New Prop Speed Mod

Bob Axsom · #1 10-13-2009, 02:19 AM

After 5 years using my trusty Hartzell 72" C/S prop with F7666 I have finally bit the bullet and ordered a new Hartzell 72" C/S prop with F7496 blades to pick up an expected 3 kts for racing. I have some fairly long term limitations on my ability to work on my RV-6A to further modify its configuration for more speed but this is hoped to be a bolt on speed gain. My current top speed is 184.4 kts at 6,000 ft density altitude and everything max'd out.

Long term "thinking about" mods I hope to incorporate before next year's racing season are:

1 - a fairing with a cowl flap on the rear of the cowl cooling air outlet with the exhaust moved outboard into new faired in cooling air outlet positions and
2- improvement of the aileron mounting gaps.

We will see how this develops.

I wish I could be in Courtland, Alabama this weekend (10-17-09) to race with the rest of the planes but it is not to be. The latest entry list I have seen at www.sportairrace.org under "Calendar of Events" is:

Race # Name Aircraft Class
Race 44 Lynn Farnsworth Lancair Legacy "Miss Karen II" Unlimited
Race 14 Wayne Hadath F1 Rocket "Little Bit" Sport FX
Race 109 Tom Martin EVO Rocket "Evo One" Sport FX
Race 73 Steve Hammer Glasair I TD "White Fang" FX Blue
Race 91 Bruce Hammer Glasair I TD "Red Dog" FX Blue
Race 38 Steve Reeves Glasair I FT FX Red
Race 23 Chris Brooks RV-6 RV Blue
Race 26 Mike Thompson RV-6 "El Lento" RV Blue
Race 57 Gary Wilcox RV-7 RV Blue
Race 34 Chris Murphy RV-4 "Mister Twister" RV Red
Race 41 Cam Benton RV-4 RV Red
Race 151 Mark Phillips RV-6A "Mojo" RV Red
Race 83 Dave Adams LongEZ Sprint
Race 448 Jim Porter Cirrus SR20 "Plane Jane" FAC3FX
Race 112 Stu Morse Grumman AA5B FAC4FX

Bob Axsom

jthocker · #2 10-13-2009, 06:47 AM

Hey Bob,
Any particular reason you didn't go with the 7497? It doesn't have the rpm restrictions the 7496 has.
Regards,

Bob Axsom · #3 10-13-2009, 08:55 AM

According to the charts I got from Hartzell the 7496 is more efficient at high speed. That's all I care about.

Bob Axsom

6 Gun · #4 10-13-2009, 07:35 PM

bob i went to reno this year and was talking to one of the pit crew for the little mong bi plane that won the race again this year he said that a guy that had an rv built the prop for the mong wish i had gotten more info but what stuck in my mind was he said it got them 20mph over last prop its a wried looking 4 blade but it gets the job of speed done maybe you can dig up some info on it
bob willis

GSchuld · #5 10-13-2009, 07:55 PM

Turbo Super RV-10,

I'm fairly sure that you are refering to the "ellipse" prop designs Paul Lipps.

http://www.biplaneracing.com/files/Issue77_8-13.pdf