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aerodynamics
#1197139
06/04/2011 02:31
06/04/2011 02:31
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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with wanting to post the fastest ever coupe speed i am looking at aerodynamics..anyone know anything about it and what are the best things to do with the car i expect the best front would be zenda? anyone?
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Re: aerodynamics
[Re: ]
#1197140
06/04/2011 03:00
06/04/2011 03:00
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zimpara
Unregistered
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zimpara
Unregistered
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I assume you will be attempting this on a dry day. Loose the wipers and skuttle panel and make a smooth version, just an idea.
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Re: aerodynamics
[Re: ]
#1197258
06/04/2011 12:12
06/04/2011 12:12
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Marco20valveT
Unregistered
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Marco20valveT
Unregistered
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the areodynamics of the coupe are ok...
they only start becoming a REAL issue at the 160mph+ mark..
Nigel and a few other have all said they coupe will whip upto 160 but then hit the areo wall and then it takes a while to climb to the 170+ area.
to make the car better on a 1/4 mile mark you need to firstly lose as much weight as possible...
then make it a consistant flow over the body.
fitting a underside body pan cover would help keep the flow of air smooth.. as posted above, keep the car slim with nothing sticking out past the body of the car...
so wing mirror's would go too!
i think it would be good to get a coupe in a windtunnel jsut to see if any thing listed would make that much of a difference!!
we had a problem with a mini scoop that my mate designed, he found over 100mph, the scoop didnt take air in, it caused a ripple effect and pushed the wind into the wipers lifting them OFF the windsceen!!
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Re: aerodynamics
[Re: ]
#1197263
06/04/2011 12:24
06/04/2011 12:24
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jonone
Unregistered
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jonone
Unregistered
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marco winds car will give you some ideas
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Re: aerodynamics
[Re: ]
#1197264
06/04/2011 12:25
06/04/2011 12:25
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Steve^
Unregistered
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Steve^
Unregistered
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..and the wipers lif off the screen all together at above 140 mph..... which was fun
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Re: aerodynamics
[Re: ]
#1197277
06/04/2011 12:34
06/04/2011 12:34
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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so leave the undertray on find the skinniest wheels ..then i think the front bumper would make a difference..is there nothing known about this? i had heard that zender were wind tunnel developed...also the rear spoiler my green car has a small one that fits across the back corner of the boot with a bit on either back quarter..its literally completely attached.. my mates car has a rear that sits in a similar place but is fixed to the back face of the bumper by 2 arms or whatever you call them both are auto ds any ideas which would be better as i could borrow the boot lid from my mate..rather than one of the others as the one on the green does not come off
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Re: aerodynamics
[Re: ]
#1197493
06/04/2011 18:46
06/04/2011 18:46
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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Boundary layer will come into effect, keep it as smooth a flow of air over the car as you possibly can (no spoilers Per ) reduce anything that will cause a pressure change on the airflow, wing mirrors front and rear windscreen wipers, etc. Anything with an edge will cause the boundary layer to detach from the body of the car and cause drag. That is why aerodynamically designed cars are shaped so that the boundary layer remains attached to the body longer, creating a smaller wake and, therefore, less drag. Pop a spoiler on the boot, larger wake turbulence, more drag.
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Re: aerodynamics
[Re: ]
#1197526
06/04/2011 20:18
06/04/2011 20:18
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Joined: Oct 2010
Posts: 549 Bulgaria
Ferrarist
Enjoying the ride
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Enjoying the ride
Joined: Oct 2010
Posts: 549
Bulgaria
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Make your floor as smooth as possible, then try to smooth it better......saw on some italian forum test with Alfa 156 3.2GTA - stock without even engine guard plate, and with smooth as mirror floor - 13kmh difference.....if you doubt my words, put your hand outside the window with 170kmh and imagine how aero can affect top speed.....
Last edited by Ferrarist; 06/04/2011 20:19.
