riding tgether with “naked” bicycles (not naked bicyclist but I mean “naked bike itself”) gives somehow strange social feelings. And … going faster with the same efort (due to better aerodynamics) means that You need to take much more control of cadence to stay together with guys riding without a fairing.

    • Lonnie Morse says:

      Good points ~

      Most Velomobile riders are lone wolf riders until they socially gather into pods. I saw approx. 40 velomobiles Roll Across AMerica “ROAM” having no difficulty traveling faster than a well season’d upright bike rider.

      “Refined” velomobiles are way faster – if – the rider knows how to utilize the generous amounts of available momentum to attack the face of a up-coming hill. If your uncomfortable with 50 mph + down hill speeds – then you will never tap into valuable momentum that feels like kinetic energy.

      As you have pointed out – the performance envelope is quite different than up-right bikes. This is where the incompatibility of the different human power vehicles are challenging to deal with. The Velomobile may be of heavier vehicle but can climb slower/easier uphill for no fear of falling over. Velo’s are rocket fast down hill and cruise missles on the level. So where are the up-right bikes now ? ? usually waaay behind. The up-right bike can do only one thing well – “climb”. That is only “one” out of “three” categories of bike performance it does well. I will take being the best of the other two categories any day.

      I ride a Socked ti-Rush – – yes the wind buffs me around sometimes when out in the central plains – if it becomes too much – I remove it and tuck up under the front fairing. More times than not – I can wind tach/sail “with body sock” in winds up to 25 mph. The front fairing has always shown to be an improvement in winds from all directions.

      You mentioned – going faster with same effort. Yes – I too do a lot of coasting when riding along with upright bikes – even un-faired bents – they say I’m cheating – I say they too can buy one of these comfortable efficient machines. By the way – my first recumbent was a 1997 “Tour Easy”. I immediately noticed I climbed one cog faster than I was on my Cannondale upright. So bents “can” climb.

      Take note that picking the flock you want to ride with is important when choosing the bike.

      Thanks you for your comments Maciej ~

  4. Greg Cantori says:

    Very informative Lonnie!
    I’ve always wondered how much benefit I’ve been getting from my carbon fairings (Front and tailcone) on my Windcheetah – I know it’s substantial but haven’t seen any quantified information. Any leads?

    • Lonnie Morse says:

      Hi Greg ~

      Sorry – no leads. However if I may comment? Anytime front fairings and tail cones are installed, there are significant variables that will come to play – what bike used – component position for rider size. What may be a best for you would be different for another sized rider. There are ways to find out your personal cd and cdr by Google-ing other websites to use their math formulas. For this site – It will be simple as “101” of aerodynamics with illistrations. All data that I aquire is seat of the pants observation while riding “real time” with other faired/non-faired bikes.

      Windcheetah makes a beautiful/efficient fairings for road use.

      Thank you for you interest ~

  5. Randall Mathews says:

    Wonderful stuff Lonnie. I too get off on efficiency for it’s own sake. My commute is 12 km each way and I use a Bacchetta strada, so the bottom bracket is high enough that a front fairing won’t make a huge difference. Still the temptation to fair it exists strongly. Lycra body sock seems the best compromise for practicality, but can you recommend a lexan unit for the front?

    • Lonnie Morse says:

      Hi Randall

      If I were to set up a high racer with fairing – I would use a longer fairing than most do. The objective is to direct the air over the shoulders of the rider to not allow the air to trip into the chest of the rider. When a rider is in a more prone position of a high racer, there is a long distance hortizontally from the feet to the rider to deal with. Yes, a sock is another way to address the issue however due to the Bacchetta platform design. I might note that the sock doesn’t have to be a stretchy material. Why? – The fairing isn’t attached to the steering bars where a stretchy material would be required. The steering is independent from the fairing. I would opt for a more solid material such as coroplast. With practice – one can get a nice professional look from this durable material. Go to some of the pedal prix websites to see how they use the coro material for some darn nice exotoc designs. http://www.trisled.com.au/formula-trisled.asp

      WISIL is another website that have tutrials of the coro material. http://www.recumbents.com/wisil/tailbox/barracudatailbox.htm

      The Windwrap fairing would be my choice for this application because of it being quietest of road noise.

      Have fun with the project.

  6. Mark M says:

    This was or is a great page. I loved the examples ,especially the nature pics/examples.
    I use to have a fairing called the Breeze Cheater by “Fairfield?” but unfortunately no longer do and wonder if you would know any information about it or other diamond frame fairings like the AreoEdge pictured. It is still a lot cheaper to add a fairing to a very light co0nventional bike than buy a very light recumbent and add a fairing to it.
    There are very good reasons to still ride a conventional bike and even though I have a somewhat fully faired recumbent ATP Vision R42 + Zipper fairing and a “possibly aerodynamic trunk” the Cannondale is faster at least on short quick trips.
    Thank you again for the page. I was and am looking for fairing’s’ for “conventional” bikes.
    I hope to visit some of the other pages.

