Hi All, I always thought a hi gloss finish was to create a smoother surface, creating a lower drag coefficient, glide thru the air with less resistance or drag, why would anyone want to cause more drag, get less power from drag, create a bigger surface area, each bump creates more surface up and down the bump, not much more until you add up every bump, I wonder if the airlines would paint a matte or matt, jet?, lvmci...
The thinking has changed completely on this in the relatively recent past - but in fact it was thought to be the other way round to what you suggest - ie, the belief was that that rougher surfaces had less drag.
Hulls of racing yachts (so we're talking hydrodynamics rather than aerodynamics, but the principles are identical) used to be deliberately roughened slightly because it was thought to reduce drag. It's very easy to observe how water apparently seems to flow better over a rough surface - on a glossy surface the water forms into droplets which 'stick' to the surface, but if the same surface is slightly roughened with wet'n'dry sandpaper that slight roughness is enough to break the surface tension of the droplets, and the water flows easily away. This was thought to mean that they'd be less drag on a boat with a slightly roughened hull as it moved through the water - but this belief has now been completely reversed and everyone now tries to get their hulls as shiney as possible
But another twist to this comes from investigations into the properties of sharkskin:- sharks (apparently) move through the water with much less drag than they should do, and they have particularly rough skins. In fact the surface of shark skin is 'grooved' front to back - so a shark's body is covered in thousands of tiny grooves which run along the length of their body from nose to tail, and it's been proven that these grooves reduce the surface friction and hence drag of the shark because water prefers being directed down a channel to flowing over a smooth surface. 3M now produce a stick-on film featuring these microscopic channels, which is applied to the blades of wind turbines and the hulls of racing yachts and so on (and could theoretically be used to reduce the fuel consumption of a bus)
Jeremy