20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT
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Re: aerodynamics
[Re: Jimbo]
#1197534
06/04/2011 20:35
06/04/2011 20:35
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Joined: Sep 2009
Posts: 5,022 ation
szkom
Club member 2000
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Club member 2000
Forum is my life
Joined: Sep 2009
Posts: 5,022
ation
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Pop a spoiler on the boot, larger wake turbulence, more drag. Not quite. It depends on the type. Halfords special then yes. But something like a correctly mounted zender should reduce the form drag. Essentially, as the coop won't break mach 1 the air won't flow around a corner (the edge of the boot lid). What it will do is roll off the edge (think winglets). What fitting a rear lip type spoiler will do is delay this roll off thus preventing impingment and reducing drag. However it's academic as we are only guessing where the roll off starts; it may be at the window. But totally agree if we could minimise the wake caused it would be better than "cheating" with the slab back end the coop has. Maybe some kind of fairing? KTM, what kind of speeds are you thinking of?
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Re: aerodynamics
[Re: ]
#1197536
06/04/2011 20:42
06/04/2011 20:42
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tim42
Unregistered
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tim42
Unregistered
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with wanting to post the fastest ever coupe speed i am looking at aerodynamics..anyone know anything about it and what are the best things to do with the car i expect the best front would be zenda? anyone? Rob, you are a Coupe nutter!! Good luck mate... but the Coupe is not designed for dragging. You'll break it big time. See you soon, Tim
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Re: aerodynamics
[Re: szkom]
#1197546
06/04/2011 20:56
06/04/2011 20:56
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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Pop a spoiler on the boot, larger wake turbulence, more drag. Not quite. It depends on the type. Halfords special then yes. But something like a correctly mounted zender should reduce the form drag. Essentially, as the coop won't break mach 1 the air won't flow around a corner (the edge of the boot lid). What it will do is roll off the edge (think winglets). What fitting a rear lip type spoiler will do is delay this roll off thus preventing impingment and reducing drag. However it's academic as we are only guessing where the roll off starts; it may be at the window. But totally agree if we could minimise the wake caused it would be better than "cheating" with the slab back end the coop has. Maybe some kind of fairing? KTM, what kind of speeds are you thinking of? I hear what you're saying but you don't get the roll off on the coupe. Ever looked in the wing mirrors on the motorway when you're driving through spray, it's a very clean break from the rear, there is a vortex but it's caused by the haunches on the sides and it's rolling longitudinally , however it does separate cleanly and doesn't roll off the boot, that's why a spoiler isn't really needed. If the air is leaving the boot cleanly I'd just let it be and not add a spoiler that will cause turbulence and extra drag.
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Re: aerodynamics
[Re: ]
#1197612
06/04/2011 22:30
06/04/2011 22:30
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Joined: Dec 2005
Posts: 17,367 Staffordshire
Nigel
Forum veteran
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Forum veteran
Joined: Dec 2005
Posts: 17,367
Staffordshire
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Rob - where are you going to prove your speed?
The longest UK runway is Bruntingthorpe at two miles, which is nowhere near long enough for a proper top speed run
You could try Millbrook's banked circle, but anything above 120mph requires positive cornering effort, and I wouldn't fancy trying to corner a Coupe at 180+ mph, regardless of how well its set up
Personally, I think you're getting it all wrong - its simply not possible to go very fast with no money (and I assume your finances are tight, seeing as you're looking to borrow tyres for TOTB). At best, you'll simply not go very fast, and we'll all take the mickey for a few days. At worst, you'll go fast enough to show up a major deficiency in the Coupe chassis, and you'll end up in a hospital or a coffin.
I'm not kidding - at my first TOTB event, the top speed run was 1.2 miles and I got up to around 160 before having to brake VERY hard - the car was getting a bit wandery under power and it got notably worse while trying to stop.
You've already stated publicly that you've never done a trackday, let alone a top speed run. I think you're biting off more than you can chew.
Please think long and hard about trying to go above 170 in a Coupe without spending a lot of cash making sure it won't end in disaster.
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Re: aerodynamics
[Re: Jimbo]
#1197644
06/04/2011 22:58
06/04/2011 22:58
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shinyshoes
Unregistered
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shinyshoes
Unregistered
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I'd just let it be and not add a spoiler that will cause turbulence and extra drag. And look crap.
