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Vertical stabilizers S550 aero

33
18
Exp. Type
HPDE
Exp. Level
Under 3 Years
Cantley
Has anyone tried vertical stabilizers, dorsal fin, like we see on the LMP cars or the old Jaguar D?
I am new to the sport and have done twenty 20-minute HPDE lapping sessions and the basic course at the Jim Russel racing school. I am aware I need to get more seat time and quality coaching before I start thinking about wings and other gizmos. This is more about discussing ideas, not my most logical next step for the car.

My limited experience gives me the following feedback:

-front grip on the car is generally excellent, any instance of understeer is usually easily fixed.
-rear grip is also good, but oversteer situations are less easy to predict and fix.

Adding a big wing will help with rear grip, but without commensurate change to the front end, I might not have such nice predictable handling anymore.
Would adding a dorsal fin instead of a wing yield better predictability for the rear end without changing the front end balance, since the fin does not add downforce at the back?

Your thoughts/experience?
For reference, my car has slight mods and sits 3 inches lower vs stock (lowering springs + shorter tires). Tires are 305-30-19 on all 4 corners, 200 TW. Alignment is zero toe front, 2.2 camber, 7.2 caster, .30 total toe back, 2 camber, zero thrust
Cheers!
Jerome
 
3,483
3,244
Hartman is the aero guy on here, from what I've observed, the dorsal is more to straighten the airflow before it comes into contact with the wing, I guess it does add some stability, but you have to remember things like wings stall at around 15 degrees of slip, so IMO the dorsal is there to sort of help that situation going through the corners. I doubt the dorsal itself will do much good alone, unless your at Bonneville or someplace where keeping the car dead straight is paramount. I have long recommended that you simply use the GT4 components, (or the IMSA or PWC components on the S197 platform) because all of the work is already done for you, there's no need to go down the aero rabbit hole of death. Keep in mind, the more wing and splitter you have, the more HP you will need to drag it down the straights, so there is a compromise there, if the wing allows you to come off the corner faster, then it would overcome any drag that you may encounter at the top of the straight, but if it's a long straight, then.. maybe not.
The other thing is that you may show faster lap times with big aero, but if the passing zones are not in a place where that aero is beneficial, you will get passed, thus there are "qualifying" and "race" wing setups. This is what I mean by going down the aero rabbit hole of death.
Nothing is simple.
 

yotah1

Ford Employee
330
433
Detroit
The vertical fin on the LMP cars serves a few different, a debatable, purposes : it adds real estate for sponsors and graphics that is easy to see from the grandstands (no kidding here, the FIA rulebook actually states it ...), it also helps reduce unwanted turbulent airflow before the rear wing upper planes (because LMP cars have a very narrow cockpit and that rear wing gets most of its air form each side of the cockpit rather than over it, like our cars do), it also helps reduce the risk of going sideways or losing the car at high speeds.

In almost no way does it really help cornering or improves lateral grip or oversteer in low to mid speed corners.


Regarding the "go with the GT4 stuff" from Blacksheep : yes, but no. Yes a lot of work has been done, it's been wind tunnel tested and approved, so you know it "works", but it's been designed to fit a specific set of rules set by IMSA which requires downforce and drag numbers to be within a set bracket in order to balance performance between all the manufacturers. The production Mustang suffers from lift in the front, and too much downforce in the back for the GT350, GT350R and GT500. One way to balance the car better is to vent the hood as much as possible, cf GT4 hood louvers. One thing where the GT4 suffers is rear downforce. That rear wing is actually almost too big for the car, the teams have had to angle the wings quite a lot to avoid creating understeer because of un-balanced aero. Oh and the rear diffuser does nothing but lift dust as there is no flat bottom and the rear subframe / diff / suspension in front of it generates so much turbulence that the airflow under there is useless. But the big wing and diffuser were required elements per the IMSA rulebook.

My 2 cents as an enthusiast, from chatting with the dev team at Ford on various occasions and picking their brains for my GT350 :)
 

yotah1

Ford Employee
330
433
Detroit
Very rear biased ... just like the 350R and 500 for example which get more than 65% rear downforce. In a way, a lot of cars are like that, because average Joe can't drive anyway and a really balanced car with a 50/50 downforce setup would mean most people would spin them at the entry of every corner, and they'd say it's the OEM's fault.
 
Very rear biased ... just like the 350R and 500 for example which get more than 65% rear downforce. In a way, a lot of cars are like that, because average Joe can't drive anyway and a really balanced car with a 50/50 downforce setup would mean most people would spin them at the entry of every corner, and they'd say it's the OEM's fault.
Interesting because i always thought they were front biased. Thank you for the insight,
 

yotah1

Ford Employee
330
433
Detroit
Most cars are designed to understeer either through their suspension geometry, tire size, aero package. It's much easier to have a customer struggle to turn than spin out of control (maybe a legacy of the Corvair "unsafe at any speed" story ahahah).

The Mustangs suffer from a lot of frond end lift because of all the air trapped under the hood. I'm sure you've noticed how much the hood moves at high speeds on our GT350s ...
 

Grant 302

basic and well known psychic
Would adding a dorsal fin instead of a wing yield better predictability for the rear end without changing the front end balance

Not to a great effect, but it should. It’s placed where it is relative to the wing on purpose.

since the fin does not add downforce at the back?
Are you sure about tgat

This is more about discussing ideas,
I think you’ll likely continue to get more discussion than answers.

Your thoughts/experience?

The way the fin works with the wing is a lot simpler than any of the explanations found online. It’s comical what some of the YouTube clowns say on the matter.
 

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