Michael Posted December 30, 2006 Share Posted December 30, 2006 The hypothesis that "adding up a bunch of little things can make a huge cumulative difference" is attractive, but again, be prepared for a possibly counterintuitive result. I would venture to speculate that flushing the glass, deleting the rear-view mirrors and windshield wipers, and taping-off the body panel seams is worth several hundred counts of drag (the lingo is one count = 0.0001 Cd; a stock Z's Cd is about 0.45, so 4500 counts), but the effect on lift/downforce would be minor. One suggestion for the testing program is a large sheet-metal spoiler, of the type posted earlier by Johnc, with adjustable rake angle - from 0 degrees all to way to, say, 75 degrees - to be varied in 15-degree increments. I do not believe that there is a huge difference between a spoiler that spans the entire width of the car, vs. one that only spans across the hatch. The vertical fins in one of the above pictures, by the way, is probably a yaw-stability device more than a means of managing drag or downforce, though of course the various effects are mutually interdependent. Another suggestion is a shorter, more bulbous homebuilt alternative to the G-nose. The rationale is that while the G-nose certainly helps with the sharp lip in the stock hood, the G-nose is itself too "sharp". I'll try to work-up some sketches. As for doing parameter studies of yaw angles, pitch angles and roll angles - well, yaw is normally set by rotating the ground-plate in the wind tunnel. Does the A2 tunnel have that option? For roll (which, BTW, is probably of secondary importance) and especially for pitch, how will the car be set precisely at the desired angle, and how will the angle be measured? Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 The spoiler thing is going to require mounting several custom pieces... We can accommodate a variety of angles with one piece... but not the entire range of options... I would like to make use of some of the available fiberglass pieces to try the near vertical angles that they all have(see what happens)... Then I would like to try our near horizontal pieces that extend the rear upper surface(4" to 18" extension)... We can try several angles on the side pieces... but that will likely require more than one set of sides to accomodate different angles and lengths for the center section... Here is a LSR Camaro rear lip with the right idea.. but we would incorporate the sides as well.. I can't wait to see Michael's drawings for a new front end... We will do our best to fabricate it... Our initial plans draw a vertical line from the hood to the bottom of the air dam and cover it with cardboard.. all the way across... then cut a 2"x6" inlet for the radiator... just under the front lip of the hood (high pressure??) Here is an example from the Camaro... ^^Notice too that the horizontal edges of the grill lines are SHARP where they meet the hood^^ I realize that these are land speed ideas... but I think these guys have something good going here... LOL... The Moby is EXACTLY what I had imagined from the discussions yesterday... But that is WAYYYY over the top for our needs... And the biplane needs to be swatted off the back... ... Quote Link to comment Share on other sites More sharing options...
proxlamus© Posted December 30, 2006 Share Posted December 30, 2006 be sure to WAX the car.. make sure its nice and smooth clean paint... Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 A thought about the rounded vs the hard edged front end treatments... The LSR cars are getting into a speed realm that involves shock waves and interesting break off of flow... yes.. even at 250MPH these effects begin to show up... But... we will not be designing for anything more than 170MPH... I am not sure what to make of the various front end options... A new Z-car front end would also count as a major body modification... The G-nose was already offered by Nissan... I would love to see some designs... but we have some decisions to make about the extent of the changes we make to the front end on the first tunnel event... That may be better for a follow up event... Quote Link to comment Share on other sites More sharing options...
Carl Beck Posted December 30, 2006 Share Posted December 30, 2006 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... Hi BJ: Doesn't the use of a 280Z rule out the testing of the BRE Front Spook? The lower front finishers on the 280Z are lower and rounded to allow more air flow into the larger radiators on the 280Z's.. and the BRE Spooks were made to fit the lower finishers on the 240-Z's... The BRE Spook was the most effective at offsetting front end lift - at least in the C & D Tests... FWIW, Carl B. Quote Link to comment Share on other sites More sharing options...
boodlefoof Posted December 30, 2006 Share Posted December 30, 2006 Don't know if this is within the scope of possible testing, but what about testing the effect of lowering the roofline and raking the windshield? http://forums.hybridz.org/showthread.php?t=101672&page=2&highlight=chop+top http://forums.hybridz.org/showthread.php?t=94779&highlight=chop+top I'd also like to see the data on deleting the side mirrors. For my car I'm planning on some low-profile motorcycle mirrors that I found, which extend quite far off the body (from a Yamaha sport bike if I remember right). Another possible testing point is air extractors in the wheel wells to reduce Cd. I'd like to see the data on that. As for the under-body effects, these certainly can be dangerous when pushed to the extreme. Some racers experimented with having the exhaust exit into the diffuser to accelerate the under-body airflow only to find that downforce suddenly disappeared when they let off the throttle! Oops! Then you have lift-off. I don't anticipate weight transfer being too much of an issue. The car will be somewhat stiffly sprung and I have designed the front suspension to have what should be more than enough anti-dive. I also don't anticipate my diffuser design generating anything near the 2000# of downforce that the F1 guys are running, so suddenly losing any downforce generated by the diffuser, while unnerving, shouldn't be quite so catastrophic. Speaking of diffusers, you could also test the combined effect of your rear wing designs with the under-body diffuser. Using the rear wing to help drive the diffuser flow. That would be interesting. I plan to have my car into a tunnel (Langley tunnel down in the Tidewater) prior to attempting my 200+ mph run. If I am incorrect about my designs, I would much rather discover it in the tunnel than while I am in the car! While at the tunnel (this is still years away unfortunately) I also plan to try out various "nose-cone" designs. I will make a bolt-on nose-piece for the car to reduce drag on my high speed attempts. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Hmmmm... interesting... So the 280Z might not fit the BRE SPOOK... we will see what we can do with the stock 240Z then... That may rule out the BRE if the owner of the concourse 240Z objects... Boodlefoof... We are not going into major body shape changes... If I had all the money and time in the world for this... sure... But we don't have enough time in one day to asses all of the currently available parts and designs... If we get the funding for another day at the tunnel there are a lot of possibilities... but changing the roofline was never on the table... Quote Link to comment Share on other sites More sharing options...
