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streamline fairings?

Posted: Sep 23 2022 12:19am
by red
Back in the day, Vetter made "full" (front end) fairings for motorcycles; one was called Windjammer. I would like to add a reasonable fairing to my (someday soon) 26" diamond frame ebike. The motorcycle fairings are much too big and heavy. What I want could be done with one formed sheet of low-density polystyrene (Frisbee stuff), and maybe a small windshield. I have seen the full pod bike enclosures, such as Vetter once made, but they are not what I want. Those things are heavy, noisy, stuffy, and well, pompous. A small Windjammer clone in front would be good, for me. I could even see using a modest tailcone to put the air back together behind me, but that item would be optional here. The closest commercial item that I have seen so far is the old Hutch bike fairing. It is angular, but reasonable in size, and of course, not available now. I see some recumbents that have decent fairings, but I'm just not a recumbent rider.

All that to say this: Air drag costs performance, both in speed and range. I am surprised that upright ebikes usually do not use streamline fairings similar to Windjammer and Hutch. Are there any commercial front fairings now on the market, short of the full-bike pod enclosures? TIA.

Re: streamline fairings?

Posted: Sep 23 2022 4:14am
by BalorNG
Small partial fairings that are inobstructive, light, and do not affect handling are useless aerodynamically.
You want at least something like a 'dustbin fairing' - but they were banned for a reason, and funny enough because there were 'front only'.

You want a balanced front and rear fairing. Heck, you want something akin to a vertical stabilizer as well!
Have you seen BM two-wheeld streamliners? How long their tails are? That's actually mostly for stability.

You might want to consider tail-fairing only, but that is pretty hard in an 'upright bike' formfactor. Very high center of pressure, also - very hard to make them work due to human body being extremely poor 'leading edge':

Image

See the difference between the 'prism' and the 'bullet'? Counterintuitive, isn't it?

Re: streamline fairings?

Posted: Sep 23 2022 8:02am
by DogDipstick
I got a set of pit bike fairings made by Kawasaki for a Kawasaki pit bike that would fit a short wheelbase bicycle just perfectly.

Re: streamline fairings?

Posted: Sep 23 2022 8:59am
by Warren

Re: streamline fairings?

Posted: Sep 23 2022 9:01am
by tomjasz

Re: streamline fairings?

Posted: Sep 23 2022 9:05am
by red
DogDipstick wrote:
Sep 23 2022 8:02am
I got a set of pit bike fairings made by Kawasaki for a Kawasaki pit bike that would fit a short wheelbase bicycle just perfectly.
DogDipstick,

Sounds interesting. Got pix? How much does your fairing weigh?
Thanks.

Re: streamline fairings?

Posted: Sep 23 2022 9:17am
by Chalo
Motorcycle touring fairings typically increase drag, because they are designed to form a "bubble" for the rider that is larger in frontal area than the unfaired motorcycle and rider. Vetter Windjammer was definitely designed for rider protection/comfort and not aerodynamic improvements.

Likewise, any fairing you add haphazardly to a bicycle could easily increase drag rather than decreasing it.

Re: streamline fairings?

Posted: Sep 23 2022 9:18am
by DogDipstick
red wrote:
Sep 23 2022 9:05am


Got pix? How much does your fairing weigh?
Sure gimmie a sec, they re light. i will update this post with pics.

Re: streamline fairings?

Posted: Sep 23 2022 9:23am
by tomjasz
Chalo wrote:
Sep 23 2022 9:17am
Motorcycle touring fairings typically increase drag, because they are designed to form a "bubble" for the rider that is larger in frontal area than the unfaired motorcycle and rider. Vetter Windjammer was definitely designed for rider protection/comfort and not aerodynamic improvements.

Likewise, any fairing you add haphazardly to a bicycle could easily increase drag rather than decreasing it.

Any comments or experience with the Zipper fairings?

Re: streamline fairings?