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Re: aerodynamics
[Re: Jimbo]
#1197658
06/04/2011 23:19
06/04/2011 23:19
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Joined: Jan 2006
Posts: 3,034 Sweden
Per
I need some sleep
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I need some sleep
Joined: Jan 2006
Posts: 3,034
Sweden
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Boundary layer will come into effect, keep it as smooth a flow of air over the car as you possibly can (no spoilers Per ) reduce anything that will cause a pressure change on the airflow, wing mirrors front and rear windscreen wipers, etc. Anything with an edge will cause the boundary layer to detach from the body of the car and cause drag. That is why aerodynamically designed cars are shaped so that the boundary layer remains attached to the body longer, creating a smaller wake and, therefore, less drag. Pop a spoiler on the boot, larger wake turbulence, more drag. Since I was mentioned I better answer.. Jimbo you are correct about smaller wake - less drag. However, the truth is even more complicated. Assuming Coupe has lift at the rear at speed (very few cars have rear downforce as std. First Audi TT had a LOT of lift..), there is a resulting force vector upwards. This vector adds force to total drag. It's like lifting a moving toy car by a string, or going into a bend at speed - it'll slow you down. So - by reducing lift you gain force forwards; drag is lost. That gain is bigger than that of smaller wake, on most cars. Hence "spoilered" M3's, M5's, AMG's or RS4's from factory. They're no stupid people! The most effective tool though is a diffusor, which in most cases results in BOTH smaller wake and less lift.
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Re: aerodynamics
[Re: ]
#1197776
07/04/2011 05:41
07/04/2011 05:41
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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ok guys thanks for all advice.. nigel my strategy for dealing with failure is simple just don't tell anyone when and where! that takes care of that one! i will break cover if i suceed..i am not going into it gung ho although i only race bikes i know all about preperation, fail to prepare,prepare to fail and all that,thats why i am discussing these things first and openly as it always throws up things you haven't thought of and opinions that even if you don't agree with are illuminating none the less.. i have had my old coupe over 160 and my only real issue was on lift off it moved around a bit and i needed the lane either side for a second or two so i have no worries on this as that was just a standard car with suspension refreshed and eibach springs..i understand the likely issues pushing the extra twenty odd miles will throw up but i am confident i can overcome them..this is where preperation will be the key although i am a little cash light at present i will recover and i will have an extremely well set up car anyway so i don't think there will be much more needed than i already have..nothing at all has been compramised on this build which is the reason i am strapped! but it will be as capable a platform as has yet been run which with a few bits specifically tailored to the run i think i will beat whatever the top speed is i am that confident i still don't know what it is all comments/thoughts/information on this will be gratefully recieved gents
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Re: aerodynamics
[Re: Per]
#1197820
07/04/2011 10:24
07/04/2011 10:24
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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However, the truth is even more complicated. Assuming Coupe has lift at the rear at speed (very few cars have rear downforce as std. First Audi TT had a LOT of lift..), there is a resulting force vector upwards. This vector adds force to total drag. It's like lifting a moving toy car by a string, or going into a bend at speed - it'll slow you down. So - by reducing lift you gain force forwards; drag is lost. That gain is bigger than that of smaller wake, on most cars. Hence "spoilered" M3's, M5's, AMG's or RS4's from factory. They're no stupid people!
Absolutely they aren't stupid Per and I don't disagree, unfortunately for us, we don't have any images of a coupé in a wind tunnel so we are only working off assumptions where as the clever people at BMW, Audi and Mercedes had access to all that. I think you're spot on with a diffuser to clean the air from under the car, spoiler we'll agree to disagree on but the most important area to focus on would be the front end on a coupé, any high speed run leaves the front feeling very floaty, it's all well and good cleaning up the wake but a better front bumper/splitter is needed to keep the nose from lifting.
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Re: aerodynamics
[Re: ]
#1197981
07/04/2011 15:02
07/04/2011 15:02
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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any ideas on a splitter design just for the one off run?
