Rf 117

[Straight 8 Racing]

At the risk of offending the "afficianados" I have a few pictures showing the front air dam we plan to try on the car, I have no doubt it will provide some significant increase to the downforce on the front of the car at speed, what I am less conviced about is how it will affect the overall balance...... only time will tell

Iain

[JackW]

Looking bad ass.

Jack

[Peter D]

Iain, that looks really nice & I reckon that it will be very helpful with front-end down-force.

Some interesting analogies might be drawn from GM's experience in the development of the C3 Corvettes (68 onwards) using the earlier C2 (early 60's) models as a benchmark :

- 1965 C2 (no front or rear spoilers) needed 155 bhp to move it at 120 mph - body lifted 2.75" front & 0.5" at rear.

- 1968 prototype C3 (Kamm tail & rear lip spoiler) need 210 bhp to move it at 120 mph - body lifted 3" at front !!, but only 0.25" at rear.

- Cutting vents in the front fenders behind the wheels reduced the 120 mph horsepower to 175, with minimal change in lift.

- Adding a chin spoiler reduced the horsepower required to 105 !!, and reduced the front body lift to only 0.5". Not a bad gain for a $50 bit of plastic !!

Admittedly, this data really only relates to Corvettes, but it would not be unreasonable to conclude that a chin spoiler and adequate "under front-clip venting" might also have a fairly significant effect on a GT40 (known for front-end lift).

Your chin spoiler should address one part of the issue, but what about venting ? I notice that you have the twin nostrils - do these go right down to the bottom of the radiator ? Also, no front air vents either side of the rad intake - any plans for these to cool the brakes or vent frontal air into the wheel arches ?

Nice work mate.

Kind Regards,

Peter D.

[Bobski]

Nice work Ian, I love it. I also agree with Peter that a single nostril with a divider in the middle, sealed to the radiator would work much, much better as it done in the sixties.
Keep up the good work.

[Pat Buckley]

That looks awesome - well done!

It isn't often that an aero aid is added to a design that has been around for 40 years and looks like it was meant to be there.

[Big-Foot]

I really like that front end.. Would be great to have one that could be fitted with hidden brackets for those that would like to take their Forty on the track periodically..

Oddly though - the front end is remiscent of another car.. Perhaps the FFR GTM;

[Richard O'Clery]

I love the look of the spoiler and agree it will cut a lot of air that would otherwise have 'packed' under the front of the car.

If air flow from the front air intake was not restricted by the radiator, it would seem clear that the nostril area should equal the intake area. Perhaps someone with more experience could chime in here, but I would expect that as the radiator would block some of the airflow the outlet should not be as large as the intake. If it's too big, wouldn't this mean there is a risk of the area behind the radiator becoming an even lower pressure area than it ordinarily is? If so, turbulent air could even come in through the outlets to fill this low pressure area, adversely affecting cooling efficiency, and the amount of stagnant air at the front of the car could increase causing extra drag.

If you do end up with a low pressure area here, perhaps you could bleed air in from the wheel wells (similar to the louver effect mentioned by Peter) to offset and get some useful lift reduction.

Sorry to wax all theortical on you Iain, but there may be some efficiencies to be gained with this kind of stuff that make it worth exploring a bit during testing. A couple of different nostril configurations, variable ducts and manometers might be enough to ensure the airflow is doing what you really intend it to. Air - a tricky business...

[Russ Noble]

Originally Posted by roclery

I love the look of the spoiler and agree it will cut a lot of air that would otherwise have 'packed' under the front of the car.

If air flow from the front air intake was not restricted by the radiator, it would seem clear that the nostril area should equal the intake area. Perhaps someone with more experience could chime in here, but I would expect that as the radiator would block some of the airflow the outlet should not be as large as the intake. If it's too big, wouldn't this mean there is a risk of the area behind the radiator becoming an even lower pressure area than it ordinarily is? If so, turbulent air could even come in through the outlets to fill this low pressure area, adversely affecting cooling efficiency, and the amount of stagnant air at the front of the car could increase causing extra drag.

Aerodynamics is way over my head at present but most single seaters you see with front mounted radiators have a front opening considerably smaller than the radiator. There again they don't have flow through the radiator blocked by fans either.

If you think a big oulet would lead to a greater low pressure area behind the radiator then I would have thought that would aid airflow through the radiator and help the cooling, not hinder it.