boodlefoof Posted December 30, 2006 Share Posted December 30, 2006 I didn't think so. Just thought I'd throw it out since the high windshield in conjunction with the sloping fastback design seems to be one of the problems. Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 30, 2006 Share Posted December 30, 2006 I can't wait to see Michael's drawings for a new front end... We will do our best to fabricate it... ... who is Michael? *edit* Oops...never mind:eek2: I'll go scan my sketch now...it looks too familiar...I'll try to come up with something new tonight. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Wheel wells: We have some interesting ideas for trying to improve airflow in the wheel wells... If nothing else we hope to improve brake cooling... lowering Cd would be nice as well... We are adding spoiler strips(canards for lack of a better description) to the front of the wheel wells... kind of like this: also... simply adding material in front of the wheel well lips is an option... like this... I have also punched some holes for engine compartment venting that may or may not help once the nose is addressed... This is my car... This is another example.. I dont think the holes in the forward facing surface are a good idea... ... Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 30, 2006 Share Posted December 30, 2006 meh... and the vent-ish thing is some sort of oil cooler thingy...I guess. Just playing with ideas there. A different hood bulge as well. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Well... that is a neat idea... but we need these things drawn on the body plan views... There is nothing about that front end that uses any of the stock body shape... That would have to be a fiberglass one piece tilt front end Quote Link to comment Share on other sites More sharing options...
OlderThanMe Posted December 30, 2006 Share Posted December 30, 2006 you could make it just a front end bolt on...the fenders aren't too much different than stock. I'll try to do a decent sketch of a spoiler tonight and base it off of photos of my Z so that it could be realistically done. I may even get up on the roof and get a top shot of my Z to sketch up... Quote Link to comment Share on other sites More sharing options...
Carl Beck Posted December 30, 2006 Share Posted December 30, 2006 Hmmmm... interesting... So the 280Z might not fit the BRE SPOOK... we will see what we can do with the stock 240Z then... That may rule out the BRE if the owner of the concourse 240Z objects... I'm sure he would object!.. you have to drill holes in the lower finisher panels (right, center and left) to properly affix the Spook to the car!! Perhaps there is an owner in the area - with an otherwise stock bodied 240-Z, that has already added the BRE Spook, and which you could then use to swap rear hatches to measure the rear Spoilers as well. Given the front bumper on the 280Z's sticking out like it does - I'd think that comparing a stock 240-Z to a 280Z would be less than the ideal apples to apples comparisons we'd want to make. You know, make one change at a time and measure the results.. (unless the 280Z has been retro-fitted with 240-Z bumpers). When it comes to "downforce" none of the air dams that C&D tested resulted in the reduction of Lift that the BRE Spook generated. It would be a shame to not be able to include it... Everything is a trade off of some kind - the trade-off between Spooks and Air-dams would seem to be the trade off between reduced lift and increased drag... but if we can't measure both.. we'll never know to what extent or degree they vary. FWIW, Carl B. Quote Link to comment Share on other sites More sharing options...
spotfitz Posted December 30, 2006 Share Posted December 30, 2006 Replacing the front lower valance pieces with ones from a 240 or early 260 would allow the use of the BRE spook. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Well there you have it... I have a garage full of 240Z body parts... half a dozen bumpers, numerous front valances... bracketry from all models 1970-1973... The only 280Z parts I have are hubs and differentials... I have a set of early stock 240Z bumper brackets... they are just strips of 3/16" steel.. they bolt to the headlight bucket inner side... Yea they are cheesy... but the early bumpers were just trim... not much thicker than the body... Quote Link to comment Share on other sites More sharing options...
Michael Posted December 30, 2006 Share Posted December 30, 2006 The bumper is going to be another exogenous variable that will complicate comparisons of front-end treatments. My recommendation is that once we do the test on the stock 240Z and move to the 280Z, take one data point with the 280's stock bumper, then remove it, repeat the data point, and henceforth no longer use the bumper at all. Quote Link to comment Share on other sites More sharing options...
bjhines Posted December 30, 2006 Author Share Posted December 30, 2006 Good thought.. I was wondering how to budget time for that part of the testing... Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted December 31, 2006 Share Posted December 31, 2006 Wow... a flashback to the 1950's era rear winged coupes. Cool:wink: Quote Link to comment Share on other sites More sharing options...
Guest Mike Posted December 31, 2006 Share Posted December 31, 2006 BJ... I know I asked this question in the "Wind Tunnel Test" thread but I imagine folks in this thread are interested too. If you and MK raise more funds than necessary for testing a stock body, is it feasable to add another day and test wide-bodies and perhaps a GTO? Quote Link to comment Share on other sites More sharing options...
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