can someone explain to me why spoiler reinforcement plates work?

[kolosy]

I'm looking at this piece from Burkhart: https://burkhart-engineering.com/sho...-fuer-gts-gt4/

...and I don't get the idea here. If you're trying to spread the downforce load over a larger area, how are plates that sit *underneath* the trunk lid going to help? What am I missing?

[omgzirra_exe]

Originally Posted by kolosy

I'm looking at this piece from Burkhart: https://burkhart-engineering.com/sho...-fuer-gts-gt4/

...and I don't get the idea here. If you're trying to spread the downforce load over a larger area, how are plates that sit *underneath* the trunk lid going to help? What am I missing?

the alu trunk is very weak when you add weight (downforce) its really just to prevent damage to your trunk it tends to flex. this prevents it.

you can do the same thing with just a 16gauge alu cut to size.

[kolosy]

Originally Posted by omgzirra_exe

the alu trunk is very weak when you add weight (downforce) its really just to prevent damage to your trunk it tends to flex. this prevents it.

you can do the same thing with just a 16gauge alu cut to size.

no, i get what it's trying to do, i just don't understand why it works. forgive the mspaint skillz, but why does the plate on the bottom prevent this kind of deformation?



if it sat between the spoiler support and the trunk, that would make sense -- you're spreading the load over a wider area than the foot of the spoiler and therefore decreasing the PSI. but in the under-the-trunk arrangement, i don't see what you're gaining?

[omgzirra_exe]

Originally Posted by kolosy

no, i get what it's trying to do, i just don't understand why it works. forgive the mspaint skillz, but why does the plate on the bottom prevent this kind of deformation?

Attachment 3360286

if it sat between the spoiler support and the trunk, that would make sense -- you're spreading the load over a wider area than the foot of the spoiler and therefore decreasing the PSI. but in the under-the-trunk arrangement, i don't see what you're gaining?

A good real-life test you can perform is to take a pen, a piece of paper, and a thicker material, such as a piece of cardboard.

Lay the tip of the pen on the paper and push down slowly to observe how the weight is now causing the paper to be pushed down. You'll notice that it doesn't push down in just one singular spot. it typically starts outwards then towards the point of contact.

Next, reinforce the bottom of the paper with a slightly thicker material, in this case, a piece of cardboard. Observe the same scenario again and notice that it now requires more force to push down. thus prevent deformation.

In this case, the distribution of force is now spread across a larger surface area. This minimizes stress points, which, in this case, would be where the GTS/GT4 wing is mounted. The added support counteracts the downward force applied at the top of the airfoil to the trunk. Because our trunks are made of aluminum, they are easily deformed when direct contact is made.

You sandwich the trunk between the wing mount and trunk plate because the GTS/GT4 wing mounts are bolted in from the bottom. This configuration creates pressure pushing up against the trunk, generating a clamping force and resulting in a more rigid surface.

At least that's how I look at it..

A good example is the APR wing mounts; they feature extended mounting plates to distribute force evenly, preventing deformation. Some wing mounts utilize the outermost edge of the trunk, effectively leveraging the double-layer pinch seams to mitigate deformities as well.

[kolosy]

Originally Posted by omgzirra_exe

A good real-life test you can perform is to take a pen, a piece of paper, and a thicker material, such as a piece of cardboard.

Lay the tip of the pen on the paper and push down slowly to observe how the weight is now causing the paper to be pushed down. You'll notice that it doesn't push down in just one singular spot. it typically starts outwards then towards the point of contact.

Next, reinforce the bottom of the paper with a slightly thicker material, in this case, a piece of cardboard. Observe the same scenario again and notice that it now requires more force to push down. thus prevent deformation.

In this case, the distribution of force is now spread across a larger surface area. This minimizes stress points, which, in this case, would be where the GTS/GT4 wing is mounted. The added support counteracts the downward force applied at the top of the airfoil to the trunk. Because our trunks are made of aluminum, they are easily deformed when direct contact is made.

You sandwich the trunk between the wing mount and trunk plate because the GTS/GT4 wing mounts are bolted in from the bottom. This configuration creates pressure pushing up against the trunk, generating a clamping force and resulting in a more rigid surface.

At least that's how I look at it..

A good example is the APR wing mounts; they feature extended mounting plates to distribute force evenly, preventing deformation. Some wing mounts utilize the outermost edge of the trunk, effectively leveraging the double-layer pinch seams to mitigate deformities as well.

the paper analogy doesn't work (i actually tried it out of curiosity, can post pictures if you want haha). other mount types make sense. i'm specifically thinking about this burkhart one that's just a plate from underneath.

if the whole surface of the plate was somehow secured to the trunk lid (epoxied on for example), then it makes sense. the whole plate is engaged, and you're now trying to deform a much larger piece of alu, so it's stronger. but in this configuraiton, it's just a glorifed washer. if there were lift on the spoiler, ok fine that makes sense. but i don't get the downforce piece.

or are you sayinf that it's helpful because now the entire foot of the spoiler is engaged, instead of just the two screwheads? in that case, why make it so much bigger than the foot of the spoiler?

