Debating the side skirts...

[Canadian818]

Anyone else debating the side skirts? I've already ordered the kit with the diffuser, race splitter and road race wing, but I'm still torn on if I should get the side skirts. There's no question that they look awesome, but I'd be paying $400+ for a part that causes lift, taking away from the $2500 worth of other aero parts. Anyone have any other ideas? Any thought as to a how they could be redesigned to be neutral or even produce downforce?

[Mechie3]

I got them. I dont recall total numbers but thought the reduction in downforce was minimal while it improved drag numbers. I did it mostly for looks.

[C.Plavan]

I was in the same boat with my R. I didn't buy them.

It would always be easy to fabricate something if I needed to (Just cover it in CF vinyl wrap). The car is going to be low, and I scrape stuff at the track in a car that is higher. I just figured it would be $400 loss without any real benefit.

The real issue is going to be mounting the front CF splitter. I am going to make templates of it when I get it. Those are the first things to go- and $400 a pop + $150 for shipping...... don't get me started :)

[Santiago]

I wasn't aware they caused lift (or a significant amount of it). I thought they were just disappointed that they didn't do anything positive (a zero effect).

If they caused lift, do you know how much? If it's a small amount, you may find the aesthetic value is worth the cost in marginal lift. That's just a judgement call for each to make on his own. Personally, I'm with you, I LOVE the look of the side skirts...

So, that means I have also been thinking of ways to make them work. Honestly though, it's really hard to say though without having one on hand and without having access to more info from the wind tests. It's even harder to say since my knowledge of aerodynamics is quite limited. But, with what I (think I) know, I suspect that extending them out at the rear and using spats to help air get around the rear tires might help. On the underside we might benefit from a taper up towards the rear and a fence leading around the entrance to the rear tire area. Really though, if you're building an R-car, you might want to consider a vertical skirt (or extension) with a sacrificial bottom to seal itself directly to the road. If you did that, the side skirt's task would be limited to keeping air moving along the side as an entrance to a spat (might also block side flow from crashing into the lower part of the rear tire, but a spat would be the more effective route).

Because of the effect of spinning tires in the vicinity, I don't think the bottom plane of a side skirt is going to extend the plane along which the car is benefiting from the Bernoulli principle. Side skirts work either to offer a plane to feed a specific diffuser design or as an air damn to keep unwanted flow (from either the side or the tires) from entering under the car. So I think any effort to improve upon the skirts FFR offers needs to keep this in mind.

By the way, without a really well thought out and executed test program (or big bucks for another trip to the wind tunnel), we're guessing at all this. I have some stuff in mind for pretty accurate test procedures, but until I get the basic build I'm not likely to get into it. Still, short of a wind tunnel, you also need a super consistent driver for much of this to matter anyway. Consider that if XYZ part leads to an ideal test-case loss of .20 seconds on a 2 mile course, most drivers are varying their times by more than that just in the inconstency of their outputs and leaving far more time than that just in their as-yet undeveloped skills. I want to make my car as good as it can be too, but all of it is a bit of a mental exercise until it has any practical impact for me. And really, for guys like me, the real practical impacts have more to do with the feel of the car's balance and it's impact on our confidence in pushing the car. So even an absolute lift value means nothing until it translates into me not being confident in the car's balance at some point in the corner.

Sorry...got a bit astray of the topic...

Best,
-j

[RM1SepEx]

Bought them for looks, the numbers were slight

[Xusia]

I had the same debate. I think the aero difference is negligible (don't forget, they do decrease drag, so it's not all negative). Ultimately I decided against them because I'm still planning a daily driver, which where I live means rain. I didn't think it was a good idea for rain to get on them and sit there - it's basically a shelf...

[Canadian818]

I'll have to search for the thread, I believe it was 10-15lbs of lift. I don't recall them reducing drag, must have missed that.

[Canadian818]

Really though, if you're building an R-car, you might want to consider a vertical skirt (or extension) with a sacrificial bottom to seal itself directly to the road.

I've been considering this, possibly trying to angle it inward at the rear to "feed" the diffuser. I was thinking of using the 3" or 4" industrial baseboard, used in shop bathroom and commercial offices, it's quite thin but stiff, and cheap. Riveted to some 1x1 aluminum angle thats bolted to the floor. If it snagged, the rivets would rip out first. You'd have to only uses a few rivets to ensure this, and probably only use at the track, but it's an idea.

Anyone considering using front canards?

[Santiago]

Sick minds think alike...all the way down to the aluminum angle, man! :o

It's something to try, and it shouldn't be too hard to pull off if it's a flop.

Haven't really given much thought to canards - not subtle looking devices, but a subtle effect. They're not directly adding much of any downforce; they're there to direct flow to areas where the downforce is being generated most. I think of them as efficiency optimizers, not generators. So you really have to have a sense of what the car's doing with a given aero package to start with before canards become relevant.

On the other hand...I confess, I think they look pretty cool. And that's just gotta' add 15 hp!

Best,
-j

[Westview]

Here's a quote from the wind tunnel testing:

"The news from here only got better as almost every addition we tested showed a large gain in downforce, with the only exception being the side skirt panels which added a small amount of lift but did give a slight decrease in drag."

Here's the link to article (https://www.factoryfive.com/whats-new/wind-tunnel-testing-the-new-factory-five-818/)

[Canadian818]

"In the end our best numbers came with the extra radiator ducts taped off, the new splitter with the air gap taped off, 5 degrees of wing angle, the rear diffuser in place, no side skirts, and a level ride height of 3-3/8 inch. The max downforce produced was 120 lbs front and 164 lbs rear at 100mph, this increases to 271lbs front and 369 lbs rear downforce at 150mph."

[Xusia]

The "best results" though is only talking about downforce. The lowest drag is achieved WITH the side skirts.

In my opinion the side skirts make so little overall difference I wouldn't base my decision on the aero factors.

[EricScottZehnder]

In my opinion, the car looks better without them. They add a squaring effect to the side which is actually curved. Without them it would look more like a track ready Lotus with that scalloped side and wider front and rear sections. It would cost less and look better, in my opinion.

To each their own.

[Harley818]

They look good, but I think I'll wait a few months and hear some more feedback first.