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help with a new prop

Bigells66

I'm New Here
I have an RV6 which I Built. It has an 0-320D2a with a a Warnake 72 x 72 prop. At 8000 ft, 2350 prm I'm getting 124 ish knts indicated. I was told I could do better.

Is there a concerted opion out there on a good fixded pich prop which I could get to increase my performance in cruise.

Thank you

Bigell66
 
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Catto (http://www.cattoprops.com/) makes the most popular wood core/ composite overlay fixed pitch props on the market today. They usually have a long wait for production/delivery though because their products are so popular there's always a long waiting list. They are proven performers and dominate the market for RV fixed pitch props.

Performance Propellers (http://performancepropellersusa.com) in East Texas is also a good source of wood props. If I remember correctly, his props are descendants of the original Warnke / Clark Lydick design.

Sensenich makes metal fixed pitch props that perform well an O-320 on an RV but you do have a 2600 max RPM limit to live with on those.

Sensenich and Whirlwind both make ground adjustable carbon fiber props that work extremely well. The Sensenich is the more expensive of the two. A great benefit of these is that you can custom adjust the pitch to best fit your engine and airframe for climb, cruise, or a compromise of the two.

I have the Sensenich ground adjustable prop on my RV-6 and can get 190+ MPH (165 knots) TAS with it. I like this prop a lot, but it was quite pricey. I probably spent literally twice as much for this prop than what a new Catto or Performance prop would've cost, but availability and shipping were immediate.
 
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Pretty sure you are going to get a lot of recommendations for a Catto.

They seem to be very popular here.
 
??

Are you throttling back to 2350, or is that WOT? If you're running wide open, then that prop is way overpitched.

Best,
 
Prince P-Tip

A different data point to consider. I have an RV4 that came with a Prince P-Tip 68 x 76 on an O320 E2D (160hp).

At 8,000ft pressure altitude and 2700rpm (not wide open throttle), true airspeed is 164kts.

I realize that the poster was asking about a -6 and not a -4, but give Prince a look.
 
At 8000 ft, 2350 prm I'm getting 124 ish knts indicated. I was told I could do better.

Depending on temp and altimeter setting, 124 indicated is somewhere near 145 knots true. There are quite a few reasons that your indicated airspeed may be lower than expected, and it may not be the prop.

1) Are the wheel pants and gear leg fairings on?

2) Can you push the throttle forward and get 2700RPM at that altitude? If so, what's the indicated airspeed? If not, how high can you get RPM and what's the indicated airspeed at max RPM?

3) Have you verified that there are no gross static errors in your setup? In other words, have you measured both your true airspeed and average GPS ground speed in a 4-direction box pattern or some other meaningful manner, and were they close?

4) For better accuracy in calculating true airspeed, what is the OAT and altimeter setting at that altitude during your test runs?

The answers to some or all of these questions may point to reasons you would be indicating a lower-than-expected airspeed. Other folks may have even better ideas.
 
You may not need a new prop. Depending on the current Warnke prop you have. It may just need an adjustment. Give me a call and I will be happy to help.
 
why 2350

piere's question of why 2350 rpms is the starting point. the cruise speed means different things to different people.
 
RV-6A PROPELLER 160HP

I have a RV-6A with a 160HP with the 70CM7S9-0-(79), which is what Vans recommends.
At take-off ( grass strip) I'm only getting 2250 RPM. I'd like to get a good balance between take off (2400-2500 RPM) and cruise. I like to ask for some recommendations as what I should adjust this Sensenich prop to. I have been given recommendations of 2-4 degrees.

Thanks
Bill
 
Bill,

I have an O-320 powered 6A with a metal Sensenich of 80" pitch. On the runway I get around 2250 rpm. Low down I can exceed the 2600rpm limit, so I throttle back. High up at full throttle my TAS is usually around 170kt.

To make a 70CM7S9-0-(xx) rev to over 2400rpm on the runway is the limit of adjustemnet for your prop as a metal Sensenich prop can only have its pitch altered by 7" during its whole life. 1" is around 25rpm on the runway. A 72" pitch prop will be a real dog in the cruise. Assuming you can reach 2600rpm at 8000 ft now (WOT), I'm guessing your cruise speed will be down by 20 or 30 mph. 1" of pitch in the cruise is worth around 40rpm. If you can't get close to 2600rpm at 8000' now (leaned off), there's something wrong with your engine.


Bigell66,

You could add additional pitch, but take-off performance will suffer quickly - perhaps that is not a factor. Climb performance will also suffer and the engine will probably run hotter while climbing. I would suggest answering all the questions krw5927 posed first. What is the max rpm and airspeed at 2500ft and at 8000ft? What kind of take-off performance do you need? Its all a compromise.

Pete
 
penguin your informations about the pitch and how it affect's the RPM seem's to be extacly in accordance with reality i've heard about, but do you got numbers on how the clim perf is affected by a "+1 pitch up". i'm still questioning myself on re-pitch or not.

i got the RV6 O-320 (160hp) 79" pitched sensenich and wonder if a 80" or a 82" is not better for me..
i got 2325RPM wide Open in static at sea level 1013hpa. the static limits given by sensenish are minimum 2100RPM maximum 2250rpm

would like to cruise at the same 180mph TAS (at 4000ft) i got with 2600RPM:( but with something around 2500RPM:)...

is my climb performance will suffer a lot? i got 1500ft-1700ft solo half tank filed.


using your numbers is a +3" seem's to be good? if not how many do you recommend?

79" +3" = 82" a 82" is declared as cruise prop on the 160hp RV7 by sensenich, (on the 160 RV6 cruise prop is an 81")

static WOT calculation for expected change:
2325RPM - (3x25RPM) = 2250RPM

cruise 8000ft WOT calculation for expected change:
2700RPM - (3x40RPM) = 2580RPM
 
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Hi Antoine,

I get around 2200 static on an 80" prop with an O-320 with one P-mag. When I installed the P-mag (10 years ago), it gave me an additional 50rpm static and provides benefits in the climb, not so much at full throttle. I often fly from short strips - say 500m (1600') long - so I don't want to reduce the take-off and initial climb performance any further, so 80" is good for me.

I would have thought 80" or 81" would be good for you - 82" would give you more cruise speed but your take-off and climb performance will suffer - I can't offer any numbers.

My max speed at 2600rpm is between 160 and 165kt (184 to 190mph) down low, depending on weight and temperature, with some more throttle left - I have never been brave enough to find out the max possible rpm. 170kt TAS (195mph) is possible at 8,000' or 10,000'.

Pete
 
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