APR wing mount question
 

So I am looking at upgrading my current extruded aluminum dual-element APR wing to something with a better profile. There are a lot of used carbon skin APR wings available out there for not much money.

My wing mounts are already built on the car, not a trunk mount. Problem is, they are not at the usual upright attachment spacing that APR uses on their wings. So, if I get an APR wing I'll have to add new attachment points on the wing for the uprights.

I did this on the aluminum wing I have now and it was pretty straightforward, just a matter of rivets and skins. But I have not done this on a composite wing. Based on what I have seen the composite wing skins are really thin, and there is usually a foam core to contend with. So I am thinking it will require something different, like bonded-in hard points for hardware attachment.

Anyone ever done this? I'm looking for suggestions. Note that valid responses do not include "Just buy Emilio's GTC wing and be done with it."

Are you looking for Miata specific wing or the universal one ?

Wondering if 42,5" can fit at the edge of trunk/quarter.

Any pictures of your current setup?

Universal

It is a rear panel mount with the wing mount pillars about 12" apart.

Only thing that is important here is how to relocate the mount points on a composite skin APR wing.

Make it happen, Mr. Engineer. I know you do a lot of aero work, lolol.
https://www.miataturbo.net/attachmen...ine=1329094130

Ok, so what I'm guessing you're referring to, is the threaded inserts the upright's attach to. This particular GTC-300 has two sets of upright mounts seen here:

https://www.miataturbo.net/attachmen...ine=1329157487

I take it, you want to place your own upright mounting points on the wing/airfoil itself in a spot that lines up with your existing mounts on the body?

I think you would have to drill through the airfoil and do a nut and bolt attachment to do it securely, but I doubt you want to hack up the wing like that.

Or, I think you'll need to drill the airfoil to a particular depth, and epoxy a threaded insert/bung into the spot you need it to be. I imagine the original threaded inserts in the APR wings are installed this way, but who knows how exactly. This goes without saying, but whatever way you decide to affix them to the wing though, has to leave you 100% certain and confident, that wing won't separate at those insane loads it surely sees.

Yep you got it, that is what I am after

Yes, exactly.

Yes not good for aerodynamics. More importantly though that would crush the core and screw up the wing profile unless the hole was sleeved.

Yes I am looking for someone who has done this. Threaded inserts are common practice for honeycomb core composites, not sure if that works here or not. But yes depending on the AOA and the speed the loads can be huge, hundreds of lbf. so it needs to be a strong connection.

Maybe I should just call APR tech support.

Yea give them a call and see what they say.

I was in a similar boat; wanted to grab one of the many cheap used GTC wings out there for sale, but most of them have a mounting base width greater than the 41" miata trunk span. Contemplated epoxying in some custom inserts, maybe even adding a layer of carbon over it and then drilling it out again, but after all said and done, figured it would be a safer move to just buy the right wing to begin with. GL!

It would be way easier to modify the mount as it come up to the wing, think L bracket.

Where are these inexpensive APR wings you guys speak of and how can I get my hands on them?

I had called APR and got a price on putting new threaded inserts in a new location on my wing and they quoted me $70 plus shipping. They are more than happy to put the inserts in the correct location witch will make it easier to mount to your current bracket. I will assume there will still be some sort of adapter needed. From your mount to the wing.

It would be a really big L-bracket I think.

OK thanks for the info.

You know, looking at that picture of the APR GTC wing above, the inserts look kind of like rivnuts. That is what APR used on the aluminum wing I have now.

Really good info there I wasn't aware of... gonna give them a call tomorrow myself...

Called APR today... rep said GTC-300 wing's have their uprights permanently rivet'd and epoxied to the airfoil itself... The GTC-200's have threaded inserts that can be redone for about $40...

Could swear the GTC-300's have threaded inserts too... the pic I posted of an APR wings underside with the threaded inserts I thought for sure was a GTC-300...

Tex post pics of your rear :) seriously the rear of your car.

I just got off of the phone with them as well. I called them during lunch. The rep told me that on the older GT wings they just used rivnuts riveted to the skin. I asked about the GTC series and he said they do the same thing there, although I did not specify a 200 or a 300. So it could be different between those two like they told you.

