Here's update #2. So far, so good. But I think it might accurately be said that it's easy to do a lousy job cutting foam, but much, much more difficult to actually get the finished product right.

https://youtu.be/z_QnXyTOECM

My apologies for the loud tone sound (from the cutter) and my basement-level production values. :)

Damon, I got my previous wings from flyingfoam.com, and I've got to say that I've got no complaints about the company at all. I got my airfoil from a Pelicanite who goes by Peter Bull. We looked at a lot of different airfoils, and chose a modified version of NACA63-520. (And what you've done is awesome. I'm very jealous of your access to CFD equipment!)

This thread is a perfect example of why I spend time on this forum despite not posting much

I really enjoy reading about Porsche owners who are not afraid to jump out of their comfort zone and have a go at what some people may think is the impossible.

Jack, I have over 20 years of designing Le Mans 24hrs and F1 racing car wings, lost track of the count a long time ago and would be glad to help you in any way I can.

This is the last wing I did to go on a car with a roof, was a bit of a monster as wings go, from memory about 300mm chord and about 1.8m span

http://forums.pelicanparts.com/uploa...1432204146.jpg

I am suprised how nice the part (at least on vid) came out. I made the expirience that moving with the cutting tool is much more easier to control concerning moving speed and following along the profile. So I prefert to fix the foam block and move with my cutting tool.

Jack,

Thanks for the NACA info! I'm currently running a cheap, heavy, STRONG, extruded aluminum wing on my M3. The profile looks very similar to the NACA profile you mentioned and I have added a wickerbill. I chose this route after watching a video of an EVO (or maybe it was a WRX) have a high speed wing failure resulting in a very violent crash. With that said.....I still want to see if I can make a lighter wing which is more efficient. I'm assuming your wing failure resulted in no real drama?

I actually started learning CFD a number of years ago using a fairly basic home computer and running free (VirtualBox, Linux and OpenFoam) software. The higher end equipment and software is now just a perk! I'll always be a life time learner/doer.....

Cheers,

Damon in STL

Hey Damon, where did you purchase your aluminum wing?

Wow. That's one of those center-seat McLarens.

Well, watching me mess around with this stuff must border on the comical. But your offer is very generous. I built my first wing out of aluminum flashing nine years ago. Wore it out. Switched to foam cores (with an aluminum spar), and did a fair amount of 'poor man's wind tunnel' testing, which involves back and forth 100-mph runs with wool tufts, cameras, and inexpensive ride-height sensors feeding my data logger. The airfoil shape I use was worked out with the help a Pelicanite Engineer in Sweden. I'm currently playing around with a two position wing, controlled by Miata headlight motors, one position for high-downforce, the other for lower drag.

http://forums.pelicanparts.com/uploa...1157157709.jpg

http://imagizer-cv.imageshack.us/a/i...838/05tape.jpg

http://forums.pelicanparts.com/uploa...1171562803.jpg

http://forums.pelicanparts.com/uploa...1159630646.jpg

http://forums.pelicanparts.com/uploa...1159142269.jpg

My work is pretty crude. And my understanding of what I'm doing would guarantee failure if it weren't for the help I've gotten online. But the car sticks pretty well, and just barely manages to keep up with a pro driver in another street-and-track Porsche at my local track. :)

(There's a video in this link showing how I can sustain higher cornering speeds than the 991 GT3 with its all-wheel steering and other gizmos.)

http://imageshack.com/a/img537/6007/kSb5BG.jpg

I think you're right about that approach. The only real virtue of what I came up with was that I didn't need to build anything.

With the longer span of a single-piece wing, I had to bring in additional voltage (car batteries, wired together) to get enough heat in the wire. And the bowing of the line at that length was an issue in my initial test. And I couldn't control the heat enough so my wire snapped. I've got more on order, and I'm considering the benefits of a two-piece wing (31" + 31", instead of 62").

We'll see.

