Understood Chuck, and at about 180 MPH the rear of the Pantera will lift off due this effect but not the front because of the downward pressure from the frontal hood area. An aluminum front hood will actually collapse inward at about the same speed. Larry On 8/2/16, 7:26 PM, "DeTomaso on behalf of Chuck and Linda Huber" <detomaso-bounces@server.detomasolist.com on behalf of lindahuber@cox.net> wrote:
I might respectfully disagree (obviously not having tested this on my own...)
The airflow over the car (like that over a wing) will be accelerated. The air going over the top of the car will create lift (as in the front of the stock Pantera lifting up at speeds above 125 mph, such that handling gets squirrely). This lift is due to low pressure over the top of the car (again like an airplane wing), which will tend to pull air out through the hood vents.
I agree that ducting like GT-40s, Goran's picture, and Comp2 will be much more efficient at exhausting air than the hibacci grates that most use.
I do agree this effect would be more pronounced with a flat bottom.
Chuck
-----Original Message----- From: Julian Kift [mailto:julian_kift@hotmail.com] Sent: Tuesday, August 2, 2016 7:55 AM To: James coyne; Rod Kunishige; scottcouchman@yahoo.com; detomaso@server.detomasolist.com; Ken Green Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
Okay, let's put our engineering hats on and have some fun technical discussion..... it sure beats the discussion over POCA of late!
I think (but readily admit my engineering degree is not in aerodynamics!) hood vents and location play a minor part in overall aerodynamics.
Hood vents are a great way to provide additional cooling in traffic, but perhaps limited value at high speed when the front of the hood becomes a high pressure area. Now you have opposing forces at play and at speed 'x' the pressure is likely enough to overcome that produced by the radiator fans (I imagine that 'x' would not be excessively high, perhaps even highway cruising speed). So outside air now reverse enters the hood vents or at a minimum restricts fan flow resulting in air that is forced under the car i.e. back to the original Ford design concept. A Gurney lip on the frontal edge of hood vents would help create a low pressure area, but I still believe the air from the radiators will ultimately be forced under the car at some speed now x+y.
As testament to the pressures on the hood Larry Stock told me that Mike Cooke collapsed an aluminum hood at high speed.
As alternative thinking, most cars that employ an aerodynamic frontal hood vent do so in combination with a full flat underside. I think this is a critical element in the success of the design and one without the other is likely non productive. Furthermore most running Pantera's in ORR have reported that a front air dam is a key element in preventing front end lift at +150mph, again attesting to restricting air flow under the car is the most critical element. I'd go for the front air dam in combination with a fully enclosed flat floor/tray as my first modifications and leave cutting the front trunk aspect (and the ensuing frontal rigidity impact).
As an a side the popular radiator fan shrouds also become restrictive at high speed and require opening up, some have achieved this with simple hinged flaps that can freely open as the pressure through the radiator increases.
Julian
________________________________ From: Ken Green <kenn_green@yahoo.com> Sent: Monday, August 1, 2016 10:28 AM To: James coyne; Julian Kift; Rod Kunishige; scottcouchman@yahoo.com; detomaso@server.detomasolist.com Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
Probably more correct to say I intend the car to be able to run well over 150. Not sure if I want to drive that fast on a country road. I would be a lot more comfortable having fun at lower speeds in an ORR, and trying the flying mile type events to see how fast the car can actually go.
The older we get, the longer it takes to heal.
Ken
________________________________ From: James coyne <tecnosound@hotmail.com> To: Julian Kift <julian_kift@hotmail.com>; Rod Kunishige <rkunishige@hotmail.com>; "scottcouchman@yahoo.com" <scottcouchman@yahoo.com>; Ken Green <kenn_green@yahoo.com>; "detomaso@server.detomasolist.com" <detomaso@server.detomasolist.com> Sent: Monday, August 1, 2016 9:00 AM Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
I believe it is indeed Ken's intension to run in the 150mph+ classes at open road events .
________________________________ From: DeTomaso <detomaso-bounces@server.detomasolist.com> on behalf of Julian Kift <julian_kift@hotmail.com> Sent: Monday, August 1, 2016 7:49 AM To: Rod Kunishige; scottcouchman@yahoo.com; Ken Green; detomaso@server.detomasolist.com Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
This seems like an awful lot of work for little to no gain, is this a dedicated race car that will be running the 150mph+ classes at an Open Road Race?
Julian
________________________________ From: DeTomaso <detomaso-bounces@server.detomasolist.com> on behalf of Ken Green via DeTomaso <detomaso@server.detomasolist.com> Sent: Monday, August 1, 2016 7:00 AM To: Rod Kunishige; scottcouchman@yahoo.com Cc: detomaso@server.detomasolist.com Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
My gut feeing is the opening needs to be moved back to reduce air pressure over the opening. And that probably depends on speed. Ken
From: Rod Kunishige <rkunishige@hotmail.com> To: "scottcouchman@yahoo.com" <scottcouchman@yahoo.com>; Ken Green <kenn_green@yahoo.com> Cc: "detomaso@server.detomasolist.com" <detomaso@server.detomasolist.com> Sent: Sunday, July 31, 2016 10:13 PM Subject: Re: [DeTomaso] Has anyone researched hood vent designs?
I really like the idea of boxing the trunk in your design.
It means moving the support ribs for the hood.
Can you enlarge the opening by starting closer to the radiator? From: Ken Green <kenn_green@yahoo.com> I think photos of that car were posted a year ago? I want the car to look like a Pantera, not a GT40. en From: "scottcouchman@yahoo.com" <scottcouchman@yahoo.com> You should talk with Tony Ortiz in Arizona. He modified his Pantera to install front and rear GT40 clips.
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