Which spoiler works best?

[Michael]

So evidently...

 

(1) different-looking (and different-named!) spoilers tend to produce similar results.

 

(2) production of downforce is fairly easy, but getting the downforce without extra drag is not so easy.

 

This suggests, in my view, the value of testing a "simplified" spoiler (straight piece of sheet metal) with adjustable inclination angle. Generating lift and drag data vs. inclination angle, one would have a table from which to select the optimal setting for a given application - be it highway cruising, road racing, drag racing etc.

[260DET]

Hi John / OTM (everyone):

It is certainly contrary to what Car & Driver found in their tests in 74.

 

Stock:

140 lbs of Lift on front wheels @ 70mph

20 lbs of Lift on the rear wheels @70 mph

 

BRE Front Spook canceled 105 lbs of Lift and increased gas mileage by 0.4 mpg

BRE Street Spook (no brake ducts) canceled 115 lbs of Lift

 

BRE Rear Spoiler added 75 lbs. of down force @ 70 mph and 0.2mpg

 

C & D custom 7" rear spoiler (at 50 degrees from horizontal)

Added 160 lbs of down-force to the rear but off loaded an additional 20 lbs from the front. It also hurt gas mileage by 0.6 mpg.

 

 

FWIW,

Carl B.

 

Thought that the Car & Driver rear spoiler lay @ 30 degrees from the horizontal and actually reduced drag, as well as giving down force. Maybe there was another one?

EDIT: Reading back, there were several, shutup Richard

[capt_furious]

(I'm putting this in an existing thread instead of starting a new one...)

 

I really like speedgato's spoiler, both from the shape / looks standpoint and the execution. It's got a nice hand-fabbed no-nonsense look to it, and from the look of it, it's inexpensive. Attachment is straightforward, just a series of what looks like bolts through the back lip of the hatch.

 

 

(apologies to speedgato for using the photo without asking first, in the sake of expediency)

 

Downside, it's non-adjustable.

 

This could be fixed, however, by using a piano hinge along the edge and NASCAR-style spoiler braces...there's not much real estate to attach the braces on the lower edge.

 

 

I'm not a fabricator by any means, but I LIKE this design and would like to replicate it with the above changes. Anyone have suggestions as how to best do it?

 

speedgato, any chance you could post a template of some sort based upon yours?

[rturbo 930]

I am also a big fan of speedgato's spoiler. In addition to what's posted above, I'm wondering if he reinforced the lip of the hatch, since it doesn't look too sturdy as is, at least to me. If it's necessary, I was thinking of welding in some bracing from the bottom of the lip, all the way across it, to that flat piece on the hatch where the latch is mounted. Hopefully that made sense. I checked on my parents 280Z, and doing such a thing shouldn't interfere with the hatch closing properly.

[capt_furious]

I'm going to give this another poke. Anyone care to lend a hand in getting a design like speedgato's refined into an adjustable version and put together?

 

My idea is to use the same basic shape, put a split down the middle and attach another small piece to the forward face of one of the halves to cover the resulting gap. Both halves would attach to the hatch lip via aircraft piano hinges, and the whole thing would get two NASCAR style braces per side. Countersunk aircraft screws would be used.

 

I checked my hatch, and it looks as if there's room for a strip on the inside as a reinforcement, so the rear lip of the hatch could be sandwiched by the hinge and bracing piece, with bolts / screws going through.

 

I'm going to get some chunks of cardboard and start mocking up how I think it should be done. There's a warbird restoration shop at the local airport and they might be interested in doing a quick fab job once I've got it sorted out.

 

Tell me I'm crazy. It'll give me something to disprove.

[johnc]

I guess I'll chime in here because I've built a few adjustable spoilers. Here are some tips:

 

1. You need at least a 15 degree angle between the adjustment rods and the spolier itself for the adjusters to work.

 

2. Given the size of the Seedgato spoiler example you need to figure on about 200 lbs. of drag/downforce and must design accordingly.

 

3. ALuminum sheet metal is fairly flexible so a single piece part will work in most cases, even if there's a small curve in the mounting surface.

 

 

EDIT: Deleted the examples. The site doesn't like hot linking. Go here and scroll through the images from the San Diego Solo2 NT. You'll see lots of examples on pages 7, 8, 9, 16, and 17.