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Re: aerodynamics
[Re: ]
#1198016
07/04/2011 16:06
07/04/2011 16:06
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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A splitter will reduce airflow under the car but it may not give downforce to stop the front floating, a set of canards or dive plates set at the right angle (say 10-15 degrees) will give just enough down force at the front. As a non crap looking alternative, a set of LE front lips will be an improvement on a standard front bumper. The cadmuro front bumper lip may be better: Oh and if you do fit a splitter just for a one off run, it HAS to be level, don't just bolt it on to the under side of the bumper, get the angle wrong and you'll end up like Donald Campbell!
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Re: aerodynamics
[Re: ]
#1198027
07/04/2011 16:27
07/04/2011 16:27
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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fabrication is not my strong point i might just try and borrow a cadamuro i was going to fit a zender anyway but if anyone has a cadamuro i can borrow at some point..i have a good undertray..anything else? i would try a splitter but wouldn't know where to start making one or the design to use ..anyone fancies getting involved they are welcome
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Re: aerodynamics
[Re: ]
#1198155
07/04/2011 20:16
07/04/2011 20:16
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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i will sign a disclaimer if anyones worried and do an on camera admission that its all my own doing whilst i am making the video for my family with my final wishes
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Re: aerodynamics
[Re: ]
#1198196
07/04/2011 21:08
07/04/2011 21:08
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sediciRich
Unregistered
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sediciRich
Unregistered
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I would make the floor of the car smooth, this sounds simple but would need a fair amount of time on a chassis lift and you may not want to enclose the exhaust tunnel completely - I know the alfa 156 ST had the 'flatness' increased by bringing the flat floor towards the exhaust tunnel then turning 90deg up to the sides of the exhaust system leaving a narrow opening just under the exhaust no doubt done for heat management. A diffuser keeps the flow tidy from the exit of the rear of the car but its main aim is tidy high velocity flow to complement the air flowing under the rear spoiler - maximising its down force (needs a much large explaination really). Don't confuse flat floors and diffusers with having a tunnel and ground effect thats something different and not the aim. While you dont want lift I'd say avoid creating down force just cut drag. Thus an air dam at the front is useful rather then a splitter - but just for interest all of the wind test results I have read in RCE pretty much show splitter to be very efficient -F/D thus downforce with little drag.
Tape up door shuts, panel gaps, boot lines, reduce radiator openings (you only need 1/4 of the frontal area of the rad/ic to be effective at speed.
More drastic is venting the wheel arches that create huge drag, on the coupe louvre (sp) bonnet vents sealed to the arch liner would vent the front arches nicely but its a cosmetic change you may not like and bonnets aren't cheap. For the rear you want air to leave the back of the car nicely so a simple strip of sheet material at the boot's trailing edge blended to the top surface would work (look at a golf mkV boot edge), loose the wipers, and as much weight as you still need to get to the terminal velocity as quick at possible. The fiat has a good shape to start with so game on.
Last edited by sediciRich; 07/04/2011 21:13.
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Re: aerodynamics
[Re: ]
#1198250
07/04/2011 22:18
07/04/2011 22:18
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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ok i have a spare bonnet here i can hack up and spare doors i was going to try and lighten for totb anyway..i would be happy to vent the bonnet to make this work but wouldn't know where to start or how to work the liners to vent through them..the nads for the job i have but the technical/fabrication skills i don't so would really be grateful if someone with at least the design ability could help explain enough for me to collect whatever items i need to make the bits to help the car up to speed.. up to now all i am likely to use without assistance is cadamuro bumper ,undertray, taping bits up and removing wipers.possible skinnier wheels.. rich so a little boot spoiler on the edge? which of the auto ds would you think best
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Re: aerodynamics
[Re: ]
#1198528
08/04/2011 10:30
08/04/2011 10:30
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Marco20valveT
Unregistered
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Marco20valveT
Unregistered
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ktm - I would go with making the under side of the car smooth and flat, from under tray back! that will help a bit! i can see there is alot of GOOD ideas here, i would pick the best options and get busy!! i can see a lot of rolls of gaffer tape being picked up!!
