How effective would the rear wing be on the below car? I imagine that the flow over/through the cabin would be very turbulent and not do a whole lot of good and would it be better with or without a windscreen?
In this example the exhaust is routed below it so it is hopefully in effect a blown wing, but would raising it into cleaner airflow and taking away that feature be better?
Thanks,
The blown area would only be (relatively) behind the exhaust, but the whole wing will be in dirty air. I'd raise it up out of the turbulent air.
If I read the intent in your main thread correctly that this is mostly a design exercise, then the wing is fine where it is currently placed.
As an aero guy, I have thoughts. Looking at the overall layout the rear wing is too far forward. Move it aft to help with some of the front downforce the body is going to generate. The blown bottom surface between the pylons will help offset some of the dirty flow across the top surface from the cage/airbox/windshield. Yes run a windshield, bugs and rocks hurt... The outer end will do what they are going to do fairly well as the flow rolls inward around the cockpit/engine. In a best case the center of the wing would be modeled with less aggressive angle of attack to account for the flow over the center rolling down toward the rear of the car.
Look for cars like the Ferrari 333SP for inspiration on a similar platform. There were others that competed in the series called World Sports Car from the early 90s to the beginning of the 2000s that all had the same basic layout (open cockpit, rear engine, ducted rads, rear wings). These most closely resemble what you have modeled.
Blown aero has some disadvantages, primarily being your downforce changes with how much hp you're making at the moment. This is worst at highspeed corner exits where you may need to lift which then cuts some of that downforce.
This assumes that the exhaust is making a significant difference though. As a first estimate, calculate the volume and flow rate of the exhaust (not hard) and compare that to the volume and velocity of air going under the wing. Is it doubling the air or adding 0.1%? If your gut tells you the number is too small to matter, moving the wing up (within the rules) is a no-brainer.
What is that giant tank on top of the engine though? Intercooler? If there's any way you can move that away from the airflow, both your drag and your downforce would improve, and it is rare to get both like this.
stafford1500 said:If I read the intent in your main thread correctly that this is mostly a design exercise, then the wing is fine where it is currently placed.
right now it is somewhat of a design study, however if i get the chance to built it I will.
the reason for the placement of the wing is that is where the chassis ends, but extensions are not hard to do.
Thanks, will check those cars out.
In reply to cyow5 :
yes, all valid points, I just figure it can be driven to suit that characteristic as a benefit>cost situation.
the tank is two water-air intercoolers, the engine shown here is just an example I pillaged from another car and is configured for 1600hp, real world expectations is probably a junkyard big block with ebay turbos and side intercoolers, I have tested multiple diffenerent engines for size.
In reply to stafford1500 :
how much benefit would the extra long endplates like on the ferrrari contribute? I assume it is to clean up flow under the wing?
A current example of what stafford1500 is talking about.
In reply to Mugglesworth :
Larger end plates will help the wing work better. You can try to incorporate the end plates into the bodywork sides to give the wing more support. You don't need to extend the endplates very far behind the rear edge of the wing.
Couple of things I'd mention in reading through this (pulling from memories from a decade or more ago):
Moving the wing back is absolutely the way to go as Steve suggests (and provides an example for). Something else to consider about very rearward wings with big endplates is that they can be induced to interact with the underbody flow, extending the effect of the underbody/diffuser and even providing some degree of extraction via a larger low pressure section. IIRC the Ferrari shown was required to have a flat underbody with no diffuser, so they ran them with some aero rake (you can see it in the photo) to generate some negative pressure underneath and used to rear wing and endplates to get some extra pull through out from under the car. If you look at old IMSA or Group C cars, and even the new IMSA GTP/WEC machinery, you'll see rear wing endplates very aggressively employed to enhance underbody interaction.
Re. exhaust-driven underbodies and wings, clearly they are driven by exhaust speed, but remember how Renault F1 engines for blown-diffuser cars used to artificially accelerate their exhaust speeds at low RPM/low vehicle speeds by dumping fuel into the engine and/or exhaust system off-throttle, giving them better low-speed traction than their rivals until the other teams caught on. Underbody blown diffusers were regulated away, but teams started using Coanda effect exhaust systems, taking advantage of fact that air (and exhaust) flow tends flow along the bodywork it's close to, so they started this to direct engine exhaust out of the sidepods ahead of the rear wheels, along the coke bottle section between the rear wheels, along the upper surface of the diffuser and right out into the top of the rear edge of the diffuser, using the increased flow to pull more volume out from underneath. Again, they often employed fuel-dumping to increase low-speed downforce and traction.
Anyway, these kinds of things might be interesting to consider as you're developing your project. Stafford, if I'm confused about any of this, feel free to check me, brother. You are the house expert here.
- Bill C
In reply to BillCuttitta :
You got it all right.
The best thing to consider with Mugglesworth's project is: It is a design exercise and he does not have any rules to limit what he can do.
He might as well employ all the things that have been banned/outlawed/regulated over the years. There are plenty of ideas out there that have not been mentioned yet. I think we had a thread about banned aero stuff a few years ago. It may have been started by Robbie.
there are constaints, however they are very lax and not set in stone,
it needs to be easy to construct,uncomplicated and most importantly as cheap as possible. and while it would mostly be a dedicated track car it should also have the ablity to operate on the road which is the reason it has fenders in the first place (new zealand requires mudguards for the rear 3/4 of the tire without certain exemptions). fibreglass components should also be uncomplicanted and relitively easy to make.
anti-lag can gladly come aboard this ship for its blown aero properties if not for its sound.
In reply to Mugglesworth :
Yeah, an anti-lag system would work well for blown aero. I have driven a rally car with an anti-lag system, and it was a little spooky the first time I headed into a corner at speed. I'm used to a moment of coast off-throttle between braking and picking up the throttle (which I exaggerate in an enduro to save fuel if needed) to accelerate through and out - but when the anti-lag system kicked in, it started powering me into the corner on boost with my foot off the throttle, which was a little disconcerting as I was trying to find the balance of the car. Realized right there that I had to drive it two-footed, either on the gas or the brake (or both for little trail braking for stability), but there was no such thing as coasting with the AL system on.
- Bill C
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