80 years smooth surfaces - aeronautical engineering

[kach22i]

May 24, 2026
Aeronautical Engineering Has Been Overturned
It’s long been accepted that the smoother the surface, the lower the aerodynamic drag. That turns out not always to be the case.
https://www.wired.com/story/a-fundam...x-newtab-en-us

Two types of DMRs were used in this experiment: a convex pattern made of glass beads with diameters ranging from 38 to 53 micrometers and a concave pattern applied by sandblasting. The height of the DMR coating is only 1 percent of the thickness of the boundary layer and is classified as a “smooth surface” from a hydrodynamic point of view.

I skimmed this article, and reread several sections more than once carefully. Still not seeing if concave or convex is better, but do get into an "it's not golf ball dimples" claim.

If invisible to the human eye because the irregularities are so small, then a slightly dirty car is more aerodynamic than a totally clean car?

[Piwoslaw]

So getting your car's paint sanded by drafting behind that dump truck was not that bad...

[freebeard]

Ver-r-ry interesting.

Research that combines magnets and fluorescent paint sounds like fun.

aerohead would approve of attacking the problem at it's root.

The rivulet (“shark skin”) process was falsified by the Ford tri-motor, Junkers and other corrugated skin aircraft. Air doesn't always go where you point it.

'38 to 53 micrometers' is in the range of mettalflake paint.

Originally Posted by DDG Search Assist

Metal flake paint particles typically range from 5 to 100 micrometers in size. Smaller particles, around 7 to 20 micrometers, are often used for finer applications, while larger flakes can exceed 30 micrometers.
wetcanvas.com malvernpanalytical.com

(I quote DDG for the linked sources)

So the ulimate Ecomodder paint scheme would be a satin finish hypershifting metal flake?

Originally Posted by DDG colorshiftpearls.com
[URL="https://colorshiftpearls.com/shop-custom-paint/metal-flakes/"

https://colorshiftpearls.com/shop-custom-paint/metal-flakes/[/URL]
Metal Flakes for Custom Finishes - Color Shift Pearls
The finest metal flakes in various sizes ranging from Micro .004" to Mini .008", and Bass Boat .008". Lots of colors for your custom paint jobs.

________________

43.6% is not trivial, it leverages everything else you can do. The omnidirectional nature is important. I've always wondered about the range in Cd between a smooth sphere and an icosahedron or octahedron. I suspect the advantage goes to the icosahedron. It has a dihedral angle of 138°. The octahedron is 109°.

[freebeard]

(Can't edit in the missing ']' in post #3. )

With this, laminar flow becomes paramount.

Otto Celera 500L
Airplane

The Otto Celera 500L is a business and utility light aircraft developed by American startup Otto Aviation. By November 2021, 55 successful test flights had been completed, as introduction is targeted for 2024–2025. It has a single RED A03 diesel piston engine in a pusher configuration and can seat six passengers. It is named after the latin word for 'fast,' celer. Continued in Wikipedia

[redpoint5]

Originally Posted by freebeard

(Can't edit in the missing ']' in post #3. )

With this, laminar flow becomes paramount.

The prototype should reach a fuel economy of 30 mpg‑US (7.8 L/100 km) in cruise, to be improved with integrated heat exchangers replacing radiators nacelles.[5] A second turbo-compressor should allow reaching a 38,000 ft (12,000 m) altitude, and a third for 50,000 ft (15,000 m).

460 MPH and enough range to reach anywhere in the US.

I'll have to wait until they hit the used market.

[freebeard]

"introduction is targeted for 2024–2025"

Here're two videos a month old:

Why Everyone Wants This 450 MPH Bullet-Shaped Plane --18:03

Why the Otto Celera 500L Is Disrupting Private Aviation

...that I haven't watched yet.

[freebeard]

I was watching the video at 2x when I hit this

10:37 But here's a detail most people miss.
10:40 The propeller isn't in the front, it's
10:43 at the back. This is called a pusher
10:45 configuration...

I don't need my eyesight/perception questioned. What I was waiting to see mentioned were the three things that I notice: the nose wheel doors on 4-bars, the potential for Meredith effect with the radiator blisters, and the active flaps on the radiator outlet (with the heat resistant paint).

If anyone watches the rest let me know.

[redpoint5]

I'd just be excited to do the better part of the speed of sound with my whole family and get 30 MPG on a low maintenance plane.

[kach22i]

Originally Posted by freebeard

43.6% is not trivial, it leverages everything else you can do. The omnidirectional nature is important.

I'll check into his, most certainly would be a game changer.