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  #241  
Old December 23rd 2011, 15:51
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Quote:
Originally Posted by judgie View Post
the aim is to get the air to flow quickly under the car, thus reduceing its presure. so as flat, leval and clean a underside as you can get will help. also deeper running boards to stop the air under the car spilling out at the sides.
the other option is to stop as much air as possable getting under the car but this can cause a lot of turbolance at the rear of the car creating a lot of drag.
Thanks judgie I was trying to find time to call you today as I would like to talk to you about setting my cars suspension up properly, are you about tomorrow for a chin wag ?
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  #242  
Old December 23rd 2011, 16:00
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Aerodynamics of a bug

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Originally Posted by Jadewombat View Post
Nice car. I think dispersing the air under the car from the front grill may create more lift by making a pocket of more air between the car and the road as you're trying to minimize the amount of air passing under the car. Sending the air up and over the hood through a scoop about 1/3 way up has been proved to create more downforce on the front end as seen on this Acura here:

http://www.germanlook.net/forums/sho...t=2820&page=14

and 911:



...although I don't think you'd want to cut up that beautiful black hood of yours though?? Looks like your car is pretty sleek as it is. You could maybe install ducts from the grill to the backing plates of the front brakes to keep them cool. What kind of front bumper is that?
Thanks Jadewombat
I did think about cutting the hood but as you have said cutting it would not be something I would want to do .The bumper is from a Rover 400,It has been modified a bit but not heavily.
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  #243  
Old December 23rd 2011, 20:09
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Aerodynamics of a bug

I have been pretty active recently on this site as I have spent the past three or four days on the sofa with the sodding Flu. Anyway this is an idea I have had for a rear bumper/spoiler.It would work by releasing the pressure from the rear of the bug where the cars original design seems to act like a parachute.ie wings,apron,engine lid.The holes/vents in the wings etc would escape through vents and get channelled into the rear bumper at an angle to produce down force.In addition to this, the top of the bumper would be angled to produce more down force.It would be built to fit close to the body to eliminate what seems to also be the parachute shape of the standard bumper.Also the bottom center section could include veins.I have seen engine lids with holes behind the number plate this could be angled to produce more directional airflow.I am not sure of how it would effect the rear of the car but as I see it, it could possibly
1. create and add down force
2. release pressure from the rear wings,apron,engine lid.
3 create some rear end stability at high speed.

I have got an old porsche style body kit rear bumper that I was intending to use as a starting point .

All input welcome

Hope it turns out better than my sketches .

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  #244  
Old December 24th 2011, 02:15
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Hey Graham,

I like your sketches! The vents in the rear fenders and apron is something that Remmele has done to his cars for a long time also and I think the reasoning behind that is strong. It will surely help some, same as it would on the rear of the front fenders.

Not so sure there would be downforce as such on a rear closed bumper though as turbulence behind the car is probably very high. I do agree they act as parachutes otherwise. For that reason I filled mine up with expanding foam (PUR)

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  #245  
Old December 24th 2011, 05:09
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Couple of aero basics for you:

To get downforce the rear exits would have to be channelled to point upwards, the downforce is a result of a reaction force.

The air over the top of the car would be detached from the surface way before the engine cover, typically at the top part of the rear window.

Downforce is mostly a result of STATIC pressure and the difference of this between top and bottom surfaces of a body. Target is to get higher pressure at the top surface which will result in overall DOWNforce. According to Bernoulli's equation: faster fluid flow results in lower static pressure. Using this, you want to get the air under the car flowing as fast as possible to get the static pressure as low as possible giving any increase in pressure over the body a chance to create the downforce.
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  #246  
Old December 24th 2011, 07:19
spannermanager spannermanager is offline
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Graham, well done so far, a very nice side step to the usual copy cat builds, but do you want all that venting on a road car? i have exactly that type of venting on my race car, but its not subtle. with a water cooled road car, why not work towards a diffusor and flat bottom it up to the bumper line? this was a factor in my water cooled engine choice, together with diminishing DB control thresholds at the races, i'm now 3/4 db quieter over aircooled with water cooling alone. you will need to move the lower shock mounts to make a worthwhile flat bottom workable, and the exhaust needs attention with any engine to get it out of the way. Just my view, but i think a road car, or a race car come to that, should be as understated as possible, its easy to get carried away and the KIS rule always applies. but well done so far anyway.
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  #247  
Old December 24th 2011, 07:29
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i'm in work next week so give me a call.
this is the sort of thing you wnat under the car

