jhaag Posted August 23, 2001 Share Posted August 23, 2001 The October, 2001 issue has an article titled Aero 101 by Larry McReynolds (of NASCAR fame) that might be interesting to those who liked the Aerodynamics thread on this forum several months ago. As I dreaded thinking about how much typing would be involved, however, to convey some ideas from the magazine, I had a wild idea: why not try a Google search using "Larry McReynolds Aero 101" as the key words? Voila! Go to the web site www.nascar.com/2001/TECH/08/02/circletrack/ to see virtually the same article. NACA ducts were talked about on the earlier Hybrid Z thread and as I recall, at least one person here wondered whether a NACA duct, turned 180 degrees would suck air out. He says YES and calls them "suca ducts" which made me smile. He doesn't quote statistics or wind tunnel evidence, which in a perfect world, I'd like to see, but then Larry was pretty successful in his day. Hope you like the article. John nullthe web page (http://www.nascar.com/2001/TECH/08/02/circletrack/ )Aero 101 Quote Link to comment Share on other sites More sharing options...
pparaska Posted August 23, 2001 Share Posted August 23, 2001 I was one of those wondering about backwards NACA ducts for removing hot air from under the hood (too bad, I just got the car back from the paint shop last night ). To my simple, untrained aero mind, it only makes sense that they'd extract air if turned around. But hey, there's lots about aero that is very counter-intuitive, except for a handful of very experienced, smart aero people. Thanks for the heads up! [ August 23, 2001: Message edited by: pparaska ] Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 23, 2001 Share Posted August 23, 2001 I too am kicking around ideas for backward ducts in my hood. Can't seem to settle on a particular design. Yeah, too bad we can't get some free advice from Eghbal Hamidy, aerodynamicist for Formula 1 teams. He has designed cars for Williams, Stewart, Arrows, Jaguar, and currantly the Jordan team. However, since Ferrari decided that they couldn't afford his salary, I kinda doubt that Hybrid Z has anything to entice him with. Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted August 23, 2001 Share Posted August 23, 2001 anyone running louvred inspection lids? seems to me it wouldn't cost a ton to have a louvred hood as well? Quote Link to comment Share on other sites More sharing options...
Modern Motorsports Ltd Posted August 23, 2001 Share Posted August 23, 2001 "maybe the air came out because it was pressurized in the confined space vented by the duct?" I've bought into that concept much stronger than the 'vaccuum' concept from external suction. Engine bay has higher pressure than above the hood. We know that, so it seems natural for it to exit ANY available opening to the lower pressure side. AIR my dad was popping his inspection lids on occasion...he just got a set of louvred ones back from MSA he's going to try. (very slow MSA service BTW, he got his supplied 'cores' back louvred so they had not stock on hand!) Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 23, 2001 Share Posted August 23, 2001 I failed to mention earlier that I do have the louvered inspection lids. However after a casual drive I noticed that the underhood temps are still very high, the hood being to hot to rest your hand on. Consequently I cut two vents in the hood and made an aluminum grill that runs front to rear in the vents. It looks very good IMO, however on a very hot day here in Sacramento I went for a drive in traffic with the new vents and louvered lids and the temp gauge went to 250*! Back to the drawing board for me. After looking at the vents I cut head on, I decided that air was probably being forced into the vents (due to the slope of the hood) with more pressure than the underhood air and therefore not letting the hot air escape. Thus the need for a rear facing "suca" duct design. Also seriously contemplating a GT 40 style hood that removes the hot radiator air with a reverse scoop just behind the radiator. Not sure if there will be adequate space to do this though. If I find a definite solution I will post. Meanwhile, back at the ranch... Quote Link to comment Share on other sites More sharing options...
BLKMGK Posted August 23, 2001 Share Posted August 23, 2001 Consider a cowl hood for heat extraction. The SubtleZ hood I've got is a very mild scoop but I can see the heat flowing out of it pretty readily. It also has the later Z style vents on the sideswhich can't hurt. odn't think I'll have much problem with underhood heat with this puppy... Quote Link to comment Share on other sites More sharing options...
johnc Posted August 24, 2001 Share Posted August 24, 2001 Who am I to argue with Larry McReynolds... I searched the NASA Technical Reports Server using the terms: "extraction", "extract", "exhaust", and "vent" in conjunction with "submerged duct" (the proper term for a NACA duct) and didn't find any documents. It appears that no one at NASA, NACA, Langley, Ames, Dryden, etc. felt a need to research how a submerged duct works as an extractor. That doesn't mean it doesn't work and I'm not saying that Larry didn't get air out using a reversed duct, but maybe the air came out because it was pressurized in the confined space vented by the duct? Here are probably the most relevant research papers on the design of submerged ducts: An Experimental Investigation of NACA Submerged-Duct Entrances Charles W. Frick Wallace F. Davis Lauros M. Randall Emmet A. Mossman NACA ACR-5I20 November, 1945 http://naca.larc.nasa.gov/reports/1945/naca-acr-5i20/ An experimental investigation of the design variables for NACA Emmet A. Mossman Lauros M. Randall NACA RM-A7I30 January, 1948 http://naca.larc.nasa.gov/reports/1948/naca-rm-a7i30/ An experimental investigation at large scale of an NACA submerged intake and deflector installation on the rearward portion of a fuselage Holzhauser, Curt A NACA RM-A50F13 August 30, 1950 http://naca.larc.nasa.gov/reports/1950/naca-rm-a50f13/ Quote Link to comment Share on other sites More sharing options...
Mike kZ Posted August 24, 2001 Share Posted August 24, 2001 Henry Costanzo added some pancake fans to the bottom of the engine compartment, check out his article: http://www.Georgiazclub.com/tips/ztech/v8cooling.htm Quote Link to comment Share on other sites More sharing options...
pparaska Posted August 24, 2001 Share Posted August 24, 2001 Mike kZ, since I just had the car painted, All my underhood cooling options will be just that - under hood first, so as to save the bodywork. Henry's idea of fans in the inner fender is good, but I may put a fan or two in the firewall into the cowl area instead. Stealthy and effective unless you're at speed. Plus I figure heat wants to go UP. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 26, 2001 Share Posted August 26, 2001 Has anyone seen or heard about the GT 300, GT 500 racing category's in Japan, they use some of the most advanced aerodynamics I've ever seen in a racing class, with massive rear spoilers and full belly pans, and more carbon fiber than you could poke a stick at, might be worth searching, Also i've seen some interesting concepts on some full bodied salt flat racers, that might be worth looking into. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 26, 2001 Share Posted August 26, 2001 I found a couple of pics of an GT500 NSX, i have'nt found any of the bellypans yet, hope this works You can just see underneath the rear in this one. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted August 29, 2001 Share Posted August 29, 2001 I found this article on the bellypan in the honda NSX, racecar, it has a couple of good pics, and a bit of info.NSX bellypan Quote Link to comment Share on other sites More sharing options...
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