A Not So Perfect Belly Pan.

[Christ]

Don't parachutes have vents in them to keep air going through it, so that it stays billowed instead of collapsing as air rushes around the sides of it?

I think that's the reason that parachutes are so... parachute-y... if you sealed a parachute, I presume it wouldn't even work effectively past the opening point.

[Frank Lee]

Key Concepts

[Deezler]

Yeah. I want my parachute sealed in this case. Or, perhaps, not a parachute.

Made a few tweaks to the panel today, I think it's on the right track now.

Lowered the rear edge to better meet the spare tire well curvature, and added some precision coroplast:



Started on a set of small aluminum panels that will help seal off the front and side edges completely.



Also tweaked it around to bring it a bit higher off the ground. I'm now able to convince myself that this thing should be helping, but I'll have to get some FE results to feel better about it. Today's commute was inconclusive, but also not great.....

[Deezler]

I think the tweaks were good. Took a long(ish) road trip down to Cedar Point yesterday. For those of you who aren't familiar, it's a place designed specifically to do one thing: use energy.



I think the energy requirements to fire the "top thrill dragster" just once probably exceed the amount of fuel I'll ever save through eco-modding. A 5 ton train accelerated from 0-120 mph in 3.8sec.... But that's neither here nor there. (and btw it is a truly amazing experience)

Back on topic: Recorded my best ever scan gauge readings, without any special attention to driving. The roads in Ohio are great, aside from the 5" rock left right in the middle of my lane! doh. Ripped off one piece of coroplast and left a nasty scrape in my skid plate. Thank goodness its there though, or I would have lost an oil pan instead. I can just picture the inbred farmer trying to save fuel by leaving his tail gate down as he transports his load of rocks.

I think this thing is really helping though. sweet.

[Christ]

LOL - There's a door at the hospital that my son was born at that just rotates all day... even if noone is in it/walking through it.

I call it "The several thousand dollar renovated massive rotating waste of energy."

Just inside that door, they put a traditional automatic sliding door... apparently, they figured out that the giant rotating door referenced above made a huge hole for air exchange...

[almightybmw]

Ever driven down a dirt road? I think I'd want something a little quieter than metal for driving around here.

[Deezler]

Not a peep out of this panel so far. Haven't driven down any dirt roads though; I avoid them whenever possible. Perhaps not feasible in Bozeman!

I still wouldn't really expect it to make a ton of noise; its centered under the car and away from the edges. My Michelin energy's tend to not throw any rocks also.

[lunarhighway]

Key Concepts

suppose it's diffult to make a rear undertray that's completely sealed at the front, so air might get above it... would there be any benefint in creating exit vents for the trapped air, this might energise the boundry layer and pervent turbulence either local on the tray, or in the overall drag of the car

[Deezler]

It might be hard to see in my pics, but I really doubt much airflow is getting on top of my panel from the front edge. Some may be sneaking around the sides, or being forced in from the wheel wells if strange aero is happening there. But the front and rear of the panel are pretty well concealed.

I thought about trying to make strategic exit points for any entrapped air pressure, but it just made more sense to have it all smooth.

My scan gauge is showing some noticeable gains for this piece; best ever commuting mileage result on the way home yesterday (and still at 75mph). woot.