Sunday, April 23, 2017


Velomobile efficiency is one of the best reasons to own a velomobile.  The subject is fairly complex and I will try to cover the subject in a few posts here.  Today I will an overview of what characteristics of makes a velomobile efficient and address aerodynamics.

Out of the box, velomobiles are fairly efficient when you compare to an unfaired bike but there are still many things that will give you an even better performance including several options available from the manufacturers. 

How efficient are production velomobiles?  Again this depends on the velomobile you compare with but if you have a Milan SL or a DF, you have one of the most efficient velomobiles out of the box.  As a rule of thumb I say that since 80% of the effort on a road bicycle is pushing the air, a velomobile should improve this by halving this effort.  This gives a 40% advantage (50% X 80%) to the velomobile.  As a result to maintain a certain speed a bike requires 300W while the velomobile requires 240W X50% +60W = 180W.  I tried to see if my rule of thumb was close so I looked at segments that I rode and compared them to the next rider assuming he/she was riding a road bike.    In one example a rider is pushing 255W for 12.5km on a somewhat flat segment, no wind and a speed of 39.5km.  For the same segment, I rode the same segment with a 10km/h headwind.  I needed 155W to travel at a speed of 47.5km/h.  Leaving the speed difference and wind, my rule of thumb would give me an effort of 204W X 50% + 51W = 153W.  While it appears to somewhat confirms the rule of thumb, the difference in speed and the extra work due to the wind has not been accounted for so the efficiency appears to be even greater on flat ground.  Of course the difference on a hillier course would be somewhat different, as the power to climb the hills needs to be much greater for a velomobile.

I get it, many people are happy with the weather protection and carrying capacity of velomobiles.  Others do not see a need for improvements or are unable to fully extract the performance of a stock velomobile or they opted for e-assist that gives them the boost they need.  Still there is a large segment of riders who want to get as much speed as possible for the power they can generate. Getting the most performance out of your velomobile requires paying attention to the details.

There are four areas where improvements can normally be made: aerodynamics; rolling resistance; weight and mechanical efficiency.

There are many ways to improve the aerodynamic efficiency of a production velomobile but it depends on the velomobile you ride.  It may be the low hanging fruit for improving velomobile efficiency.  Every thing that sticks out like mirrors or holes in the shell like the hatch for the cockpit creates drag.  I will provide some ideas on how drag can be reduced but these recommendations have to take into account your own velomobile and circumstances.  Beyond these tips there could be many more improvements that may be possible.

I was reminded of this recently as I started my season riding without any significant modifications on my DF, it was essentially a stock DF.  The only small improvement was a mini visor.  I rode a few weeks until I decided to put on the hood.  That single improvement provided me a 3 to 5km/h average speed improvement on the same courses; this is very significant in the order of 10 to 12% for the same power output.  Going down hills where I had a maximum speed of 62 to 65km/h, I was now maxing out at 72 to 74km/h, a 10 to 14% increase.

Open hatch velomobile and the rider’s head/torso have a major impact on aerodynamic efficiency.  Even a rider’s helmet increases the drag.  First let’s look at the obvious.  Many open hatch velomobile usually have a neoprene skirt that covers the hatch leaving only room for the head to stick out.  This provides a significant improvement but it can be uncomfortable to ride with the skirt regularly.  Another small improvement is the mini visor that is attached to the front of the hatch with a Velcro.  The visor deflects some of the air around the rider.  There is a small aerodynamic impact.  A hood that covers the open hatch of the velomobile is probably the best way to minimize the drag of the velomobile.  Some velomobiles like the Quest have several different hood designs and manufacturers to choose from.  Each has its own advantage and disadvantage and have differing level of efficiency while others have a more restricted choice.  The hood has the added advantage of weather protection in cold and wet conditions.  On the other hand, visibility can be somewhat more restricted, it may be difficult if not impossible to wear a helmet, the cockpit can become too hot for some or it can fog-up.   For racers, commercial hoods have also been modified to make them even more efficient for example by reducing the frontal area.  While hoods are not created equal, as I mentioned above the gain from a hood can be significant, it is probably the single biggest aerodynamic improvement that can be made. 

