Bicycle Aerodynamics for those interested.

[k.h.]

Good read, Blue.  In working on drag reduction for commercial aircraft, my favorite aspect is "fast paint."  The project has the potential to reduce aircraft drag with or without the expense and engineering issues of passive/active riblets, or shark skin simulators.  It's a matter of the nature of the chemistry of the coating, a challenge being low pressure application of small particulate paint with a quick drying time to a desired mil as opposed to large particulate mediums such as Imron with a slow drying time.  The issue of reducing drag over solid surfaces in high velocity flows is about money more than speed.  A 1% reduction in drag might save an airline company 25,000 gallons of fuel per year per aircraft.  We expect a number much higher than 25% (in skin friction, I was remiss in not clarifying that in the unedited post) in certain applications. 

And my most entertaining subsonic models for testing all wind up looking like round-nosed pub darts.

[maguromic]

k.h., Very interesting reading on the airplane "fast paints".

When we were racing in IMSA, I remember there was some pretty interesting work going on early to mid-90’s with some Lockheed (Marietta, GA) engineers trying to develop some race car stuff on the side. While in Atlanta we went and spoke to them and looked at a presentation of their project. If I recall correctly how it worked was they were essentially pumping air through a porous skin by letting air bleed from one pressure area to another. We had spoken previously about the fact that pressure pumps or reservoirs were completely banned for us. Later they came back with  some "fuzzy" skin. In the end, they were starting to get to something that might have actually worked (on wings) and had really impressive lift/drag figures. But then Rahal bought the rights to what they were doing (that’s what the Lockheed guys told me) and I never heard or saw anything of it again.  

[PorkPie]

that NSU bike looks about twice the width of a Varna . . .
A lot of the bike guys ride enduros - but the bikes must have a provision for cooling that the Varna does not.  Even bikes w/ multiple riders presented more frontal area could not match that bike's speed.

Lots to learn there, I believe.\\cheers,

to understand how big the NSU Baumm III was, it was less than an inch wider than the Varna.......when you see them in reality you will surprised how small this streamliner is and will not believe that a normal adult will match into this vehicle.....but there was still enough space to get a ashtray into the racer for the rider H.P. Mueller.

By the way - this was not a speed record streamliner....this was a economy attempt.....around 195 mpg............no this is no typing mistake....they run this attempt at old Hockenheim course

The streamliner is unfortunately not anymore complete.....some years ago someone stole the front suspension

The shape comes very close to perfect water drop shape.

[Buickguy3]

   When you talk of the fast paint, it reminded me of the US attempts to win the sailing challenge maybe in the late 70's. Someone developed a vinyl decal wrap for the hull that simulated fish scales and it worked to reduce drag, and was banned immediately. I suspect the same ban would be true in motor-sports. Interesting concept, though. Doug

[jimmy six]

Buick. Look up www.dimpletape.com  Things I would look for in impounds..........when I worked there for DW

[wolcottjl]

The tape was from 3m.  A few years ago they still listed it on their website, I forget the name of the tape.  Found the article.

http://www.nasa.gov/centers/langley/news/factsheets/Riblets.html

3M under the type designation 3M 8691 Drag Reduction Tape (Riblet Tape)

[maguromic]

Buick. Look up www.dimpletape.com  Things I would look for in impounds..........when I worked there for DW

JD or Dan, Curios why a car or bike covered with this stuff wold be illegal.  Some of the body warps that are used have a interlocking pattern to them, and what about a paint job with a uniform "orange peel." I have seen good painters (and some very bad painters LOL) purposely do this to a car by playing with the air. Just like like to know where the line is drawn.  Tony

[1194]

Back in the late 1990's early 2000's Mike Corbin
raced a new type Triumph Triple with success using a fairing with a surface like a golf-ball
at SCTA/BNI events......................................................

Mike has always understood "aero" and was a great help to us on our 1990 sidecar streamliner.

[sheribuchta]

Hey Blue,
Just curious about the shape of the streamliner. Trying to visualize it in my head. Is there a naca number that describes the shape of the streamline body that you are talking about. I have a list of all the naca shapes.

Thanks Willie Buchta

[dwarner]

Tony,

To answer your question, "Just like like to know where the line is drawn."

There is no rule against employing paint strategy on an LSR Car. Just interesting to see.

DW

[roygoodwin]

Blue,

      Could you clarify this for me ? "...short and fat is better than long and skinny..."  that would be with the same frontal area, right ? 

thanks

roy

[Stainless1]

Tony,

To answer your question, "Just like like to know where the line is drawn."

There is no rule against employing paint strategy on an LSR Car. Just interesting to see.

DW

OK, you guys caught me.... the extra MPH we needed came from the bad paint job I gave the bike last year...    I just didn't know it would work that well   

[oz]

Did someone mention Golf balls  oops! well hush my mouth.

[Glen]

Only orange golf balls are allowed on the salt. Steel keeps losing the white ones.

[Blue]

Blue,

      Could you clarify this for me ? "...short and fat is better than long and skinny..."  that would be with the same frontal area, right ? 

thanks

roy

Nope, that's one of the big misconceptions.  Taking the same volume from a long and skinny streamliner and rearranging it in a short and fat profile creates more frontal area, less wetted area, more laminar flow and as little as one-forth the drag (presuming neither car had any separation).

Willie,
As airfoil sections for wheel driven LSR, we need to look at NACA 66-018 and 021 sections.  If we have a body of revolution, we can go even fatter.  A "body of revolution" is when we create a body from a profile like turning it on a lathe.  A body of revolution can be much fatter than a wing profile for the same peak velocity and pressure recovery.

One of the more important things we can learn from these profiles is the reflex in the pressure recovery.  This is where we close the back of the vehicle very abruptly and then reduce the closure angle.  This reduces length, wetted area, and is much lower in drag than a straight taper.  Not to criticize LSR too much, but the idea of this straight, "7 degree" closure has got go away.  It died in aerodynamic science over 70 years ago.  On my last drag reduction project, I closed the fuselage at a peak of 18 degrees to PREVENT separation.  Along the wing trailing edge vortex sheet (the actual streamline), the angle peaked at almost 30 degrees.  Tufting showed no separation where the more gentle profile had previously separated.  I do not recommend these angles, each application requires analysis.

With no turbos, a lot of detail work by Mountain Air Aviation and the owner, and the described drag reduction, the aircraft is now 55 mph faster than stock: 343 vs. 287 mph on the Reno Sport course.