The Search for Fuel Economy

Pages from a Designers' Notebook

June 8 - 17, 2008

Chap. 10: Finishing the rear structure and going for a ride
Now is the time to see what might interfere with the streamlined body. The snorkle sticks out and the center stand won't work. I need both,so another day is consumed in making the changes necessary for a smooth, streamlined shape. After a hundred miles of riding, the thing is coughing a little when I shut the throttle down. Either I have reduced the volume of the airbox too much with the flat plate or it really needs the "tab" replaced in front of the snorkle.
Slimmed down air intake
Next: Finishing the bulkheads:
The seat and rear bulkheads will support the skin. I had hopes of webbing the bulkheads with CoroPlast- recycled election campaign signs.
My buddy, Don Ask donated his. It turns out that CoroPlast was not strong enough. Reluctantly, I had to cut up some .100" aluminum to make webs for strength.
Webs make the bulkheads extremely strong
A good thing about aluminum webs is that they will help to make the flimsey bulkheads symmetrical, too.
Cut out with a saber saw
Reinforce with little angles
Finished Rear bulkhead
This is slow but easy work. I used jillions of 8-32 screws. If I make a mistake, they are easy to change. Pop rivits, by the way, simply are not strong enough for this application. This is becoming more and more "airplane-ish."

Of course, I like this.

And now for a surprise
Most readers expect me to finish the foam pattern for the other side, make a mold and then pull fiberglass or carbon fiber parts.

Not this time.

Composites are heavy. They are expensive. If I ever produce this as a kit, shipping such parts will always be a problem. It is time to break new ground. Wherever I can, I will use very light, inexpensive materials. After all, the air does not care about going over a super-shiney, painted surface. Air just wants a smooth, continuous shape to slip past.

This is a fine example of Classic American Design

Strong and simple. Never goes out of fashion.

(We don't care how anybody else does it.)

Show your true colors with a genuine Vetter Classic American Design T-Shirt

For this prototype, I wrapped the bulkheads in bright yellow .035" polyethelene sheet, normally used for notebook covers. The material is very light, inexpensive, durable and drapes easily around the bulkheads.

To attach the sheets, on the web I found, plastic "barbed" nails with large, almost flush (streamlined) heads.

I intentionally made the rear section of my pattern a "simple" curve so it could be easily made from sheet stock. Paper... plastic or aluminum.
Testing barbed plastic fasteners
I ordered three different kinds and tested each. It took many weeks of work to get to this point. Attaching the bright yellow skin was the easiest part.
Plastic barbed fasteners are tapped in
Dealing with the tail light, turn signals and license plate
We really do not want to deal with this. but we must. In California, I cannot cover my license plate.

The air behind my head sticking up will never be streamlined so we might as well take advantage of this area for the tail light, turn signals and license plate.

The air is not streamlined around my head. This is a good place for the lights and plate.
I plan to add the pointed tail for highway use... leaving it off for around town. Therefore, the lights and plate must be there all the time. This location acts to stop the air from making my neck cold. It is also more visible to the Peterbuilt behind me. There is no downside to this compromise.
Craig on 5" foam
Zak on 1" foam
Different seat heights allow a great variety of rider heights to fit into the streamlining.
Three months work. The price of fuel has risen about a dollar in this time period.
As you can see, it is not really hard to design and build a streamlined vehicle. It just takes time and perseverance. My experience so far is that if driven hard... 65 mph on the freeway, both the red and the black Helix get 60 mpg. The foamboard streamlining made no difference in mileage. It was just for side wind testing.

Putting around, running errands, without much freeway travel, mileage goes to 64 mpg.

What is interesting about my first trip on the yellow tailed machine is that mileage instantly went to 69 mpg, running hard. I must put it back in my shop to build the front, so it will be some time before I can make a backup run to verify this 69 mpg figure. Actually, until the thing has its tail and is completely enclosed, I really do not expect any change in mileage.

Let me mention this: Into the fierce 50 mph wind coming back from Big Sur, I opened the semi streamlined, yellow tailed Helix up on the only straight section there is. It actually got up to its top speed of 71 with no effort. It felt as if there was no headwind at all. It still gave me 69 mpg.

I'd call this encouraging, wouldn't you?

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Master Index to the Last Vetter Fairing Story

This page updated June 17, 2008