bjhines Posted December 29, 2006 Share Posted December 29, 2006 Please use this Thread to discuss Aerodynamic testing candidates... I really want this to be a broad community development process... Post pics and please use whatever photo editing skills you have to point out specifics.... Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 29, 2006 Share Posted December 29, 2006 great read on reducing drag!! Here are some of my sketches from a while back that should help with aerodynamics...some are original to me and others aren't. GT40-ish front end...would look a bit odd. a clean-ish front end would be a big time pusher. * I came up with this widebody and the hood vents* I think this above one could be modified like a front end like the Janspeed Z or similar to the Gnose to extend the hood down and foreward. Something like this E-type-ish Z would make airflow a lot smoother over the front of the Z's foreward body. Maybe a bigger scraper to cover the tire would be in order.. Something like this below sketch would be good for road racing. Whale tail and closed up front end. *This is basically a modified standard front air dam and JCR type flares* I'll do a new sketch tonight just for this thread...Critique and suggestions welcome for a new sketch... Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 29, 2006 Author Share Posted December 29, 2006 1. We are planning on testing a BONE STOCK concourse 240Z as it came from the dealer the day it was new... shiny paint and all.. everything... This will be our baseline... We will get detailed information from this car at a variety of angles of pitch, yaw, and roll... over several runs... We will also try to determine airflow around the radiator and the engine... We will remove the front splash pan for one of these runs... That is the only modification we will try with this car.. ======================================================== 2. The second car we test will be our test mule... This is the car that will be used for 95% of the testing time... It is a 1976 280Z... We will be screwing, gluing, and taping everything to this car... It will be tested at a variety of ride heights and with 7" wide wheels and with 10" wide wheels... We are still developing the parts list... Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 29, 2006 Share Posted December 29, 2006 Boodlefoof's sketch Boodlefoof has done a good little writeup on Z's aerodynamics. Pretty much basics but it is still good stuff. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 29, 2006 Author Share Posted December 29, 2006 The cars that use the underbody for downforce also have tunnels that are not included in the underbody picture... that would require changing the floorpan of the car... our unibody cars are what they are underneath... We are planning on testing a lower front splitter in combination with an underbody pan and a rear diffuser... but the owner of this car has already removed it due to instability at speed... and he could not get the car on and off the trailer or perform any work on the drivetrain without removing the underbody parts... We are not holding out for any great results from this addition... and the wind tunnel operators concurr... We expect to be able to reduce drag while increasing downforce in a straight line... but a combination of factors could make the underbody stuff more dangerous than is tolerable... A worst case situation has the car moving at 130MPH and braking hard for a turn... the nose pitches down and the tail rises up... the downward angle in front means the the splitter suddenly increases downforce IN FRONT OF THE FRONT AXLES... This suddenly loads the front end and unloads the rear even more... Then the wake from behind the car rolls off the back and begins running under the tail... When the driver slams on brakes... The front lip nearly touches the ground... airflow under the car is suddenly cut off... air pressure under the front of the car suddenly drops....the wake of air following the rear of the car suddenly slams into the rear end and finds this huge diffuser there(and low pressure under the car also draws air in toward the diffuser)... the diffuser gives the air something to push on and lifts the rear even more... As the driver tries to figure out WTF is going on... the rear end begins comming around... the car presents it's side to the wind in a yaw angle and then it gets exciting... Imagine thinking to yourself "I wish I didn't recklessly add the underbody parts" while you are slowly rotating upside down in mid air.... Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 29, 2006 Share Posted December 29, 2006 There have been many pics of race cars going over a hill with a slight turn and getting 10 feet of air and landing off the track. I am guessing what you described BJ is what happened to these cars. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 29, 2006 Author Share Posted December 29, 2006 Those splitters and diffusers are VERY EFFECTIVE... TOO effective... The cars that use them run very low to the ground with very little suspension travel... they have highly modified underbodies ment to use more than just a flat bottom and an upturned back end to get the effects they want... the entire car and suspension were designed around using the undbody aero effects... We cannot make use of these modifications on our cars... the first problem being consitent ride height and attitude... the second problem is there is no room for the tunnels without a tube frame chassis... The 3rd problem is the fact that the first 2 problems make these things highly unpredictable... downright dangerous... Quote Link to comment Share on other sites More sharing options...
74Adam Posted December 29, 2006 Share Posted December 29, 2006 BJ, you have a donation. Can we make this thread a sticky? Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 29, 2006 Share Posted December 29, 2006 I think this testing should be for cars that are track cars that are still "streetable"...that way we still have a good viewpoint to look from. We aren't doing full blown race cars or everyday drivers...cars with decent (175-275 lb/in) spring rates and 3"+ of ground clearance. just another of my 2 cents. Quote Link to comment Share on other sites More sharing options...
