E-Type Aerodynamics!

graysgarage · Post by **graysgarage** » Sun Jan 25, 2015 3:59 pm

Full video on the aerodynamics of the E-type Jag! Enjoy

Post by **Heuer** » Sun Jan 25, 2015 4:56 pm

Superb! The Factory always refused to release CD figures for the E-Type although we do know the D-Type Jaguar had a CD of about 0.54 (love to see a flow test on one of those!). Interestingly the Factory 'Lightweight' race cars were based on the OTS with a hardtop fitted rather than the FHC. Some owners did experiment with a coupe body (Lindner and the Low Drag Coupe) but they were not a runaway success. The E-Type's biggest rival in period was the Ferrari 250GTO which used a 'Kamm' style tail.

The battering we got when we toured France encouraged me to fit a wind jammer in our OTS and it works brilliantly.

Mark Gordon · Post by **Mark Gordon** » Sun Jan 25, 2015 6:20 pm

The turbulent flow shown for the OTS demonstrates clearly what I feel at speed with the hood down. 4-6 hours of 60-70 miles per hour is tiring, but a shorter run or 45-50 mph is a joy on a nice day. Since I seldom drive farther than an hour or so one way, I wouldn't consider trading my OTS for a coupe even with the turbulence factor. I found it particularly interesting where he explained why the flow separation at the front of the car is the reason for the front end becoming light at higher speeds. One thing that I would question is whether the model accounts for the airflow through the mouth of the bonnet and underneath the car. Any criticism aside, this is a very interesting video for the E Type enthusiast.

Dave K · Post by **Dave K** » Sun Jan 25, 2015 9:40 pm

I found that out using a cruder method when I stick bits of string to my screen and around the back of the car testing different home made screens.
The screen alone doesn't do a lot you need the curtain underneath to stop the wind coming back between the seats.

Dave

David Oslo · Post by **David Oslo** » Mon Jan 26, 2015 11:44 am

Excellent.

I do wonder however about the comment early on in the video regarding top speed of the 9" stretched FHC. Graysgarage mentions the increased frontal area (higher A in the CdA equation) and higher & longer roofline giving more turbulence (higher Cd in the equaton). Quite true. But what about different rear axle ratios? Not having the data in front of me, I wonder if a like-for-like car (e.g. UK spec) has a different rear axle on the 2+2 vs 2-seater.

Anyone got a book to refer to ?

christopher storey · Post by **christopher storey** » Mon Jan 26, 2015 6:28 pm

It was interesting, but not entirely representative of reality , because his model was in fact a long wheelbase car throughout, ( note the flared wheelarches ) and thus his " coop" ( what a word ) had a roofline which was unlike either the fhc or the 2+2 , being a hybrid of the 2 and actually having a lower profile than either . Also, he seemed to me to attach rather more importance to screen rake and resultant high pressure areas than applies in many situations . The majority of induced drag arises not from high pressure areas, but ( as he correctly identified ) from the detachment of airflow and resultant turbulence , which requires work to create it which has to be paid for . In the 1970s for some years I had an aeroplane with a laminar flow wing ( Falco F8L ) and the trick worked by the designer was that there was virtually no moving airflow at the wing surface and for about 1 inch above it , a static pool of air acting as a kind of lubricant for the main airflow which travelled outside it . This made the Falco one of, if not the, fastest light aircraft of the post war era, but there were penalties of a thin wing, with an approach speed of 100 knots . It is in the detail that modern cars have lowered drag - bonded in screens with no lip ; flush windows and handles ;no gutters I understand to be particularly important ; rear spoilers to prevent premature detachment of the flow etc. Incidentally, proof that screen rake is near irrelevant comes from the Lancia Appia of c.1955 which despite its sit up and beg appearance had one of the lowest drag coefficients ever, at IIRC about 0.28 ! ( and if one needed further proof, look at the rake of the cockpit windows on most modern jet airliners )

Simon P · Post by **Simon P** » Tue Jan 27, 2015 9:43 am

A Falco? Lucky chap! Lovely planes by all accounts.

Gfhug · Post by **Gfhug** » Tue Jan 27, 2015 9:52 am

Simon. I agree, a type I'd enjoy getting my hands on.
There seems to be a reasonable number of pilots on this forum. Must be something to do with the pleasures of flying nice handling aeroplanes like the Falco, CAP10, my Emeraude, etc. and the similar pleasures of driving a beautiful car.

Simon P · Post by **Simon P** » Tue Jan 27, 2015 10:48 am

Monocoque body. Big engine hung out the front on engine bearers. Big long nose stretching out in front of you. Surrounded by curvaceous beaten metal and faced with a multitude of dials. Surely every E-type driver sees themselves as a Spitfire pilot, don't they?

PeterCrespin · Post by **PeterCrespin** » Wed Jan 28, 2015 9:08 am

Simon P wrote:Surely every E-type driver sees themselves as a Spitfire pilot, don't they?

Tubular frame, spoked wheels, polished alloy covers, multiple carbs and twin exhausts, great performance - I assumed every E-type driver sees themselves as a motorcyclist. Plenty of those here too :-)

Simon P · Post by **Simon P** » Wed Jan 28, 2015 10:53 am

PeterCrespin wrote:I assumed every E-type driver sees themselves as a motorcyclist. Plenty of those here too :-)

The problem is, this is what you motorcyclists see in your mind's eye when you head out on the road:

Whereas this is what the rest of us see....

Post by **Heuer** » Wed Jan 28, 2015 4:23 pm

And this is who they think they are going to meet on the way:

Mark Gordon · Post by **Mark Gordon** » Wed Jan 28, 2015 5:25 pm

Have Pete tell you about the Virginia State Trooper that he met via his motorcycle.

Post by **Heuer** » Wed Jan 28, 2015 6:06 pm

PeterCrespin · Post by **PeterCrespin** » Wed Jan 28, 2015 9:04 pm

That would be Park Ranger Elizabeth Jordan, Mark. :-)

Taller than you or David, with long blonde hair, she stepped out of her chunky SUV in a crisply-ironed uniform hugging her shapely curves that sunny morning on Skyline Drive in the Shennandoah National Park. Sadly, all she took down were my particulars, and then she hit me with a $185 fine.

Not for ogling her but for doing double the speed limit on the deserted scenic road. I can't complain though, as it was pure chance she caught me coming round a corner on a slow section, otherwise it might have been three times the limit and jail food. Just as well it was Federal land, so no courthouse, no lawyers or licence points and no insurance hike.

Fonda would have come a cropper on the first bend and the old-school cop would also have grounded his Harley foot boards and sailed over a parapet into oblivion as he failed to complete the turn. On the other hand, if Officer Jordan had been first on the scene and administered the kiss of life... :-)

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