Non APR rear wing options

[Hobby Racer]

I'm looking to purchase the rear wing for my 818R. I rather like the straight style like the APR GT-250 but was wondering if anyone had some other options I should consider before laying out the $1600 bucks APR wants for their wing!

Any ideas?

[jkrueger]

I'm in the same boat with my Daytona coupe. The APR wings just cost too much. I decided to try and build my own. I found a RC airplane company that will cut the wing shape out of EPS foam. There are a few companies that sell all the materials and tools needed to do a carbon fiber or fiberglass lay up. Google/Youtube university has lots of info on how to do it. I figured $600 for materials and new tools to do a 69" wide single element wing. I have one more project to finish on my race car then I will start this project. I am planning on doing a write up in the Coupe section of this forum.

JC

[Hobby Racer]

I thought about doing my own wing as a wet layup but I do not have an accurate way to create the form. Is the RC airplane company you are using creating the foam core with a CNC mill?

[CdnCarNut]

A long time ago, I helped a buddy make foam cores for wings using a hot wire. We had wing profiles on each side of the foam with numbers running around the perimeter so we could synchronize our movement by counting out the numbers as we each passed them. The cool thing was that this also worked to make a tapered wing by using a different size profile on each side of the foam block. IIRC, the foam was about 4 feet wide and the hot wire was about 5 feet wide. (Think of a huge violin bow with a single steel wire with a lot of current running through it.) We managed to make two sections and fused them together then added a composite spar along the length for strength before covering the outside. Total cost was insignificant -- mostly labor.

[jkrueger]

I thought about doing my own wing as a wet layup but I do not have an accurate way to create the form. Is the RC airplane company you are using creating the foam core with a CNC mill?

I think he is using a hot wire. See the picture below. In the back ground you can see the block it is cut out of.

IMG_4500.jpg

[DSR-3]

I've seen nice results from the DIY foam/hotwire core (with a stringer as I recall) method.
Also great work from Hurley Racing Products and Dauntless

[Hobby Racer]

I think he is using a hot wire. See the picture below. In the back ground you can see the block it is cut out of.

IMG_4500.jpg

That profile looks great! I am interested in your process. How do you plan to create the wing from the foam core?

Also, where did you get the profile from?

[Sgt.Gator]

The problem with wings is trying to get the actual wind tunnel data on them. APR does the best job of publishing that data, the rest seem to be in the "it looks good so it must be ok" type aero testing.
If you're going cheap, Megan Racing makes a dual element aluminum wing, $155 msrp, $115 most dealers. The Main element adjusts on the base, the Secondary element has it's own range of adjustment. I've used it on a couple of cars. It's heavier than an APR carbon fiber, but not too heavy. ( Megan Racing makes carbon ones too, but not in the dual element.) For $115 it's a heck of a wing value.

http://www.meganracing.com/product.asp?prodid=773

[Hobby Racer]

The problem with wings is trying to get the actual wind tunnel data on them. APR does the best job of publishing that data, the rest seem to be in the "it looks good so it must be ok" type aero testing.

I know what you mean there, APR is the only one that I've seen that published any kind of wind tunnel data!

If you're going cheap, Megan Racing makes a dual element aluminum wing, $155 msrp, $115 most dealers. The Main element adjusts on the base, the Secondary element has it's own range of adjustment. I've used it on a couple of cars. It's heavier than an APR carbon fiber, but not too heavy. ( Megan Racing makes carbon ones too, but not in the dual element.) For $115 it's a heck of a wing value.

Wow, that's beyond super affordable, thanks for the link. I may just try it. If I don't like it at least I don't have a lot of money tied up in it.

[jkrueger]

That profile looks great! I am interested in your process. How do you plan to create the wing from the foam core?

Also, where did you get the profile from?

I'm going to lay the CF directly on the foam core then vacuum bag it. Mount (either mechanically and/or with panel adhesive) an upright mount to it. Mold in some nut sleeves into the edges for the wing end panels.

Finding the profile I wanted, I started with the database listed below, but there are just too many there to browse through, so I googled "high lift low reynolds number.

