The Seat Back Bulkhead

The final component for making a streamliner tail

Updated August 6, 2014
This the first one out of the mold. Son Zak holds it next to my Streamlined Helix to illustrate the subtle shapes. It is intended to allow the air to slip around me without even noticing I am there. The headrest keeps cold drafts from making my neck cold while providing a place for the license plate and tail light. The bigger opening into the tail allows the packing of bigger items. The backrest Bulkhead does a lot for its 7 pound weight.

Like the Nose Streamlining, one size fits all. Everything begins with the seating position. When the rider is seated comfortably, the backrest is adjusted to where the rider's shoulders and head match up with the streamlining.

After the Seat back Bulkhead is in the right place, making the tail is easy.

Designing the Seat back Bulkhead
You have probably noticed tht the Seatback on none of my streamliners has been finished. It has been 'cobbled' together. This is because it is a very complicated piece to figure out.

I cannot put this off any longer. Alan is going to need it soon. So am I on my Helix. And Terry on his Zero. In fact, everybody making a streamliner has been waiting a long time for this promised setback.

Last summer, we drew a line around every rider we could find. Now it was time to actually make the seatback bulkhead. I began with the outline shape that fit everybody and translated that basic shape into wood. Then I added Bondo to the outside, trying to imagine how it would direct the air smoothly past the rider and tail.

This just might be the most complicated thing I have ever designed

Consider its functions:

It serves as the basic fiberglass structure for the tail.

It is the access door for the storage compartment.

It holds the tail light and license plate.

It is the headrest and "locking pad" for the rider's helmet.

It eliminates air from curling around and/or backwards that can make the rider cold and wet.

It streamlines the air to help it pass the bike cleanly.

It must have the right drafts to be made of fiberglass and come out of the mold.

It would be nice if it looked good but don't count on this.

Above all:

The Seatback Bulkhead must allow the rider to go thru the air more comfortably while consuming less energy.

Clay, Bondo and MDF - ready for the fibergass mold

This is the pattern for the rear bulkhead. Its main function is to be the main structure for the tail. Secondarily, it is designed to help the air slip around the rider and the motorcycle. It provides a door frame for access to the tail and a headrest. As such, it is a backdraft preventer. All in all, this was a very complicated piece to develop because I could never put in in place to see if it would fit proberly. It went to the fiberglass shop May 21, 2014.

Dave Smith in Salinas does all my fiberglass. The first thing he does is wax it and spray PVA which acts as a parting agent. Then he sprays orange "tooling" gel coat. After it "Kicks off" (gets hard) the first layer of fiberglass matt and resin can be applied.

Black laminating resin makes it easier to see bubbles that need to be worked out. After several layers of fiberglass, the mold is ready to be separated from the pattern. Clay patterns like this do not come out in one piece. They come out in chunks. Dave had to sawcut the back plate to begin.

Later by layer, Dave and Miguel revealed the evolution of my design. It must have looked like an archeological dig to them. In a few minutes, my many hours of work had been reduced to litter.

The low imperfections left in the original clay pattern show up as high imperfections in this mold. A small amount of sanding is required to make the the surface smooth.
Finished! It only took a year. Zak and Dave smile.

Master Index to the Last Vetter Fairing Story

Updated August 6, 2014

Posted May 11, 2014