  7. Todd says:

    It is obvious that a fairing reduces drag tremendously but there an MIT study showing that drag reduction is minimal. At 30 mph, a non-faired recumbent has 24 lbs of drag compared to 19 lbs with fairing. I thought the numbers would be near half. Thoughts? Guessing the square of the speed formula would show greater gains at higher speeds.

    • Lonnie Morse says:

      Hi Todd ~

      I did a quick Google search regarding your MIT comments. I could not find the data comparisons that you spoke of. If you could provide a link – then I can provide comments.

      However – I would not put much faith in “out of date” research – if – it is. Example: the Vision Saber study with a Mueller fairing. Most any recumbent rider that uses a fairing much at all will notice the turbulator effect fairings cause when placed to far away from the rider mass. Rule of thumb to follow – if you can feel the air in your chest, your fairing is either to low or the body is too far away from the fairing. MIT admits “at the time of the 1999 test” (quote) Large wind tunnels, such as the one at MIT, run into resolution problems at the low airspeed and drag numbers presented by a bicycle. A contribution could be made by designing a wind tunnel optimized for low airspeeds and drag.

      My opinion differ of this 1999 MIT paper when a fairing is used on a rider reclined high racer platform. The larger size of the fairing compared to the uprite rider has nothing to do with the test data of equality – it was the location of the fairing from the rider that was dumping the air into the riders lap. “MIT” not being experienced with bicycle fairings were not able to reason the variables – as discussed in my blog content.

      Here is the “old MIT data” link I base my info from – http://www.hostelshoppe.com/atp_archives/mit_windtunnel.pdf

      Thank You for bringing the topic to my attention. I should use this old MIT data in my blog for the reader to further understand how a fairing works more clearly.

      Please send me the link you came across – I would like to read it.

      Thank you for your interest in recumbent aero dynamics blog.

  8. Lynn Miller says:

    I have had several different recumbents over the years. My first was a Rans Stratus A followed by a Haluzak Horizon, and a Lightning R-84. I’ve had or ridden many others along the way. My son and I did three self contained Alaska tours. I still own and ride the Stratus and R-84. For my money the Lightning seat is by far the best seat of all. You can ride for hours in complete comfort. The Stratus is my main ride now but it is much changed from when I first got it. It started life with oddball braking and shifting controls mounted mostly on an upright stock between my knees. About two years ago the handlebar broke while on a ride. Fortunately I wasn’t hurt. I replaced it with an Easy Racers front end. This allowed me to add a fairing and body sock. What a huge difference! About a year ago I replaced the original steel fork with a carbon fiber one from Easy Racers. At the same time I replaced the Lexon fairing with one made of carbon fiber. I also added carbon fiber fenders and Aero Spoke wheels. The original Rans seat is now a hybrid Rans/Lightning seat. I added a curved top tube to the seat back to hold the body sock in place and used seat mesh from a Lightning. This allowed for the use of a Lightning seat back bag which is hidden inside the sock. The seat is much improved but still not as comfortable for long distances as the Lightning. In my humble opinion a Lightning P-38 is the best all around touring machine. Super comfortable, easy to pack, easy to stash on ferries, or in wooded areas when doing clandestine camping, and handles better on rough roads. We hit plenty of rough roads crossing the Yukon and the short wheelbase Haluzak handled them much better than the long wheel based Stratus. The Lightning is better than the Haluzak because of the up right steering. If I were to tour again I would choose a P-38 even though I would miss the fairing and body sock.

    • Lonnie Morse says:

      Hi Lynn ~
      Is it not wonderful that recumbent bikes provide ergonomic choices “unlike up right bikes”. I have seen my customers on a perpetual hunt for the perfect bent by swapping back and forth for years. I can understand your opinion for your love of a Lightning product. I feel the same with the Easy Racers Gold Rush. Each of us riders evolve into a fit that have a comfortable preference. I have a similar story much like yours but with a different preference out come.

      One day coming home “on my Corsa” from a 40 mile outing I got to thinking that I wasn’t evolving into the performance window that I had with my GR. I also had too many bikes hanging in my shop. I knew that I had to stay with one type of platform to have optimum bent legs for the season. I just knew I was losing ride performance from my GR by spending too much time on a very different platform “the Corsa”. I was not anywhere as fast on the Corsa as was on the socked GR. The Corsa was also laden with non user friendliness IE horrible trying to get started going up hill from a stop sign “high BB”. Not user friendly at all in traffic being reclined for aerodynamics. The straw that really peeved me off was when the front wheel promptly took my riding shoe off my foot while turning a corner “wheel heel” over lap. I simply do not have any tolerance of a design that does these things to this rider. These are none issues with a GR.

      So, I made the decision to make a “decision” that day, which of the bikes were going to be sold. As soon as I got home I grabbed the un-sock faired Javelin and went for a 10 mile ride. Heading back home I decided it would be sold.