Here are my resources for finding the wing profile:

A data base of wing profiles
http://m-selig.ae.illinois.edu/ads.html

A website that searches that database and gives lots of info on each profile
http://airfoiltools.com/search/index...=14&yt0=Search

The profile I'm using:
http://airfoiltools.com/airfoil/deta...rfoil=s1223-il

A master thesis on the s1223 profile (lots of good data)
http://scholarworks.sjsu.edu/cgi/vie...ext=etd_theses

JC

[Hobby Racer]

I'm going to lay the CF directly on the foam core then vacuum bag it. Mount (either mechanically and/or with panel adhesive) an upright mount to it. Mold in some nut sleeves into the edges for the wing end panels.

I assume you will be using pre-preg carbon fiber for your wing to encapsulate the foam core, so now I have some questions:

1. Are you going to have any internal structure to distribute the load on the wing and give it additional bending strength?
2. Will the foam hold up to the ~300 degree temps during the cooking phase?
3. How do you keep the thin foam perfectly flat during the whole process?
4. How many layers are you planing and what's the total thickness going to be?

I hope you will post lot's of pics in your thread when you start this. BTW what's the thread URL so I can follow it?

Also, great info on the profiles!

[Hindsight]

I've heard REALLY good things about these wings: http://www.goodaero.com/
Supposedly the quality, and the airfoil are incredible. They aren't extremely expensive, but they aren't super cheap either.

I have not heard really good things about APR's wings.

[Hobby Racer]

I've heard REALLY good things about these wings: http://www.goodaero.com/
Supposedly the quality, and the airfoil are incredible. They aren't extremely expensive, but they aren't super cheap either.

Wow, looks like a nice wing, I have emailed them for info and pricing.

I have not heard really good things about APR's wings.

What have your heard? I have not heard anything good or bad.

[johngeorge]

Not sure if this is any cheaper, but take a look at http://rhrperf.com/

[Hindsight]

What have your heard? I have not heard anything good or bad.

This, for one:
https://www.vadriven.com/forums/auto...d-away-340064/

[Hobby Racer]

I've heard REALLY good things about these wings: http://www.goodaero.com/
Supposedly the quality, and the airfoil are incredible. They aren't extremely expensive, but they aren't super cheap either.

I have not heard really good things about APR's wings.

Talked with Rob at Good Aero today. Great wing and it performs better than the APR GT-250, due to their 14" cord length. But, man at $3,199.00, I'm going to have to pass

[Hindsight]

Speed costs money. How fast you wanna go?

Sorry, I couldn't resist!

[DanielsDM]

This, for one:
https://www.vadriven.com/forums/auto...d-away-340064/

That is a sobering video. A few F1 drivers died in the late 60s/early 70s when they first started using aero. Changes made to increase downforce without considering what the extra force will do to the structure and when something fails it turns ugly. Thankfully cars and tracks are a lot safer today.

[jkrueger]

I assume you will be using pre-preg carbon fiber for your wing to encapsulate the foam core, so now I have some questions:

1. Are you going to have any internal structure to distribute the load on the wing and give it additional bending strength?
2. Will the foam hold up to the ~300 degree temps during the cooking phase?
3. How do you keep the thin foam perfectly flat during the whole process?
4. How many layers are you planing and what's the total thickness going to be?

I hope you will post lot's of pics in your thread when you start this. BTW what's the thread URL so I can follow it?

Also, great info on the profiles!

Not going to use pre-preg. Going to wet lay it up and then vacuum bag it. I'm going to use a room temp epoxy resin with a 2hr pot life to give me time to get all the layers in. I don't know if the foam can handle oven heat which is why I am going to use a room temp epoxy plus I don't have an autoclave.

The foam is pretty rigid even out at the thin part so I don't think it should move. I have been thinking about the process of how to lay up the layers and I think I am going to hang the wing horizontal (leading edge up) so I can drape the layers over the wing. I am counting on the stickiness of the resin to hold everything in place until I can get it bagged up. I am going to cut the fabric a bit long so my "seam" will be off the trailing edge of the wing. I'll then trim that off once it sets up. I'll see how that works when I do some test lay ups.

