Mailing List flyrotary@lancaironline.net Message #9858
From: Al Gietzen <ALVentures@cox.net>
Subject: RE: [FlyRotary] Re: 11th test flight
Date: Fri, 16 Jul 2004 17:49:07 -0700
To: 'Rotary motors in aircraft' <flyrotary@lancaironline.net>

 

Subject: [FlyRotary] Re: 11th test flight

 

Al wrote: (big snip)

 

"Just as speed increases at as the cube root of hp, so does it decrease as the cube root of drag."

 

Al, shouldn't that be: so does it decrease as the drag CUBED?  No guarantee's, but from memory (poor), I thought this would be closer.

 

Bob Darrah

 

Bob;

Only if you are looking at it upside downJ.  The speed changes as the cube root of the hp or the drag; one directly and the other inversely. If you start with the speed, you cube the ratio of the speed to get the change in drag. So if the speed drops for 135 to 125; 135/125 = 1.08.  1.08 cubed is 1.26.  Drag has gone up 26%.

 

Unless I have it wrong . . .

 

Al

Subscribe (FEED) Subscribe (DIGEST) Subscribe (INDEX) Unsubscribe Mail to Listmaster