He cautioned that when installing the rivnuts it has to be done very carefully to keep from overstressing the carbon material. Good advice. A carbon composite is more fragile than an aluminum skin of course. I would probably also bond the insert to the core for good measure regardless.

If rivnuts work I would rather DIY than hassle with the shipping.

I'll show you my rear anytime you sexy man you.

https://www.miataturbo.net/attachmen...1&d=1329246425

You can see that the wing mounts are just a bit wider than a US license plate. This mount was a lot of work to fabricate and install. Plus it is very strong and stiff (by design) so I am not going to toss it just to accommodate someone's wing mount points.

Ok, so i just called APR again and spoke with someone a bit more knowledgeable.

According to him, on the 300 series wings, they can remove the riveted bracket and upright assembly from the airfoil. They can then move it further inboard or outboard, but not ANYWHERE along the width; the bottom of the apr wing is such that they can only place the upright/bracket in a few spots.

Furthermore, they recommend you buy new brackets and/or new uprights, to rivet back into the new location. Not completely necessary. This extra hardware was in the $150 range I think. Labour is about $40.

Furthermore, if you're buying an old or worn wing, they say they cannot guarantee successful overhaul of the mounts. Wing might be too 'worn out' and fragile to successfully transfer brackets around.

Tex, I'm curious why your not going for the Nascar wing?

Those wings are really nice but they are expensive ~$600 IIRC. I am not concerned about the weight difference (NASCAR wing is super light). Something with a more efficient L/D ratio than what I have now would be good.

I've been shopping for used GTC-200s and 300s as well.

Used GTC 200 and 300's will probably run $600 or more though, no? Nascar wing being under 600 doesnt sound too bad.

Actually I am looking at a COT wing right now. We'll see what happens.

Interesting side note... When I was researching the COT wings, I found a paper from some Engineers that had done aerodynamic modeling and flow testing of those wings. The premise of the paper was to show whether or not there was significant uplift when the car is traveling backwards (AOA is the wrong way). In other words, when the car spins and slides down the track backwards, does the wing lead to the car becoming airborne? Turns out the wing created significant upward lift, or at least took a lot away from the net rear downforce. Thus it was deemed a hazard. I do not follow NASCAR, but apparently that is the reason why NASCAR got rid of the wing on the COT and went back to trunk spoilers.

It is not a problem for us going say 140 mph and spinning on a long straight, but for a NASCAR traveling backwards at 200+ MPH it is a problem. Aerodynamically, that is a HUGE speed difference. Interesting, I do not think I have ever seen this discussed in an aero oriented race series like F1, ALMS, whatever. I guess they know more than the 'hick moonshine runners' do :giggle:

So I found a COT wing for less than $500 shipped and it is on the way. I will still need to move the mount points on it as well so I'll post up the results of that if anyone is interested.

What's this COT wing exactly?

Google, how does it work?
https://www.miataturbo.net/attachmen...ine=1329862514

COT = Car of Tomorrow ~ NASCAR effort to modernize vehicle aerodynamics

COT wing is a one-design $3000 carbon composite wing made by Crawford Composites for NASCAR COT cars. Well designed, well constructed, good L/D ratio (better than my dual element aluminum APR wing). Interchangeable end plates made for different tracks (road course, ovals). NASCAR dropped the wing and went back to spoilers for the aforementioned reason of backwards flow uplift.

Ergo, inexpensive bad-ass wings available for relatively very cheap prices on the used market.

Contact me if you see one on the cheap.

$400 - Damaged
(Looks like the duct tape fix worked for NASCAR)


If you don't care how the repair looks, that could be a DIY fix. Not sure if that's really enough of a deal over a new GTC-200 though...


Bird

I've started a trend...too bad there aren't more available. Remember, there are two different versions of the wing, one for show and one for function. More tech here...

https://www.miataturbo.net/race-prep-75/new-wing-test-62253/

Key points:
1) should have CNC aluminum finish on ends(with end plates off)
2) built in slot for wickerbill.

