How to Get Downforce on a Lemons Budget

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.

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Floating Doc (Forum Supporter)
Floating Doc (Forum Supporter) UltraDork
4/24/20 8:31 a.m.

Good article, needs more Fox.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) Dork
4/24/20 10:00 a.m.

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) 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) MegaDork
4/24/20 11:14 a.m.
sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
4/24/20 12:31 p.m.

In reply to frenchyd :

sleepyhead the buffalo
sleepyhead the buffalo 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.

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) Dork
4/25/20 3:50 p.m.
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.  

frenchyd
frenchyd PowerDork
4/25/20 4:11 p.m.

In reply to sleepyhead the buffalo :

Or instead of hours spent guessing unknown numbers, build a few different "wings" and turn them upside down and  go out and test them.  
There are number crunchers and if they have valid data they can do an excellent job. On the other hand  working with low cost materials  gives absolute results.  Sort of like when you go to the eye doctor••• is this better than that ? 
At the Grass roots level we don't all have to have masters degrees  in aeronautics. Even with a masters  degree that doesn't translate  to actual effective construction. 
 

I like foam but dealing with load points could potentially lead to fracture points.  But it's probably worth while making one wing completely out of foam, Put a layer of fiberglass cloth over it  and go out and try it.  
Remember the Wright Bros.  guessed at a lot of things in building their gliders and first planes.  

frenchyd
frenchyd PowerDork
4/25/20 4:22 p.m.

In reply to sleepyhead the buffalo :

'It's been way too long since the Navy taught me aeronautics. ( 1967-68 ) and most of what I studied I forgot once the test was over. 
 But even an AT6 trainer weighed a lot more than  the cars we tend to race.  Somewhere around 5000 pounds if my memory hasn't run off.  
lifting 5000 pounds off the runway requires something like 20 pounds per square inch and if I remember stall speed correctly for that SNJ  I flew ( Navy designation for an AT6 ) 87 mph?
  I'm guessing even  the fastest tracks frown on speeds much higher than that so if we  put that profile into a 5 foot wing span at say 40 MPH   We are somewhere around 350 pounds down force. 
Extended into clean air  say a foot in front of the body work  we'd have something approaching 7-800 pounds of down force at 40 mph ?   I'm guessing at a lot of stuff here. So there will be people correcting me.  But at least they will be looking things up instead of relying on 50+ year old memory. 
 


 

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) Dork
4/25/20 6:57 p.m.

You can use wood spars or carbon fiber tubes etc to reinforce foam.  It's done all the time in RC.  Some models turn at well over 20gs and that's when you find out if your construction is good.

 

You can also get NACA airfoil data online and know your drag and lift coefficients at various angles of attack.  I will post kore tonight or tomorrow.  It's family dinner night.

 

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
4/27/20 3:57 a.m.
frenchyd said:

In reply to sleepyhead the buffalo :

Or instead of hours spent guessing unknown numbers, build a few different "wings" and turn them upside down and  go out and test them.  

Remember the Wright Bros.  guessed at a lot of things in building their gliders and first planes.  

No frenchyd.  Just, no, no, no, no, no, no, no, no, no.  They didn't guess, they did the opposite of that... they sought out the best knowledge, and they tested... and when the tests indicated the data was wrong, they made more tests and corrected it.

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
4/27/20 5:48 a.m.

also, it should probably be said, that the easy button is probably to go forum supporter 9LivesRacing, and roll your own via...

https://9livesracing.com/collections/all/products/the-builders-big-wang-spec-your-own-size

https://9livesracing.com/collections/all/products/universal-diy-mounts-pylons

or via 'the offcut method'...

https://9livesracing.com/collections/all/products/mini-wangs-are-back

christinaylam (Forum Supporter)
christinaylam (Forum Supporter) New Reader
4/27/20 7:18 a.m.

In reply to sleepyhead the buffalo :

+1 for 9 Lives! Budget friendly aero makes a huge difference. 

kevlarcorolla
kevlarcorolla Dork
4/27/20 9:00 a.m.

