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  #1  
Old 03-17-2017, 11:05 AM
dave4754 dave4754 is offline
 
Join Date: Oct 2009
Location: Edson, Alberta, Canada
Posts: 325
Default Prop question

After years and certainly MONTHS of trying to determine the best prop for my -7 I have finally bit the bullet and decided on the Sensenich metalstandard prop ordered from Vans.

It came down to two options the Ground adjustable(GA) Sensi and the Standard metal(fixed)aluminum one. The factor that swung me was that the GA might be too light up front and cause a rearward CG and with my intent to go cross country I wanted all the available baggage weight with two people aboard that I could get.

Information from all sources was very poor, I even phoned Sensenich and talked with the rep who knew very little as regards an RV 7 fitted with the GA prop. A few VAF members here have them on RV 9 and RV 4 but otherwise not much on the RV 7 application either.

The wood props offered interested me especially the Catto, however, it appears that in a rain situation they tend to degrade, also from a weight and balance perspective the CG tended to move aft.

So I am submitting this to the VAF as my trials and tribulations on prop selection. Living in Alberta Canada my information is limited to what I read.

With all the above said I am fishing for any problems you may have experienced with the 2600 RPM limit on the Sensi metal prop?

Any Cessna product rarely goes there that I have flown and I wondered how often it may have been an issue with VAF members?

Thanks for any response, I hope that this helps other builders when searched in the archives

Dave
p.s. Constant speed options were considered to heavy and expensive.
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  #2  
Old 03-17-2017, 11:18 AM
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Mel Mel is online now
 
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In my opinion (worth exactly what you pay for it) the 2600 rpm limitation is not really a factor. With a fixed pitch prop, you will take-off and climb well below that, and in cruise, most people don't run that high of rpm anyway.
As usual, YMMV!
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  #3  
Old 03-17-2017, 01:04 PM
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jmjula jmjula is offline
 
Join Date: Oct 2005
Location: Portland, OR
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Default

I have a two blade Catto on a IO-360 7A with the nickle edges and have no issues in the rain, and I fly IFR too so that happens often. I am a little tail heavy, but I built the plane expecting that so it isn't too bad. A -7 would more likely need a heavy crush plate? It is a smooth prop with a 3000RPM limit, not that you would go that high. I do have to push 2600RPM if I want 165kts, and 2700RPM for 'full' speed, but that is so the climbing isn't overly compromised. Fixed pitch is definitely a compromise.
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Last edited by jmjula : 03-17-2017 at 01:07 PM.
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  #4  
Old 03-17-2017, 01:51 PM
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uk_figs uk_figs is offline
 
Join Date: Jan 2005
Location: Tulsa, OK
Posts: 760
Default Lots of threads on this

Search and you will find lots of threads on this. As noted, the Catto with the nickel edges is not a problem in the rain and lifts the prior 2200 limitation.
For all around performance the Catto is better but you will need to add some weight up front with a Saber crush plate, landoll ring etc to make the CG come out to a useful number for X country 2 up with baggage.
Figs
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  #5  
Old 03-17-2017, 03:51 PM
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N941WR N941WR is online now
 
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Quote:
Originally Posted by dave4754 View Post
...
The wood props offered interested me especially the Catto, however, it appears that in a rain situation they tend to degrade, also from a weight and balance perspective the CG tended to move aft.
...
The -7A's tend to be tail heavy and there are a lot of -7's flying with Catto props.

The nickel leading edge that Craig came out with a few years ago solved the water erosion issue with his props. However, that doesn't stop you from going so fast as to take the paint off your plane.

So now I slow down in rain to save my paint, not the prop.

One other thing you didn't mention, composite props are MUCH smoother than metal props.
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  #6  
Old 03-17-2017, 05:57 PM
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Mel Mel is online now
 
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Quote:
Originally Posted by N941WR View Post
One other thing you didn't mention, composite props are MUCH smoother than metal props.
When you combine composite, 3 blades, and Catto engineering, it's been referred to as "Almost Turbine Smooth"!
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Specializing in Amateur-Built and Light-Sport Aircraft
<n168tx(at)flytx.net>
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RV-6 Flying since 1993
175hp O-320
3-Blade Catto (since 2003)
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  #7  
Old 03-17-2017, 07:30 PM
rv7charlie rv7charlie is offline
 
Join Date: May 2006
Location: Pocahontas MS
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Well, you can't run 75% at altitude, so there's that. And if you do acro, you'll likely spend a lot of time monkeying with the throttle.

Can you run constant speed on your engine? If you're patient, you could probably find a used one for not much more than a new Senn. metal.

Charlie
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  #8  
Old 03-17-2017, 07:41 PM
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Ron RV8 Ron RV8 is offline
 
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Location: Okanagan Valley BC, Canada
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In Canada we have a 10 year mandatory overhaul on constant speed props. My last constant speed overhaul without issues on the Mooney cost me more than my 3 blade catto... I've flown through heavy rain with zero issues. Heavy crush plates available from Saber...
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Last edited by Ron RV8 : 03-17-2017 at 07:44 PM. Reason: addition
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  #9  
Old 03-17-2017, 07:46 PM
rv7charlie rv7charlie is offline
 
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Location: Pocahontas MS
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The same reg applies to experimentals? Even the prop makers say that the intervals are *recommended*. Kinda line an engine overhaul. In the USA, you can fly it as long as it's working properly, as long as it isn't in commercial service.
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  #10  
Old 03-18-2017, 05:09 PM
dave4754 dave4754 is offline
 
Join Date: Oct 2009
Location: Edson, Alberta, Canada
Posts: 325
Default Something like the primer wars eh?

Thanks to all responders, I have ordered the Sensi fixed metal.

Our planes are never finished and one day I will see or reread the email on that sexy three blade Catto and find the appropriate crush plate and letgo my Sensi.

For now the thing has to get into the air and when it does it HAS to fly and work well. So I will go with the tried and true for now.

Thanks again for all responses.

Dave
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=VAF=2017 Donation - and a bit extra for great work!
Empennage RV 7 - Tipper
Wings complere

Fuse coming along, Canopy looking good!
AME reviewed and repaired O-320-Lyc installed
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