Posted: Sep 23 2022 10:12am
by Chalo
tomjasz wrote:
Sep 23 2022 9:23am
Chalo wrote:
Sep 23 2022 9:17am
Motorcycle touring fairings typically increase drag, because they are designed to form a "bubble" for the rider that is larger in frontal area than the unfaired motorcycle and rider. Vetter Windjammer was definitely designed for rider protection/comfort and not aerodynamic improvements.

Likewise, any fairing you add haphazardly to a bicycle could easily increase drag rather than decreasing it.
Any comments or experience with the Zipper fairings?
I always took them at their word about reductions in drag, and I had a friend who attested to observable performance improvements from the upright bike version. Never tried one myself.

Certainly Zzipper fairings are using different principles than touring motorcycle fairings.

Image

Image

Re: streamline fairings?

Posted: Sep 23 2022 10:37am
by red
Chalo wrote:
Sep 23 2022 10:12am
tomjasz wrote:
Sep 23 2022 9:23am
Chalo wrote:
Sep 23 2022 9:17am
Motorcycle touring fairings typically increase drag, because they are designed to form a "bubble" for the rider that is larger in frontal area than the unfaired motorcycle and rider. Vetter Windjammer was definitely designed for rider protection/comfort and not aerodynamic improvements. Likewise, any fairing you add haphazardly to a bicycle could easily increase drag rather than decreasing it.
Any comments or experience with the Zipper fairings?
I always took them at their word about reductions in drag, and I had a friend who attested to observable performance improvements from the upright bike version. Never tried one myself.
Certainly Zzipper fairings are using different principles than touring motorcycle fairings.
https://craigvetter.com/images/Vetter%2 ... er-200.jpg
https://www.zzipper.com/images/DSC02846.png
Chalo,

Seems reasonable to me. The zzipper offerings are (to me) rather minimalist, while the touring fairings are a bit much. A cross-breeding of these two extremes could be a benefit to us. Here's to hope!

As I said, the recumbents do have some nice streamline options, but (so far) I'm not a recumbent guy.

@BalorNG,
I wrote a response to your input, and thanks for that, but my response went someplace unknown when I hit the Send button. If it does not appear soon, I will try that again. Don't wish to clutter up the place with duplicate posts, I'm just a New Guy here.

Re: streamline fairings?

Posted: Sep 23 2022 11:39am
by PaPaSteve
Having done hundreds of coast down tests to refine streamlined shapes I can firmly say they can an do add efficiency.
My testing was done with precision measuring equipment and are repeatable.
Sure ... it's entirely possible to get it wrong ... that's why you test.
Thing is ... the upright bicycle platform is harder to find the balance between aero stability in the same way a recumbent does.
Recumbents make a safer aero platform to start with.

Glen Brown, the original creator of the Zzipper fairing for upright bikes used to offer fork mounted aero pannier bags to accompany the clear upper fairing.
His testing showed good efficiency results.
Glen was for one year the president of the IHPVA (International Human Powered Vehicle Association) and his friendship with Gardner at Easy Racers is how the company evolved into doing recumbent fairings.

Motorcycle fairings, done properly do improve efficiency. To say otherwise is misinformed.

Cleaning up the turbulent bubble behind the rider can be just as useful as a front fairing.
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Re: streamline fairings?

Posted: Sep 23 2022 1:56pm
by JimDL
Very interesting stuff to read about. Here is some "side thought" from my experience on the Salt Flats, through the years.

Small things can be really useful, even before you get into more complete streamline work. Air flowing over anything is drag, and the faster something moves against that air is more drag. We learned that the tires carry more air than we suspected, during rotation into the airflow. Fenders that reach down in front of the tires (almost to the ground) showed drag reduction. Remember, the top of the tire, rotating into the airflow, is about double the (air)speed of the vehicle (the bottom of the tire is at zero speed to the airflow). The tire carries that airflow down in front of the contact patch, creating a "higher" pressure area for the tire to roll into. We did learn that full disc wheels were less drag than open spokes but proved to be unsafe when used on the front wheel (that is in our rule book, for many years now).

