Vetter streamliner body kit

[stiletto2]

OK a bit of trimming here and there then elevating the tail end a bit and that is just about how it is going to sit on the bike...... Looks a little better. Still needs a little trimming toward the front of the muffler and above the drive line side of the swingarm. Now I have to wait for the rain to stop so I can work on getting the backrest/main bulkhead fitted at the right angle and fit in a bulkhead behind the rear wheel. An internal support also so it will sit on the bike without needing something out at the back to prop it up.

[jkv357]

Just a comment - I wouldn't let the the top of the tail angle down too much or you will get more turbulence spilling down the back from the top/front edge.

I'd go up even higher.


Jay

[Grant-53]

I agree and suggest the belt line be at least horizontal to slightly tail higher. It is a fine point and I don't want to be only an arm chair critic. The benefits would be threefold. One is the minimum of drag from separation. Two is the overall angle of attack would minimize front lift for better steering grip. Third a slightly higher tail may generate less lift at the rear when leaned over in a side wind since the air can spill under the tail. The concern that the height and length of the tail could affect stability in crosswinds is valid. In this case you might find that the higher tail may give you some more aero steer into the wind. All these effects contribute to the balance between stability and response which we call "handling". Some experimentation and careful observations will help you find the combination best suited to your riding needs and style. Best wishes for a safe and comfortable ride.

[bschloop]

Originally Posted by Grant-53

The concern that the height and length of the tail could affect stability in crosswinds is valid.

My personal concern with long straight tails has pretty much always been more about the length than the angle. to make a straight cone that doesn't get seperation at its front edge means you have to make it much longer than the compuund curve of a teardrop. the longer you get the more you get into skin drag, and other factors, as well as the weight of/in the tail lifting the front of the bike. even with a compuond curved tail, my bike is about 2-3 feet longer than the streamlining template. the straight tailed bikes are almost twice as long as the template.

P.S. I always look at the profile from the top. the side view profile is mostly irrelevant, save for clearance, and a single continuous shape.

[PeterS]

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

[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.

[PeterS]

"minimal losses at up to 75% reduction of length."

That's what I understand too, so it becomes rather difficult for me to justify the full structure.

[sendler]

Originally Posted by PeterS

"minimal losses at up to 75% reduction of length."

That's what I understand too, so it becomes rather difficult for me to justify the full structure.

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.

[Grant-53]

Corrected. The Kamm length would 75 inches of the original 100 inches.

[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?