Vetter streamliner body kit

[Frank Lee]

I tested the Laminar Lip on a snowmobile and found nothing. However you are free to go after it until you get the answer you like.

[aerohead]

Originally Posted by PeterS

Hmmm, this is a bit difficult and I'm glad to be educated . My understanding is that a standard sit up and beg motorcycle is around .9. That works out perfectly with the calculator and a 1955 13hp Royal Enfield on test. It was using it's maximum hp and it's power and fuel consumption were very accurately recorded.

Can you link me to some site giving the cd of various bikes ? Perhaps some allowance for the rider sticking up on top? The rider must get the .9 cd surely ?

What do you think Craig's model would rate ? .35 ?

The Cd 0.9 value is from Sighard Hoerner's 1951 book,Aerodynamic Drag.It includes bike and rider.It is based upon an average 6 sq-ft frontal projected area.

[aerohead]

Originally Posted by PeterS

Could anyone estimate the CD of the current Zero Vetter ? I'm guessing .44, does anyone agree ?

Since the body is approximately a symmetrical wing section,it would be good to see a plan-view to estimate the trailing portions degree of truncation.
Baron Reinhard Koenig-Fachsenfeld and Dr.Wunibald I.Kamm researched truncated sections at Kamm's FKFS,attached to Stuttgart's Technical University.
The sections responded more favorably to the Jaray-form of truncation rather than the Koenig/Kamm form of truncation as far sa drag is concerned,although crosswind stability might be a driver for the optimum form.And ignorant as I am of motorcycle aerodynamics,I'd defer to Mr. Vetter.
An overhead view would help.

[aerohead]

Originally Posted by cvetter

Airplanes act very differently than our land based motorcycles. Airplanes "crab" into the wind. In other words, the airplane thinks it is always going straight into the wind. A flag on the nose would always point directly towards the tail. Except rare times, like when landing and taking off, airplanes do not feel side winds.

Motorcycles are not that way. We are attached to the ground with a the front and rear tire which means we cannot "crab". Winds can blow us sideways quite quickly. Where I live in Central California, there are frequent cases where motorcycles and cars go off the road on Highway 1 (Big Sur coastline) killing the people. Winds can blow trucks over. Winds delay space launches.
We need to take winds seriously.
Sometimes it is prudent to stop riding until the winds subside. I have.

Craig Vetter

The IHPV speed trials at Battle Mountain,Nevada,even though closely monitored for crosswinds,sometimes produce contestants in the bushes,as a stray gust catches the racer unaware,and confined within the shell cannot use any body English to compensate for the air blast.
The Vetter 'open' body design may be a necessary concession to drag considering the paramount rider safety which would (should) supercede drag reduction.
I'm 100% in Mr.Vetter's camp on safety.

[aerohead]

Originally Posted by PeterS

What is the efficiency loss with a Kamm tail versus the full shape?

If you'll go to the Aerodynamics Forum,under the thread:'Some added tables for AS'Template' Part-C you'll find a formula and graph for determining the drag change for airfoils based upon degree of truncation.Then below you'll find a comparison with the Jaray-type section shortening.
Hope it helps.

[aerohead]

Originally Posted by stiletto2

I wonder then... Has anybody figured a way to "fool" the air to make it behave as if the body was full length? Kind of like how airplanes have "winglets" that make the air behave as if the wings were longer than they really were?

It can be helped with airplanes,but it doesn't work in ground proximity.

[aerohead]

Originally Posted by Grant-53

We are getting into the finer points of aerodynamics and vehicle response. I look at both the top and side views for angles as well as the curves of the cross sections. As far as the Kamm effect I look at minimal losses at up to 75% reduction of length. There is more detailed info available.

please see permalink#235

[aerohead]

Originally Posted by sendler

75% reduction wouldn't be correct. Maybe 75% remaining of the full length is what was meant.
.
I have heard that the penalty of a Kamm can be a 10% increase in cd with the truncation at 60% of the original length or the point where the width at the truncation is 1/2 the maximum width of the airfoil. This is the trade off I am building my tail with in order to keep the loss of garage space to a minimum and to have a flat area at the rear for the tail light and license plate. This will save me 30-40 inches of overall length.

please see permalink#235

[aerohead]

Originally Posted by PeterS

Winglets stop air "bleeding" around the end of the wing IIRC. The tail is a different problem and the Kamm tail is as good as it gets short of being there .

Jaray is better than Kamm in this instance for drag.Please see permalink#235

[aerohead]

Originally Posted by PeterS

That was what i was suggesting / asking about. So it sounds as if it may be worth incorporating.

On aircraft,the head fairing is referred to as a 'turtledeck.' Don't ask me why.