 

http://www.pbase.com/bryanh/sdtour08

[capt_furious]

Thanks, John! What gauge and grade of aluminum would you suggest? Should I split the hinge / brace instead fo the spoiler itself to make up for the curve?

 

Pulling results from the C&D article and adjusting from what was discovered in the windtunnel, I'm shooting for a 30 degree from horizontal, 6 1/2" tall spoiler...I suppose speedgato's spoiler is serving more as inspiration than than a pattern at this point. Since my Z is a daily driver, I'm going after better fuel economy and highway stability, with the capability to pour it on when I want to.

 

At 30 degrees, it should split evenly with the braces for 15, unless there are other factors I'm not taking into consideration.

 

...this thing may end up looking...funky.

 

Side note, just so people know I'm aware of it: I need to duct my airdam to the radiator support while I'm at this or I'll just be pulling weight off the front. Bad juu juu.

 

(and John, those images didn't load)

[JMortensen]

I had considered making something like this too. I had thought of using a piano hinge across the hatch and the turnbuckles as well. My thought was that the hinge might just be flexible enough that it would still function despite the curve at the tail end of the hatch. For the actual spoiler I was thinking Lexan or Acrylic, although sheet aluminum would work too.

 

One thing I was concerned with was that the autox rules say the spoiler must not extend past the body. I would think that would mean that with a 280 the spoiler can extend beyond the rear of the hatch maybe 4 or 5 inches due to the bumper, but not quite as far on a 240. Anyone have any firsthand experience with this issue?

[johnc]

Pulling results from the C&D article and adjusting from what was discovered in the windtunnel, I'm shooting for a 30 degree from horizontal, 6 1/2" tall spoiler...I suppose speedgato's spoiler is serving more as inspiration than than a pattern at this point. Since my Z is a daily driver, I'm going after better fuel economy and highway stability, with the capability to pour it on when I want to. At 30 degrees, it should split evenly with the braces for 15, unless there are other factors I'm not taking into consideration.

 

 

Kinda like this:

 

 

 

 

[johnc]

I would think that would mean that with a 280 the spoiler can extend beyond the rear of the hatch maybe 4 or 5 inches due to the bumper, but not quite as far on a 240. Anyone have any firsthand experience with this issue?

 

Correct. See the examples I posted above.

[capt_furious]

Kinda like this: *pics*

 

...interesting approach! Height and angle look about right. I wanted to avoid coming straight down into the hatch from above, but that gives me a few more ideas. Putting the piano hinge on the surface of the hatch instead of the lip and putting just the braces through the lip would help spread out the pressure. One of the problems I've got is that the sheet metal on my hatch around the latch button is warped, and flexes up and down easily. Putting it on the lip would prevent the spoiler from making that worse, or being affected by it...now that I think of it though, that arrangement would put the braces at less than an ideal angle.

 

Looking at the photos of the Solo2, most of those spoilers seem to have an inward curve. Is that achieved with bracing, forming, or a combination of the two? A dilemma with the piano hinge idea would be preventing a reverse of that form, having it bend downward at the outer edges and 'spilling' the air over them because of the upward curve toward the center. You'd have to use longer braces on the outside edges and force them upward.

 

I need to make some cardboard forms before I think myself into a corner any further on this...

[Z-TARD]

Here's some pics of the one I made for the dreaded "Pinks" 280Z. It's shaped roughly after the spoilr on the Cobra Daytona coupe. Though not adjustable, it was sturdy enough that the team was able to push the car by grabbing the edge of the spoiler. I don't remember the exact thickness of the part, it was either 3/16" or 1/4" plate. Total weight was about 5 or 6 pounds. It wouldn't be too hard to make an adjustable version of this using a hinged mount and some turnbuckles on the backside. The spoiler would probably have to be moved forward on the hatch about 4 to 5 inches to create some space behind it to mount the turnbuckles to.

 

 

With mounting hardware installed, lots of countersunk screws up top with large washers and locking nuts below.

 

I have no idea what happened to this part once the car was parted out, hopefully someone is finding some use for it. I plan on eventually building another one, adjustable this time, for my own car. With my current work ethic, this will probably happen within the next 10 years or so...

[260DET]

Kinda like this:

 

 

....................................

 

 

 

Thats sort of like the one I have in mind. Except that the back piece would be removeable so that different length/height pieces could be used, depending on car use eg road or circuit.

 

Incidentially, from the information on the subject in Competition Car Aerodynamics it appears that the downforce (high pressure area) from such a spoiler may extend back up the hatch on a S30 to near the hatch glass.

