Quote:
Originally Posted by orbywan
When time permits I'm going to build some wheel fairings for the rear duallies and eventually for the front also. I just bought a copy of Hucho's book on aerodynamics and so far have been disappointed that it doesn't go into more details about the three things I am the most interested in at this point, which is front air dams, belly pans and especially wheel turbulence.
I say so far because I've barely scratched the surface so maybe the info is there and I haven't found it. Don't get me wrong, I think it's an awesome book.
I'm going to construct some wheel fairings using Three Wheelers construction technique, which is fiberglass over foam. I think that's the only way I'll effectively achieve the shapes I want to build. Hucho's book says the air at the rear wheels is coming at each wheel set at about a 15 degree angle from the middle. That's throwing an interesting curve ball in there, not sure what I'll do about that.
I think wheel turbulence on dually vehicles is considerable and so far somewhat ignored so I'm looking forward to that part of the build. I've incorporated mounting points on the pans in the back so I can build 'clip on' wheel spats, pants, whatever you want to call them. That way when I get a chance I can do some A/B/A testing to see how effective they are, and so I can take them off easily when it's time to play in the dirt again.
The hardest part of the pans build starts this evening, next up is one more somewhat easy pan and then the differential. I feel like this segment will be the difference between better than nothing and hell yes.
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Bro, you have no idea how much I appreciate what you're doing, which but for other vehicle distractions was to have been my summer project on my Ford E150 Econoline gas guzzler conversion van. Being so grossly inefficient in aerodynamics, it's a target-rich environment for improvements like yours. So, thanks mucho for doing all that and sharing with the rest of us.
Several thoughts:
Note Hucho's picture of the Calibri in the wind tunnel (maybe page 67 but I'm not sure). Shows that due to bow wave, the airflow impacting the front wheels is at ~60 degree angle. Hence, the plastic garbage can fairing for the front wheels should be canted inwards quite significantly to fair the air whence it actually comes. Same story rear fairings.
Consider use of polyethelene foam, which can be hotwired and sculpted and which is color-fast and weather proof. RC model airplane guys have gone to this, much tougher than fragile styrofoam. Bump a curb with this stuff and it will likely not damage it. It's the type of foam used for pipe insulation, and floats.
Your camera setup is fantastic! Do tuft testing with tape and colored yarn, or dabs of tempera water paint, and see how the realtime flow goes, at highway speed. Or, rig up your sprayer with several Ts and lines to spots on the belly pan, squirt water with food dye out of them at highway speed, see where the flow goes, then fair accordingly.
Consider NACA inlets where needed in your Coro belly pan. Cut with utlity knife, reinforce edge with alu. foil tape.
If Coro needs stiffening locally, insert wood dowel rods of proper thickness into the flutes.
Consider self-inflating rear fairing that billows out at speed, droops when stopped. This could give weather protection to anything you need to carry on the back, suck as bike or motorcycle rack, etc..
Keep doing what you're doing! I'll hazard a guess that once your project is fine tuned, fuel economy will improve ~40% or more.