Just my uneducated $0.02

[Jac Mac]

Country boys rule of Thumb- Air inlet area 1/3 of Radiator core area.

Jac Mac

[Dalton]

Looks good, Iain. The effectiveness will depend on many factors, as others have pointed out. Among them will be the car's front ride height. As you want the chin spoiler almost touching the track, it obviously will impact on bumps, so the bottom lip could possibly be an easily replaceable strip that gets renewed every few races. It is certainly going to assist in splitting air through the radiator or around the sides of the car, minimising the air getting under. I assume you will also be ducting air directly to the front discs. Of course, as with many things, testing out on the track is the final proof of the pudding. My 2c worth.

Dalton

[Straight 8 Racing]

Thanks for the comments, its interesting that most comments relate to the effect the front air dam will have on the cooling system, once again we have done as much theoretical work as is sensible but until we get it out on the track is is all just "hot air" (sorry for the pun). I confess I was expecting a fairly serious backlash for having 'ucked around with the

We do have a ducting system that seals against the radiator and snorkel which can be altered to accomodate a single snorkel if required. The radiator was sized to cope with the expected HP, water pump flow rates, head pressure etc etc and the volume / pressure of air we expect at the front of the car.

Peter, the info from the Corvette experience seems to line up with the general direction we have taken with the aerodynamics on the car, I would love to be able to vent the wheel arches but this is a complete "no no" in our rule book,

[Jim c]

Iain as per usual stunning.

Jac mac
1/3 in 2/3 out thats the one we use here in the city

Jim

[Richard O'Clery]

I concede I might have been trying to over-science things a little! Maybe missed the forrest for the trees, or some other appropriate similitude.

Iain, the sheetmetal work looks fantastic.

[Straight 8 Racing]

Jim,
I hear from a mutual friend (James) that your car is also making significant progress, and I am sure you previously set some clearly defined rules about posting pictures, so come on lets have an update.

For the benefit of other members Jim produces some really well designed and manufactured components that are of the highest standard and quality. Keep up the good work Jim,

Iain

[Ian K]

Originally Posted by Big-Foot

I really like that front end.. Would be great to have one that could be fitted with hidden brackets for those that would like to take their Forty on the track periodically..

Oddly though - the front end is remiscent of another car.. Perhaps the FFR GTM;

Actually, preceding the FFR GTM was an ERA with a splitter as seen here:

Products - Aerodynamic Devices

Mark LaVea, owner of Xtreme Classics, used to be a regular here - I haven't seen him post in a while.

Ian

[Jim c]

[quote=Iain Pretty;204390]Jim,
I hear from a mutual friend (James) that your car is also making significant progress, and I am sure you previously set some clearly defined rules about posting pictures, so come on lets have an update.

Iain

I will post at some stage it has been almost 2 years.
I never feel that I have done enough in the time I have been building RF105.

I am enjoying looking at the work Mick and the boys are doing for you, It is art.
I noticed your front wheel offsets giving a flatter wheel.
Mine will end up the same ,we must have ended up with a similar control arm lengths.

Jim

[Straight 8 Racing]

Jim,

The wheels in the picture are not quite what we expect to run, the fronts as shown are 9" wide with almost the correct offset, we will be using 10" wide with similar offset but a larger tyre both width and rolling diameter, the rears in the picture are 11" we will be using 12" the offsets differ quite a lot, basically they were the only tyre / wheel combo (from a P..... 996 with Carrera Cup Tyres) we could lay our hands on when we took the prictures. The 997 set up is a lot closer but once again it is pure conjecture untill we can turn a few laps and get some sensible data on tyre temperatures.

Regards

Iain

[Ross Nicol]

Lain
Is your car going to come in at under 1100kg? I think the rules still only allow 40" total for the 4 wheels but over 1100kg 44".Sounds like your car will be the latter.

Ross

[Ryan L]

Ian,

Build looks fantastic cant weight for the next update. I really hope that I can see the car in the flesh someday.

I was looking through the online SKF catalogue, http://www.e-webcatalog.com/cr-skf/cataloglook.aspx and found the Cayman and Cayenne bearings
Inside diameter = 2.0078
Outside diameter = 3.7795
Width = 1.9685

Are these the same size as what you have? Just wondering if its possible to swap the cup car components….

Regards Ryan