Hi, I don't recall where I bought it....it was maybe 5 or 6 years ago. It is a APR GT-250 if I recall correctly...but, in extruded aluminum and not carbon. APR use to have less expensive versions of their carbon wings in aluminum. I just looked and could not find the extruded aluminum versions. Looks like they are all carbon fiber now. I think I picked it up for under $400 and it weighs around 9 lbs. I'm able to put all of my body weight on the wing and dangle my feet.....about 185 lbs.

Jack, your old school yarn method may provide better info than the fancy CFD method! My plan is to at some point do the same thing while testing. Sometimes simple is much better.....

I also like the moving wing concept. I raced motorcycles a long time ago....a very effective braking device is the upright torso coming out of the bent over position while entering a brake zone. Why not do it with the wing and/or flaps? :)

Damon in STL

I took a detour this weekend.

I'm waiting for replacement NiChrome wire, and also realizing that a single-piece wing will probably exceed the capabilities of my simple hot wire setup. So, my new plan is to make a two-piece wing that will actually remain as two pieces -- something I can carry in the car and then assemble at the track like an all-aluminum two-piece one I made a few years back.

At the same time, I got the quote back from the outfit that cut my wings and it was lower than I remembered. So I went ahead and ordered a single-piece core as a kind of insurance for this whole project. It arrived in a few days, so I decided to jump ahead so I would definitely have a wing to test for my June 17 track day.

How fast can I make a wing? Pretty fast, now. Because I just don't make 'em strong enough, apparently. :)

Here's the thing that got this started. I'd reused an aluminum spar and also put a few holes into it in the construction process, and after several years of use, it snapped.

http://imageshack.com/a/img907/339/rXv0X2.jpg

So, the next spar will be thicker aluminum, without stress-concentrating holes. But in addition to the EPS foam core, I'll need mounting points and end-pieces to attach the end plates to. I traced the airfoil shape out and then drew the feet and piece that would provide support all the way back to the gurney flap.

http://imageshack.com/a/img912/1939/PpnfFZ.jpg

I cut the shapes out of thin plywood. I recently started using my jigsaw upside-down in a vise. For some jobs, it seems easier.

http://imageshack.com/a/img540/9215/ob15vV.jpg

And once I have a wood version of the shape, I've got a way to make as many copies in aluminum as I want. The trick is to rough cut the aluminum piece -- make it 1/8" to 1/4" too large all around, without having to worry about getting the shape actually right. Then I adhere the correct wood shape to the too-big aluminum version and use a tabletop router to trim the aluminum piece down to the exact shape of the wood model, using a straight-cut bit like you'd use to trim laminate for a countertop.

http://imageshack.com/a/img901/3818/a9JSI9.jpg

I hope that makes sense. Here's the router bit with its bearing-type guide following the wood shape and cutting the aluminum to conform.

http://imageshack.com/a/img912/9679/XLt2zm.jpg

This shows the conformed shape. My bit is pretty dull. But I'm cheap and don't want to replace it yet.

http://imageshack.com/a/img540/3685/oO1HxR.jpg

So, here you see two each of the aluminum parts sitting on top of the wood models.

http://imageshack.com/a/img540/2925/M6we1e.jpg

Ready to go, now. I conform some thin aluminum to the airfoil shape, and then rivet (with L-stock) the leg pieces to the thin aluminum. The weight is there while I wait for the cheap-but-slow-curing foam adhesive.

http://imageshack.com/a/img661/6995/KPgfGf.jpg

One setback. I damaged the thin trailing edge of the foam. You can see it in this picture where the aluminum gurney flap piece meets the wing near the far end. So I did my best to make up for it with a longer piece of aluminum for the gurney piece -- and later some spackle.

http://imageshack.com/a/img911/6224/9XPzmW.jpg

I use 3M structural adhesive to bond the aluminum pieces together where the spar meets the end plates and where the endplates and base pieces meet the gurney flap.

