GT Mk1 aerodynamics

[Howard Jones]

Gary. You could be right. It may well be that as race cars developed in the late 60's downforce became recognized as more important than low drag. You are correct that the MK2's had the single opening. They also had at least 150 more horsepower to overcome drag with. You see this a lot in F1 durning the turbo years. More power allowed big wings, along with skirts and underbody blackmagic,created more drag but a lot more downforce with about the same top speeds on the straits and the resulting increase in speed thur the turns. This has been the main problem in f1 for the last 25 years or so. Whitness the chicains (Sp?) at silverstone and everwhere else for that matter. Progress I guess. Maybe this is why some many people still love the old gt40's. Kind of a rememberance of a more simple age.

 

[Gary Gibbs]

[ QUOTE ]

I noticed you have the single nostril on your 40...???

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Yes I let the performance win over looks in this particular battle. Of course I have no data to back the aero issue on this car. Just going by the historic records.

 

[Malcolm]

Twin nostril V Single nostril? With the airflow on this part of the car having come through the radiator the effect of aerodynamics would be reduced. I changed from a twin to a single as the area of the opening in front of the radiator was bigger than the area for the air to exit behind the radiator. It improves the cooling of the car. In addition you ought to consider putting a flat tray at the lower edge of the rad facing forwards to stop air hitting the rad and then going under the car. Sides to this tray will also help.

Malcolm

 

[Julian West]

Here's a picture of the nostril on the Chris Melia/MDA Mk 2 at the Goodwood Rev. The ally splitter adds a nice touch...

 

Hi Guys, theres my car again! Nice Photo Julian! The Splitter Chris made for the black car is simple, but effective.Like Malcolm says above another mod is to dam the air through the rad so that it exits right into the Single vent and upwards over the front end. As most of the English guys will tell you, riding in a twin vent standard nostril car at 130mh watching the front end lift in front of your very eyes is facinating! It baloons to the point where you think it will burst open.. Then if youre really lucky and have a standard GTD with those stupid Dzus fasteners fixed on the wrong side of the body! The nostril panel will fly out, smack your windscreen and hit the rear end as it smashes on the ground behind you!! What fun that is, NOT. This is all due to the amount of Lift the twin vent panel kept under itself and therefore not allowed out of the front body areas.

If nothing else gentlemen, learn from those that have been there, done that and got the T shirt!

The Other favourite GT40 trick is the Air Brake! This is the rear deck flipping open when you least expect it to. This is usually when the rear safety clips have been left unlatched, you hare off at some speed to find the body lifting up and no matter how quick you slow down, its too late, its ripped along the floor and the tail section and lights have gone! To my recollection, I have sold 11 back ends due to this one major issue, dont be a statistic!

One of the most modified GT40s I ever saw was a Great Swedish Guy Called Jimmy Larsson. He had a GTD MKll sort of: It was heavily areo foiled, dammed and winged. I didnt look much like a GT, but boy did it go..... It was a 427 engined car with a Hewland box. ~Extremely Powerful and had great down force.

I was informed earlier this year that Jimmy Larsson had died last year. Another great guy sadly missed. Ive been to his house a watched race videos of Swedish circuits and had great food. On that same trip I met Sven Erikson Ex Can Am driver, now motor racing journalist. Sven also knew of Brian Pepper (another race driver)and great GT40 car builder, Sadly again no longer with us. On this same trip I was introduced to the original Lola T70 mklllB driver that survived Six months in a coma after his Lola went off in a very big way many years ago. And that is another story!

Whilst doing business for GTD in the Early Ninties i met many people Including Len Bailey, in many peoples eyes the designer of the GT40 and many others. Again sadly no longer with us. To GTD I thank them for the experiences, both good and bad.

Best regards to all

Mark Sibley
MDA

 

[Knighton]

MDA,

This is the first time I have had a look at your GT40s and I must say I am impressed. I visited the MDA website for the first time this afternoon and suddenly took a liking to the MKII (I have always liked the MKI and really disliked the MKII) and has me ask the question; Are the MKIIs on your site MDAs or are they the real thing? They look very authentic!

Do you build a turnkey car? I suppose I should direct this question to your new Canadian dealer.

Will you post a few pics of the interior?

What size rubber can you run?

 

Hello all, If you need specific details you will have to mail me directly im afraid. The Forum is to discuss issues and is not really to be a platform for any manufacturer in specific, though i does happen. That said:

The cars are replica MKll. They are authentic in detail from the topside, but underneath quite different. Ican mail you pictures of any item including interiors. And yes we can supply turn key and turn key minus. And yes for the interim i can handle the equiries for RCR, but all business will be via RCR when site established in the next few weeks or so.

And the Mkl was always more appealing to everyone for some reason, including me. But the more a stare at the Mklls the more Im hooked.. The Black car will be the MDA MKll demonstrator when I have chance to finish it properly, but We keep doing shows and there is much demand for exhibtion work for them all.

They Go to Spain soon for a month long tour. I dont know if I can let them go for that long, I'll miss em... /ubbthreads/images/graemlins/frown.gif

Regards

Mark Sibley
MDA

 

[Malcolm]

[ QUOTE ]
.... The nostril panel will fly out, smack your windscreen and hit the rear end as it smashes on the ground behind you!! ....
Mark Sibley


[/ QUOTE ]

No it doesn't, if you go quick enough it will clear the whole car in one fell swoop and just trash itself! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif Not that I have done this one yet myself!

