I thought it interesting that Speedo's new racing suite (for swimming) lead to significant reductions in times at the Olympics; which got me thinking if anything similar has been developed in F1. Have any formula one teams experimented with different materials to reduce drag? In my research I haven't found anything. Maybe something like the lotus effect (superhydrophobic)? Is there a corollary for gases (air), similar to the lotus effect for liquids?

mick viper - 17 September 2008 12:13 PM

I thought it interesting that Speedo's new racing suite (for swimming) lead to significant reductions in times at the Olympics; which got me thinking if anything similar has been developed in F1. Have any formula one teams experimented with different materials to reduce drag? In my research I haven't found anything. Maybe something like the lotus effect (superhydrophobic)? Is there a corollary for gases (air), similar to the lotus effect for liquids?

From what I understand of the new Speedo suits, their primary method of decreasing drag is to reduce turbulence of the body moving through the water. Part of that is built-in streamlining, part of it is tightly holding the muscles, subcutaneous fat and skin from wobbling about, and possibly being smoother than a nylon weave.

To the best of my knowledge there isn't any magic "drag reducing" material that suddenly makes something quicker -- no paint, no special spray-on stuff or special foam or whatever. A hard, smooth surface is about as good as you're going to get; drag reduction comes from shaping the sufrace so it has as little cross-sectional area and bumps, pits, etc., as possible.

I'm not quite sure what you mean by "lotus effect" or "superhydrophobic" materials. There have been experiments on submarines that used injecting long-chain polymer liquids into the water stream at a critical point to keep the smooth, laminar flow attached to the hull a little longer. Essentially, it made the water more viscous (thicker, like oil), and thus more difficult to get swirling. The U.S. Navy experimented with polymer injection but abandoned it because it was expensive and doesn't last long because it has to be a constant feed.

It is true that air behaves like a fluid, but it is still a gas, and I don't know of anything that would make it stick to the surface of a car to prevent boundary layer separation and turbulence.

If you have any information on any of this, I'd be interested to read it.

GreyWolf74 - 17 September 2008 10:26 PM

mick viper - 17 September 2008 12:13 PM

I thought it interesting that Speedo's new racing suite (for swimming) lead to significant reductions in times at the Olympics; which got me thinking if anything similar has been developed in F1. Have any formula one teams experimented with different materials to reduce drag? In my research I haven't found anything. Maybe something like the lotus effect (superhydrophobic)? Is there a corollary for gases (air), similar to the lotus effect for liquids?

From what I understand of the new Speedo suits, their primary method of decreasing drag is to reduce turbulence of the body moving through the water. Part of that is built-in streamlining, part of it is tightly holding the muscles, subcutaneous fat and skin from wobbling about, and possibly being smoother than a nylon weave.

To the best of my knowledge there isn't any magic "drag reducing" material that suddenly makes something quicker -- no paint, no special spray-on stuff or special foam or whatever. A hard, smooth surface is about as good as you're going to get; drag reduction comes from shaping the sufrace so it has as little cross-sectional area and bumps, pits, etc., as possible.

I'm not quite sure what you mean by "lotus effect" or "superhydrophobic" materials. There have been experiments on submarines that used injecting long-chain polymer liquids into the water stream at a critical point to keep the smooth, laminar flow attached to the hull a little longer. Essentially, it made the water more viscous (thicker, like oil), and thus more difficult to get swirling. The U.S. Navy experimented with polymer injection but abandoned it because it was expensive and doesn't last long because it has to be a constant feed.

It is true that air behaves like a fluid, but it is still a gas, and I don't know of anything that would make it stick to the surface of a car to prevent boundary layer separation and turbulence.

If you have any information on any of this, I'd be interested to read it.

The US Air Force was experimenting with air injection on the wings of F-16 experimantal aircraft to promote laminar flow and reduce turbulence. They drilled thousands of small holes in the upper and lower surfaces of a special modified delta wing and took air from the intakes and redirected it to the interior surface of the wing. Form the little I read the air being forced out the holes caused the air flowing over the wing to bond closer to the surface causing a more laminar flow resulting in a higher speed from the same thrust. It also caused marginally less air to enter the engine which resulted in lower thrust and a less efficient engine. It also seemed to work at supersonic speeds, it had little affect at subsonic speed. The experiments were done in the late 80's and early 90's, that's all I remember.

Bill

I read somewhere that at least one of the reasons the new suits work so well is that they increase the swimmer's buoyancy, the result of the fibers from which they are made being hollow, reducing the swimmer's drag thru the water.No idea how accurate this is.