Open wheel velomobiles like the Strada, Mango, DF, Evo-K suffer to different degree from the turbulence created by the front wheels and wheel wells.  There are several ways this can be addressed with different levels of performance improvements. First wheel cover help for open wheel velomobiles by covering the turbulence from the spokes.  Some wheel covers are made of Lycra while others are made of fiberglass or carbon fiber discs glued to the rim. 

The wheel wells are a source of air turbulence.  Some velomobiles have tighter space between the wheel well and the tire to reduce this turbulence.  Small plastic deflectors that essentially cover the gap in the wheel well between the shell and the wheel leaving just enough room for the tire to pass when turning can be added to minimize turbulence. Deflectors are normally taped to the shell just around the wheel wells. This provides a small but noticeable improvement in efficiency. 
If you would like to further, increase efficiency wheel pants are the solution.  Wheel pants essentially cover the whole wheel well making the airflow past the wheel well following the shape of the velomobile.  This minimizes the turbulence significantly.  Only the bottom of the wheel is visible.  Unfortunately, there is a small price to pay because the wheel pants are restricting tire size and increasing turning radius.  Some racing wheel pants or wheel pant extensions can be installed on racing velomobiles to further reduce drag as the wheel pant/extension are made to cover the whole wheel leaving less than a centimeter of air space between the ground.  Even velomobiles where the wheels are covered like the Quest could see performance improvement with extensions of the wheel covers effectively hiding the bottom of the wheel and closing the bottom of the wheel well.

Velomobile with foot holes can see improvements by closing the foot holes with special covers that have bumps under the shell to give room for the feet to move freely on the pedals.   While I don’t have a number to give, the improvement can be significant.

The perfect tail for a velomobile is shaped like a wedge.  Unfortunately in order to provide a surface for rear lights and reflectors to increase visibility, most velomobile tails are somewhat truncated.  Many riders have found a solution and added a tail extension transforming the blunt tail into a wedge using transparent plastics.  The reflectors and lights are still visible but the airflow is better reducing turbulence. The improvement is small but noticeable for racers.

The nose is something that has attracted attention lately.  The DF, for example is a velomobile that has an air intake at the front.  While it is designed to minimize the aerodynamic drag but it still has an impact.  Closing the hole will result in a warmer cockpit but that may not be an issue for a race or when the temperature is cold but may lead to an increase in fogging up inside the hood.  To get the improvements, the cover has to follow the shape of the current nose and using clear plastics would not impede the headlights hidden inside.  While this small modification provides improvements, you can go further.

Recently I was made aware of one rider who modified the nose of his Milan SL by extending it making it pointier and saw speed increase.  This modification is not without drawbacks.  The modification makes the velomobile more susceptible to side winds and this could make the velomobile difficult to control at high speed under windy conditions.

Beyond these modifications, those racing may also try to use tape to close seams and other holes and cracks in the shell.  Anything protruding from the shell like lights, cameras and mirrors especially large ones are also creating drag.  While I would not recommend removing any items used for safety, riders may choose to reduce their impact or removing them for special events like races.


Daniel Fenn is hard at work on the DF-4, the 4-wheel DF prototype.  He recently went on a 170km ride with the prototype.  Daniel even took his dog in the velomobile on this journey, the dog can fit in the luggage compartment just behind the seat is much larger than the DF.  ICB has posted several pictures and video on their blog.  The prototype will see more refinement before a decision is made to go to production. 

There are a number of interesting innovations in the design.  The pedals will drive the left wheel of the velomobile while an optional motor providing assistance will drive the right wheel.  The DF-4 prototype has a mid-drive Rolhoff  and a 10 speed cassette at the back.  The wheel wells are larger than the DF/DF-XL and would enable the use of popular larger tires like the Shredda and the F-Lite.

Busy as usual, Daniel is also in the process of producing a new racing hood for the DF with no side windows.  This is the type of hood that Milan riders have used in record attempts.  The hood is apparently 33% lighter and hopefully more efficient than the original DF hood.


The annual Special Bike Show SPEZI 2017 will take place April 29 and 30 2017, in Germersheim Germany.  This is the 22nd edition of this annual event that started in 1996.  The show provides attendees the chance to view and test products. Several velomobile manufacturers from Europe will attend but some will not. 