Malcolm

 

[James]

[ QUOTE ]

....No it doesn't, if you go quick enough it will clear the whole car in one fell swoop and just trash itself! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif
Malcolm

[/ QUOTE ]

That rules you out then!
/ubbthreads/images/graemlins/grin.gif

Regards,

J.P

Sorry Malc, couldn't resist. /ubbthreads/images/graemlins/wink.gif

 

Now Now you two, stop mucking about!! Malcolm is right, if you go fast enough ie 130 plus and the wind is just right it will hover above your head like a empty take away carton! Then It will flutter gently sideways and then smash itself to pieces on the ground! But if really unlucky, i cant mention names here.. But it will tip up hit the screen and that is why GTD glassed a tongue in the rear of the bonnet nostril. This only just helps though, a strong wind will still tip it up and it makes a real mess.. Believe me!

That and the Air brake! are the main accidents for GTD. Funny enough I had a rear end for a Gulf GT in my old house as a garden seat! This was an air brake victims. Made a good seat though, I even had the lights working at night!

Anyway I hope the info i post here helps those who are not as versed as some of the hardcore GT guys..

James, the wheels look great with tyres on, pics tomorrow.

Malc, I hope the joys of new arrival are still enjoyable. Take care guys.

cheers

Mark
MDA

 

[Malcolm]

[ QUOTE ]
Funny enough I had a rear end for a Gulf GT in my old house as a garden seat! This was an air brake victims. Made a good seat though, I even had the lights working at night!
Mark
MDA

[/ QUOTE ]

Hey Mark, I got a gulf front end in my garden. We could make it into a table and then sell the set as designer garden furniture!

Of course if we both had known this earlier, you could have fitted both ends to that Bond car, blown those peices up and saved yourself a set of bodywork! /ubbthreads/images/graemlins/grin.gif

Hindsight is a wonderfull science.

Malcolm

JP, go see my posting on Monaco and make sure your car is ready for it! /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

 

I know it may upset the purists to have a door stuck on the front of their car.

http://xtremeclassics.com/aero_devices_pics.html

This is a positive plug for a splitter for an ERA GT40 (stuck to a door). It's still quite rough and needs radii and fences but it'll give you all an idea of the size and proportions I've planned for my splitter. Click each pic for a larger view.

So soon I may have this ungodly carbon fiber appendage tacked on the underside of the nose of my GT. Woohoo! The absence of front end lift at speed.

Sill extensions and rear diffuser next.

Mark

 

[Pete McCluskey.]

Looks pretty good Mark, It will be interesting to see pics
of the finished product.

 

[Chris Duncan]

[ QUOTE ]
1. Add chin spoiler (splitter) ala Lotus Europa.

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Three terms have been used on this thread, air damn, splitter, and spoiler. I always thought a spoiler angled forwards and down in the front and an air damn was flat. With the concept that a spoiler was angled like a wing to produce downforce and an air damn was designed just to block air from going under the car, which may also in effect reduce lift. The piece your building looks like an air damn to me.


[ QUOTE ]
2. rocker panel extensions
3. ducktail spoiler.

[/ QUOTE ]

this is the adjustable plate to extend the existing spoiler like on the MKII correct?


[ QUOTE ]
4. rear under-car diffusers.

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What is a diffuser? Is this the 4 square holes/ducts coming out the bottom rear of the new red GT? What in the heck are these things, what are they made of, how are they designed, and how do they work?




good thread, I want to get my GT up to speed and may even go to the salt flats but definitely don't want to do any flying. Nice effort BTW with the XC and the web site.

 

[Gary Gibbs]

Most of your guesses are correct. I again encourage anyone interested in this technology to look at the book on race car aerodynamics by Katz. He covers this stuff in some detail, but it does not require a Ph. D. to read (does not hurt though /ubbthreads/images/graemlins/smile.gif ).

 

[Kevin M]

On the question of single versus double nostrils, I don’t think aerodynamics had anything to do with the double nostril design on the early cars. In 1962 aerodynamics was very poorly understood and many of the things they were doing were just plain wrong. (Witness the disaster with the front-end design of the Corvette Grand Sport. The designers thought it would act as an upside down wing an pull the car down onto the track. Of course it did just the opposite and the cars had terrible front-end lift problems.)

One of the many strange rules for LeMans at that time was that you had to carry a spare tire in the car and change it at every pit stop.

I think the French were somehow hoping this sort of rule would bring back the true dual-purpose cars from 10 years earlier. In any case, the double nostril evolved because they had nowhere else to carry the spare other than behind the radiator. I think this is why the cars have that rather strange removable panel in the nose to begin with. So that they could get at the spare to change it quickly.

The spare stuck forward in the center of the nose, so they shaped the radiator exhaust around it. You can see this in some of the pictures of the early cars.

From an aerodynamic standpoint, the double nostril would be worse for drag, not better.
The single nostril is not a “hole” in the nose at high speeds. The air flowing up from the radiator actually fairs this in quite nicely. The restriction, and resulting high pressure in the radiator area on the double nostril cars would have caused more drag.

 

Road and Track had a nice article where they acknowledge the tweaks on the new GT at both the sills and the front. You can get some idea of them from the pictures.