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> Lifting rear of roof, what are the benefits
john rogers
post Jan 3 2006, 10:42 AM
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If you mean pictures of the yellow #22 car, I have some someplace that I can scare up and put in a seperate thread as this one has wandered off the original topic. You statement about not being legal made me chuckle since that little 4 cylinder car was pretty famous in it's day and you are correct that there are many clubs won't let something like that in to race. Even VARA makes it run in CP-X since it was an IMSA car, not an SCCA class car. Ron will probably have it at the June HSR West race at the CA Speedway, maybe it is time to take a road trip to So Cal???!!!
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brant
post Jan 3 2006, 12:11 PM
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John,
cool I'll look for it
would love to see more pictures eventually.

I know that my local vintage group is much more strict than most of the nation... (no aero at all, no fiberglass, no fiberglass fenders, etc)

but I can understand their decision too.
Their rule is 1972 and how it would have been presented legally in 72. (or could have been presented legally in 1972)

brant
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dinomium
post Jan 3 2006, 05:55 PM
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how about a Gurny flap on the trailing edge?
Also, doens't the high speed instability be exsaperated by the two aero dirty areas (front supension and rear engine bay) intersecting with the relitively areo clean pan area? You have turbulance then lift back to tubulance... And in the stock rear valance and you might as well fly a gollywobbler!
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TimT
post Jan 3 2006, 06:55 PM
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A gurney flap make a wing more efficient, I think this the polar opposite of what is trying to be accomplished here. I could be wrong though of course.

allow as little air as possible to get under the car

We punched some holes in the rear window of our 935 clone to allow the air an easy way out

Our scientific methods at the track are flawed though. Usually because of time constraints... ie we change more than one thing at a time.


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john rogers
post Jan 3 2006, 07:15 PM
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Since you mentioned the pan area, this should get all the engineers to thinking. On my race car the front spoiler covers the front suspension area and the pan is nearly the lowest part of the body (except for the headers) so I an thinking there is a tad bit of the nozzle effect since the air going under the pan is squeezed slightly, making it's velocity higher so to keep things in order the pressure will go down some. Some air will come out the sides I imagine but the car is moving. Bournolli thought up that stuff years ago and it is why when two ships are refueling at sea side by side they tend to get sucked together or like two NASCAR stock cars side by side.
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Jeroen
post Jan 3 2006, 07:56 PM
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QUOTE (TimT @ Jan 4 2006, 01:55 AM)
A gurney flap make a wing more efficient, I think this the polar opposite of what is trying to be accomplished here. I could be wrong though of course.

as far as I understood, a gurney reduces drag from a wing by pulling the airflow back to the bottom of the wing
(excuse my poor description, the pic should clearify it)

(IMG:http://www.insideracingtechnology.com/Resources/gurneyflap.gif)

Not sure it would work on the roof, but I have been thinking about it (IMG:http://www.914world.com/bbs2/html/emoticons/idea.gif)
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TimT
post Jan 3 2006, 08:01 PM
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good pics Jeroen The gurney does help to pull the airflow back together, making the wing more efficient. Im not sure this is what you want on the roof of a 914, where lift may be generated by the roof itself?
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brant
post Jan 3 2006, 08:53 PM
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John,

can I ask a clarification question about your front spoiler....
when you say it covers your suspension, do you mean that you have a flat bottom covering some of the suspension....

I ask because I've seen more than a few vintage cars (and am working this myself right now)... Where the front spoiler or valance has a sheet of aluminum attatched to the bottom edge of the valance and then covering all of the leading edge of the torsion bars etc. Thus making the front underside smooth.

brant
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Air_Cooled_Nut
post Jan 3 2006, 10:09 PM
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I read the aerodynamic web site...good info. Not sure if I believe that those vortex generators are of any real help. There's still the fundimental issue of the car creating a low pressure area on top and higher below. So you make little tumbly areas of air aft of the roof; the engine is still sucking air from above itself and creating a region of lower pressure. And those vortex generators are used to help a wing with lift.

Pulling air from the sides or -- better yet -- the bottom of the vehicle makes more sense. Granted, things in aerodynamics may not always make sense but I use the term with regard to aerodynamics...from my arm chair (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)
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john rogers
post Jan 3 2006, 10:37 PM
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No, the front spoiler only sits about 1/2 inch off the ground and wraps around to the wheel openings. I have never gotten the time or ambition actually to do the bottom aluminum work like Jim Patrick has done with his car.
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race914
post Jan 4 2006, 02:21 PM
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QUOTE (brant @ Jan 3 2006, 06:53 PM)
John,

can I ask a clarification question about your front spoiler....
when you say it covers your suspension, do you mean that you have a flat bottom covering some of the suspension....

I ask because I've seen more than a few vintage cars (and am working this myself right now)... Where the front spoiler or valance has a sheet of aluminum attatched to the bottom edge of the valance and then covering all of the leading edge of the torsion bars etc. Thus making the front underside smooth.

brant

Hi Brant,

Is this what you are thinking of? My front splitter extends back the depth of the spoiler. Not a full belly pan, but it helps.

Greg


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brant
post Jan 4 2006, 02:25 PM
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Greg,

yep..
nice pic
thats one of the things I'm working on

brant
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TimT
post Jan 4 2006, 05:13 PM
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We did a similar thing on our 935, The splitter extends back to the front crossmember. I dont have any pictures of it though. the rest of the 911 pan is pretty smooth, but even so we may get some ABS sheet and continue the belly pan all the way to the back of the car
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Aaron Cox
post Jan 4 2006, 05:14 PM
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greg, got a front shot?

AA
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race914
post Jan 7 2006, 01:03 PM
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I do! I went for the 'stealth' look on the entire front spoiler and duct work so it's hard to see. Sure is easy to touch up all the rock chips though!


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J P Stein
post Jan 7 2006, 01:18 PM
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Brant:
Does the rule book require a rear window?
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brant
post Jan 7 2006, 01:22 PM
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QUOTE (J P Stein @ Jan 7 2006, 12:18 PM)
Brant:
Does the rule book require a rear window?

I don't technically think so...
I know some spyder 914's in vintage that run no rear window.

but when I was contemplating this... I had a picture in my head of a carb fire I once witnessed..... thats when I decided to go with the rear window. I could imagine a big ball of flame with my head and neck 12inches away.

I do think it would be less wind drag with the rear window out though.
brant
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J P Stein
post Jan 7 2006, 01:28 PM
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QUOTE (brant @ Jan 7 2006, 11:22 AM)


but when I was contemplating this... I had a picture in my head of a carb fire I once witnessed..... thats when I decided to go with the rear window.

So........ what kinda chump has carb fires? (IMG:http://www.914world.com/bbs2/html/emoticons/laugh.gif)

I run without a top. My biggest fear is goose shit. The gaggle at PIR takes off about 7ish......bout a thousand of em'. (IMG:http://www.914world.com/bbs2/html/emoticons/w00t.gif)
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brant
post Jan 7 2006, 01:34 PM
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I don't think I'd like the goose issue...

but I remember a fire ball on a 911 where they had mounted a fuel guage on the carb itself....

all that vibration caused the brass fitting on the fuel guage to crack and spray fuel onto the headers...

poooffff!

memory kind of stuck in my head.
and then I realized that on a 911 there was a lot more between the driver and that fire then I would have.

brant
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dmenche914
post Jan 7 2006, 01:42 PM
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what about the 914's that have the raked back windshild modifcation, this tilts the roof at an angle. Has anyone knowledge on what that does to air flow?

I have seen some photos of this, even on race 914's My gut says that it would help hold the car down at speed, what do you all think?
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