re-enforced hatch

[Hiitman]

this is for those of you that use aftermarket wings for what they're made for. question is, do you re-enforce the hatch or just straight mount it up. if i had my car here i'd be looking instead of asking but any input would help.

 

[roadrunner2176]

Straight mount it on the surface. Underside, cut yourself some 2x2 or 3x3 1/8 inch sheetmetal squares. Run your bolts through the plates on the underside than put on your washers, locknuts, and bolts.

You should only have to do this on the front mounting bolts, the rear is already reinforced, but if you can get to it, do it there as well.

 

[Hiitman]

awesome thanks

 

[1stGenRocks]

Really if your going to reinforce the back too the plate should be on the top of the hatch in the back.

 

[roadrunner2176]

Depending on how far the wing is set back, the wanted downforce would be pushing more on the rear set of bolts and pulling slightly on the fronts.

 

[Defiant]

Do a lot of driving over 200, do ya? Because if not, the "wing" isn't doing shit. You don't need to be concerned with what's holding it, nor where, so long as the bolts aren't smaller than stock.

 

[Flash]

I don't understand Defiant... Brandon Davis has a wing on the back of his Acura TSX. He races Speed World Challenge and he never goes 200mph.

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[jtmcinder]

Sorry, Defiant, but you're wrong. The wings on the backs of some SM cars (M3s) are producing 100#+ of down-force at autocross speeds (i.e., 45-60 mph). That's enough to make the method of attachment a serious issue. Problem is, the SM rules don't have any allowances for this, so the placement of the supports is important.

As close to the outer edges of the hatch as possible is the key. That's where the strength is.

- Jtoby

 

[DGajre777]

I think it has a lot to do with the angle of the roof and hatch. For example, the Evo MRs have vortex generators to make the spoiler more effective, which would make you believe that without the vortex generators and just the spoiler, it is probably not creating as much downforce - just a lot of drag and eddies.

Has anyone done any wind tunnel testing on 2Gs specifically? because unless someone has numbers on 2G DSMs, the effectiveness of spoilers can't really be compared. Talking about M3s or EVOs or 2Gs with different spoilers is like comparing apples to oranges, but I digress.

Besides, it is not what the original poster asked for...

 

[jtmcinder]

Let's be technically correct, in case this thread becomes very technical. Wings allow air to pass beneath them; spoilers do not. Wings can be placed up high where the airflow is pretty clean, especially on a hatch-back. Spoilers are often in lousy air to start with.

The M3s that are getting some decent downforce at autocross speeds do not have turbulators on the back edge of the roof, but the wings are up pretty high. I'm assuming the wing in question here would have relatively clean airflow.

- Jtoby

 

[Hiitman]

this is the wing that is going to be used. the APR GTC-200 http://www.aprperformance.com/index.php?option=com_content&task=view&id=36&Itemid=44 another question though. how do you seasoned road racers that dont have access to a windtunnel measure downforce? also any input on that wing or suggestions on others would be appreciated.

 

[DGajre777]

Let's be technically correct, in case this thread becomes very technical. Wings allow air to pass beneath them; spoilers do not. Wings can be placed up high where the airflow is pretty clean, especially on a hatch-back. Spoilers are often in lousy air to start with.

The 2Gb Talon has a high rise spoiler that allows air to pass under it and is flat to create downforce, but many people don't call it a "wing".

Some more info here, if anyone is looking for it...

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http://www.aprperformance.com/index.php?option=com_content&task=view&id=132&Itemid=44

 

[jtmcinder]

One way to assess downforce without a windtunnel is by using handling-type data-loggers. You know the wheel rates, since you chose your springs. If you add to this the various ride heights when you are going various (constant) speeds, then you can calculate downforce.

As to people calling the wing on the back of a 2Gb a spoiler ... this doesn't change the technical name, just as 99% of the Great Unwashed calling our compressor bypass valve a blow-off valve doesn't change it into one.

- Jtoby

 

[DGajre777]

One way to assess downforce without a windtunnel is by using handling-type data-loggers. You know the wheel rates, since you chose your springs. If you add to this the various ride heights when you are going various (constant) speeds, then you can calculate downforce.

Hmm, didn't know that!

As to people calling the wing on the back of a 2Gb a spoiler ... this doesn't change the technical name, just as 99% of the Great Unwashed calling our compressor bypass valve a blow-off valve doesn't change it into one. - Jtoby

Good one!

 

[jtmcinder]

Thanks.

Another point: the SM rules specifically allow reinforcing the hatch or trunk when you add a wing. Why? Because a well-designed and well-placed wing can produce a lot of downforce at even autocrossing speeds.

Not that I know the best way to do the reinforcing, so the only things I can do for the OP are say "yes, this is an issue" and "here's how you spell reinforced."

- Jtoby

 

[roadrunner2176]

Hitman

If you have any doubt about the wing, I put the same one on my other car. Here's a few pics of attachment points. If anyone wants to see other angles, just ask or pm. The wing itself is no higher than the factory 97-98 talons were.

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[DGajre777]

Hiitman, here are some pics of the wing you want mounted on a Eclipse.

 

[jtmcinder]

While I agree that APRperformance wings are very popular, most of the serious autocrossers are running the Evolution GT or GT wings, which are dual-element and flat. You don't see those wings with strange center thirds on these cars.

- Jtoby

 

[Defiant]

Sorry, Defiant, but you're wrong. The wings on the backs of some SM cars (M3s) are producing 100#+ of down-force at autocross speeds (i.e., 45-60 mph). That's enough to make the method of attachment a serious issue.

Those numbers sure sound skewed. How did they measure the force?

 

[jtmcinder]

Exactly as I explained above: suspension sensors. The wing is an APR Evolution GT. The angle of attack was something like 22*. I could search for the particular value, if you wish. But, if anything, 100# is way low.

You have to understand how much time and energy that is going into the setup of, for example, the Sias and Bimmerhaus M3s. They had to do most of it from scratch, since the known work on the subject is aimed at road racing (i.e., much higher speeds and cars not set up to be loose at low speeds).

- Jtoby