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Re: aerodynamics
[Re: ]
#1198567
08/04/2011 11:02
08/04/2011 11:02
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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will have to find some tape with gum that wont harm my paintwork if anyone knows of any
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Re: aerodynamics
[Re: ]
#1198669
08/04/2011 13:25
08/04/2011 13:25
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sediciRich
Unregistered
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sediciRich
Unregistered
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Sure don't knock using tape for the runs, its is effective, virtually all aerobytes sessions I ever read have taped on ammendments to the cars for testing, although they test up to 80mph so anything that develops force needs to be well attached for what could be 180mph in your case. Rear spoiler I was thinking something a little more DIY do you have a spare boot lid? W.r.t. the bonnet there are many ways to do this and were not talking F1 level of prep - we want a join or sorts between the top of the arch liner and a vent in a similar position on the bonnet. Vent wise you could buy something preformed and cut a hole in the bonnet to fit it - mark out the outline of the vent in bonnet in masking tape and pen, use a good HSS steel drill, pilot hole 3mm, then use a bigger drill or a step drill to open up to say 10mm, then you can use a HSS jigsaw blade to cut out the shape. Remove the tape and stick the vent to the bonnet top surface using 'serious' stuff adhesive. The vent is an exhaust vent not a scoop. You will then need some hose or tube going through a hole in the arch liner in a position towards the inner part of the arch (hole saw, jigsaw, heat with a heat gun and use new stanely blades to cut which ever option you feel will work) the hose ideally will connect to the vent but there is small issue of opening the bonnet, thus you may want a more rigid tube which then meets the vent on bonnet closure. We aren't talking air tight, but more or less working on the principle that air will follw the pressure gradiaent from the high pressure arch to the low pressure air flowing over the mid bonnet line. You may wish to test the 'solution' after doing one side, some tufts of wool or string taped round the vent opening will tell you the air direction, if they are sucked into the vent then this is a failure, bad luck, but if they stand off the vent then its doing its job, its a 2 man test with a volunteer to stick their head out of the window and see what happening say at 50mph (I suggest doing the passenger side first ). This is my idea, heres to links to items I would consider for the job vent - http://www.merlinmotorsport.co.uk/p6902/BLACK-SIDE-AIR-SCOOP-INLET/OUTLET/product_info.html run so the narrow end is near the windscreen hose - http://www.merlinmotorsport.co.uk/p4227/63MM-RED-SINGLE-LAYER-DUCTING-(PER-METRE)/product_info.html need maybe 2m to play with some shrink joiners or jubilee or some gaffaer tape works well. Not teaching anyone to suck eggs but some tools I would use drill bits - http://www.screwfix.com/p/dewalt-extreme-2-hss-drill-bit-set-13pcs/66597 Step drill - http://www.screwfix.com/p/step-drill-4-22mm/15976jigsaw blades - http://www.screwfix.com/p/starrett-metal-cutting-50-x-4-5mm-24tpi-jigsaw-blades-pack-of-5/39966 need a jigsaw of course. You could use an angles grinder with cutting discs but that a really rough way of making a hole. Hole saw for the arch liner - http://www.screwfix.com/p/titan-downlighter-holesaw-set-9pcs/71760serious stuff glue - http://www.screwfix.com/p/evo-stik-serious-stuff-adhesive-290ml/23941what are we emulating here, well this is a high end example of the dtm car arch venting http://fi.wikipedia.org/wiki/Tiedosto:Audi_A4_DTM_2006_vr_EMS.jpg ond on the rear of the N24, I think you can see a way you could do it. http://www.reverie.ltd.uk/astonmartin_archventing_modification.phpI wouldnt fit any after market 'styling' kit as thats all they are, the only wind tunnel tested item for sure would be the std. List of things 1. Tape shut lines - easy, simple 2. Tape radiator opening unused SMIC inlet - easy 3. Flatten the bottom of the car - not so easy but would reduce drag decently. 4. Make a front lip, air dam, or splitter - not so easy must be well held on. lower the car as much as you can. 5. Vent arches 6. Add tail strip to boot - easily done, stip of ally, some rivets and some serious stuff. like this but with less angle -http://www.hotrod.com/techarticles/body/hdrp_0609_aero_tricks_tips/photo_09.html These are not costmetic improvements, thus you may prefer some second hand bumpers to adjust then convert back to nicely painted items after the day. If you have spare doors gut them, cut out the inned frame, cut out the impact bars (8inch cutting disc on a grinder is how I did mine - Sparco did his also), remove the window motor, and retain glass in the best wedged in bit of wood to the bottom of the door you can way!, cut the excess strengthening out of the bonnet, do the same to boot (dont cut the hinges off). I think you really could win if the engine is up to it.
