DIY Spoiler

[JohnnyBomber101]

Okay, I have not been able to find a spoiler online that I like enough to spend several hundred dollars on. So, i decided I would make one myself.


I contacted Derrick at DJRacecars out of London and we had a little mental pow-wow over the best spacing and horizontal spacing for a truly effective wing for a Yaris. These guys have done a lot of Lupos, Citreons and Opels for every level of racing you can imagine. Their rally bodies are really awesome.

Anyway, his opinion was that the "best" placement would be slightly below (3-4mm" the actual termination of the roof line at the hatch. The company has done extensive work with Mitsubishi designing the ever so slight changes in the rear vortex generators on the MR series of the EVO. He sent me a cool pic showing what they do and why. Utilizing the generators on a notchback sedan almost negates the need for a spoiler unless the positioning of the leading edge of the foil is in the correct place. You can see from the pic that the factory spoiler is not needed on a car equipped with the generators.

On the Yaris, my intention is to use both the generators and the spoiler. By flattening out the airflow and feeding it directly on the wing, a tremendous amount of force will be able to be created that will only increase with speed.

So, let's talk about the wing. Because the shape of the car has an inherently low co-efficient of drag, a dive plane and leading edge will not be necessary. I am simply going to round the leading edge off and leave it flat. The top plane will be flat and the control surface (aileron) will be a uniform, full length upward bend at 31degrees. Why 31? Because that is the "magic" number that mother nature decided on when figuring LEMAC and MAC. Plus, there technically will not be a chord to the shape because we are not trying to create a pressure differential.

Materials:

6" x 40" 5052 Aluminum plate (5" flat with a 1" aileron)
3/4"x3/4"x3/16" 6061 Aluminum L channel (36" long piece)
12"x12"x3/16" 7075 Aluminum Plate

I drew the patterns for the brackets and the endcaps last night and I built a prototype out of cardboard. Check it out:

[marcus]

interesting.... may not be as effective when its raining...lol..

[JohnnyBomber101]

A lot of those random pieces of card board are for bracing to make sure the shape stays in place.

Here are the patterns for the endcap and bracket:

[marcus]

good luck with the project bro..

[JohnnyBomber101]

What the hell? My pic resizing does not seem to be doing anything for how huge these are, sorry!


You might have noticed the "speed holes" in the bracket. Those are there to save on precious ounces of weight and also to look cool. The pressure that the downforce will create is actually absorbed by the "neck" of the bracket. The size and placement of the holes keeps them completely out of the area that has any pressure on it. The mock-ups I made are out of a New Balance shoebox and I was able to put a 5lb Yoga weight on the wing and it did not bend or break. If anyone wants the actual, super technical explanation just let me know.

The main wing will be 5052 because there will need to be a little flex to compensation for the endcaps. The brackets I am making out of so-called aircraft grade aluminum because I do not have a mill, so I will be using WD-40, my Roto-zip, Dremel and hole saws for this project.

To attach the L-brackets, I am going to through drill one of the L's and the bracket and then tap the opposite bracket for a machine screw to go through and hold it all together. This probably sounds confusing, but as I build this I will take all kinds of pics.

That is as far as I have gotten as of this morning. I am trying to find someone in VA Beach with a metal Brake so I can get this bend done properly. I could do it with a couple of 2x4's and a protractor, but I am only willing to go so shade tree...

Oh, and here is that pic of the generators.

[JohnnyBomber101]

Oh, laugh it up Marcus!


Thanks, I actually miss prototyping. But then again, blowing stuff up is a lot of fun too!

[JohnnyBomber101]

I just realized this should be in the Cosmetic Exterior section! How do I change that?

[Klink10]

I like the effort and will be a fan till the end. Very interested. Think aluminum might be heavy in the long run but a mold for a fiberglass application well....hmmmmm.

[Midnight Drifter]

I would totally rock one of those.

[Klink10]

Thought about this last night and would like to see how this would attach to the car. Any mock up pics with it on the vehicle?

[JohnnyBomber101]

I am actually building this here in Afghanistan! My wife sent me a bunch of pics and I could photoshop a drawing on there, would probably look pretty hokey though.

I have been doing a lot more design work on my off time and I just got a series of tunnel test pics from DJ for a Suzuki SX-4 body that they built as a Rally Car. The top "shell" has a 10degree down slope which is very similar to the Yaris 9degree. The wing they ended up using was a pedestal mount that was used in conjunction with a set of 1" Vortex Fins (like on an EVO). The AOA was a 15degree bite 3" above the terminal line of the roof, 7" aft of the VG's. This put the full length of the aileron directly mid-way in the flat stream flowing off the rear of the car.

My original idea was to put the 31degree lip 1degree above the mid-way and allow the flat flow from the VG's to create my low pressure. However, looking at the results of the SX-4, it seems pretty obvious that the spoiler would do very little in the intended, original position.

All, that being said, my NEW plan is to mimic these results to some extent. I am re-designing the brackets into pedestals and I have decided to definitely go with the VGs. I am going to have to noodle out the math and see what my AOA is going to have to be since the chord of the roofline is almost 9" shorter on the Yaris than it is the SX-4. That will make my Lead Main Aerodynamic Chord quite a bit more forward than I had originally theorized. It is going to take me a little bit of time to figure this out. It has, unfortunately, been a few years since I have gotten this much into the weeds on prototyping!

I can not get the pics to upload on the site and Paint does not recognize the file type. I will forward them to my wife and see if she will upload them for me...no promises though.

I will keep you updated as I fumble my way through this. I will also make sure to post all my templates and cut lists in case anyone else wants to build one. Right now, unless I come up with some crazy 3 or 4 tier design, the total cost with shipping is $73.46 for the aluminum and the ABS. I have not priced the hardware yet, but that will not be that much more. I feel confident is saying that this will stay under $100 and it will be an actual functioning wing.

Just as a last bit of info, with a 0degree pitch on the endcaps and the total surface area of the wing, this design should produce right around 2.5g of down force at a peak speed of 110mph with just over 1g of nominal drag. I have all the numbers if anyone wants them. I am far too lazy to just randomly transpose them from my notebook unless someone is truly interested.

As always, I am very interested in everyone's opinion of this and if anyone knows more about this than I do or someone sees a flaw I am not recognizing, please let me know so I can correct here at the beginning and not waste too much time, cool?

[Klink10]

You keep driving on with what you are doing. Stay safe.