IT’S A DRAG

Boating - - MOTORHEAD -

Drag is the ad­ver­sary of speed, and it’s an un­fair op­po­nent be­cause drag in­creases to the square of gained ve­loc­ity. Iconic has stated it would like to break the 180.836 mph UVB speed record by a sig­nif­i­cant mar­gin — say to 185 mph. That’s 13.12 mph, or 7.6 per­cent, faster than the 171.88 mph mark Foun­tain set in 2004. To go 7.6 per­cent faster will re­quire over­com­ing 16 per­cent more drag. The horse­power re­quired to go faster in­creases with the cube of gained ve­loc­ity, so it will take 25 per­cent more horse­power to over­come the 16 per­cent in­crease in drag and go 7.6 per­cent faster. Some com­bi­na­tion of less drag and more power will also get you an in­crease in ve­loc­ity. Re­duc­ing aero­dy­namic drag has to be a fo­cus of the ef­fort, be­cause more power can be very ex­pen­sive, heavy or un­re­li­able. Foun­tain set the 2004 record with a pair of 1,500 hp Ster­ling en­gines, so if the new tur­bocharged Ster­ling en­gines each make 1,900 hp, the team has gained 23 per­cent more power. This as­sumes no in­crease in prop slip, losses to driv­e­train fric­tion, or sig­nif­i­cant change in air den­sity, among other fac­tors.

Here’s an­other bit of math to pon­der. The elapsed time dif­fer­ence over a kilo­me­ter be­tween 171.88 mph and 185 mph is just 0.93 sec­onds. That’s what this crew is chas­ing — 0.93 sec­onds.

Newspapers in English

Newspapers from USA

© PressReader. All rights reserved.