The BIG parts are right. It is time to work on the little parts

Anold Wagner and Tuft Testing Chap. 83

Updated April 10, 2015
Real Streamlining is round at the front and pointed at the rear
Real streamlining has doubled the distance a unit of energy can take us at 70mph.

Confirming this in the Vetter Challenges has been a BIG thing.

Now it is time to see if the BIG parts can be refined.

There has always been some question about the exact shape of the tail. I always was prepared to "write off" the "dirty" air behind the rider's helmet. But do I have to? what really is happening to tha air behind the rider?

Meet Arnold Wagner

Fortunately, we were visited by a man who should know, Arnold Wagner. For those of you who might not be aware of Mr. Wagner, let me tell you a bit: Arnold is a pilot... being a European aerobatic champoin pilot as well as a commercial 747 pilot. Among motorcyclists, he is most famous for his streamlined Eco cabin bikes. This man is smart:

When you meet a man like Arnold Wagner, you listen
Arnold, Vetter and Electric Terry

Streamlined motorcycles don't act like regular bikes. They don't act like airplanes either. They are attached to the ground and cannot "weather-vane" into the wind like airplanes. These were the kinds of things we talked about. All day and into the night. Arnold made suggestions to improve the slipperyness of my streamliner bodywork: "The sides" he said "need to be wider at the rear in order to allow the air to re-attach after it passes by the rider." That made a lot of sense. Why didn't I think of that?

We decided to do some "tuft testing" to see what was happening back there.

For tufts, we use 2" long strips of black yarn taped to the bodywork. They are very effective in showing us which way the air actually goes at various speeds. I have been doing it this way since 1969.

Test 1:

The first test was to see what the air was doing the way Alan rode his Ninja throughout 2014. Alan rode, son, Zak videod while I drove the car.

Test 1 produced this shocking image: Look carefully at the sharp crease between the body and the headrest. The air was going backwards behind Alan's head. This was terrible. Air going the wrong way is the opposite of streamlining. Could this air reversal be fixed? And if so, would it produce a measurable reduction in cost? In spite of this, Alan was getting around 140mpg at 70mph. (2.6¢ mile)
Test 2: We filled in and blended the opposite side with milk carton paper and tape so there was no crease. This was a little better but not much. Look at how the tufts are blowing in all directions. In studying this picture, we noticed that Alan's helmet was still way to high above the tail. What was actually going on behind the helmet? We could not tell.
Test 3: It was easy to remove the headrest from my Streamliner and tape a piece of white Coroplast to the top. We put tufts on my helmet and on the Coroplast. This would make the airflow become visible.

Again, we were amazed. Look closely at the tufts in line with the top of my helmet. They are blowing straight back. That meant that the top of the rear stramlining did not need to be any higher than the top of the helmet. Disregard the rest of the tufts. I expected them to be a mess. The next step would be to reshape the seatback on Alan's Ninja to reflect what we are learning.

Foam around Alan
The front fits Alan... the back fits the streamlining
At this point, we have no idea what this thing will look like. Alan sits and I add foam between him and the Streamlining. Then I file the foam down, blending it to the streamlined rear. Whatever it is, it is. Actually, this is my favorite way to design. There is nothing arbitrary. It must be this way.
Adding Tufts
Adding milk carton paper skin
January 8, Alan rode at 75mph. We watched the tufts.
Test 4: As you can see, the new seatback made huge changes to the area directly behind Alan. Look at how straight back the tufts now flow behind Alan's helmet.

I have never seen the air behind the rider's helmet so clean!

For the first 12" the air has re attached to the skin straight. But notice what is happening: About 24" behind Alan's head, the tufts along the top of the tail are no longer going straight back. They are fluttering which is an indication of the air not smoothly flowing to the rear.

25° is too steep a closing angle

It looks like the top of the tail is angling down too quickly. 25° is too steep. We decided to make the top of the tail close down at less of an angle. 17° seems to work for the speeds we are riding.

Back to the shop.

Alan added about 12" to the rear with a piece of plywood to raise the top. Now the tail closed down at 17 degrees.

We made all new tufts. We couldn't wait to go out on the road to see how we affected the air flow with the new 17° taper.

This was it!

Test 5: We were stunned at the great results. Compare this picture with the beginning picture above taken December 20.

It was time to make a new backrest pattern.

End Chap 83

Master Index to the Last Vetter Fairing Story

Updated April 10, 2015

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