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SDet
SDet New Reader
3/12/23 5:25 p.m.

Anyone ever play with more effective front splitters than just a flat board? 

 

I can't find much info on airfoil shaped splitters besides a few videos and this interesting paper. 

https://www.mdpi.com/1996-1073/15/15/5543

 

Are more complex splitters banned in most series, or do people just jump to front wings? 

 

This is for a 24 hours of lemons car, so no big gains, but not many rules either. 

 

Thanks

stafford1500
stafford1500 GRM+ Memberand Dork
3/13/23 6:01 p.m.

Shaped splitters have benefits and cons that need to be considered for every application.

Benefits:

They can generate more down force more efficientlly. They can be used to better control flows onver/around/under the car. They can more effectively be tied into existing bodywork.

Cons:

The shape usually requires a serious development effort with wind tunnel or CFD work, in order to get it "perfect". The shape will likely require composites work and possibly tooling. Spares are more difficult to prepare/store.

The simple flat shape is fairly easy to build and produces most of the gains of a " perfect" shape with much less effort (for the same platform area). Materials can be cheaper and easier to work with.

Adding shape to a flat splitter element is a simple as radiusing edges and allowing angle changes with the mounting scheme.

stafford1500
stafford1500 GRM+ Memberand Dork
3/13/23 6:03 p.m.

Generally, it comes down to effort. You can get a big chunk of the benefit with little work.

As far as rules, there are some limitations within some sanctioning bodies, but not all.

sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand PowerDork
3/13/23 9:11 p.m.
SDet said:

Anyone ever play with more effective front splitters than just a flat board? 

I've done a bit of theoretical poking around, as well as some work along the lines of what stafford's referenced above (at his direction).  There's a fair amount going on with this stuff in the "TimeAttack" series/world/environment.

I can't find much info on airfoil shaped splitters besides a few videos and this interesting paper. 

https://www.mdpi.com/1996-1073/15/15/5543

My understanding is, that one of the things that you need to be cautious of when trying to go "wing shaped" on a production-based car... is that, because of ground proximity / ground effect, there's a benefit to having a flat section between the rounded acceleration zone at the front of the splitter and any 'trailing edge shaping'/'diffuser'... in order to reduce sensitivity to the flow of having laminar flow bubbles or other discontinuities.  (this is what stafford is alluding to w.r.t. 'serious development')

Are more complex splitters banned in most series, or do people just jump to front wings? 

Lots of series have limitations on splitter dimensions and shape.  Part of that is in order to limit overall downforce, and part of that is to reduce complexity/cost.  I suspect there's also a certain amount of "inertia" around most splitter discussions, since 'flat sheet is good enough' is floated frequently.

one area of splitter design that's relatively easy to add additional performance/complexity is via what's commonly referred to as "splitter diffusers"... which are commonly available in ABS molded plastic, up to CarbonFiber pre-preg, parts that you attach to the back edge of the splitter into the 'wheel well' area.  This enhances the exit flow of the splitter, which allows a stronger low-pressure peak to form at the front of the splitter.

This is for a 24 hours of lemons car, so no big gains, but not many rules either. 

A lot of times, what you're able to do is primarily limited by the car you're racing... less so what the series allows/disallows.  Can we get a bit more information about the platform, and the current "aero state" of the car (if you add front downforce, you'll want to think about balancing out rear downforce).

SDet
SDet New Reader
3/13/23 11:15 p.m.

In reply to sleepyhead the buffalo :

Currently, it's a stock 89 pontiac lemans. Low drag coefficient allegedly, for its time. 

 

We've just started on a rear wing, 72 or 80 inch wide (depending on how the 3d printing goes) and 15" chord, mshd profile and we're thinking swan neck mount. We have alumalite for making a flat floor, and materials for an air dam, grill blocking, and side skirts. 

 

The wing should be enough to get a lot rear downforce, so we're looking at the front. We've had a few high speed spins, and the tire wear confirms that the rear is very light and just along for the ride. At the same time, the front becomes very light above 80, and unsettling in flat corners above 70.

We're in this for fun, and nerding out for a 3% gain when a botched driver change loses 10% is just part of the fun. 

 

 

sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand PowerDork
3/14/23 8:19 a.m.
SDet said:

In reply to sleepyhead the buffalo :

We've just started on a rear wing, 72 or 80 inch wide (depending on how the 3d printing goes) and 15" chord, mshd profile and we're thinking swan neck mount. We have alumalite for making a flat floor, and materials for an air dam, grill blocking, and side skirts. 

I'm curious where you got the coordinates for that from?  I wasn't aware they were freely available?

SDet
SDet New Reader
3/14/23 10:41 a.m.
sleepyhead the buffalo said:
SDet said:

In reply to sleepyhead the buffalo :

We've just started on a rear wing, 72 or 80 inch wide (depending on how the 3d printing goes) and 15" chord, mshd profile and we're thinking swan neck mount. We have alumalite for making a flat floor, and materials for an air dam, grill blocking, and side skirts. 

I'm curious where you got the coordinates for that from?  I wasn't aware they were freely available?

I used the image from this article, https://viraatsh.wordpress.com/active-aerodynamics-system/ 

And a solidworks tool that traces lines in images. Scale to size, and print. 

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