If it does not have these elements, it is a wing built for show only!

Yes kudos to Ryan for coming up with this approach. As much as most of us road racers generally dislike NASCAR, it is ironic that in effect we are being partially subsidized by them with this wing purchase.

What did you end up doing for this? It seems you have the ability to make custom mounts, why not make new angled uprights that a universal gtc will mount to? Ill try to cad what i mean when i get back to the office, but essentially make uprights that mount to your current license plate width then flare out to the 42.5" span to bolt to the gtc uprights. You would retain the turnbuckle adjustment of the gtc

I changed my mind about my previous suggestion. The width it would need to span in order to go from 12" to 42.5" without making the wing too high in the air would make the angle pretty small. Instead, you could eliminate the apr mounts altogether and make something like this to bolt up to the available mounts on the wing. I'm not sure what wing you're getting or the details on how it mounts etc...but maybe this will give you a few ideas.

I forgot to "dimension" the angle, but a quick calc yields something around 31.24 degrees.

https://www.miataturbo.net/attachmen...ine=1330462524

Monkeywinky yes I could do that but without at least some truss cables it is not going to be as structurally stable or as stiff as what I have now. Plus, between the cables and the above brackets, the additional cross-sectional area compared to what I have is going to add drag, not to mention disturb the flow over the wing. What I am doing now is less obtrusive.

BTW you need to go start a post in the meet and greet section.

I like how your current mounts are done. I am building my wing mounts now, and I'm trying to tie it directly into the chassis/cage, while meeting some other requirements.

Are you mounting the wing below the roofline?

What I like about the rear-end mounted bracket, such as those you have now, is how it situated the wing 6" rearward, effectively putting more leverage on the chassis so to speak.

I wonder how far back you can mount a 3D airfoil like GTC-300 and have it still function properly...
Or do you use a straight foil once you're really far past 'trunk mount' range (what a 3D airfoil is designed for afterall)... but i suppose it depends on height too...

The main reason I went with the rear mount is that I plan to add a diffuser later on, and the low pressure zone under the wing augments the performance of the diffuser.

There is a downside to using leverage to weight the rear axle more. It also unweights the front more than if the wing was mounted closer to the rear axle.

Indeed, but if you're getting that heavy into the rear wing game, you should definitely be addressing front aero as well.

I have a tubular front frame/rad support, that all my coolers hang from, as well as a very strong front splitter mount, so in my particular case I think I can take advantage of the leveraged wing out back.

Front aero is already in place. I have a DIY air dam and a big splitter, also well mounted. I can stand on it in fact.

So emilio posted this pic of new 2D APR wing with custom bumper mounting.

This is EXACTLY how I plan to mount my GTC-300; I'm going to build a tubular section off the rear frame rails and bolt up-rights through the bumper skin into the tubular frame underneath. Going to keep it pretty low though.

https://www.miataturbo.net/attachmen...ine=1331009247

Is this the same Crawford wing you guys are referring to?

http://www.casc.on.ca/forums/showthread.php?t=24740

I'd give Emilio a call about the mounting location of the 3d wing. I talked to him before making my custom risers and he had some great info about how high to mount it, and how it will effect your AOA.

It looks similar but is not exactly the same. The aluminum insert plates are different. Also mine does not have the slot in the end plate for removal of the Gurney flap nor the retainer latch. The attachment plates for the mount also look a bit different.

That is all somewhat superficial though. I cannot tell from the picture if the profile and the chord are the same as the COT wing. They look similar. From the ad though it is a Grand-Am GT wing for a Porsche so it is a different application completely. Only way to know for sure is to call Crawford and ask them.

It looks like a nice wing. Personally I am too cheap to pay $1500 for it.

It is same design but the grand am wing is longer and the mounting holes are a bit different...other than that...yes. One of the guys I talked to when shopping around is selling his remaining COT wings for $350 I think. I'll see if I can find that info.

Here is his info:

Crawford Composites Carbon Fiber Nascar Cup COT wing

approx. 57"x11"

have different types of end plates

excellent condition

reduced to 450 plus shipping

bosco022022 at yahoo dot com