The lotus effect is when a material has the ability to roll liquids off it's surface. The term comes from observing the lotus flower and how it reacts to water; they never get wet or dirty. This is a function of the contact angle between the surface and the liquid. On a hydrophobic material (contact angles above 90 degrees) water beads up and rolls off the surface, like wax on a car. A superhydrophobic material has a contact angle of 150 degrees. These materials are sometimes considered self cleaning because as the water rolls off the surface, it picks up dirt and carries it away. The opposite effect is superhydrophilicity; or liquid attracting. It would be possible to design materials that have both properties which could then be switched back and forth to control the flow of liquids.

It may not be directly applicable to drag, but I can certainly see a few applications in F1. Helmet visors that never fog up, get dirty or wet. You could use it on bodywork to keep it clean (which would help reduce or rather maintain drag).

There's a pretty good article in the August 08 Scientific America on self cleaning materials that explains the lotus effect way better than I can.

mick viper - 18 September 2008 08:05 AM

The lotus effect is when a material has the ability to roll liquids off it's surface. The term comes from observing the lotus flower and how it reacts to water; they never get wet or dirty. This is a function of the contact angle between the surface and the liquid. On a hydrophobic material (contact angles above 90 degrees) water beads up and rolls off the surface, like wax on a car. A superhydrophobic material has a contact angle of 150 degrees. These materials are sometimes considered self cleaning because as the water rolls off the surface, it picks up dirt and carries it away. The opposite effect is superhydrophilicity; or liquid attracting. It would be possible to design materials that have both properties which could then be switched back and forth to control the flow of liquids.

It may not be directly applicable to drag, but I can certainly see a few applications in F1. Helmet visors that never fog up, get dirty or wet. You could use it on bodywork to keep it clean (which would help reduce or rather maintain drag).

There's a pretty good article in the August 08 Scientific America on self cleaning materials that explains the lotus effect way better than I can.

That makes sense. Thanks for the reference (I always like people who cite their sources!), I'll have to look for it when I go to the library. I think they have Scientific American.

One material I remember hearing about, ages ago, was called "Hydron Speedcoat," manufactured by Hydron Protective Coatings. It was a kind of paint sold to racing yachts that absorbed water or something like that, allowing lower skin friction. It also kept marine organisms like alge, weeds and barnacles from adhering to the boat's bottom. Like the material you described, it was also an effective anti-fog coating. I saw a demostration at the New York Boat Show, once. They had the plastic from a pair of ski goggles that was coated with the stuff. No matter how hard I tried to breath on it, the plastic would not fog up.

Speaking of "hydrophylic" or more correctly "hygroscopic" materials, brake fluid is one of them. Believe it or not, brake fluids -- other than the high-temp silicone ones -- do absorb water over time. Further, since water is heavier than brake fluid, it eventually collects in the brake pistons. There, it can boil if heavy braking gets the pads and pistons hot enough. The result -- suddenly, the car has no brakes, but nobody can find anything wrong with the system when they check it. I've seen it happen.

So, if your race car has been sitting all winter, change the brake fluid before you hit the track. You may also want to have your street car's system flushed, if you're going to be towing a trailer or attacking mountain roads.

Addeneum to previous post:

I read the article in Scientific American that MickViper cited.

Thanks again for the information and the reference, Mick, it was a fascinating article!

I learned more about the "lotus effect" and what it does. At first look, I thought he was talking about Lotus cars, as if someone had uncovered yet another of Colin Chapman's brainstorms. Instead, the "lotus effect" concerns the aquatic Asian flower, which is considered a symbol of purity because, even though it grows in a swamp, is always dry and clean.

Here's how:

The lotus plant is covered with microscopic bumps that hold water droplets off the main surface, using the water's surface tension to keep it round, or nearly so. Think of it as a little like blades of grass holding a golf ball above the dirt on a fairway. When the drop has gathered enough water, it starts rolling along on top of the bumps, carrying dirt away with it. Thus, the plant cleans and drys iteslf with rain and mist.

The other thing the article mentioned are super-hydrophilic surfaces that absorb water into microscopic holes and capillaries. When they become saturated, the water runs off, rather than forming mist.

Now about the "lotus effect" as a method of reducing drag on race cars. Given that air is a gas (although its flow can be described like a very thin fluid), I don't think it could "bead up" on top of microscopic bumps and flow away. It's just too thin for that.

What the bumps could do is generate very small flow vortexes. These would keep the boundary layer of air attached to the bodywork and maintain laminar flow along the car's skin for a little longer, thus reducing surface friction and turbulence. Incidentally, that is another secret of the Speedo super-suits. They, too, use vortexes and bumps to smooth flow and keep a layer of air close to the body as the swimmer moves through the water.

Ah, the joy of science applied to sports!