While the foam adhesive for the end pieces cured, I spackled over the damaged areas on the wing and also checked the fit on the uprights and the angle of attack.

http://imageshack.com/a/img909/6920/ZmgfHn.jpg

Now, I've never done fiberglass work. And I'm not going to start with a quick project like this. But I recently read in the RC aircraft community about using fiberglass fabrics with latex floor finish and even a Glidden primer that also (oddly) happens to be a very effective adhesive for EPS foam.

So here's the wing draped in a sheet of fiberglass fabric I picked up at a local surfboard shop.

http://imageshack.com/a/img913/6307/TmjmQu.jpg

And here it is with the primer rolled on to adhere the fabric to the wing. It will never be as hard or (quite) as strong as if I'd used resin. But it will be lighter than a resin-made piece, and stronger than the different foam coverings I've used in the past. I did test pieces with both the floor finish and the primer, and found the best bond with the Glidden Gripper primer.

http://imageshack.com/a/img540/5965/wKYgPR.jpg

Here's the thing with the fabric roughly trimmed off. Later, I was able to use a razor blade to clean all that up. But you can see the fabric pattern in the inset, which I learned after a second coat that primer is not going to fill in without MANY coats.

http://imageshack.com/a/img673/7604/PCLl28.jpg

So, since I'm lazy, I looked up a way to thicken up the primer for the next coat. I added inexpensive microballoons to make the stuff thick as pancake batter, and then used a bond squeegee to fill the pattern.

http://imageshack.com/a/img537/848/ZbRQ49.jpg

I'll have to sand this smooth. But it will be a lot easier than doing 10 coats of the unthickened primer.

http://imageshack.com/a/img538/9932/zH35Hk.jpg

Sanded, painted, and drying in the sun.

http://imageshack.com/a/img540/9518/DW8AAi.jpg

This one is significantly more rigid than the last one I made -- and still weighs less than 5 pounds.

Jack,

It looks like you have one central spar: alum tube, 3/4" dia?

Alum strip on the trailing edge and no reinforcement on the leading edge.

The skin is one layer of glass cloth with floor paint.

I wonder if that is enough strength for the (awesome ;-) downforce you will generate.

Well, there's no knowing for certain until it breaks. But I think the answer is yes. The previous wing, which I ran monthly at a high-speed track for over three years, had a thinner tube (it's 1" in diameter) and was covered with packing tape and contact paper. It failed, but only because I'd put a pair of screw holes into the spar as part of the construction and the flex of the wing finally made that weak point crack.

Now I'm using a thicker-walled 1" spar as well as a more substantial gurney flap reinforcement (1"x1/2" L stock) on the trailing end, and the fiberglass fabric, which makes the wing noticeably more rigid. I've also got better adhesives at work in this one -- a combination of EPS-foam-specific stuff and also the 3M Scotch-Weld Structural stuff. Finally, this one has a longer chord (12") but a shorter overall span (62", down from 69" on the last one), so the shape itself will be less prone/susceptible to flex.

I think even if I'd skinned this one the same way, it would last indefinitely. But I've made it stronger as a precaution.

And here it is with end plates. I also made a larger pair of them, for go-for-broke days. But this is the set that's less painful to look at.

http://imageshack.com/a/img537/2812/SRML2N.jpg

$78 for the foam core (from FlyingFoam.com)
$8 for the fiberglass
$20 for aluminum (although I had it all on hand)
$40 for primer, paint and micro balloons (although I only needed about 20% of what I bought)

That's $146 -- which is not as cheap as the ones I've done before. But still, a lot less than commercially available wings -- and I got to choose my own airfoil.

Nice job.

How do you plan on testing?

Do you think the primer you used is as strong as resin?

I don't know that testing is really needed. This is the third one I've made, and it's stronger than the other two. But absent a problem with the spar (which was my own fault, last time), this wing would work without any skin at all. Still, I'll take it out to Willow Springs next week and report back. It's possible the skin will be prone to separation from the wing's resonance. But I'm pretty confident it'll work more or less like the last one.

Necro-post... But just stumbled across this.

Jack, what are the rivets on the wing end aluminum pieces riveting together? Aren't the end pieces glued to the wing/spar?