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  #248  
Old December 24th 2011, 18:20
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Of all the aero. tricks I've tried so far, venting the fenders made the most difference I could feel right away. Took the car out on the highway the next day and it felt much more planted to the road than before. I used a punch and flare tool on mine to make the holes. The turbulent air of the spinning wheels causes the fenders to act like wings and give the car some 'lift' at speed. If you look at new(er) cars they have a fender liner to minimize this distance between the tires and the inside of the wheel well.



Made a cheapo. roof spoiler out of garden edging recently. Just couldn't bring myself to spend $200 on a little piece of carbon fiber strip. Seems to help, car scoots off the line a hair quicker, could be my imagination too as I'm not being very scientific here but it definitely doesn't feel likes it's creating any drag.

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  #249  
Old February 9th 2013, 10:00
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I just found this interesting youtube vid & facebook item and thought I had to share it here.

See: Youtube video VW bug in a wind tunnel

And there was a poll on the face book page, see the top red box. The answer is in the bottom red box:


(click on it to get to the entire facebook page, I couldn't link directly to this item)

The beetle has 6% less drag when going backward.
I think it's because of attached flow staying attached to the rear window, which creates drag. Going backwards, there's nothing to attach to after the windscreen point. So the airflow can form itself like a teardrop.
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Last edited by Gerrelt; February 9th 2013 at 15:51.
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  #250  
Old February 9th 2013, 12:37
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Thats very interesting and sad at the same time. Shows us also here's a lot to gain with aero improvements.
We're probably on the right path Gerrelt
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  #251  
Old February 9th 2013, 15:36
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Yep!!
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  #252  
Old February 8th 2014, 13:02
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Here is my underbody at its present stage. the rear ARB need moving to finalize the airflow, and is next for the chop saw, its going inside a tube running through the cars rear wheel boxes, bugs are hard work aero wise, the exhaust is particularly difficult to package away from everything in order to fit streamlining panels that wont be ripped off in the first race, my car already bottoms on the spring plate bolt heads and its not low enough yet, ideally the torsion tube needs raising and the horns chopping out.
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  #253  
Old February 11th 2014, 03:05
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Aerodynamics of a bug

My car has been hibernating whilst I am waiting to finish a large building project before work begins again on it. I am still looking at the builds here and seeing peoples ideas and views.

Spanner, it's interesting that you mention raising the torsion tube and chopping out the frame horns .Thats got me thinking.

Part of the next stage of mods on my car will involve cutting the torsion tube in the centre and replacing the frame horns to aid the g50 gearbox fitment.Do you think raising the torsion tube or removing it completely may be worth considering whilst I am at it ????

What are peoples views/ideas on the best possible rear end set up to accommodate the g50 minus a torsion tube.I will be using one of Alex's uniball set up's.I am now thinking of a gearbox cradle/frame horn combo to tie into the cage and hold the uniball kit at the same time raising the top shock mounts.Here's the car as it is at the moment.[IMG]~original[/IMG]
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  #254  
Old February 11th 2014, 12:39
spannermanager spannermanager is offline
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Hi Graham, I would look at Ricolas layout, he made up new horns to suit a G 50, but to answer your question, unless it's a race only car, and running at circuit type ride height, ie, 40mm, raising the t/tube isn't strictly required, what it does is allows the car to run lower with good trailing arm angles for effective launching/traction, on the other hand, a powerful motor needs as straight a driveshaft alignment as you can get, so a gearbox raise is required in any case, removing the horns completely requires either a very strong mid mounted yoke set up, noisey for a road car, or a Porsche type rear engine support bar with lots of body/apron strengthening to hold the weight of motor, trans, and control the dynamics of driving forces on the supports, my racer uses a mid mount yoke, as I originally planned to loose The horns, I even tested with the end bolts removed with no problems, but they got a reprieve for packaging and mounting other stuff off them reasons, race only cars are easy, less compromises than a road car has, more for you to consider.
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  #255  
Old February 11th 2014, 13:36
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Quote:
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Hi.., race only cars are easy, less compromises than a road car has, more for you to consider.
Aint that the truth!
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