How to Get Downforce on a Lemons Budget

Staff
By Staff Writer
Apr 25, 2020 | lemons, Low-Buck Tech | Posted in Features | From the Nov. 2018 issue | Never miss an article

Story and Photography by the Staff of the 24 Hours of Lemons

What do you do if you want a fancy wing but your team doesn’t have the money? If you’re competing in Lemons, you improvise.

For Team Sticky Man from Alabama, that meant scavenging in the aviation world. The rear wing on the team’s Nissan 200SX SE-R is fashioned from a Piper airplane’s aileron. Custom oversized “FAR-RARI” wing supports match the valve cover and intake found on the car’s SR20DE engine.

If aviation salvage yards aren’t your thing, you can always grab wing ingredients from a regular yard. Just look at Tennessee team Knoxvegas Lowballers: Their Mercedes-Benz 560 SL, known in Lemons circles as Sputter, sports a rear wing fashioned from the front clip of a 560 SL parts car. A blank piece of aluminum covers the down-facing fascia to form a flat wing surface.

Sputter’s owner even wired up the wing’s signal and hazard lights.

Like what you're reading? We rely on your financial support. For as little as $3, you can support Grassroots Motorsports by becoming a Patron today. 

Become a Patron!

Join Free Join our community to easily find more lemons and Low-Buck Tech articles.
Comments
Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) GRM+ Memberand UltraDork
4/24/20 8:31 a.m.

Good article, needs more Fox.

Guys, I am also into RC airplanes.  There is a place in Arkansas called Eureka foam.  They will cut you any sized foam wing any profile you want in foam for a reasonable price.  Fiberglassed foam is very light and strong.  A lot of RC models use foam core wings how due to it's favorable properties.  I had never thought about using them for auto use until I saw it advertised on their website as a potential.  I bet they are cutting cores for more people than you think.  Heck it could be covered in carbon fiber if you want it to be really sexy. 

 

chaparral
chaparral Dork
4/24/20 10:09 a.m.

Plywood ribs, a spruce spar, and polyester cloth were good enough for airplanes for sixty years...

MotorsportsGordon
MotorsportsGordon HalfDork
4/24/20 11:02 a.m.

here is your easy way 

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
4/24/20 11:05 a.m.
AnthonyGS (Forum Supporter) said:

Guys, I am also into RC airplanes.  There is a place in Arkansas called Eureka foam.  They will cut you any sized foam wing any profile you want in foam for a reasonable price.  Fiberglassed foam is very light and strong.  A lot of RC models use foam core wings how due to it's favorable properties.  I had never thought about using them for auto use until I saw it advertised on their website as a potential.  I bet they are cutting cores for more people than you think.  Heck it could be covered in carbon fiber if you want it to be really sexy. 

 

that's a freaking excellent tip! THANK YOU!

quick perusal of their website shows a 66" span 16" chord flat bottom wing comes in at $45. That's pretty reasonable for a good size wing, very similar to the plywood ones I made for the AMC (7.3 sq ft!), even on a challenge budget. You'd still need the fiberglass, but nice.

 

frenchyd
frenchyd PowerDork
4/24/20 11:12 a.m.

In reply to The Staff of Motorsport Marketing :

If you want down force, build a wing. Sitka spruce and a fabric covering  is all it takes  to build a wing that will fly at much greater speed than  most ( cheap ) cars can drive around a race track. 
If you're on the north west coast or up in Alaska Sitka spruce is cheap and readily available.  
Here is the Midwest  a semi decent alternative is blue spruce followed by white pine ( heavier and less strong.  But  I would use Luan plywood.  It's really really cheap. Cuts really really easily. Glues up reasonably well and there are ways to make it dramatically   stronger without spending a lot of time or money. 

The profile ( cross section)  choice you make should follow an airplane wing. Heck,  go on line and pick something out.  A Piper Cub gives lots of lift at relatively low speed. A  F 104  will give less lift at speeds. For number crunching type guys you should be able  to turn it all into a formula.  
Increase it or decrease it to whatever your gut tells you. Bigger more lift ( or anti lift if you mount it upside down )  smaller less lift. 
Make a template and repeat it.  Look at how kit wings are made and follow that template. Then select a fabric. Make your life easy, but it from Aircraft spruce.   Slide it over and then shrink it with a heat gun .  You might want a stronger leading edge with all the debris kicked up on a race track. Thin sheet of aluminum screwed into the ribs should provide that.  
Mounting points should be simple.  Don't get clever and mount it at an angle. Keep it flat, it will have lower drag. At an angle it will stall at slow speeds so right when you need the most down force you'll have the least. 

Robbie (Forum Supporter)
Robbie (Forum Supporter) GRM+ Memberand MegaDork
4/24/20 11:14 a.m.
sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand Mod Squad
4/24/20 12:31 p.m.

In reply to frenchyd :

sleepyhead the buffalo
sleepyhead the buffalo GRM+ Memberand Mod Squad
4/25/20 5:47 a.m.

so, there's a bit of a 'hidden genius' in using an aileron for your wing... because they often designed to be either 'end mounted' or 'hung' off to semi-span tabs to rotate around.

an issue with 'following how airplane wings are made'... is that aircraft wings work a bit backwards to how race car wings are used.  Aircraft tend to have a centralized 'main mass' and wings that come off of that symmetrically (not always, and yes... fuel, engines, and struts... can 'complicate' that simplification).  So the FBD of a wing is that all of the Lift, Drag, circulation, twist, bending moment, etc., loads are resolved at the wing-body junction.  Thus, structurally, wings are generally described as 'fixed at one end cantilever beam'.

Some model aircraft wings take this setup into account, and thin the spar as it goes out to the tip.  Some don't include this complication to reduce parts/complexity.  But, it is something you should keep in mind if you're following 'and aircraft wing buildup' to make your own wing, because...

Race car wings are generally 'fixed at two point' beam setups... with the point of fixation varying along the chord depending on the installation.  trunk mount, means two fixed mounts... say 3/4 semi-span out from the center... and that's where the lift/twist/bending moment stuff is resolved... and thickest part of your beam should be at.

Generally, this probably means you can get away with 'constant structure' beam for your spar... but you'll be able to generate more force from your wing 'model a/c size wing' than most models do... the heaviest AMA legal models are 55#s, and those models will have bigger wings that what we're proposing for race cars, iirc.

one of the biggest challenges to this type of building is that the chord for most race car wings are in the 5-10" range.  Most airfoils for race cars fall in the 10% to 18% maximum thickness range (that being a percent of maximum chord).  So, you'll have a main beam who's height is 1/2" to 1.8" tall in order to hold upwards of 900#s of downforce (outside case, of a 10" chord wing, 70" span, at 150mph and Cl of 3).

Doable?  Definitely
Can you 'just follow how an aircraft is built'?   Probably not without some analysis and number crunching.

chaparral said:

Plywood ribs, a spruce spar, and polyester cloth were good enough for airplanes for sixty years...

Foam is lighter and easier to shape.  

You'll need to log in to post.

Our Preferred Partners
naJQEjB5UfZmzYmWordESJPdgRi3mTzVdMzJr5Uvgok7gq3490ZlKWVPShKM2ONm