Fairings and drag
 

Here are some pictorial drag tables I did at the Aero Forum.
http://i1271.photobucket.com/albums/...2/8-16-132.jpg
http://i1271.photobucket.com/albums/...2/8-16-131.jpg
http://i1271.photobucket.com/albums/...d2/8-10-13.jpg
http://i1271.photobucket.com/albums/...head2/8-24.jpg
http://i1271.photobucket.com/albums/...titled-1-1.jpg
http://i1271.photobucket.com/albums/.../drawings2.jpg
http://i1271.photobucket.com/albums/.../Untitled2.jpg
http://i1271.photobucket.com/albums/.../Untitled1.jpg
http://i1271.photobucket.com/albums/...rohead2/-2.jpg
Hope they help
PS the bottom table was a rush job.The values enclosed within the boundary of the sections are their drag coefficients for each configuration shown.
The values for the yellow portions are a Cd value assigned to the section wake itself.
These values were measured at the FKFS under the leadership of Dr.Ing.Wunibald I.Kamm.
And you'll notice that the 'Kamm' bread-slice truncation produces a larger drag than the J-form (Jaray) boat-tailed truncation,for wing/strut section only.
For streamline body of revolution-based half-bodies,you WANT to use the 'Kamm' type chop-off.
Here is a fuselage drag table from Hoerner,1951
http://i1271.photobucket.com/albums/...d2/Scan1-1.jpg
Here's another table from Hoerner
http://i1271.photobucket.com/albums/...d2/Scan2-1.jpg
Here's another from Hoerner
http://i1271.photobucket.com/albums/...d2/Scan1-2.jpg
Here's a canopy drag table adapted from Goro Tamai's 'THE LEADING EDGE'
http://i1271.photobucket.com/albums/...2/Scan2-14.jpg

Having just return from the BUB motorcycle speed week at Bonneville it was interesting to wander around the pits to see what people are doing with/to there semi-streamlined bikes. The first thing that stands out is the lack of any attempt to deal with the tail section. This is mostly due to the class rules not allowing anything further back than 8" behind the rear wheel & a height limit for the seat behind the rider. one could of course start from 8" behind the rear wheel and see what kind of motorcycle would fit, but the rear seat height limit would remain, and it would be far easier to build something for the RWB [run what you brung], so no world records. For the most part it seemed to me that many of the class records at Bonneville are more about horsepower than aerodynamics.
The Vetter aproach is far more condusive to the development of good aerodynamics, so your posting will be far more usefull to the FE set. Do you know of any research/testing of air foil sections with opening on the sides like a stream lined motorcycle? It would be interesting to see what gives when an opening is introduces...

Would it be wrong to assume a slight flair outward, just before the side opening would create a minimal adverse effect? I think as long as the area behind the opening was slightly narrower than the the area in front of the opening, the adverse airflow would
be minimized, so in a practical sense, be a non-issue.

3rd pictures, there might be the answer :
Accident along the way (2nd shape, 0,29 Cd) vs no accident (4th shape, 0,16 Cd)
Twice as much Cd, overal shape being equal ...

opening
 

I added another table above for a Clark Y section with slots of differing position and their influence on the Cd.

effect
 

Once the air gets to a void,it turns 90-degrees and goes in.It must have a solid surface to support flow.
That's not to say that the outer-lying flow won't make the 'jump' as Hucho refers to it.
In a dead calm,with only a pure air 'source' from the front,we'd have symmetry,but in a crosswind,the windward static pressure would induce a transverse flow through the body void,setting up vorticity as the jet collides with the flow on the leeward side,tearing the boundary layer to shreds and forcing separation.
You'd want to do 'something!' The hole in the body would not allow traditional spoilers to function as a boundary is necessary to capture a locked-vortex.

What about putting the void under pressure from the cabin by using cooling flow for example ?

cooling flow
 

Aerodynamically,it's a sound proposal,as Dr. Wunibald I. Kamm is famous for using cooling air ejected at the windshield base to help re-energize the boundary layer there where it was tending to stall over the windshield.
The hitch would be fair-weather riding,where the heat flux coming off the radiator would be unwelcome to the rider.
With a nose scoop as on the E-Z-HOOK LSR streamliner,you might be able to create a stabilizing curtain of air.You'd lose some kinetic energy to heating aside from what the engine was rejecting,but worth a shot.
A wind tunnel would sure be handy for sorting this kind of thing out.
Professor Alberto Morelli spent untold hours in the Pininfarina wind tunnel designing the air extractors for the 1978 CNR 'banana' car.And at $1,000/hour,in 1978 dollars,that's a lot of Lira.:eek:

