Quote:
Originally Posted by moonmonkey
i've been reading and reading but im just a little slow to learn, i dont know how to use those templates for a deck lid, calculation, from what aerohead said i would calculate a 15 deg angle from my roof to the back edge of my lid ? and make the decklid hang off the trunk of my car far enough for the air to reattach ? do i stop it right at the 15 degree line or make it alittle longer for the air to reattach, also i think blocking it up a few inches to make it higher ,i can go about 3 inches and still see out the back window i would seal it against the trunk lid so no air would flow under it and also rubber gasket it against my back glass, also would vertical "wings" like the fusion flats racer help or is that for stability? i have a hard time figuring out what is for CD and what is for down draft. You guys are doing great work with this site and i have Too much to learn, i will post all my work with photos and a how to, if i can make the mods = good demonstrable gains. thanks for the template and seminars aerohead!
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moonmonkey,all these materials are for members to use at their own pace.Life is stressful enough without adding extra pressure,and slow can mean methodical which is very good!
With respect to the template,imagine a sheet of plywood or stiff sheetmetal with the streamlined teardrop cut away where you could literally place it over your car.
Any part of the back of the car which does not "meet" the curve is a candidate for flow separation and the drag it produces.
Adding the rear spoiler is a compromise between the more ideal teardrop form and the real world.
Going straight back to the curve is drag friendly and allows low pressure to get underneath creating a suction if you will,under the tray for downforce.If you hung a 100-pound weight at the back of the shelf,measured the suspension deflection with that 100-lb load,removed the weight,and then drove to a speed which created the same amount of suspension deflection,then you'd know it was producing 100-pounds of downforce at that speed.That's how hot-rodders measure their spoiler's performance.The shelf has to be pretty long!
By angling the spoiler up at a shallow pitch you can get your drag reduction with less material,as you can "reach" the curve with less distance to the rear.
Anything you do should pay dividends.
Cardboard and duct tape are a great way to prototype a spoiler.If you like the results you see on your Scan-Gauge or MPGuino,tank mileage,then you can commit to a more permanent and costly unit.