[omgzirra_exe]

Originally Posted by kolosy

the paper analogy doesn't work (i actually tried it out of curiosity, can post pictures if you want haha). other mount types make sense. i'm specifically thinking about this burkhart one that's just a plate from underneath.

if the whole surface of the plate was somehow secured to the trunk lid (epoxied on for example), then it makes sense. the whole plate is engaged, and you're now trying to deform a much larger piece of alu, so it's stronger. but in this configuraiton, it's just a glorifed washer. if there were lift on the spoiler, ok fine that makes sense. but i don't get the downforce piece.

or are you sayinf that it's helpful because now the entire foot of the spoiler is engaged, instead of just the two screwheads? in that case, why make it so much bigger than the foot of the spoiler?

idk i thought of the paper thing because i had those items laid out on my desk LOL

I was mocking up wing brackets for my M3, and I thought, 'This could work... as an example,' but I could see why it wouldn't work as an analogy just made sense once I put the cardboard under.

You should see the M235Ir wing brackets used on the M235iR race car; it has a pretty neat support piece for the trunk.

And yeah, that BK mount is just a giant washer to support the underside of your trunk.

As far as the downforce goes, if you have this wing, go and press on the wing with some force and see how much force it requires to flex the trunk. I think the GTS/GT4 wing generates minimal downforce, but enough to deform the trunk without the support underneath.

you don't need such a large surface area like burkhart uses dj_dub has a good alternative with just a strip of metal. see below.

the M235IR wing support is the image below the E90M.

[bigjae1976]

Actually, the issue is the wing pulling up on the trunk lid. The rear of the wing support is pushed down but the front is pulling up on the trunk lid. So extra material makes sense especially for the front.

What you really need to do is make the rubber bump stops on the trunk lid solid and reinforce any spots where the trunk lid bump stops come into contact with the chassis sheet metal.

[Redd]

Originally Posted by kolosy

if it sat between the spoiler support and the trunk, that would make sense -- you're spreading the load over a wider area than the foot of the spoiler and therefore decreasing the PSI. but in the under-the-trunk arrangement, i don't see what you're gaining?

The plate is to spread the load on the attachment bolts over a wider area. It's not meant to carry the aero downfoce acting on the wing.

[omgzirra_exe]

Originally Posted by bigjae1976

Actually, the issue is the wing pulling up on the trunk lid. The rear of the wing support is pushed down but the front is pulling up on the trunk lid. So extra material makes sense especially for the front.

What you really need to do is make the rubber bump stops on the trunk lid solid and reinforce any spots where the trunk lid bump stops come into contact with the chassis sheet metal.

this i forgot about the front mounting point haha i literally stare at that on my trunk every day too...

[kolosy]

Ok, that makes sense. And that 235 mount is intense.. might try to mock something like that up.

[roastbeef]

you want the wing to be as rigid as possible. you're just spreading the load as much as possible. since most uprights are angled with two bolts, if you're pushing down on the rear bolt, you're pulling up on the other. a wider footprint simply helps increase rigidity.

[kolosy]

this is interesting.. was re-watching the video clip of the GT2 drive by from the main forum, and noticed how the spoiler is mounted here



hard to tell from the video clip if it's mounted topside to the quarter panel, or sitting inside the seam, but regardless it's over a much stronger structural point than the trunk lid...

[DRLane]

Originally Posted by kolosy

this is interesting.. was re-watching the video clip of the GT2 drive by from the main forum, and noticed how the spoiler is mounted here

Attachment 3361687

hard to tell from the video clip if it's mounted topside to the quarter panel, or sitting inside the seam, but regardless it's over a much stronger structural point than the trunk lid...

That example isn’t trunk mounted at all. It’s akin to most race builds where the wing uprights are tied into the rails directly. Given the GT2 is a modified tube chassis I’m sure it’s even more complicated.

[bigjae1976]

Originally Posted by kolosy

this is interesting.. was re-watching the video clip of the GT2 drive by from the main forum, and noticed how the spoiler is mounted here

Attachment 3361687

hard to tell from the video clip if it's mounted topside to the quarter panel, or sitting inside the seam, but regardless it's over a much stronger structural point than the trunk lid...

You can mount to right on the lip for the trunk opening weatherstrip. If you can get the custom spaced mounts then this is the route I’d go. All you need to do is notch the sides of the trunk lid.

[MineralWhiteF80]

Originally Posted by bigjae1976

You can mount to right on the lip for the trunk opening weatherstrip. If you can get the custom spaced mounts then this is the route I’d go. All you need to do is notch the sides of the trunk lid.

this is kinda like what they did for the G82 M4 GT4 cars, notching the trunk lid, and chassis mounting the wing:

[reidetailing]

Curious what the solution would be to mount my Voltex Type 1S spoiler to my Seibon CF Trunk (fiberglass structure with carbon outer)?

[bigjae1976]

Originally Posted by reidetailing

Curious what the solution would be to mount my Voltex Type 1S spoiler to my Seibon CF Trunk (fiberglass structure with carbon outer)?

If its Seibon, its FG chop mat and polyester resin. You can just laminate FG mat on the backside. Better to use S-glass which has better stiffness and strength properties than E-glass.

Use a twill or plain weave, biaxial and then another layer of the twill or plain weave.