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  #11  
Old 11-06-2019, 06:20 AM
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rocketbob rocketbob is offline
 
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200nm trip @ 155 kts would take 77.4 minutes.
200nm trip @ 160 kts would take 75.0 minutes.

Ask yourself if that 2.4 minute difference on a 200nm trip is worth a couple AMU's.
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  #12  
Old 11-06-2019, 07:54 AM
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scrollF4 scrollF4 is offline
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Quote:
Originally Posted by rocketbob View Post
200nm trip @ 155 kts would take 77.4 minutes.
200nm trip @ 160 kts would take 75.0 minutes.

Ask yourself if that 2.4 minute difference on a 200nm trip is worth a couple AMU's.
Yep,
That’s the basic math I’m having trouble ignoring.

OK, thanks y’all.
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Sid "Scroll" Mayeux, Col, USAF (ret)
52F Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper, YIO-360M1B with Danny King “Beautiful Doll’s” old Hartzell CS prop, dual PMAGs, dual SkyView, GTN-650, VPX, EarthX LiFePo4.
Nose Art by VictoryGirl.com. Smoke by Smoke System Helper.
90% done, 90% to go...
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  #13  
Old 11-06-2019, 09:09 AM
sf3543 sf3543 is offline
 
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I have built two RV8s exactly the same except for avionics and prop.
Both had ECI 180 HP engines with fuel injection.
The first one had the 74" BA prop and the second had the 72" BA prop.
I originally got the 74" prop, even though VAN's recommended the 72" for tail draggers, since I felt there was plenty of clearance and in the event I had some tip damage there would be plenty for trimming/repair. The second one got the 72" prop because one became available from a new builder who decided to sell out.
Anyway, although I don't have any actual test numbers, I can say I couldn't tell the difference between the two.
Word on the street is that the longer blade climbs a little better and the shorter blade cruises a little bit faster, but I can't substantiate that.
At any rate, the BA props are definitely faster than the older straight blades. A friend of mine changed from the old straight blade to a BA and gained about 5MPH, as a previous poster also stated.
Good luck.
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  #14  
Old 11-06-2019, 06:36 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by sf3543 View Post
I have built two RV8s exactly the same except for avionics and prop.
...
I originally got the 74" prop, even though VAN's recommended the 72" for tail draggers, since I felt there was plenty of clearance and in the event I had some tip damage there would be plenty for trimming/repair.
That's not totally correct. Van's recommends both the 72" and 74" diameter props for the RV-8. But they only recommend the 72" prop for the other tailwheel models since they sit closer to the ground and have less ground clearance.

Ref: https://shop.vansaircraft.com/cgi-bi...sprop-hartzell
"The 74" blade diameter propellers are applicable to the "A" or tricycle gear aircraft except for the RV-8, while the 72" blade diameters are recommended for the tailwheel aircraft to ensure adaquate ground clearance."

This is a clip from their older order form showing that the 74" prop was offered for the RV-8, but not for the other taildwheel models:



The current Hartzell order form on Van's new website is actually incorrect as far as model applicability is concerned, as it does not differentiate between "A" models and non-"A" models.
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(Pic 1),(Pic 2)
- Out with the Old, In with the New
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RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

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Last edited by RV8JD : 11-06-2019 at 06:52 PM.
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  #15  
Old 11-06-2019, 07:15 PM
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scrollF4 scrollF4 is offline
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...but the guidelines haven’t changed. Talking to the Mothership tech support verified that the 74” is still recommended and sold for the 7A as you posted:

"The 74" blade diameter propellers are applicable to the "A" or tricycle gear aircraft except for the RV-8, while the 72" blade diameters are recommended for the tailwheel aircraft to ensure adaquate ground clearance."
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Sid "Scroll" Mayeux, Col, USAF (ret)
52F Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper, YIO-360M1B with Danny King “Beautiful Doll’s” old Hartzell CS prop, dual PMAGs, dual SkyView, GTN-650, VPX, EarthX LiFePo4.
Nose Art by VictoryGirl.com. Smoke by Smoke System Helper.
90% done, 90% to go...
www.mykitlog.com/scrollf4/

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  #16  
Old 11-06-2019, 07:53 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by scrollF4 View Post
...but the guidelines haven’t changed. Talking to the Mothership tech support verified that the 74” is still recommended and sold for the 7A as you posted:

"The 74" blade diameter propellers are applicable to the "A" or tricycle gear aircraft except for the RV-8, while the 72" blade diameters are recommended for the tailwheel aircraft to ensure adaquate ground clearance."
I was responding to Steve's post where he indicated that the 74" prop was not recommended for the RV-8, and I wanted to correct that so other RV-8 folks would know that the 74" prop is indeed suitable for the -8 per Van's.
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Carl N.
Arlington, WA (KAWO)
RV-8, 620 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B - Sold
Rolladen-Schneider LS1-f - No longer owned
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  #17  
Old 11-06-2019, 09:10 PM
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scrollF4 scrollF4 is offline
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Got it, sorry.
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Scroll

Sid "Scroll" Mayeux, Col, USAF (ret)
52F Aero Valley Airport, Roanoke TX (home of DR's Van Cave)
"KELLI GIRL" N260KM RV-7A tipper, YIO-360M1B with Danny King “Beautiful Doll’s” old Hartzell CS prop, dual PMAGs, dual SkyView, GTN-650, VPX, EarthX LiFePo4.
Nose Art by VictoryGirl.com. Smoke by Smoke System Helper.
90% done, 90% to go...
www.mykitlog.com/scrollf4/

Proud and grateful 2019 -=VAF=- Contributor
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  #18  
Old 11-06-2019, 09:22 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by scrollF4 View Post
Got it, sorry.
No problemo!

Good luck on the prop decision!
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Carl N.
Arlington, WA (KAWO)
RV-8, 620 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B - Sold
Rolladen-Schneider LS1-f - No longer owned

Last edited by RV8JD : 11-06-2019 at 09:30 PM.
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