Last edited by sediciRich; 08/04/2011 18:51. Reason: well if you edit a shorter link would have done!!
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Re: aerodynamics
[Re: ]
#1199065
08/04/2011 22:37
08/04/2011 22:37
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MiniMetaller
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MiniMetaller
Unregistered
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Re: aerodynamics
[Re: ]
#1199075
08/04/2011 22:57
08/04/2011 22:57
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sediciRich
Unregistered
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sediciRich
Unregistered
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Yes! good man, remove or much smaller, forgot that, and wipers as said before
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Re: aerodynamics
[Re: ]
#1199152
09/04/2011 01:52
09/04/2011 01:52
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MiniMetaller
Unregistered
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MiniMetaller
Unregistered
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Maybe also remove headlights and replace with a flat/smooth panel?
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Re: aerodynamics
[Re: ]
#1199447
09/04/2011 20:12
09/04/2011 20:12
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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szcom..i'm thinking that 600 bhp will drag the car kicking and screaming to a serious speed even without all the little bits i have made well over 160 couldn't keep my eye on roasd and speed (sat nav) but saw the 160 and got past it with the 358 bhp i used to own that was just lowered/piu front with all the above bits done and a far better engine/power i'll be right..i am confident the car will take it as its the best chasis i haev yet had with new subframes all new drop links ,bushes,bearings,arbs comp brake kit etc its designed for big power/speed..its braced with various braces so all in all its as good a platform to try it from as there is
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Re: aerodynamics
[Re: ]
#1199643
10/04/2011 03:04
10/04/2011 03:04
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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gearbox we are working on
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Re: aerodynamics
[Re: ]
#1200061
11/04/2011 01:52
11/04/2011 01:52
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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never seen one but if its the type of thing i need then great thanks
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Re: aerodynamics
[Re: ]
#1200141
11/04/2011 11:19
11/04/2011 11:19
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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ok what options does that give me on tyres
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Re: aerodynamics
[Re: ]
#1200165
11/04/2011 12:08
11/04/2011 12:08
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Marco20valveT
Unregistered
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Marco20valveT
Unregistered
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Re: aerodynamics
[Re: ]
#1200522
11/04/2011 22:49
11/04/2011 22:49
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dlongstaff
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dlongstaff
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Re: aerodynamics
[Re: ]
#1200543
11/04/2011 23:19
11/04/2011 23:19
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sediciRich
Unregistered
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sediciRich
Unregistered
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erm dont think so, open wheel race car perhaps.
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Re: aerodynamics
[Re: ]
#1200624
12/04/2011 07:19
12/04/2011 07:19
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zimpara
Unregistered
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zimpara
Unregistered
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couple of things i have picked up on, firstly putting in bonnet vents,
Ill mention scoops even though your not talking about them , they are stupid! unless you need them for a top mount IC they are stupid, end of
Now back on track with vents
you have to be very carefull and watch that they do,. with airflow under the bonnet,
there also then needs to be sufficent air flow through the engine bay to give it the push that it needs in the right direction,ie not just mountains or air getting pushed in from the top . alot of boys find that putting vents or scoops actually pressurises the engine bay and the hot air cant get out, (ME infact) being totally unproductive. these vents are there to tease the air from under the bonnet out to a certain threshold and then to get whipped away by the airflow passing outside of the car,
ie might need to be running with a improved undertray( better sealed) and then have very well placed air scoops underneath the car flowing air into right areas to help with this,
many have found this a complete waste of time so do the very best you can , but have a spare bonnet around just incase,
Next thing, how lowered is your car?
