Hacker News: paj26

New comment by paj26 in "Why does it take so long to release black fan versions?"

paj26 — Sun, 03 May 2026 07:17:16 +0000

For the same reason a winglet is used on an airplane, or a ducted fan is more efficient than a propeller: there is a large pressure difference on the end of a wing or propeller, and the high pressure side will jump around to the low pressure side and cause a tip vortex. This causes an induced drag, which moves the lift vector backwards (as drag, but not skin friction drag). Higher aspect (think wind turbine blades or glider wings) minimise this, as do winglets or ducting.

New comment by paj26 in "Urea prices"

paj26 — Thu, 12 Mar 2026 06:59:45 +0000

Not sure which natural gas that’s referencing, but looks to be a US index (Henry Hub or so) - note the peak corresponds to a cold snap, not the Iran war. Natgas is tricky because it’s: difficult to store and difficult to transport (aside from well-established pipelines), so you have a massively disjointed market between various deliver markets (look at NY Henry Hub vs Dutch TTF), and also a massively disjointed market between delivery delivery dates (natgas calendar spread trades has been nicknamed “widowmakers”)