I noticed this article:
Sharkskin has scales (denticles) that can reduce drag and increase lift, by acting as tiny vortex generators.
In wind tunnel tests, they found lift/drag improvements of up to 323 percent.
Now all we need is inexpensive shrink wrap coated with denticles (would have to be careful about aligning the wrap with the actual flow).
In reply to clshore :
Fascinating article .Ain't science fun?
An FSAE team tried sharkskin texture on their car's nose section once, I don't know how they did, but I haven't seen it done on a race car since, so I'm guessing it didn't make a meaningful difference. It would be more interesting to try it on a landspeed car where the effects of reduced drag would be more obvious.
Even myth busters showed mpg improvements with the golf ball treatment, so my guess is it is real. And it's real for swimmers!
Is it disallowed in series that actually have the budget to pull it off? Like Nascar, f1, Indy, etc. Maybe that is why we don't see it.
Robbie said:Even myth busters showed mpg improvements with the golf ball treatment.
"Those aren't dents all over my car, they're efficiency dimples"
Robbie said:it's real for swimmers!
Former competitive swimmer here- the difference is insane, especially with the full body suits, it felt like swimming in air by comparison. They actually banned certain suits from competition to prevent people from being able to buy their way into a major drag advantage.
If a similar difference is possible on a car body moving through air, that's a pretty big deal- but it's hard to imagine it being as significant, or it seems like someone would have done it by now.
I can see myself trying to polish the car wax from under those scales.
^^ this. hydrodynamic resistance is substantially larger than aerodynamic resistance, especially at the speed that cars race at. Plus the main parts of cars that create drag are vertical or near-vertical surfaces like the radiator/front bumper, wheels/tires, or suction created behind the car due to its shape or aero design. Until all of those things could be mitigated to the maximum potention, not sure if the shark-skin woudl make a significant difference. For the price of a dimpled custom wrap, you could probably add in underbody aero, splitters, winglets, etc that would have a much more noticeable effect.
That said, once I win the lottery, I'll dry the dimpled thing ;)
Or get a small ball-peen hammer and set aside a week of time to kill :)
In reply to irish44j
The researchers actually built and tested airfoils in a real live wind tunnel, with and without the scale treatment.
Theory is great, but real live numbers beat theory every time.
Assume that some clever person creates a textured roller (hello 3D printer) that lets you easily apply directional scale-forms to a surface which has
been coated with a layer of thick semi-cured material. Once cured, the result is a lightweight flexible 'skin' that reduces drag.
Given that aero drag varies as the cube of velocity, and that it is the primary limiting factor at speeds we are concerned with as enthusiasts,
A consistent 1% advantage is a pretty big deal in competitive classes, say an average of 1 second per lap?
I think the cost/benefit equation starts to look pretty good.
I agree with Irish on his assessment. I have been trying to avoid posting anything on this thread for a few hours... but here goes.
The majority of the TYPICAL CAR surfaces that would benefit from this treatment are not going to provide anywhere near the overall gains mentioned in the original post, or the linked article. Vortex generators work by increasing the airspeed close to a surface so that it can remain attached further down the surface. This always comes at a price as redirecting the air costs some amount of energy. The cooling system in particular is one of the largest drag items on a car and you can't do with out that.
In the airplane (and shark) world, symmetry is generally a very good thing. Not so in cars, especially race cars. Additionally, car tend to work in very low aspect ratios while airplanes work in higher aspect ratios (think length vs width). Race cars generally will sacrifice a significant portion of drag for downforce, pushing them to a less efficient design with respect to drag/power. Nature has a a way of going the other way, so that the limited amount of energy that animals can produce is used best for sourcing food.
A well designed car will do better without vortex generators, than a badly designed car with surface treatment to fix the inherent problems.
I'm certainly not denying the technology is valid. But it's only an advantage if 1) you're the only one who uses it (which , if it is affordable, woudl certainly not be the case) and 2) the weight of the material (would need to be thicker than, for instance, vinyl) doesn't offset 1% aero gains at car speeds.
But I'm sure someone here has a 3D printer, so I think GRM needs to do a real-world test with a car :)
So hail storm damage is actually increasing the value of your car. Who knew. 
If somebody makes me a sharkskin roller, ill try it on the challenge car.....
dean1484 said:So hail storm damage is actually increasing the value of your car. Who knew.
i think hail storms are actually just Mother Nature trying to help us fix the environment by getting better MPG's.
Ill take some for my sailboat hull!
Enyar said:Ill take some for my sailboat hull!
I have read marine engineering journal articles discussing such a thing on ships. I'd have to go back and look but I think it was cost-prohibitive to dimple the steel, and coatings just didn't last sufficiently long.
In reply to stafford1500 :
Most cars, and racecars in particular, exhibit bi-lateral symmetry, and aspect ratio becomes more significant with velocity.
While it's true that keeping the boundary layer attached to promote laminar flow is a matter of postponing the inevitable, doing a better job of that task yields better results. And while the researchers observed cases of 300+ % improvement of lift/drag figures in their testing, my assertion is that even a modest 1% gain on a racecar would be worthwhile, all else equal.
BTW, chances are very good that any 'well designed racecar' (ie one that wins) at the professional level ALREADY employs vortex generation devices. It's become impossible to seperate the aero component from the rest of the design, the trick is to integrate everything by balancing the compromises for the best result.
But we will see.
I expect that we will see aircraft surfaces routinely given surface treatments to affect the aero behavior, and perhaps the same will become true for cars and trucks.
Laser ablation machining would be my guess, rather than mechanical, given the size and shape and fine feature detail required.
The problem is with things moving through air instead of water is surface contamination. Bugs, and dirt. Laminar flow on wings generally goes south once you start adding dead critters.
I'm probably going to look stupid here, but how does one get a 323 percent improvement in drag and what does that work out to? If drag is expressed as X, I would think that drag reductions would give you numbers less than 100 percent, not more.
clshore said:In wind tunnel tests, they found lift/drag improvements of up to 323 percent.
From the linked article " The researchers tested 20 different configurations of denticle sizes, rows and row positions on airfoils inside a water flow tank. "
I don't see any mention of wind tunnel testing anywhere in the article.
it's relatively common to test inside of water tank... because that way the model can be smaller (this is because of Reynolds Number relations)
re:323%
it's important to note, that's related to Lift/Drag ratio... as far as I can tell. thus:
L/D_1 = 3.5
L/D_2 = 11.3
iihmmc; i.e. it's a fancy way to say the L/D ratio is "3 times better"
Yeah, it's easy to forget that air doesn't scale. 
Dusterbd13 said:If somebody makes me a sharkskin roller, ill try it on the challenge car.....
Why does 'sharkskin roller' sound like a gold mine? I can see the TV ad now!
You are all forgetting what the GRM approach to this should be. How can I do this for cheap and right now?
Easy answer: shark leather. Just go catch you some sharks and tan the hides. Then apply to car as needed.
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