Quote:
Originally Posted by Otto
I can't find my Hucho photocopied pages at the moment, but the Calibra wind tunnel picture I refer to is taken from the left front, shows longitudinal smoke trail diverts outboard at about 60 degree angle, apparently due to bow wave effect, with area of entrainment due to front wheels. So, fairings of front wheels would need to be canted in (pigeon toed) into the relative wind. Rear wheels need fairings smoothing the airflow out somewhat laterally, at a lesser angle, more or less like Prius has.
Outlets: NACA did lots of work on these during WWII. An efficient outlet is not just an efficient inlet turned around backwards. Rather, it should bring exhaust air as parallel to ambient flow as possible. Carefully study the exit gill geometry of fast swimming fishes, like tuna. Venturi and Bernoulli dynamics draw the water over the gills and out, else the fish does not get breakfast, but rather is breakfast. With Coro panels, this should be easy. The somewhat recessed leading edge of the exit ramp should have radiused edge contour. Proper inlets and outlets make the craft into a linear pump, with no moving parts...
Hot spots around exhaust pipes, etc.: Consider paneling this part of the belly with aluminum window screen, as alu is a superb heat conductor, so instantly dissipates any hot spot. Others with Coro belly pan experience report that the stuff can be used much closer to hot spots than I had imagined, but any such Coro could be faced or edged with aluminum foil tape, similar to duct tape. For the hottest spots, alu. window screen. Might could get some suitable stuff already framed in rectangular panels from a building recycling store, or discarded after a house remodel.
Some folks report aero improvement by sealing up those gaps in the face of the vehicle. Ford Econoline vans may so profit by use of strips of polyethelene pipe insulation, properly inserted into such gaps.
Your Econoline van has a plastic valence under the front bumper exactly like mine. I've seen others with valences that hang several inches lower, acting more as an air dam, so maybe some research at a Pick and Pull junkyard would find a bigger dam to fit that stock metal bumper, and also serve as a leading edge mounting surface for the belly pan. Alternatively, such valence could be a mounting surface for a combined splitter and belly pan. The Porsche guys figured out by trial and error that a splitter of ~4" protrusion is optimum.
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Thanks Otto, more good information. When you say splitter do you mean they run an air dam on each side of the front with a gap in the center? I saw that a while back and wondered what that was about.
I just went to Lowes and bought some fiberglass insulation that has an aluminum foil backing on it, close enough for now. They've got silicone wrap at the auto parts store but I didn't want to spend $50 on it.
Good point on the exit air. The louvers I bought at the demo yard are adjustable so I can lay them all over to get a good angle on the exhausted hot air.
This undercarriage is turning out so smooth I'm going to leave the front air dam for later. If I can find a good source for on-demand smoke I think that will give me some good clues as to how to build the front wheel pants (and rear especially), which may include a split air dam up front.
I'm stumbling around in the dark here trying to figure this out but everyone keeps turning on flashlights here and there to help me find the way. Thanks to everyone for their help!