  1. Have you ever thought of introducing dimples into the front of a velo - to imitate a golf ball effect that introduces turbulence to cause a layer of air to cling to the shell - with the effect to reduce drag. I will have to try this on my velo.

  2. Well I will not be the one trying golf ball dimples on my velomobile. I don't know that they make a difference, I do know that Mythbuster tried them and may have seen improvements on a not so aerodynamically efficient car to begin with. If you look at the Battle Mountain streamliners, you will see that they are extremely smooth, no dimple there. The level of detail to make it to the record speed of 89mph is incredible including very advanced flow simulations. I would expect that they would have used dimples if they thought these would help. It is so precise that last year ETA scrubbed a run because they encountered an insect that disturbed the airflow and as a result of that splat they realized that they would be unable to reach the record setting speed. After a cleanup, the streamliner broke the speed record. There are so many things that could be improved on most velomobile that IMO would give a better bang for the buck than dimples.

  3. For dimples you would need to drill holes in your expensive velomobile and considered many are already built as a very light monocoque designs they would lose structural integrity doing that. Or apply a thick layer of material ( as the mythbusters did ) you can impress with dimple holes. Adding weight.

    Both a no go unless you can produce streamline hulls yourself to experiment with. It may be more reachable with experimenting with self made hoods, not touching the (expensive) velomobile itself.

    Still the Battle mountain teams could be locked into a certain direction of thinking ( improving things, but not too radical different from their predecessors ) to even consider such things. I know that in aircraft wings air pockets or micro turbulence designs are being used to get increased fuel efficiency. But those are incomparable (air)speeds, velomobiles operate at speeds where air resistance only begins to come into play while being hampered with very limited (human)power.

    1. I would never touch my velomobile skin either - I would rather carve out a piece of my own skin!

      My idea would be to introduce a foam dimpled skin onto the front of the velo - minimal weight and easy to remove.

      I have read enough about aerodynamics and fluid dynamics to know that I know nothing! But I am intrigued by the shape of marlins and sword fish - which have bodies radically elongated and with very pointy noses - but otherwise they are shaped close to velomobile dimentions. They can travel through the water at 80 kPH or more - in water! This shape makes me think that my velo should have a beak or nose shape. And a much more pronounced tail.
      This is another possible experiment that could be done non-destructively. Coroplast is cheap and light.

      My last thought is very radical but I know I will implement it - a tail propeller! Please google DWFTTW (down wind faster that tail wind) to see this real effect. Basically, a tail propeller - linked directly to a back wheel (wheel spins the propeller and the propeller spins the wheel) - will push against the wind in a way to multiply the effect of a tail wind by 3 times.

      Enjoy your spring cycling.

    2. Good to know that you will not take a hammer or drill to your shell. Be careful in your experiments as elongated nose and tail not to mention any type of sail have major impact on your ability to ride a straight line except in the most favorable wind conditions. You would not want to end up in the ditch if a tractor-trailer passes next to you on the road. From experience it is a real danger with a regular velomobile under gusty conditions. Good luck!

    3. The velomobile is the rarest vehicle on the planet. As you know - we are the 1 percent of the 1 percent of the 1 percent of the 1 percent of cyclists.

      There are 100 times more Rolls Royces than velomobiles!

      So it is a very small club - and I am very happy to have joined it.

      As for danger in cycling - I believe that if you do something for 2 hours a day - for 40 years - whether riding a bike or watching TV - you will probably die doing it.

    4. Swordfish also use oil from glands in their sword snout to further reduce friction in water. Burst speeds up to 100 km/u through water are very impressive.

      Oil won't make us faster in air though...probably a very smooth wax coating might :-))

  4. There is pressure drag and friction drag. It looks like faster velomobile models improved on pressure drag and record attempting "velomobiles" even more so. Mostly by means of reduced width and frontal surface. There is probably nothing to be gained on existing models without changing the model as you probably cannot make it smaller. ( lower or less width )

    Then there is friction drag. Not necessary holes, seams and objects sticking out the streamline as mentioned are part of that. That is simply a matter of making the streamline surface as smooth as possible. Reducing hole size or preventing them ( hood over man hole ) as mentioned. Still a foam cover - without use of a plump cycle helmet (!) - will be hard to improve on (by much) with a hood.

