How to build a splitter for only $100 | Against the wind: Part 3

Tom
By Tom Suddard
Sep 20, 2022 | splitter, Shop Work, Aerodynamics, Against The Wind | Posted in Shop Work , Features | From the Nov. 2022 issue | Never miss an article

Photography by Tom Suddard unless otherwise credited; Lead by David S. Wallens

Our LS-swapped 350Z has sat quietly while we’ve worked on its digital twin, one built in CAD. Without getting our hands dirty, we’ve virtually tested all manner of aero add-ons: wings and splitters, vents and dive planes. 

One big takeaway from our time in Morlind Engineering’s virtual wind tunnel? We needed to build a splitter. 

And while we arrived at …

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Comments
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Shawn_D
Shawn_D New Reader
9/20/22 8:43 p.m.

So, what's the source for this proprietary "rocket nose coating"?

Tom Suddard
Tom Suddard GRM+ Memberand Director of Marketing & Digital Assets
9/20/22 9:41 p.m.

In reply to Shawn_D :

NLR said it's a trade secret, but it's a pretty cool process. 

VolvoHeretic
VolvoHeretic GRM+ Memberand HalfDork
9/20/22 11:36 p.m.

"And if the front of the splitter deflects enough to touch the ground, it will block all airflow under the splitter. No airflow means no downforce, which is why a flapping splitter can suddenly remove all front downforce mid-corner. That’s bad."

I'm having a difficult time visualizing why this is true.

Also, is a flat bottom side to the splitter the best shape? Wouldn't a curved wing like airflowish like shape be preferred?

VolvoHeretic
VolvoHeretic GRM+ Memberand HalfDork
9/20/22 11:36 p.m.

Deleted duplicate. 

jfryjfry
jfryjfry SuperDork
9/21/22 12:08 a.m.

This may be common knowledge but my buddy ran a nascar truck team for a minute and they set up their suspension so the splitters just touch the ground.   Of course they're not deflecting but the truck compresses in the corners, lowering it so it scrapes.  And they're thick - they are not folding down.  
 

 

stafford1500
stafford1500 GRM+ Memberand Dork
9/21/22 7:47 a.m.

To VolvoHeretic: it is not a case of the splitter touching the ground removes ALL downforce, just that it reduces the downforce by a very large portion (~30% is typical). The downforce is generated by the air reacting on the bottom surface at increased local speed. On the flat vs curved surface question, there is a case to be made for non-flat surfaces, but the first 90% of performance can be had with a simple flat shape. After that testing and development are required to get the rest.

To jfryjfry: On the trucks, the splitter is just under 1/2" thick so it does have some stiffness benefit over thin materials. However, the material spec'ed for the Truck series is not the stiffest stuff out there. It does deflect. Setting the trucks up to just touch the splitter to the ground is typical, but generally only happens on the first few laps with low tire pressures. The peak downforce occurs with the splitter not touching the ground (by a small amount, less than 1").

I post this while I am waiting for the wind tunnel to give me the green light to start my test this morning...

Johnny_at_NineLives
Johnny_at_NineLives GRM+ Memberand Reader
9/21/22 6:21 p.m.

In reply to VolvoHeretic :

we need air to make aerodynamic parts work. we can reduce the amount of airflow to manipulate the speed of said air. But if we seal off the airflow (by touching the ground), we are working in a vacuum and have no air to make the parts work. 

Johnny_at_NineLives
Johnny_at_NineLives GRM+ Memberand Reader
9/21/22 6:26 p.m.

In reply to jfryjfry :
also, NASCAR is another level. they generally want as little drag as possible. Because 200mph. also their splitters are quite short (depending if we are talking about cup or Xfinity). They will do things slightly differently than club racers should. One thing is for sure,  no matter the class the height of the splitter is very important to downforce. The lower the better, but once it touches the ground you lose all downforce. get it low but not too low.    

 

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