When I first published my fairing design on June 7, I received many comments regarding my ideas and approach. After considering all of the expert advice, I have decided to change the design for a few reasons:
1. The griffith fairing design was based on a predominantly laminar flow shape. Achieving extensive laminar flow in the real world which includes cross winds, road vibration, dust, water, bugs, etc... isn't realistic. What you end up with typically is this big negative pressure zone at the back end which if turbulent, will slow you down. A more robust, but still aerodynamically efficient shape would be based on a turbulent airfoil - so with advice from Gabriel DeVault of EasyRacers I'm going with a NACA 6 airfoil.
2. I did not take into enough consideration how the fairing would handle in cross winds - and this was kindly brought to my attention by Bob Stuart who invented the Carcycle. After taking a second look at the Griffith laminar fairing, I realized that it was over 12 feet long!!! Then I tried imagining having to control a 12 foot long 'sail' in a cross wind and thought perhaps it might be prudent to try and come up with something with a little less area. I did some research on fairings and cross winds and found some usefull information. In my case, with the lean steer configuration, if the center of pressure of the fairing is ABOVE the steering axis, then a cross wind would tend to push my steering in the direction of the wind - something I would rather avoid. If the center of pressure is slightly BELOW the pivot axis (steering axis) then a cross wind from the right would tend to push the steering to the right and would act as a balance keeping the trike pointing straight in any wind conditions. Or that's the theory anyhow.
So - I went back to the drawing board and came up with a fairing based on the NACA 6 series airfoil which ended up at around 8 feet long. The center of pressure is in front of and above the pivot axis, but I can easily add fairing material to the rear to effectively move the center of pressure rearward in steps to find exactly the best spot.
My plan is to build a Styrofoam plug and wrap it with fiberglass then cut it in half and carve out the foam. This method is quick and probably the easiest way to make a crude fairing suitable for testing. When I am ready to make a final fairing, I'll have HeavyIndustries here in Calgary CNC machine a new plug from my CAD file. Then I'll make a mold from that and carbon fiber fairing from the mold.
Here are some 3D renderings of the new fairing (click for larger):
Tew Dew LIST:
1. Buy and install right brake (FINALLY ordered it!)
2. Invent new cable tensioner to allow more steering bar turn radius3. Add front derailleur
4. Order 20mm axle bolts for the rear wheels (I'm using 1/2 inch now which isn't right)5. Design and machine 2 seat mounts out of aluminum to replace current steel ones (e-machineshop.com) LATER.
6. Design and machine 2 steering tensioners out of alum to replace LATER
7. Order a new front wheel! (Helen is kind of upset that I am user her Zipp race wheel!)
8. Start work on the first fairing (starting now)
9. Invent steering stiffener10. Add larger chain ring
and modify chain stays12. Fabricate new steering bar (aluminum or composite?) or rework existing
11. Make clamp-on out riggers and try to flip it (changed to#25)
13. Lathe an aluminum collar for .5" hub axles (
Ben E. said he'd do it for me) (That didn't work - I'll get someone else to machine it).
14. Design and build a trainer to fit mag trainer (donated by Michael Hoenig).
15. Replace steel cables with Kevlar (maybe not - I think the flex of steel is good....)
16. Crotch guard / fender
17. Narrow chain stays to allow foot to clear
18. fix derailleur
19. crank hitting chain stay
20. chain stay frame flex?
21. Narrow, high density foam for seat
22. Make front quick release safety23. Change steer cable sheaves to Pete Heals idea
24. Add missing and new webs26. Firm up relationship with a charity (Helen???)
25. Add a g-meter and quantify turning g's at flippage threshold. (add outriggers)
27. Find a PR person
|TOTAL distance on TCR1|
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