This is why you see the small spats in front of the tires on many modern cars. The most efficient cars have them in front of all four wheels. When we set up the Prius for 2004 Speedweek, we actually lowered the car to where the spats were nearly in contact with the ground.

In the land speed world we have learned that any components not hidden from the airflow, add drag. My last bike project used a water tank instead of a radiator, with the entire front of the fairing closed off. That wouldn't be good for human powered stuff!

I have had the opportunity to visit with some folks who worked with bicycle streamlining, and they said the best streamlining overheats the "motor". Streamlining bicycles is certainly a puzzle, and I bet the folks successful with it have learned just the right compromises. Streamlining for efficient ebikes may be a little more realistic project if the goal is reducing the calorie burn (and heat generation) of the human motor while improving battery range. That will certainly be a little different formula, than what is best for non-assisted bicycles. This could really get interesting!

Re: streamline fairings?

Posted: Sep 23 2022 5:35pm
by PaPaSteve
Based on Glen Brown's work I've always thought a composite touring bike where the stowage was integrated into the design could make a fast upright bike. i.e. the stowage area is the bicycle frame structure.
An analogy would be a comparison of the Brightstar Swift composite hang glider verse a stretched fabric hang glider.
https://en.wikipedia.org/wiki/A%C3%A9riane_Swift

Watching this video causes a rethink ...

https://www.youtube.com/watch?v=Ue_Tz7e0DmE&t=55s

His final statement in the video does reinforce common recumbent knowledge.

And note the fork design of this bike and how it shields most of the tire ...
Image

Re: streamline fairings?

Posted: Sep 24 2022 8:31am
by BalorNG
Chalo wrote:
Sep 23 2022 10:12am
tomjasz wrote:
Sep 23 2022 9:23am
Chalo wrote:
Sep 23 2022 9:17am
Motorcycle touring fairings typically increase drag, because they are designed to form a "bubble" for the rider that is larger in frontal area than the unfaired motorcycle and rider. Vetter Windjammer was definitely designed for rider protection/comfort and not aerodynamic improvements.

Likewise, any fairing you add haphazardly to a bicycle could easily increase drag rather than decreasing it.
Any comments or experience with the Zipper fairings?
I always took them at their word about reductions in drag, and I had a friend who attested to observable performance improvements from the upright bike version. Never tried one myself.

Certainly Zzipper fairings are using different principles than touring motorcycle fairings.

Image

Image
Zziper fairings like pictured work despite being 'small and unobstructive' because they cover your 'air pocket' around your lower body and groin, that has Cd like 1.5 or something. It causes the air to 'pile up' and a spike in stagnations pressure, and air than 'splashes to the sides' so to speak, creating a huge wake, a negative pressure separation bubble behind you that 'pulls you back' and due to air being 'splashed wide' even if you add a tailbox to converge air behind you, it would be mostly useless - again, see the picture from NASA. The tailbox would have to be significantly larger then your body, creating a 'bevel' to guide the air from your body to the tailbox.
The problem with such a nose cone that is far from the body is that it will just add drag AND worsen handling in any but the smallest crosswinds I presume - because your body will no longer ride in it's wake, but both will produce their own.

This is why you want a combination of front and rear fairings, and you want them positioned JUST right.
The easiest to manage set of fairings is a front nose cone, a tail fairing and a lycra between them to form a 'semi-full fairing', it works best in a LWB recumbent form-factor:

Here is a great article:
https://lonniemorse.wordpress.com/2013/ ... un-faired/

Re: streamline fairings?

Posted: Sep 24 2022 9:26am
by PaPaSteve
Covered front wheel, WindWrap front fairing, coroplast body panels, and spandex.
This bike won 6 criterium races
Cherry-Pie-Race.JPG
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Re: streamline fairings?