      I then grabbed the faired GR “with out sock” and went for an eight mile ride. For the very first time it dawned on me “the why” I kept coming back to the GR after riding other bikes off and on. It was the low center of gravity that I enjoyed so much when carving a speedy turn.

      I have always been a long wheel based fan because of the relaxed geometry. Let it be known – I was never an upright rider that appreciated road bikes. I always preferred the touring bike geometry for it’s forgiveness of being able to lollygag around sight seeing and still hold a decent straight line speed. This is why I like the longer lwb GR “with low BB”, it is forgiving when I’m looking way off yonder or getting my feet on the ground quickly in an emergency and or starting from an up hill start at a stop sign.

      So – two bikes were promptly sold and I settle down to confirming, what I had, is what I enjoyed the most. By the way, I have really never felt the lwb GR to be that much of a inconvenience because of length. As far as aerodynamics – in doesn’t get much better than socking up a GR. It is like they were made for it even though it was an after thought.

      Yes – I have had my experience with bent butt in past because of the up-right rider position putting more pressure on my sit bone. I do know what you mean when liking the Lightning sling seat – I had a Rotator with a similar seat design. But, since then – I have come across a seat for my GR that fixed the bent butt issue. It is the Cool Back seat with one extra layer of the high density foam on the seat base. I can stay on this seat all day long. Bent butt is a thing of the past for me. I’m sure this would work on a Cobra seat base also.

      So, once again – we are so lucky to have many choices that we can find what is best for each of us. As for aerodynamic touring – – – as you may or not have read – I and five other bent riders rode a TransAm in 2005. Four of us were Socked – two of us were socked 95% of the trip.

      http://www.crazyguyonabike.com/doc/?doc_id=820

      While crossing Kansas I had a lot of time to ponder different scenario’s. I did some math “knowing the approx. distance of the trip” to affirm the benefits of a sock while touring. It is a know fact a properly set up Bock Sock on a GR gives 30% more efficiency over an upright bike in return. As a long time sock rider, I considered the parasitic drag of the panniers hanging on the outside of the sock so I backed the 30% equation off by 8 -10%. I used a 10% factor just to make the math easy. If things went according to plan, we were to ride approx. 4200 miles on our journey across America.

      With out panniers, a Socked GR is 30% more efficient.
      With panniers, a Socked GR 20% because of pannier wind drag.

      4200 miles minus 20% aero efficiency = 840 miles of free to no effort miles. That is quite a sum of miles that I benefitted from IE easier pedaling economy, or just coasting along free riding, plus faster down hill roll out with an abundance of up hill inertia and cross wind enhancement. All being considered, I think of it by this analogy of mpg. If an upright touring bike is getting 10 mpg where as I “aerodynamic” was getting 12 mpg at 1.5 mph faster speed, “based upon passing younger upright riders along the route”. Other kudos like “being protected” from the sun with my ride along aerodynamic ventilated sunshade for thousands of miles is pretty convincing. All-n-all, two of us did ended up riding 4200 miles. Would I ride with out a sock on tour? Not a chance.

      As it turned out – knowing I am a confirmed lwb rider – I purchased a 2.0 ti-Rush a year ago and have never looked back.

      Enjoy life Lynn and thanks for sharing your story.

      PS – Not trying to convert you – you already know the differences of lwb vs swb. I will say this – a entry level Easy Racers Tour Easy will probably impress you over the Status. My experience is, the two bikes are quite different. I found the TE to be a more lively performer as well as being lighter, with a supple frame ride when comparing the two. The Gold Rush will give a rider one more cog faster climbing for the same effort. Why? Stiffer BB. The ti-Rush gives yet another cog for climbing. Why? Like all ti frames – the frame stores energy – un-believable. I would have not believed it until I got one. Bear in mind – a rider has to be a performance rider to experience these differences. Passive riding does not make a notable difference to the rider.

      http://www.crazyguyonabike.com/doc/?doc_id=820elocity

      Lonnie Morse
      Recumbent Services of Portland

  9. Leo Horishny says:

    I’m curious about the front fairing on the lwbs and why not extend them around the front of the wheel? At least, in some fashion. Have you thought about modifying one such and doing some testing to compare the two configurations?

    • Lonnie Morse says:

      The “now past” Rotator manufacture already has. Makes sense to fair forward of the front wheel for a aerodynamic reasons. However – the caveat of additional weight out in front sometimes cause’s a un-user friendly side effect. The additional weight cause’s a flop effect that can be felt in slow manuvers and or parking the bike on a side kick stand. The bike will just fall over because of the additional weight out front causing the handle bars to turn toward the low side, over riding the kickstand. All-n-all, I like the Rotator fairing – I just wish it was wider. It is narrower than the other manufactured fairings IE Windwrap and Zzipper”. Keep in mind, the small 20″ front wheel doesn’t add much aero drag as you might think. Narrow tires with bladed spokes cleans the wheel up pretty good.

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