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Old 05-08-2008, 09:52 AM   #21 (permalink)
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Quote:
Originally Posted by i_am_socket View Post
For the un-enlightened among us: what is this "Hucho's book"?
i agree,,, droping a bill on something i can't read

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Old 05-08-2008, 10:03 AM   #22 (permalink)
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Oops. I'm somehow utterly lacking the brains to think "hmmm... maybe I should search the site" this morning. LINK!

I'll be getting that second cup of coffee now... *facepalm*
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Old 05-16-2008, 03:15 PM   #23 (permalink)
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modifications-data-% change,or Cd change(nose-jobs)

Hello all. Randy_the_Hack asked about a breakdown of aero mods and their potential for savings.I've been pulling what I have together and since there is a lot of ground to cover,I'm going to post it as installments,in case the computer crashes and to respect the little time I have at the computer as of late.General note: all this data is dated now.All current production cars,pickups,vans,and SUVs should be employing some if not many aero refinements empirically proven over the last hundred years.Since carmaking is still ruled by the stylist it will be the last industry to evolve into the "form follows function" philosophy as in aircraft,ammunition,artillery,boats,canoe,kayak,pu mps,turbines,ordnance,ships,and submarines.The upshot is that ecomodders will have access to some of the existing fruit,which for their class of vehicle offers added mpg.As always,we need to be careful and mindful of the other motorists we share the road with.
I would like to have presented the material in tabular form although its beyond the scope of what I can do right now.(Nose-jobs):In 1937 Carl Breer used a "raked" front end to help his ecomoddered Chrysler Airflow to achieve Cd0.244.In 1938 the Jaray/Adler demonstrated a 15 % drag reduction with 100% grille-block.In 1962 L.W.Farington utilizes the 1976 VW "ideal" nose to help his 1956 Ford Thunderbird achieve 228-mph.In 1963 Walter Korff suggests that the optimal grille/radiator/nose/headlights/turn signals are good for a Cd0.07 improvement.In 1968 R.G.S.White allows an ideal nose to produce a 28% drag reduction.In 1974 CAR and DRIVER get 0.9mpg from airdam and 0.4 mpg from grille-block,1.4 mpg for combined,with "Crisis-Fighter-Pinto".In 1974 C and D get 1.2 mpg with 260ZG nose,and 0.2 mpg with plex headlight covers with "Crisis-Fighter-Z-Car.!975 VW Rabbit cuts Cd by 14% with Hucho's "ideal" nose.1978 Ford Capri gets a 6% drag reduction with wrap-around bumper with integral airdam and airfoil grille.1981 Pontiac Grand Prix flush headlights=1.5%,downward-sloping hood/fenders=1%,and softened hood leading edge = 1.5%.1982 Peugeot VERA cuts Cd by 0.015 with integral front airdam.1991 aero nose with headlight covers and lowered airdam add 1.526 mph to Phil Knox's CRX.1986 SAE Paper 860212: 100% grille-block cuts Cd by 0.003,airdam hurts bellypan car,airdam helps dirty-bottomed car.1986 SAE Paper 860211: 4.25-inch minimum radius needed for attached flow at leading edges,vertical or laid-back nose lowers Cd by 0.01.1986 SAE Paper 860216 (Subaru XT): front airdam cuts drag 6.9%,lowering nose by 10mm drops drag 1.7%.1997 Ford NASCAR with 1/4-inch lower front airdam beats Dale Earnhardt's Chevy.There are some other articles involving front mods however they are lumped into "kits" done for specific vehicles and no single-item breakdowns are given.I'll include this info in a future( Kits ) installment.Again,most of this info or similar will be found in Hucho's book.One member got it with inter-library loan for cost of postage.It's the Mother-lode!
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Last edited by aerohead; 06-12-2008 at 05:44 PM.. Reason: Additional material inadvertently missed with original post
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Old 05-16-2008, 03:25 PM   #24 (permalink)
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mods-data-Cd reduction ( hood/cowl )

Hello all. Just a quicky,as I found only one source for this data,and you'll find it in Hucho's. ( hood/cowl ): 1986,SAE Paper 860211, the reporter demonstrates that a maximum drag reduction of Cd 0.0475 occurs when the hood/cowl is angled up 15-degrees above the horizon.And from the previous installment,when the hoodline of the Subaru XT was dropped 10-mm,they achieved a 1.7% drag reduction.
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Old 05-17-2008, 02:55 PM   #25 (permalink)
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I fly R/C sailplanes and gap seals work. Nowadays, most sailplanes are molded with a wiper/gap seal build in, but back in the day (10 years ago or so) you would cut 1" wide strips of mylar and paint them with contact cement on about 1/2 of the width. The gap seal is always attached to the furthest forward part, so if you wanted to make a seal at the gap at the front of the drivers door, it would be glued to the front fender.
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Old 06-12-2008, 05:56 PM   #26 (permalink)
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When I posted this originally,I forgot an important tidbit.In most fluid books of my day,the example of E.Moeller's work on the nose of the 1951 Volkswagen Van was always cited.The Volkswagen began quite literally as a "brick-on-wheels" with a drag coefficient of 0.76.With some clay,Moeller sculpted the front of the Volkswagen with generous radii,and the Cd dropped to 0.42.With the exception of the HUMVEE,there are no current production vehicles that possess square leading edges.Today,the example of the VW serves to demonstrate the significance that a little softening of leading edges has meant in the meantime.
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Old 06-17-2008, 02:58 PM   #27 (permalink)
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Hello,

Maybe this has already been posted?
http://www.recumbents.com/car_aerodynamics/
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Old 06-26-2008, 10:07 AM   #28 (permalink)
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hi.. new here so steep learning curve for me. I think you guys are awesome for putting into practise what others just talk about. Question.. is it possible that the reduction in drag from lowering a vehicle is coming from the resultant reduction of the gap between tyre and body rather than anything else? Hence the varying degreesof success when doing this?
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Old 06-26-2008, 12:47 PM   #29 (permalink)
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Hi gary -

I don't think there's a single reason why lowering helps (also note: it may not help every vehicle). But the reduced tire to wheel arch gap won't hurt, that's for sure. It's a good point.

Other contributing factors: a better "fineness" ratio; reduced frontal area (tires); diversion of air away from the "dirty" underside.

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Old 06-27-2008, 02:44 AM   #30 (permalink)
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thanks for the reply and welcome. Yes you are right about the other benefits and after my coffee this morning I realised just how dumb I had been. Lowering would have the same effect as putting on side skirts as well as a front air dam of the same dimensions as the drop... as well as having better cornering due to the drop in cg and there being able to maintain more momentum through and out of the corne.. hence less acceleration etc etc.

ps our gas in SA is now about $5.8 per gallon. not funny anymore

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