Posted: Sep 24 2022 9:32am
by Warren
PaPaSteve wrote:
Sep 23 2022 5:35pm
His final statement in the video does reinforce common recumbent knowledge.
Yup. Aerodynamics of recumbents are clearly superior, as is comfort, and crash safety.

I ran a Zzipper for one year. Sadly, my pitiful power output meant, what was gained on the flats, was lost on the climbs around here, especially in hot humid conditions. With electric assist, there is no contest. A recumbent, especially with aero fairings, is in another league altogether. Decades of knowledge gained from folks like you, and other HPVers, is going to waste.

Re: streamline fairings?

Posted: Sep 24 2022 9:58am
by Warren
Even without electric assist, a really strong rider in a streamliner can make conventional bikes look really bad. Back in 2018 BC (Before COVID), the Trans America Bicycle Race was won by Swiss rider Marcel Graber, riding a 38 pound velomobile. He was so far ahead of the pack, he spent the night in Charlottesville. He still finished 20 hours ahead of second place. As usual, his amazing accomplishment was completely ignored. I chased him down in the Bolt, and cheered him on. By the time I found the camera button on my new smart phone, he was gone. :) But this guy got some video.

https://youtu.be/CUhsImxflvY

Re: streamline fairings?

Posted: Sep 24 2022 10:12am
by BalorNG
PaPaSteve wrote:
Sep 24 2022 9:26am
Covered front wheel, WindWrap front fairing, coroplast body panels, and spandex.
This bike won 6 criterium races
Cherry-Pie-Race.JPG
How that is a very interesting solution that is must be effective *and* easy to fabricate without going for composites and hence dealing with PITA of CNCed plugs...

Re: streamline fairings?

Posted: Sep 24 2022 10:16am
by Warren
BalorNG wrote:
Sep 24 2022 10:12am
How that is a very interesting solution that is must be effective *and* easy to fabricate without going for composites and hence dealing with PITA of CNCed plugs...
Yup. Steve is pretty smart.

https://mrbill.homeip.net/albums/powerP ... tml#anchor

Re: streamline fairings?

Posted: Sep 24 2022 10:19am
by BalorNG
Warren wrote:
Sep 24 2022 9:32am
PaPaSteve wrote:
Sep 23 2022 5:35pm
His final statement in the video does reinforce common recumbent knowledge.
Yup. Aerodynamics of recumbents are clearly superior, as is comfort, and crash safety.

I ran a Zzipper for one year. Sadly, my pitiful power output meant, what was gained on the flats, was lost on the climbs around here, especially in hot humid conditions. With electric assist, there is no contest. A recumbent, especially with aero fairings, is in another league altogether. Decades of knowledge gained from folks like you, and other HPVers, is going to waste.
No, they are not. It would *simply* take someone to take those AND build up on them in a way that it has handling that is 'good enough' for most people in most conditions, form-factor that is just compact enough and design that would scream 'buy me' to an average consumer. I suspect that among those, latter is the toughest challenge...

Re: streamline fairings?

Posted: Sep 24 2022 10:21am
by BalorNG
Warren wrote:
Sep 24 2022 10:16am
BalorNG wrote:
Sep 24 2022 10:12am
How that is a very interesting solution that is must be effective *and* easy to fabricate without going for composites and hence dealing with PITA of CNCed plugs...
Yup. Steve is pretty smart.

https://mrbill.homeip.net/albums/powerP ... tml#anchor
Cool. You simply use flexibility of the side panels to enter and exit I presume?

Re: streamline fairings?

Posted: Sep 24 2022 10:32am
by Warren

Re: streamline fairings?

Posted: Sep 24 2022 11:51am
by tomjasz
My intent isn't as much aerodynamics as some winter protection from wind chill.

Day6 Joy 38" wheelbase. 9C front or BBS01B.