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  #1  
Old 04-12-2017, 06:55 AM
bkervaski's Avatar
bkervaski bkervaski is offline
 
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Default Hartzell 72 vs 74 in RV-14A

Hey guys,

Vans says either 72 or 74 inch Hartzell works on the 14A, any recommendations?

Seems 74 would bite harder but 72 would be smoother and quieter, seems to be a bit of a debate "out there" as to if there is any benefit to the 74 over the 72.
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  #2  
Old 04-12-2017, 08:34 AM
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74. Still a lot of ground clearance (11.5") and I believe a more efficient prop over the 72.

The latest Van's RV-14A is flying with a 74" Hartzell BA prop.

Carl
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Old 04-12-2017, 11:40 AM
TimO TimO is offline
 
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I have the 74" and it's got more ground clearance on the RV-14 than my standard prop (80") does on the RV-10. I figured if it has more clearance than my other plane, then I'd prefer the larger prop. It's been working out well.
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Old 04-12-2017, 03:27 PM
frghtdg frghtdg is offline
 
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74".I went with the ' recommended ' 72" base on certificated drop testing results
and regret it now that I know the pros and cons.
My understanding is Lycoming position is the 74" is ideal.
I have a 14.
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Last edited by frghtdg : 04-12-2017 at 03:28 PM. Reason: Additional info.
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Old 04-12-2017, 03:29 PM
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Quote:
and regret it now that I know the pros and cons
What are the pros and cons?
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Old 04-13-2017, 07:18 AM
frghtdg frghtdg is offline
 
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Somewhere here in Airforce world is an earlier thread on 72" vs. 74" that mentioned 74" is Lycoming ideal. 72" was needed to meet minimum established aircraft prop tip clearance during a specific drop test (hard landing ) ...for the 14.
The 14a has a nose gear to help maintain prop clearance, the 14 pitches over.

With two prop choices, logic points to the 74 as the preferred one.

A voodoo pro......it was mentioned the extra " on the tip gives you some 'nick filing room. Whatever.

More voodoo....more prop less gas....hmmmmmm ..a gas micrometer

You mentioned smoother , quieter...that's new and I hope you're right because
it has grated my nerve.
Once your prop ships, it's yours. No returns
Wait till you see it.....beautiful curves.
Can't beat ideal.
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Old 04-13-2017, 12:51 PM
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Quote:
it has grated my nerve
Thanks for the reply! So your prop is noisy to the point to where it's bothering you? i.e., "grated my nerve"?
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  #8  
Old 04-13-2017, 05:52 PM
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Default Pros & Cons

Quote:
Originally Posted by bkervaski View Post
What are the pros and cons?
Bill,

This has been discussed on another thread, see http://www.vansairforce.com/communit...d.php?t=139482.

Bottom line is that we don't really know the performance tradeoffs of the 72" vs 74" Hartzell on an RV-14 until somebody does comparative performance testing (which is a lot of work to get really good data, and the difference in takeoff/climb/cruise performance is going to be very small between the two). Generally as the horsepower increases you need larger prop diameter to convert the power into thrust efficiently, so I suspect the 74" is the better choice for a 210 hp RV-14.

I'm far more interested in knowing how the 74" aluminum Hartzell compares to the composite Whirlwind 74RV. I'd prefer the latter due to the 15 lb weight savings, smoother operation, less chance of issues with slinging grease out of the hub, and reduced chances of crankshaft damage if I ever have a prop strike, but there's not a lot of people flying the 74RV yet so the jury is still out on how well it performs.
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Old 04-13-2017, 09:15 PM
frghtdg frghtdg is offline
 
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Quote:
Originally Posted by bkervaski View Post
Thanks for the reply! So your prop is noisy to the point to where it's bothering you? i.e., "grated my nerve"?
No, my decision on which one.
Not a big deal.
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  #10  
Old 04-13-2017, 11:46 PM
TimO TimO is offline
 
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I always find it interesting when people talk about wanting to get less weight on the nose. The RV-14 isn't nose heavy at all, and I actually was even glad to have changed out my starter knowing the new one was 1 lbs heavier. The aerobatic CG range isn't really all that wide, and I find that I have to think about my loadings a bit to ensure I stay forward enough CG for things like that. If anything, I've been thinking that maybe it would have been nice to have the ELT not mounted in the tail but mounted right behind the baggage area just to move more weight forward.

So I personally think trying to adjust the plane by making the engine or prop lighter is likely to be a mistake. There's not much you can play with in the back end to make lighter as well, to keep your CG as far forward as possible.
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