In reply to frenchyd :

I thought the navy used boats?

AnthonyGS (Forum Supporter)
AnthonyGS (Forum Supporter) Dork
4/27/20 5:55 p.m.

The Navy has more aircraft than the Air Force last I heard.

I am not advocating a foam wing but a foam/composite wing like used in model airplanes some of which way a lot more than 55lbs.  AMA suggested limit is 55 lbs and my biggest planes are about 10 lbs.

You can use MDF spars, plywood, or carbon fiber epoxied to the foam.  Then the wings are typically sheeted in lightweight balsa and then finer glassed.  It makes for a much lighter, much stronger and better surface quality than a built up wood wing.  They are also easier to repair.

Typically a foam wing will have spars and wooden leading and trailing edges.  They add rigidity and are easier to shape when the composite sandwich is complete.  

Pick your airfoil based on lift and drag properties.  You "could" have different airfoils to change downforce and drag for different tracks.  You can also change angle of attack to change downforce and drag up to a point.  

A good start on airfoil data are the various NACA databases.  The data are recorded in stations percent.  So you pick your "chord" or airfoil length at 10 inches or so.  The airfoil will tell you in percent of chord the percent above and below the centerline for each station.  By picking a known airfoil you can know drag, center of pressure, coefficient of lift and acceptable ranges for angle of attack.

I actually have a few great books on airplane design if you want to go nuts.  Yes, I have built and flown airplanes where I started with blank paper amd a pencil.  One modeling book is actually highly valued by aeronautical engineers it is do good.  Street value last I checked is textbook price for a paperback.  

After you choose your airfoil, chord, width and get your core, you will need to make spars.  You can simply glue some carbon fiber strips down and add leading/trailing edges, but I'd probably go with MDF for a car wing.  I might add a few CF strips too.

I'd actually cut the core vertically and probably insert a full height MDF spar right at the center of lift for that airfoil.  

Then I'd probably do carbon fiber strips in front of and to the rear (half way forward and aft) the full length.  Then I'd cut the core front and rear off and add MDF leading and trailing edges.  

Then since its a car, I'd do fairly thick balsa skins.  These skins are made joining balsa sheets on edge and cut to shape.  Once glued on you can stack them in the opposite shaped foam blocks and make a weighted sandwich or you can vacuum bag it.  Then you sand it to final shape.  Then you glass it.  

You will end up with a better to spec, lower drag, lighter, stronger wing than you can make from any wood.

Airfoil database:  http://airfoiltools.com/search/index?m%5Bgrp%5D=naca4d&m%5Bsort%5D=1

Links on this page for installing spars and sheeting a foam core.

http://www.eurekaaircraft.com/foamwings/

If I had a dedicated track car, I'd probably build aluminum uprights and have them drilled for one chord length, multiple angles of attack and mounted to the car at even spacing.  I'd probably start with a NACA 0009 and 2412 airfoil and rock on.  If I needed something with more downforce than an upside down 2412, I'd check the database for something less symmetrical. I'd do a convex high lift airfoil before a flat bottom too, less drag in some cases and more downforce (when flipped).

Oh and here are some of my planes, some built some bought.  

kevlarcorolla
kevlarcorolla Dork
4/27/20 6:26 p.m.

I have a couple very big wings built exactly as you described.....vertical spar at the cop cnc cut(hollowed to save weight) and foam cnc'd to match.

 Mdf trailing edge insert,wrapped in glass on the cheap.

Schump
Schump New Reader
4/28/20 10:47 p.m.

In reply to MotorsportsGordon :

Nice work boys & girls (IDK who your team is comprised of and I figured it's best to cover all the bases.)

Been there, done that!

My experience was a few years ago.  GOD it makes me feel old to say it was Virginia Tech's 1996 Formula SAE car, the 1st ever FSAE car to have semi-active aero.  Carroll Smith was lead design judge for several years, we couldn't convince him of our supsension design philosophy but certainly learned a lot from him and had every one of his books in our shop.  (Tune To Spin, Prepare To Crash, Engineer To Explode, Drive To Wreck, and the only one we didn't name in the shop, Screw To Win.)  RIP Carroll (BTW, he was Carroll Shelby's manager in CA after racing for John Cooper in Europe.)

