Sounds a bit iffy with regards to keeping the blades balanced.

Quite surprising that noone thought of using this on fans and propellers for so long (this is actually quite similar to the flutter dampeners present on most aircraft wingtips).

It will be interesting by how much it will drop the average noise from a modern turboprop. It should increase fuel efficiency and MTBF as well because the dynamic drag from turbulence where the two airflows meet is the one of the biggest factors to make propellers noisy and shorten their lifespan.

There's a fan in my XjunkXspares box with exactly this feature; -must be at least 10 years old.

TBF the notches are the same on each blade, so 'different spacing on each blade' to spread the noise spectrum may be a new feature.Even so, Mercedes have used cooling fans with each blade a dfferent size on some of their cars for years.

"The Noctua NF-P12 fan design has nine, not seven, blades" - is this a reference to Life of Brian?

Anyway, nice idea, I'm off to take a Stanley to my fan to improve cooling.

From Monty Python's Life of Brian...

"For the demon shall bear a nine-bladed sword. Nine-bladed! Not two or five or seven, but nine, which he will wield on all wretched sinners"

Mines the anorak with "Romanes Eunt Domus" on the back.

right im off to see to my home computer with a penknife.

technically no reason it shouldnt work :)

I remember seeing a fan (was a Xerox one, if I'm not mistaken) with dents on the blades. About 17 years ago. True, it had 5 blades, not 9. But still...

Um, the notches in the picture are on the -leading- edge, not on the trailing edge.

...have notches much like these on their flippers. Supposed to hugely benefit stall performance, increase lift and reduce drag.

...Frank beat me to it.

The bumps on the front of humpback whale fins (called tubercules) greatly extend the range of windspeeds at which laminar airflow occurs. There is a company called Whalepower ( http://www.whalepower.com/ ) which is testing wind turbine blades with bumpy leading edges; they apparently work quite well.

Murray, I didn't know whales could fly. Probably a result of evolutionary pressure from exposure to Infinite Improbability Drives.

Hi,

Noctua sold those as CPU and case fans for quite a while. They are quite efficient. Replaced all my fans with them a while ago and they are very effective (silent) (especially as they are around the same price as your standard fan....).

Why yes, I believe it is.

Lacie (Yes LACIE not La Cie -- ask them, they pronounce it lacy) make horrible, heavy, expensive crap. We are forced to purchase some for our apple mac labs as some idiot in a tie told our director that only lacie is supported for firewire 2 video work on mac... ha!!

I would much rather go out and buy a WD disk drive and a caddy than one of these things. On the other hand, when they die, they make great door stops due to their weight.

Fascinating article and links (thanks to everyone above), spent a good while reading about whales and such which I didn't expect!

This is really going to annoy most here I imagine, but after doing a search for the fans - since they're so damn fantastic, do I find they're also so damn ugly! Looks like recycled plastic to me with no option for LED ones!

Poo poo and pish pish I hear you mumbling as you start to climb on those ever so high horses, but surely the PC modding / gaming or the just really shallow "I want my PC fans to light up" market is huge and yet the ultra quiet fan market seems (for the most part - I know there are a few exceptions) to shun us, sorry - them!!!

Seems like a bit of a waste of R&D not to make the most capital return you possibly can.

That's me! Flame away

Quantum - no, the notches are on the trailing edge.

But Why???? - the transparent polycarbonate used to make lighty up fans is unfortunately more brittle than that used to make non-lighty-up fans and as a consequence is less well damped and more prone to audible resonance, something you'd understandably want to avoid in a "silent" fan. Or so I've heard.

Oh, and in addition to the article... I seem to recall the large fin area and small gaps being a design feature adopted by Noctua in their CPU cooler fans to make them cope better with the back pressure provided by your average modern tower heatsink; something Noctua's earlier fans, with their narrow, widely-spaced fins, were not very good at.