next thing, POWER
If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type>( yes me again)
have you thought some nitrous?
you have pm
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Re: aerodynamics
[Re: ]
#1200628
12/04/2011 08:03
12/04/2011 08:03
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Joined: Dec 2005
Posts: 33,568 Berlin
barnacle
Club Member 18 - ex-Minister without Portfolio
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Club Member 18 - ex-Minister without Portfolio
Forum Demigod
Joined: Dec 2005
Posts: 33,568
Berlin
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If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type Doh!
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Re: aerodynamics
[Re: ]
#1200682
12/04/2011 10:33
12/04/2011 10:33
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Joined: Dec 2005
Posts: 9,706 Gone
Jimbo
Je suis un Coupé
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Je suis un Coupé
Joined: Dec 2005
Posts: 9,706
Gone
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I'm not sure I could take any advice seriously from someone with If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type in their admitted technical ability range.
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Re: aerodynamics
[Re: ]
#1200704
12/04/2011 12:36
12/04/2011 12:36
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Nobby
Unregistered
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Nobby
Unregistered
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Would a foam one work better Jimbo?
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Re: aerodynamics
[Re: ]
#1200730
12/04/2011 14:01
12/04/2011 14:01
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sediciRich
Unregistered
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sediciRich
Unregistered
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couple of things i have picked up on, firstly putting in bonnet vents,
Ill mention scoops even though your not talking about them , they are stupid! unless you need them for a top mount IC they are stupid, end of
Now back on track with vents
you have to be very carefull and watch that they do,. with airflow under the bonnet,
there also then needs to be sufficent air flow through the engine bay to give it the push that it needs in the right direction,ie not just mountains or air getting pushed in from the top . alot of boys find that putting vents or scoops actually pressurises the engine bay and the hot air cant get out, (ME infact) being totally unproductive. these vents are there to tease the air from under the bonnet out to a certain threshold and then to get whipped away by the airflow passing outside of the car,
ie might need to be running with a improved undertray( better sealed) and then have very well placed air scoops underneath the car flowing air into right areas to help with this,
many have found this a complete waste of time so do the very best you can , but have a spare bonnet around just incase,
Next thing, how lowered is your car?
next thing, POWER
If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type>( yes me again)
have you thought some nitrous?
you have pm no we are not talking scoops, we are talking exhaust venting, using the high velocity air over the mid bonnet region to extract the higher pressure air from behind the wheel with a duct hose(the pressure gradient is as its max here, if you put the vents nearer the wind screen the effect could be no pressure gradient or flow.). Venting the bonnet with rearward facing NACA ducts would aid the pressure gradient across the radiator and help cooling, but reducing the rad opening area will cut drag and thats the plan here. Rearward facing ducts especially with a gurney placed mid to front bonnet can be pretty sure to have an extraction effect on the bay; we arent pushing any air in from the top! The test method with tufts would prove if the vents are effective, if not out with the gaffer tape. Also don't consider what fools in RS turbos do and raise the rear of their bonnets, because at speed the lower edge windscreen pressure will force air into the engine bay, keep the rear edge sealed.
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Re: aerodynamics
[Re: ]
#1200846
12/04/2011 18:07
12/04/2011 18:07
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sediciRich
Unregistered
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sediciRich
Unregistered
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Jim not sure what you are estimating here, its is the high pressure that lifts the wipers off the screen not some venturi effect sucking them off. If you vent the bonnet here air will flow from the windscreen base into the engine bay - we don't want that. But convesely a scuttle panel 'fill in' creating a smooth transition from bonnet rear edge to say half way up the windscreen would reduce the transition and seperation like you mentioned but in a different way. Not sure about visability mind.
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Re: aerodynamics
[Re: Jimbo]
#1200907
12/04/2011 20:24
12/04/2011 20:24
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Alesi
Unregistered
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Alesi
Unregistered
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@Per: Why don't you give the bearded guy in the picture a shout? As you've bumped into mr.B himself recently you might have his contact details. If not why don't you try his office Chris Bangle Associates in Italy.
