Quote:
Originally Posted by MetroMPG
It seems that an angled airdam that lowers the stagnation point makes sense. Haven't seen any hard data or testing against a simple vertical dam though.
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I know, I've been thinking my jacknut installation is well suited to doing a Cd vs angle test suite. Unfortunately I'm not ready for coast-down testing right now, and I don't see any way to answer the question with tufts.
Quote:
Originally Posted by MetroMPG
Why err high? Do a mockup with cardboard: go aggressively deep (say 3 inch clearance) and compare to 5.5-6 inch clearance.
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1) Clearance is desirable. I angled into my driveway and measured 4.5" corner clearance before I put on the dam - the problem being that I was not in the car when I measured (also it's hard to put the tape measure in the right imaginary spot). I put the dam on last night with 5" corner clearance and scraped in 3 different locations, a) my driveway, b) an intersection dip, not even the worst dip I expect to encounter, c) at work, in all cases doing my best to hit the low spot at an angle. Either I'm going to get better at this, or the PETG is going to get cut even higher than 5". SLC in general has some really gnarly dips and driveways. It's a headache.
2) My own personal untested theory: you can either A) push the leading edge of the dam forward until it more cleanly shears top and bottom flows, or B) push the leading edge of the dam down to throttle the flow coming from the high pressure zone in front of the dam going under the car. I expect option A should be the best choice for FE as well as clearance, all other things being equal, since the final result is less frontal area. (Option C would be an underbody airfoil, i.e. paneling and boattail, with a smooth nose but no air dam, like the Aerocivic.)
Again, it's a big hindrance that I'm not ready for coast-down testing... yet. It may even be a mistake to do this type of mod without mockup and coast-down. But maybe I'll get lucky.
Or maybe I'll be able to edit the design as I go without making it look too chopped up.