    Such things are on par with everyday usability however. You either own a practical velomobile or a racer....not having anything sticking out of the streamline will prove to be rather hardcore...( mirrors must become camera's and a lightwight screen such as a mobile phone )

    Interesting is dimple holes are "slow" (air)speed effective, and velomobiles are certainly within that speed range but i guess it is rather impractical to use on an existing velomobile model. Another thing is where to place them, research on that subject didn't use velomobiles yet. So i guess :-))

    Another more proven method is placing vortex generators to prevent the air layer to let go of the velomobile too early but (air)speed may be to low for a real difference. Where to place them exactly is another thing, i guess they should be on the broadest with part of the velomobile. Easy to find for a "fat" Quest...but in a DF ?

    1. Thank you for your contribution, you mention some good points and I did gloss over many details. I did not want to provide a thesis on velomobile aerodynamics, just an account of the best ways people have used to make their everyday velomobile faster.

      Again, I would not recommend removing mirrors for daily use because it would remove an important safety equipment but if people are racing they could consider removing one or two for an event.

      There are some riders who are exploring the use of cameras as a replacement with very small screens but there are several issues including the reverse display so the items appear on the correct side when looked at from the rider's seat and dealing with dirt.

  5. I always wondered if an aerospoke on rear wheels would bring anything as turbulences occurs also inside the wheel arch.
    Also the mirros with aero cones can benefit the drag as a study showed that at last velomobil seminar ( i will try to find the link back).
    Last, another point is stiffness. Without pants, the DF plays equals to the Milan thanks to his improved stiffness I think (also, smaller size).
    One more think I have in mind: Air intakes are ok if you canalize the flux, and also let it out! See Milans and their multiple rear holes or the DF hood.
    I will be at Spezi and share pictures and info on the fb group.
    Nice work as usual Luc, thanks!

    1. I use canvas covers on the rear wheel of my WAW when wanting to be - or feel - faster. The idea is of course that the many round spokes move around in the rear wheel well with enough speed to cause drag. Wheel covers should to some extent prevent some of that "internal" drag. In every day use, I have however removed one of the covers in order to have better access to the valve. I also have canvas covers on the inside of the front wheels (for the same reason). A couple of years ago I also got wheel house covers - or "wheel pants" - for the WAW. Haven't done any measurable tests in order to see improvements - but there should theoretically be some effect I suppose.

    2. Thanks Robert, I did not mention wheel spoke covers that are especially important for open wheel velomobiles. I don't know how much of a gain is made when the velomobile has covered wheels wells like the Quest or even for the rear wheel. There must be one but I have not seen any report on the subject. As you mentioned, having covers makes it much more difficult to put air in the tires. I actually remove the front wheels of the DF to put air in my tires instead of trying to find the valve and put the pump head on the hidden valve.

  6. This is off-topic Luc but maybe you or one of your readers can discuss the cleaning and waxing of velomobiles. And also the repair of small damage - like flaking fiberglass repair. I almost have my new velo on the road but I would like to give is a clean and high shine. I have looked over your archive briefly - but could not find any discussion of this topic. I was thinking of going to a boat shop - but would like your advice.

    I will be riding around downtown Ottawa soon.

    I also have a BionX 350 watt system I want to put into my Quest. This is a legal ebike system but will I have trouble with police stops anyway?

  7. I'm not an expert in repairing fiber and would let someone else take this. There have been numerous threads on BROL regarding fixing cracks and gelcoat and probably on

    If you are in Ottawa there was a high performance carbon fiber shop in the west end near Carp.

    Regarding police stops if you live in Ottawa and eastern Ontario, the police is pretty cool about my velomobile, I was never stopped in about 6 years of riding. I don't ride downtown Ottawa very often. Across the river is another story but not too bad. The use of a motor is usually the first question and I have none so it isn't an issue but in your case they may want to probe further (see motor and see that you are restricted to the 30km/h or so that is permitted.

    1. I was riding my EVOX semi-recumbent today downtown and into South Keys - and I must say that the pot holes are terrible - I want to ride my velo in the city - but the roads are terrible this year. I am scared that I will hit a pot hole and destroy the velo. I will have to stay on bike paths.