4-new drag tables
 

I've added four additional pictorial drag tables up at the top of the thread.
Of particular interest to motorcyclists will be the 'wing/strut sections' table.
The center section has the lowest drag of traditional symmetrical sections,with a thickness-to-chord ratio of 3.92.
The upper,very thin section suffers from an overdose of surface friction drag.
The bottom 'stubby' section suffers from separation-induce pressure drag.
--------------------------------------------------------------------------
The center lowest-drag section is at the crossroads of the drag curves for surface friction and pressure drag.It's right at the 'sweet spot.'
If the section is any shorter,it suffers separation.
If it's any longer,it's surface friction begins to climb.
--------------------------------------------------------------------------
From a purely aerodynamic standpoint,your streamlined bike should be as near to the center profile as you can make it,when viewed from above.
The drag curve in this region is rather flat,like a nice torque curve with a stump-pulling engine.So you've got some wiggle room dimension wise.But you won't want to stray too far afield.

One question I do have is what or how much does the void volume inside the fairing matter? I am wondering if filling the void with solid stuff reduces the mass of air that is involved in causing drag? My suspision is that the relationship is not linier and that there is no way to make the space between the windshiel and the cargo bay full enough to have much effect anyway. Has any one done any research on opening size/volume and drag for bluff bodies?

void
 

If you'll go up to the Aero.Forum and do a Search Ecomodder for 'full-boat-tail trailer for T-100' you'll find some pictorial drag tables for tractor-trailer rigs which include 'gap' drag.
Also,in wind tunnel research on top-down convertibles,the wind tunnel personnel discovered that placing mannequins in the test vehicle seats positively influenced drag.
You could patent a line of Velcro-attached,break-away, clothing -fairings which would close off the transverse contamination of the body fairing void,while allowing the rider range of motion to dynamically balance the bike during crosswinds and gusts.
Better hurry to file your patent,as at least two others are currently drafting their's!

I am currently working on a light full body fairing for upright bicycles too.

Interesting that the gap drawings show it to be a very slight penalty if the terminations are treated properly.

New drag table for fuselage 'canopy' area
 

I posted this up at the Aerodynamics Forum and wanted to add it here.I've placed it in the #1 permalink at top of page 1 at bottom.
It's very simplistic but you can see the general degradation of Cd as the fuselage is adulterated by holes and excrescences.
I'll add additional images as schedule permits.

slight penalty
 

If we had a chunk of cash we could spend a day at Cal Tech and do 'optimizing' studies.
I believe that I could virtually eliminate the gap drag with clothing.
Downhill skiers have already proved-out aerodynamic 'costumes' which affect the foot/calf/thigh area.Boat-tailed helmets are addressing the head drag.
The upper torso and arms could be addressed.
Integrating the helmet back into a deformable turtledeck/head fairing leading edge could kill the head drag entirely.
The appareldynamics would allow for extreme body English when encountering fierce crosswind or gust conditions which require significant keeling to maintain a straight path.

Thanks for all the good info aerohead.

Now let me see how does one patent "The Void"?

My fear is that The BORGE do not honor patent law anyway...

patent
 

A Dallas patent attorney and the Senior Corps of Retired Executives told me in the 1980s that if I didn't have $250,000- $500,000 cash on hand to prosecute for infringement ,that a patent would be worthless to a guy like me.
And no venture capitalist will invest without patent protection.
Dr. Wunibald I.Kamm took moral issue with patenting things which would actually improve the general welfare of the population, so he avoided them as a rule.
Default philanthropy if you will.

Added 11th and 12th drag tables
 

I've added two additional drag tables from Hoerner which are germane to fuselage design.They're at the top of page-1 with others.

Nearly linear.

Patent attornies are definetly part of the BORGE Collective...

I will now go and read chapter 9, Commercial Vehicals; Aerodynamics of Road Vehicles, Volf-Heinrich Hucho, to see what I can learn about the void...

void
 

Up at the Aero Forum,under the thread 'Full-Boat-Tail Trailer for T-100' you'll find some graphical drag tables derived from wind tunnel analysis which cover 'gap-drag.' Some of the tables I derived from composite tables Hucho published.You don't have to measure or calculate anything,just look and read Cd. There might be something of interest to you there.

Well that explains to some extent the shape of the fairings behind the prius's rear wheels. I've long admired that detail of those cars.

-james

recent 'void' drag example
 

A recent example of drag degradation due to a 'void' would be the 2013 Bugatti Veyron 16.4 Grand Sport Vitesse.
When the roof panel is removed the top speed falls from 255 mph,to 233 mph.
A 22 mph drop.Or,a 9.44 % reduction in top speed due to the extra drag created by the void.
Using Wolf Heinrich Hucho's drag/top speed relationship loosely,this 9.44 % change in top speed would indicate an approximate 28.3 % drag increase.:o

Wow, and that's on a very high drag vehicle too!

another canopy drag table
 

I read through 'THE LEADING EDGE' by Goro Tamai,and have adapted an expanded version of a canopy drag table he published.It's below the other images at top of page one.