Mounting of rear wings to bootlid

mx5gem · Postby **mx5gem** » Mon Nov 25, 2013 5:16 pm

I'm planning to get a 3D wing, and the mount points are too narrow to mount anywhere but the bootlid.
I've noticed a lot of the mx5 track cars running at Wakefield use the Mania style 3D rear wings and most are just bolted straight to the bootlid.

Reading on the big forum suggests you would be mad to mount just to bootlid as the forces will dent the bootlid bigtime, yet so many on here seem to do just that with no apparentl side effects.
(And these are on the front running cars too, not just tail enders who may be running no AOA)

Can anyone with a bootlid mounted spoiler offer first hand advice on this please...

ja9 · Postby **ja9** » Mon Nov 25, 2013 5:30 pm

Yes I've done exactly that, boot mounted with no apparent issue. I felt the same as you but it was too much trouble and money to do it the "proper way".
So if the front runners are boot mounting theirs why are you concerned. It may distort the boot eventually but better than cutting it up. It was hard enough for me to drill 4 holes in a perfect boot but does look the goods when done.

mx5gem · Postby **mx5gem** » Mon Nov 25, 2013 11:02 pm

ja9 wrote:Yes I've done exactly that, boot mounted with no apparent issue. I felt the same as you but it was too much trouble and money to do it the "proper way".
So if the front runners are boot mounting theirs why are you concerned. It may distort the boot eventually but better than cutting it up. It was hard enough for me to drill 4 holes in a perfect boot but does look the goods when done.

thanks ja9,

Nice to hear you have done it with no issues. What AOA are you running?

I was/am concerned cos many suggest that it's a recipe for disaster, and was wondering if there was underboot bracing or similar, and hence why i'm wanting to hear from those that have successfully done it.

M1474 · Postby **M1474** » Tue Nov 26, 2013 3:26 am

What wing is that ja9?

Patrick Bramston · Postby **Patrick Bramston** » Tue Nov 26, 2013 6:50 am

I squeezed some aluminum checker plate on the under side of the bootlid between the stock bracing and the bootlid and bolted through it.. the bootlid does deform but is surprisingly strong.This is also not my original bootlid.

Magpie · Postby **Magpie** » Tue Nov 26, 2013 8:03 am

Here is my install on the boot.
http://mx5cartalk.com/forum/viewtopic.php?p=697984#p697984

This thread I started to test the AOA of the rear wing. However the greater the AOA the greater the drag. I will be repeating these tests soon as I have changed the splitter as well as the engine so I need a new baseline. Note the Drag coefficients are for my car and yours may not be the same.
http://mx5cartalk.com/forum/viewtopic.php?f=30&t=58238&hilit=+drag+coefficient

Drag coefficients (Wing Angle):

00 Deg: 0.25293
05 Deg: 0.36337
10 Deg: 0.34050

Wing 0 Deg (F/R ride height)
000 Kmh 98mm 118mm
110 kmh 106mm 117mm
130 kmh 103mm 115mm

Wing 5 Deg (F/R ride height)
000 Kmh 98mm 118mm
110 kmh 100mm 114mm
130 kmh 105mm 113mm

1mm on the front is approx 24kg downforce and 1mm at the rear is approx 12 kg. So my results show that with a splitter the best AOA is Zero deg as this causes the least amount of lift at the front. Accordingly the splitter needs to be re-designed (it has) to generate some downforce. However I do not have any base data for a stock MX5 NA6.

I hope this helps.

david_syd_au · Postby **david_syd_au** » Tue Nov 26, 2013 9:50 am

I have a CF wing on my track car, which looks very similar to one on Ja9's car.
It has 4 bolts through the boot and is positioned so that 2 of those bolts pass through both the boot lid and the bracing. There are no other mods to the boot lid.
There was some deformation of the boot lid surface when the wing was fitted and tightened down, but no obvious change since then.
The wing is set to 4 degrees, relative to flat ground.
The car has a mostly stock 1.8 and doesn't see over 180 km/h at any of the local tracks.
Note one inconvenience is that with the wing fitted the boot lid will no longer stay open, even though I have used cable ties to tighten the springs.

ja9 · Postby **ja9** » Tue Nov 26, 2013 12:55 pm

M1474 wrote:What wing is that ja9?

No sure as it came with the car. It maybe the same as the ones sold by Mx5 Mania.

I started off running approx 9 degrees AOA at SMP South and had no issue with understeer but when I went to WP there was a huge amount of understeer. So I backed it off to < 1 degree and made some small adjustments to the coilovers and now everything works well.

lightyear · Postby **lightyear** » Tue Nov 26, 2013 4:47 pm

I mounted my wing of the side of the car, where the bumper meets the quater panel. The boot mounted wing does work, but I was using a thin carbon fibre boot this time. My boot that I used previously has pretty big dents in it from the wing force pushing down.

You need to make a pretty decent front aero treatment to be able to use any advantage the wing will give.

rascal · Postby **rascal** » Wed Nov 27, 2013 12:37 pm

lightyear wrote:My boot that I used previously has pretty big dents in it from the wing force pushing down.

Was that from the 3 element wing you were using?
I think the OP and all the others mentioned are single element 3D wings, which wouldn't have anywhere near as much downforce generated.

lightyear · Postby **lightyear** » Wed Nov 27, 2013 1:04 pm

Yes, that wing has unbelievable amounts of downforce. I made the end plates to also be the wing uprights. I pushed on it after it was all together with all my weight and it flexed a little. But at the track with it set at 0 degrees, it snapped the fasteners, and bent the alloy end plates. So I redid it at the angle it dropped to, and mounted the extra support rods closer in to stop the alloy bending. And, took the 3rd element off. Top speed was still about 200kmh, but it really needed a big splitter to take any advantage of the wing. It had plenty of under steer going up the hill at Luke heights.

On a plus, I bought some 6mm hollow core alcubond to make flat floors, front splitters and diffusers.

mx5gem · Postby **mx5gem** » Wed Nov 27, 2013 1:35 pm

Thanks to all the responders. Sounds like it will be ok with just boot mounting.
I doubt I'll see as high a speed as Patrick's car would and his survived so gives me confidence to just do it..

lightyear wrote:You need to make a pretty decent front aero treatment to be able to use any advantage the wing will give.

Will this do? Not my car, just what I will be copying..

NB.jpg

rascal · Postby **rascal** » Wed Nov 27, 2013 2:08 pm

Something like the front of 949s crusher would be better, with an airdam as well as the splitter, but understand if you dont want to mess up the front of your car.
The one you posted would be easy to remove and leave no evidence behind. (though might need some reinforcement with cables/stays at the front.)