[capt_furious]

Wow, that's thick. Funny, first thought I had was, 'Looks like a Cobra Daytona'. Looks as if there's some curve in the bend. How was that done?

 

I'm getting better ideas of how I want to do this. I don't think I can mount it the way speedgato did if I want adjustability, there's just no room for braces if I want a decent angle on them. Looks as if I'll unfortunately have to drill down through the top of the hatch. Since I'm not going to autocross any time soon, I can take some license with positioning / overhang.

 

 

Here's a mockup that I did in Illustrator/Photoshop on my car. Dark area is the spoiler, light area is the hinge. Braces are obvious. The question is, will it hold weight, and how thick / rigid should the material be?

 

 

Depending on the angle / height, it might look taller from behind.

[Carl Beck]

EDIT: Deleted the examples. The site doesn't like hot linking. Go here and scroll through the images from the San Diego Solo2 NT. You'll see lots of examples on pages 7, 8, 9, 16, and 17.

 

http://www.pbase.com/bryanh/sdtour08

 

Hi John:

Can you tell me who/which "The site" is? The site we are on or the site you are pointing us to?

 

Secondly - what is meant by "hot linking" - I'm not certain I understand what it is that the site doesn't like.

 

thanks,

Carl B.

[johnc]

Can you tell me who/which "The site" is? The site we are on or the site you are pointing us to?

 

Secondly - what is meant by "hot linking" - I'm not certain I understand what it is that the site doesn't like.

 

The site I was referring to above is the site hosting the pictures (http://www.pbase.com). Hot linking is where a poster like me or another web site links directly to an image on another site. Pbase.com's web site has to load the image every time someone comes here to HybridZ and looks at this page. That drives up the usage on Pbase.com and increases their web hosting costs.

[Z-TARD]

Wow, that's thick. Funny, first thought I had was, 'Looks like a Cobra Daytona'. Looks as if there's some curve in the bend. How was that done?

 

I'm getting better ideas of how I want to do this. I don't think I can mount it the way speedgato did if I want adjustability, there's just no room for braces if I want a decent angle on them. Looks as if I'll unfortunately have to drill down through the top of the hatch. Since I'm not going to autocross any time soon, I can take some license with positioning / overhang.

 

 

Here's a mockup that I did in Illustrator/Photoshop on my car. Dark area is the spoiler, light area is the hinge. Braces are obvious. The question is, will it hold weight, and how thick / rigid should the material be?

 

 

Depending on the angle / height, it might look taller from behind.

 

The flange on the spoiler was cut at a slight curve to accomodate the curve of the hatch. After that I clamped the material to a large welding table so that only the flange hung over the edge, and bent it gradually using a large crescent wrench. I worked from both outer edges towards the middle, it took about an hour of levering on the wrench combined with some hammer work using a dead blow mallet. There was a little warpage once it was bent, but it wasn't too bad to correct by reclamping the part and twisting it back to shape slightly.

 

For thickness, I wouldn't go with anything less than 1/8" for aluminum when used in a flat design like this. If it's going to be capable of generating up to 200 pounds of downforce, then I would think of it more in terms of building a shelf capable of holding 200 pounds of weight. Granted, a certain percentage of the downforce generated will be acting directly against the hatch surface rather than the face of the spoiler, but overbuilding never hurts.

[johnc]

Incidentially, from the information on the subject in Competition Car Aerodynamics it appears that the downforce (high pressure area) from such a spoiler may extend back up the hatch on a S30 to near the hatch glass.

 

Did you notice that the poly rear window braces are inside the window on my pictures above? I saw a lot of inward bowing of the poly window (away from the original outside mounted braces) during some testing at Willow Springs.

[johnc]

For thickness, I wouldn't go with anything less than 1/8" for aluminum when used in a flat design like this. If it's going to be capable of generating up to 200 pounds of downforce, then I would think of it more in terms of building a shelf capable of holding 200 pounds of weight. Granted, a certain percentage of the downforce generated will be acting directly against the hatch surface rather than the face of the spoiler, but overbuilding never hurts.

 

FYI...the one I built above was .050 (16 gauge) and it worked just fine up to 150 mph. Weighed about 2 lbs.

[capt_furious]

Good to know. Any thoughts on how that mockup looks? Not enough braces, bad positioning, etc?