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.
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.
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.
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.
Notice that both – marine and air animals have one thing in common – Their body mass has a “the tear drop shape”
From all dimensions – the tear drop shape is natures aero dynamic shape for high performance animals/mammals.
This OWL is one of my favorite pictures of all time.
Now – lets take a look at some easy to understand illustrations.
Notice when messing with natures shape the aerodynamic coefficient diminishes – or does it ? ? ?
Even Moche knew how beneficial streamlining was back in the 1933
Up-right bike aero dynamics most riders don’t know about. Think about wattage as horsepower. 746 watts = 1 horse power.
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.
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.
The higher the BB – riders tend to not use fairings because of the near horizontal body position.
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.
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.
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.
Ironically – the tear drop shape disappears when looking at from different angles. It is still there – but hard to see.
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.
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 …
Current World Record: September 18, 2009, 82.819 MPH
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)!
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.
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.
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.