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Re: aerodynamics
[Re: Jimbo]
#1200985
12/04/2011 22:22
12/04/2011 22:22
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sediciRich
Unregistered
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sediciRich
Unregistered
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Sure Jim that would show what you want to know, but having seen countless wind tunnel reports via McBeaths aerobytes column I can be sure that what I mention is for real. Your analogy is a little too simple, sure if the body was a continuous ark then the velocity would potentially create a drop but the change in vector from the bonnet to the windscreen is huge, which creates turbulance at the base of the screen and a high pressure zone. But some tufts would tell the story real easy, and the coupes ranked screen may just level any pressure differential - you know another way is a U tube manometer, simply get some clear cappillary tube, use fence staples to make the U shape on a board, fill the U with some water, mark it in a level position (vertical board), the short end of the U is open to atmosphere and the other end extends and is taped to the test area - in this case the scuttle panel. With a friend holding the board drive the car at speed (the long end should not be facing into the direction of travel). If the water come flying out of the short end you have greater then ATM pressure in the scuttle, if its sucked towards the scuttle then you have lower than ATM pressure there. KTM the u tube manometer test is useful for testing behind the wheels and in the engine bay to establish pressure differentials. the chap made a huge manometer but the plan is the same http://www.youtube.com/watch?v=0nKaGEMLZjsHave a look at this and some of autospeeds other articles on practical things you could do http://autospeed.com/cms/article.html?&A=2159
Last edited by sediciRich; 12/04/2011 22:34.
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Re: aerodynamics
[Re: Jimbo]
#1201024
12/04/2011 23:19
12/04/2011 23:19
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shinyshoes
Unregistered
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shinyshoes
Unregistered
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I'm not sure I could take any advice seriously from someone with If you decide to use fire extinguisher mod for a IC spray make sure you dont use the powder type in their admitted technical ability range.
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Re: aerodynamics
[Re: ]
#1201143
13/04/2011 11:24
13/04/2011 11:24
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Joined: Jan 2006
Posts: 3,034 Sweden
Per
I need some sleep
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I need some sleep
Joined: Jan 2006
Posts: 3,034
Sweden
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SediRich is right, all cars of this basic body shape have pressure at the bottom of the windscreen. And underpressure (not sure that's the english word for it..) over the bonnet centre, if anyone's considering extra engine bay venting.. @Per: Why don't you give the bearded guy in the picture a shout? As you've bumped into mr.B himself recently you might have his contact details. If not why don't you try his office Chris Bangle Associates in Italy. Yes, we've already had some mail conversations. Quite interesting, and he's a very laidback guy . For example I found out it's the same guy who designed the Pininfarina proposal for the Coupe (and of course also the 406 Coupe) and the E60 BMW 5-series.. Davida Archangeli. " a nice irony since I later hired him into BMW and did that super-special E60 5Series I love so much (and died in the process, the poor guy)"
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Re: aerodynamics
[Re: ]
#1201548
13/04/2011 23:26
13/04/2011 23:26
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ktm450exc
Unregistered
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ktm450exc
Unregistered
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this is getting very involved and interesting i have to say..its gone from taping up and possibly fashioning a splitter to some serious posts ..thats why i spend way more time than i should on the forum! .. even if a little above my head in parts i appreciate the time and suggestions .. i am trying to take it all in but without having time to spend learning the basics of aerodynamics in order to grasp all you are telling me i can only take in so much..so i would be grateful if we can try and come up with practical suggestions i can fabricate with my limited facilities..i am happy to spend some time testing various ideas but what would really make this attept succesful would be someone that actually knows what they are doing/talking about physically helping ..so if someone fancies getting involved inbreaking the record i am happy to cover thier expenses ..i am probably asking a lot there but i have a serious lack of time with which to fill my head with enough to understand what i am doing so in truth unless someone does it will be basic stuff from whats been mentioned so far..i already know way more than i did from the links and whats been said so can at least make a better go of it will be glad of any more thoughts though
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