Wednesday, November 28, 2012

Inexpensive, Lightweight Recumbent Fairing

Inexpensive, Lightweight Recumbent Fairing
Fall 2012
by Joe McCabe

Ever since the late 80's, after reading an article in Scientific America on the forces of friction on bicycles, I've wanted to get a recumbent and install a rear fairing. Here is the results as of today:


The fairing design was completely inspired from the MOAT by Warren Beauchamp.

A few modifications to his design. For the individual sections I strategically cut only the outside edge of the coroplast (while leaving the inside edge uncut) for all the joints that just needed to be folded. And I made the top removable. I also removed 4" off the height of the design because I felt my 6'-3" body on the trike didn't need that additional height, and wanted to reduce both the frontal area and side area. The total fairing weighs about 5 lbs. That is quite good for the aerodynamic versus additional weight balance.

The following drawings are modified from Warren Beauchamp designed to help with the knowledge/evolution of this approach. Two pieces can be cut from one 4' X 10' coroplast sheet. I butted the bottom up against the back of my seat, so the total length is shorter instead of going under the seat.
Modified MOAT for recumbent trike fairing. (Original from Warren Beauchamp)

Fairing Cross Section (Original from Warren Beauchamp)
This past political election season I removed 4' X 10' coroplast boards from our town and lucked out. One had  both front and back surfaces completely "stickered". I pulled the sticker off one side and left the other stickered for the inside of the fairing, and it added to the structural capabilities of the coroplast; especially where the section joints were half cut and folded.

Installed Velcro straps at the front bottom, and four places where the top and bottom meet (rear and front). One wooden piece holds the bottom fairing to the bike rack. The fairing-top slides into the fairing bottom for easy storage. Best way to show these details is with a one minute installation video:


And this photo shows the slots (4) for the top tabs, small bolts to the wood bracing and other details.

Inside of bottom fairing showing details.
The cost of this project was minimal; one roll of high quality packing tape, some rivets, Velcro and a few spare nuts and bolts. A single sided razor blade was carefully used, no fingers cut. It is actually artistic to work with coroplast, using the rigidness where needed, and flexibility along the grain, fold even against the grain with just one side cut. Black electrical tape was used along those long cuts; and installed spare stickers for fun.

May finish this off with some blue-camp-mat-foam just behind the seat, especially if I spot some at a used store.

The first photo above actually shows the electric hub motor on the back wheel of the recumbent trike along with the fairing. The fairing effectiveness kicks in above 18 MPH. Check out the above referenced Scientific American article for specification on the air friction reduction as well as this Bicycle Speed and Power Calculator. Solar powered electric motor aspects of this project will be discussed on endless-sphere .

Feel free to drop me a line at energyideas@gmail.com ; Hope this helps.

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