The only internal structure I was thinking of is moulding in some .030" AL sheet under the upright mounts to help distribute the load on the foam. The foam has a 1000 lb per square foot load ability so it is pretty stiff. Once the CF is on it should be a lot stronger as well. The guy that cut the foam could only do 36" pieces. So I'll also have to do something internal where the two pieces join together. Reading the RC plane forums, it sounds like they just use gorilla glue to bond the foam together. I think once the CF is laid up it will be real strong in both compression at the upright mounts and flexing in the long axis. If I decide to put a beam in it a piece of AL channel would work. Even if the wing produced a 1000 lbs of down force (I don't think it will even produce 500 lbs after reading that article) that is only 1.19 psi on a wing that is 70"x12". The foam itself can handle 6.9 psi, so once the CF is on it should have a lot more compressive strength. I am going to use a something like a 2"x8" piece of .060" AL to mount my upright mount to. Then this will be bonded to the wing. So that is 32 square inches of bearing surface. Using 500 lbs of downforce number the wing structure will need to support 15.6 psi. I have an race engineer friend that is going to help me determine if I need a beam or if CF and AL plates will be enough.

I was planning of 3 layers of CF. Layer one with the weave lined up square with the wing, layer two 45 degrees to that, and layer three square with the wing again. That will be about .036" thickness.

I will post lots of pics once I start the process. I'll post a link here once I get started. Hoping to get going next month with it. I'm almost done with my winter projects on my chump car (new containment seat, fuel cell, and stiffer springs).

JC

[DSR-3]

Don't underestimate the loads.
On my last DSR, I had a 60" x 12" pro made CF wing, end mounted. It felt really stiff and secure- sitting still. When I saw pictures of the extreme flex at ~120mph I was amazed! I could never bring myself to push on it that hard by hand. I added a center strut. Also keep in mind the added loads of mounting it high. I've seen plenty of wings that shook violently back and forth.
Your numbers for the foam core seem extreme. Typical foam core is super light and non-structural. It's purpose is to support the CF/epoxy matrix that is the structure.
Definitely consider building in a stiffener in your first effort.
I've never made a wing, but have made a few other CF/epoxy layup parts including some really nice big wing mounts/endplates with a glass finish on one side and weave on the other.
Go for it!

[jkrueger]

Don't underestimate the loads.
On my last DSR, I had a 60" x 12" pro made CF wing, end mounted. It felt really stiff and secure- sitting still. When I saw pictures of the extreme flex at ~120mph I was amazed! I could never bring myself to push on it that hard by hand. I added a center strut. Also keep in mind the added loads of mounting it high. I've seen plenty of wings that shook violently back and forth.
Your numbers for the foam core seem extreme. Typical foam core is super light and non-structural. It's purpose is to support the CF/epoxy matrix that is the structure.
Definitely consider building in a stiffener in your first effort.
I've never made a wing, but have made a few other CF/epoxy layup parts including some really nice big wing mounts/endplates with a glass finish on one side and weave on the other.
Go for it!

The 1000 lbs/sq ft is compressive load. You are right that it doesn't take much flexing to break it long ways. I think you are right in putting in a beam or two to help with longwise flexing. My wing will be just below the horizontal line off the top of the roof on my coupe. The uprights are about 10" tall.

JC

[Sgt.Gator]

This, for one:
https://www.vadriven.com/forums/auto...d-away-340064/

I hadn't seen Phil's wreck before, thanks for the link.

Although I wouldn't condemn APR wings as bad because of this incident. I look at it as more of another "Experience" type learning (see my signature below) about mounting a wing designed to go behind a sedan rear window (hence the curve in the middle) on non APR extensions up high in the airstream. Did the wing break because the extensions weren't stiff enough to hold it steady? Did having it mounted to the trunk lid (which was fine for the amount of downforce in the normal position) induce flex in the trunk lid that amplified thru the non APR extensions and cause vibration that broke the wing under extreme load? We don't know.

APR has hundreds or possibly thousands of wings being used on race tracks all over the country. I'd have to see some evidence of them failing in "normal" mounting situations before I would be worried about them.

[Hobby Racer]

I ended up ordering the 67" APR GT-250 wing. I did get a great deal online at $1080. Almost $600 less than APR wanted for it if I bought it directly from them.

[Sgt.Gator]

If anyone is interested this NRG wing just popped up in a Scratch & Dent sale from my wholesaler. It's got some scratches on it.





They describe it as:
*CONDITION: NOT THAT BAD
*PACKAGING: NOT ORIGINAL OR DAMAGED
*SCRATCH AND OR DENTED : YES
Length: 69in
Rack: 7in x 14.75in
Width: 15.25in

This is a no return, no refund item, so if you want it I'll send more images.

The normal dealer price is $490, and some charge shipping on top of that.
I can have it shipped to you via FedEx ground for a total of $345.