74Adam Posted December 29, 2006 Share Posted December 29, 2006 Well, we have until March to get it ironed out. I think that's a good thing. Hell, we may still get enough donations for two full days. Wouldn't that be cool? Quote Link to comment Share on other sites More sharing options...
bschiltz Posted December 29, 2006 Share Posted December 29, 2006 I don't know if it's been brought up, but are you going to test the effect of headlight covers? Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 29, 2006 Author Share Posted December 29, 2006 Headlight covers..... YES... Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 29, 2006 Author Share Posted December 29, 2006 Here are some pics to chew on.... Front splitter Front splitter 2 This is what we expect to end up with... A flushed rear window... otherwise NOT the right rear lip... interesting deck treatment... I want to try this... notice the flares are widened in front of the tires.. This is more like what we expect to use for a rear spoiler... notice the side strakes... but imagine the deck lip laid back more... Wind tunnel with a 280ZX... just for fun... it is an improvement over the S-30s ... Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted December 30, 2006 Share Posted December 30, 2006 A worst case situation has the car moving at 130MPH and braking hard for a turn... the nose pitches down and the tail rises up... the downward angle in front means the the splitter suddenly increases downforce IN FRONT OF THE FRONT AXLES... This suddenly loads the front end and unloads the rear even more... Then the wake from behind the car rolls off the back and begins running under the tail... When the driver slams on brakes... The front lip nearly touches the ground... airflow under the car is suddenly cut off... air pressure under the front of the car suddenly drops....the wake of air following the rear of the car suddenly slams into the rear end and finds this huge diffuser there(and low pressure under the car also draws air in toward the diffuser)... the diffuser gives the air something to push on and lifts the rear even more... Are you sure that the front dipping was not cutting the feed to the rear diffuser? Thats how I read `the front splitter nearly touched the ground'' What springs were in the car? How close was the front splitter to the ground at static? Did the splitter have a raised middle section to reduce pitch sensitivity? I think that your synopsis assumes an awful lot, the main one being that someone has not taken into account the effects (read: benefits) of aerodynamics when designing the rest (read: suspension) of the car. If you have soft springs like a lot of people here seem attached to, you are going to have a chassis that is significantly affected by aerodynamic forces, and will have to tune accordingly. Just because someone you know didn't, does not mean underbody aerodynamics are ``more dangerous than is tolerable''. It means more development/tuning is required, and/or some proper rate springs for racing. Dave Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Absolutely... more development is required... Also the suspension set up and ride height are more than most S-30 owners are willing to deal with... We are trying the underbody modifications... but we will be toning them down a bit... NO overhanging front splitter... underbody pan from the floor to the rear skirt... only a minor rear diffuser area.. with a slight upturn... and the rear diffuser will not stick out past the rear valence... that should clean up airflow under the car without causing any dangerous conditions... We might(hope) to see a noticable improvement with a toned down design... Dave... you have hit on some design facts that will make underbody development very expensive.. time wise... We hope to clean up the airflow without getting the car too close to the ground... Quote Link to comment Share on other sites More sharing options...
thehelix112 Posted December 30, 2006 Share Posted December 30, 2006 Sounds great. Time is one of those things most are gaurunteed to have too little of. I am sorry this opportunity for scale testing has come a little soon for me. I have some significant plans for my track car, and would love the opportunity to test them. Maybe we can do a repeat in 18 months or so? Anyway, back on topic. I would maybe suggest, though I know its a lot more work, making as much parts adjustable as possible. That would include front splitter, rear diffuser (rear extension, height, number and orentiation of strakes), spoiler, and wings. Dave Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 30, 2006 Share Posted December 30, 2006 notice that if you look close that it appears that the flow seperates about 2/3 of the way down the hatch. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Notice too that the car has flushed windows... and no wipers... and no trim... and no body seams... and it is a small scale model... and we can assume the underside is flat... and the worst part of the flow picture is obscured by the car in that point of view... We are expecting significant improvements over stock by doing just those things... Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 What I would love to see is pictures/sketches of a rear lip spoiler that incorporates side pieces like the 3-piece we all know... but lay it out nearly horizontal to extend and sharpen the rear hatch... These side piece extensions.. but lower on the sides with a little more angle(adjustable?) Here is another example of the sides... but we want a flat(horizontal) rear lip... Look carefully at the side sections on this rear lip..(pic is small I know) Here is the janspeed car... This is interesting... but I think the sides should slope down... and again we are trying to keep the rear lip more horizontal... (and we don't have those wicked flares) we want all edges sharp... in fact we want the entire rear of the car extended enough to give it a good sharp edge that extends an inch or less like a sheet metal lip outlining the entire rear of the car... like a cookie cutter... The upper surface will have more lip... we are thinking of trying several extensions of the rear lip and a few different angles... The idea is that we may be able to extend the length of the car on it's top surface and gain negative lift without adding drag... without using the tall vertical rear lips like a parachute to stabilize the car...(which it seems is what they were doing) Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 30, 2006 Share Posted December 30, 2006 I am about done with a sketch that I did at work tonight. The spoiler is just about like that janspeed one. What if the spoiler was filled in so that the whole top of the spoiler was flat up to the rear window. Like if you just filled the whole spoiler with something and made the top flat. Just an idea... Quote Link to comment Share on other sites More sharing options...
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