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Blended Airfoil 72" vs. 74"

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martin(at)gbonline.com
Guest

Posted: Thu Apr 20, 2006 5:02 pm Post subject: Blended Airfoil 72" vs. 74"

Dear Jim et al,

3 years ago I wanted to try to find the best propeller for my RV8.  I have a 

76" Hartzell that I have had since new, and it worked well, however, I 

wanted more speed as well as climb.  I also wanted lighter weight

---

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LessDragProd(at)aol.com
Guest

Posted: Sun Apr 23, 2006 10:46 am Post subject: Blended Airfoil 72" vs. 74"

Hi Jim,

 

I don't have any cruise performance flight test data yet.

By my calculation (with some very rough assumptions):

The 74" diameter requires 3% more power to turn at cruise than the 72"  dia.  

(Or about a 3 mph reduction in cruise speed.)

The 74" diameter could provide a slight increase in initial climb  rate.

 

The advantage of the 74" dia. Hartzell propeller would be when the blade  

tips are damaged.

 	  Quote: 	
		  From what I understand from Hartzell, if the blades can be trimmed and  

reformed to at least a 72" dia., they are still serviceable.
	


 	  Quote: 	
		  From what I understand from Hartzell, if the 72" dia. Hartzell blade tips  

are damaged, the complete propeller is scrap.
	


 

Regards,

Jim Ayers

 

 	  Quote: 	
		   



 Does anyone have any information on pros  and cons on choosing a 72" vs. 

 74" Hartzell blended airfoil prop?   Have searched archives and was unable 

 to find any specific information  relative to propeller diameter.



 Jim Thorne

 7A-QB  CHD

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