 

We also used a 4'x4' sprint car wing which we bought new @ assembled in our shop with seemingly 1k rivets.  The front was mounted solid to the roll bar, the rear suspended by surgical tubing on aluminum tubes a la a shock absorber, one tube slid inside the other.  I can't remember our max angle of attack as we ran an autocross course in the parking lot of the Silverdome during the autocross & endurance event.  The max angle was 25-30 degrees, and she flattened out to a 0 degree angle of attack when we hit max speed on the course straightaways for reduced drag ~55-60mph.  (We didn't bring the old huge radar gun the local Blacksburg police gave us, the same kind that cause a much higher incidence of testicular cancer in cops back in the day when they'd leave their guns in their laps in between shooting speeders on the road.  Live & learn...)

 

If you were wondering the genesis of the name, MEAT was aptly named because she was 620 lbs, or about 100 lbs heavier than the top 20 cars in competition. We overbuilt damn near everything as result of not finishing for the past few years in the endurance event which typically has an attrition rate of 75-80%.  What do you expect?  You take a car that is allowed by the SCCA to run in A-MOD and make it run for half an hour with 1 driver change half way through.  Inevitably, it was either cold AF in DEEtroit in May or hot as a mamma jamma.  I remember in 1996, it had to have been 90F+ and 100% humidity the day of the endurance event.  Victor Seaber was a team leader as well as our suspension designer.  Y'all might recognize the name, he won GRM's Ultimate Track Car Challenge a few times.  Speaking of weight, T00L, our 1997 car was 524 lbs, and it was the most Carroll Smith said he'd seen a team lose in one year.  I remember we lost 2 maybe 3 lbs in rod ends alone.

Brandon Thomas was the other driver and team leader.  He said that when Vic handed over the car, the 250 degree F VDO temp gauge was pegged, and he could feel the motor getting really tight and damn near locking up when he was driving, so he had to back off.  Regardless of this bump in the road (the coolant system design left a BIT to be desired, it was like how you cheated in Contra on Nintendo 30 years ago) we finished 3rd in dynamic events & 5th overall out of 82 schools.  My best year on the team out of the four years I was on the team and went to competition.  (I was lead machinist sophamore year.)

 

Now next year I really want to build a GRM $2021 Challenge car!  It would be especially cool to get a few VT Formula SAE team members involved, although Brandon and a few others are busy as NASCAR engineers and Chandler is in the UK on a F1 team.  (That kid was really smart!)  Plus my roommate has built up quite a machine shop so building stuff wouldn't be too hard, and my co-worker is a bloody amazing TIG welder too.

 

More pix from the same Brock Yates article in the December 1996 edition of Car & Driver about our friends entitled "RIT Kisses Its Sister" aptly titled as they were 2nd place overall 2 or 3 years in a row.  I know it's copyrighted material, I gave the source, and John Roe did all the photography.

 

 

 

FYI I bought two copies of this via ebay at different times (I lost my original I bought 5 years ago) so it may still be available if you want to read it.  I think I checked C&D and they no longer offer back issues this far back.

frenchyd
frenchyd PowerDork
4/28/20 11:49 p.m.
kevlarcorolla said:

In reply to frenchyd :

I thought the navy used boats?

The Navy has ships called Aircraft carriers. They also have smaller versions for helicopters and VTOLs.  Plus Helicopters for cruisers and Destroyers. 
Not to mention aircraft for all the Navy Land bases around the world.. Training planes.   Oh, and patrol aircraft  to track submarines  etc. plus all those drones.  Don't forget the Marines are part of the Navy and they have lots and lots of planes.  

Yes the Navy has more things that fly than things that float.  In fact the Navy probably has more planes then the Air Force and  China combined. 

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