general questions .. dams, pans, skirts, spats, tails etc.

[aerohead]

Originally Posted by dmac257

So these angles are based on the bottom of the wheels to prevent ripping parts off the underside of the vehicle?

My state (Connecticut) states minimum ground clearance is 4" and I am plenty high enough for that. Are you saying that the air dam should go down as low as either 4" (state limit) OR the 16degree angle, whichever is higher?
Would spats also follow this 16degree angle forward from the 4" clearance height? Would boat tails following the wheels angle up at 10degrees from 4" also?

As for the belly pan, you say highest allowable ground clearance. Ok, would this be as flat as possible from side to side or would curved higher on edges work better/worse? In conjunction with skirts it looks like you are saying flat accross and build down with the skirts to level of the pan. Is that right? And if I do full belly pan should the air dam in front extend below the pan or stop even with the pan?

And part I dont understand at all:
"The diffuser portion at its rear will be determined by where it begins" Heh, I dont even have a clue on WHAT to ask about this comment ;-)

I am going to go see if I can pick up some Clorplast tomorrow and will begin trying to figure out how to attach the big pieces so they are easily removed.

Don

Don,if you made cardboard cutouts of these angles and pushed them up snug against the tires,they would reveal the 'safe' zone recommended,of which you go below you risk a ground strike.
If you are very vigilant in your driving you can go lower.Problem around here is road-kill and especially at night.At highway velocity your headlights may not reveal a road hazard until you've almost impacted it,tearing the airdam and all your good work away.
Another trick is to have a second dam further back,even between the wheels.A curb will never get it,but again,a road hazard could.
If you go 'real low' the added frontal area may raise the CdA and start to eat into your gains.
On the bellypan,it might meander around a bit,whatever you can pull off.Completely flat and smooth would be best,with a 'diffuser' at the rear.
The diffuser is the last of the pan and angles up at a very shallow angle,from 2.5,to 4-degrees maximum angle for drag reduction.The angle is determined from point of origin,beginning well before the rear axle or well behind it.The aero-mods sticky should have an explanation and discussion about it.
For whatever you can pull off with the belly,bring the sides down to meet it,except wheel fairings,which could go to 4".
With respect to the elevation of the dam vs bellypan,my opinion is to go lower with the dam if you can.Put a bellypan on the dam itself if you can.Ford's concept car,the Probe-IV used such a dam with good success.
On the boat-tail,a lot of the guys are running steeper angles than 4-degrees simply to protect them,and 10-degrees would be the protection.
GM cheated all this with an aero-valance on their EPCOT car,which lowered on the highway to the more shallow angle.Aircraft cable, pulley,piano -hinge,and locking pull handle could render same effect.( just gotta remember to pull the thing up in city driving ).

[JackMcCornack]

> ...aero-valance on their EPCOT car,which lowered on the highway to the more shallow angle...

Why not have a scoopish dam, held up by springs, held down by air pressure? Fiddle 'till it goes down around 30 mph, comes back up at around 25?

[dmac257]

Originally Posted by JackMcCornack

> ...aero-valance on their EPCOT car,which lowered on the highway to the more shallow angle...

Why not have a scoopish dam, held up by springs, held down by air pressure? Fiddle 'till it goes down around 30 mph, comes back up at around 25?

Jack,

I kinda like that idea .. figure that at slow speeds or stop and go traffic not much pressure on front to aid in cooling flow so if dam is up pan underneath will "scoop" air into engine compartment from the space behind the dam. At speed of 25+ whatever the dam will have enough pressure on it to come down in front of the pan and backed by the pan to resist movement the air will go under the pan and to sides. I will think about this more, but it might just be over complicating a "simple" mod.

BTW wanted to thank you for your info on your web site. I posted earlier about the Dzus fasteners and link to your site in case others have not thought of them for attaching stuff they want to remove easily.

Don

[Frank Lee]

cfq made a deployable air dam. I've been meaning to ask him how it's working out anyway...

[dmac257]

I was looking at the aerocivic and seeing that it SEEMS to have rough edges and overlapps but still gets very low Cd .. I was wondering just how smooth do I have to make transitions? for example for a fairing in front of the windshield wipers. Would it be better to put it from under the hood up in front at same angle as the windshield .. or on top of the hood at angle between the existing hood/windshield angle to "smooth" the transition. Would it really make a difference at all?

I have been looking at the aerocivic so much that when I see an unmodded civic I think "What is wrong with that civic?"

Been looking at my truck a lot and wishing I never bought it.. but it is paid for and I used it both Sat and Sun to haul stuff so I guess I have to keep it.

Don

[Frank Lee]

Originally Posted by Frank Lee

cfq made a deployable air dam. I've been meaning to ask him how it's working out anyway...

bump

Also... was cruising the Ford lot today and noticed the new F150s have TWO airdams, one in front of the other. The King Ranch has one quite deep airdam. On that one they figured out how to deal with the weakness that plagued my '94: When you put curved ends on the plastic airdam and hit something, it breaks. The old, ugly flat ones simply bent up and sprung back but nooooo, we need style on there! I think I've seen one F150 of the same body style as mine with an intact airdam; all the rest are broken at the corner, just like mine. Anyway, their fix was to put some big steel stampings a couple inches behind the dam such that if the dam hits something it can flex some but not enough to break it at the corners.

On the new pickups you can sight down in front and see that the dams are low enough to "cover" all the low hanging undercarriage bits. On my '94 the dam is, oh, 4" deep but plainly needs to go at least 6" more to achieve the same coverage.