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Bicycle Bob · 03-03-2016, 10:08 AM

Don't write off underbody flow as a mess of large-scale turbulence. While there may be a lot of disturbed air near the ground in a breeze, you can also think of the ground plane as a layer of enforced laminar flow at free-stream speed. Your own laminar surface, if present, will be tripped by the front wheel openings, spreading across at 15 deg. You have to use a slight rake to allow for the progressive increase in thickness of the boundary layer.
Laminar flow is what got the Mustangs to Berlin, but it isn't easy. You need almost-shiny or better surfaces of near-optical precision to specific curves, protected from vibration. This is not a realistic goal for an inexperienced builder, but keep it in mind. It isn't hard to get laminar flow on the 1st 10%; it just keeps getting harder to maintain on the way to 70%.

03-03-2016, 10:08 AM	#31 (permalink)
Bicycle Bob EcoModding Apprentice Join Date: May 2008 Location: N. Saskatchewan, CA Posts: 1,805 Appliance White - '93 Geo Metro 4-Dr. Auto Last 3: 42.35 mpg (US) Stealth RV - '91 Chevy Sprint Base Thanks: 91 Thanked 459 Times in 327 Posts	P.S. Don't write off underbody flow as a mess of large-scale turbulence. While there may be a lot of disturbed air near the ground in a breeze, you can also think of the ground plane as a layer of enforced laminar flow at free-stream speed. Your own laminar surface, if present, will be tripped by the front wheel openings, spreading across at 15 deg. You have to use a slight rake to allow for the progressive increase in thickness of the boundary layer. Laminar flow is what got the Mustangs to Berlin, but it isn't easy. You need almost-shiny or better surfaces of near-optical precision to specific curves, protected from vibration. This is not a realistic goal for an inexperienced builder, but keep it in mind. It isn't hard to get laminar flow on the 1st 10%; it just keeps getting harder to maintain on the way to 70%.