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Ideal prop for an RV8?

T

TheNewGuy

Well Known Member
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Hi all. I pick up my RV8 next week. it is a FP IO-360 180HP with a Catto 3-Blade Wood Core Propeller. Looking at the specs I see it has a Diameter of 68" and 74" Pitch. How ideal is this for an 8? The prop its almost 20 years old so I am unsure if this was standard at the time, Catto since adjusting their options.

I don't know too much about Prop choices. Is this more of a climb, cruise, or all-arounder. Wondering if it's something I should pull, sell, and replace. Would be doing various styles of flight, primarily cross-country flying
 
That is a well regarded prop, and you'll get plenty of feedback on it. Keep in mind FP props (my RV-4 is also FP) can vary a bit due to quite a few factors. Catto is extremely well known for the support they provide, and I would direct questions on maintenance and upkeep directly to him, as well as the number/application for that particular model. If it's been on the -8 and flying for some time, I would fly behind it and see what the performance numbers are in real life before making a prop change plan. Technically, prop replacement can lead to returning to phase one and testing.
 
"Ideal" is in the eye of the beholder.
"It depends" (on what YOU want).
Are your options limited to fixed pitch, or is constant speed an option?

You will get various opinions here, but a call to Catto will probably yield the best response to what your current prop will do.
 
I have an 8 with IO360 and Catto 3 blade, 66" 75 Pitch.

I got the plane in August, my first RV (I'm a non builder), so I don't have alot to compare it to. I asked alot of questions on here about various ways to set power, since I haven't flown a fixed pitch in 20+ years- and never a prop like this one.

I have heard of guys cruising at 2600 or 2700 RPM, which to me means they must be at 10,000'+ to make that 75% power. I downloaded an app to my iPhone to calculate power settings. I have a MP gauge but no fuel flow. I usually end up around 2550 RPM at 4500-7500' which depending on the temp and MP usually is about 75%. Somewhere in the neighborhood of 170 Knots TAS. (on my next XC I'll use the TAS calculator on my Aera 760) Flat out at 6500' it will do 2750 RPM. Perhaps more if I left it there more than a minute with the red RPM light scaring me.

I only see 2050-2100 RPM static, at the beginning of the TO roll- (I don't hold brakes and do a full power run up for fear of prop strikes.) So the lower RPM on TO throws some people off. TO and climb performance seems great to me, but as I said I have never flown a CS RV. I did a sawtooth climb test a few months ago and posted it here. (My plane did not come with a POH.) I was surprised at the wide range of climb speeds that give the same rate- the faster you go, the more RPM the prop is making, so I don't know if that's a factor, but my numbers came out very close to the kit planes test with CS prop.

Here's my thread on that:

Sawtooth Climb Test

As I've mentioned my RV8 didn't come with a POH. So in my quest to create one, and get to know my airplane a little better I have been doing "tests" here and there and keeping notes. One thing I didn't have was VSpeeds. My airplane is built pretty close to plans, BUT I have an IO-360 and Catto...
vansairforce.net

I am doing formation training, and lead has to be cautious to not accelerate too fast on the TO roll or he'll lose me. (I am also carrying a 200lb+ safety pilot FWIW) He's flying a CS prop solo.

I do gentleman aerobatics, generally from cruise power settings and I don't have to touch the prop or worry about overspeeds RPM wise, unless you're doing it wrong and letting speed build up- RPM comes up to match.

Do a Google search, type in "vansairforce Catto prop" for some reason that returns more results than the search function here. Several RV8 owners have flown behind both.

From what I recall based on searches here:

Pros of the CATTO- lighter, cheaper, better CG, less maintenance, simpler, 90% of the performance of CS.
Cons- less acceleration on TO, (and thus longer TO roll) harder to fly in formation, easier to overspeed during aerobatics. Louder than CS prop for same power settings?

Some claim FP will even outrun a CS prop in cruise. But let's be real here- I think we're talking about differences of 200' on TO roll and 5 knots in cruise?

3 blades looks cool.

Maybe a worse glide ratio if you're engine out?

Congrats on the airplane, let's see some pics!

IMG_2041.jpg
 
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I bought a -7 project that had a wooden prop with a crack. I opted for the carbon fiber 3 bladed ground adjustable.

I
 
Catto was very helpful. If anyone has a cruise prop and wants to trade for a low time climb prop, feel free to reach out
 
Keep the climb prop. At 2500 rpm each, you and a cs RV-8 with same hp will be side by side. And no one wants less climb rate. CS will out perform fp for the first minute or less, but over 120 knots both will have very similar rate of climb.
 
My RV8 has a 2-blade Sensenich ground adjustable propeller with the IO-360-M1B engine. I use the pin #6 setting and I have one more pitch setting to go.

Takeoff Performance: takeoff roll at 500 MSL airport is about 1000 feet to 60 KIAS which at slightly over 1600# in calm air. I don't have reliable take off number at max gross weight. The climb RPM is 2230 at 95KIAS. At the 7135 MSL high altitude airport, my takeoff roll was 1500 feet in calm air with slight uphill gradient.

Cruising Performance: At over 9500' DA, I cruise at 172-175 TAS at 2660 RPM with 9.0 - 9.5 GPH fuel flow. The MAP is about 21inch at this cruising altitude. I have not tested at over 11500 MSL yet but the cruise performance at this altitude is similar to 9500 DA. My throttle setting is about 60% or else the propeller will overspeed.

Landing Performance: the airplane glides longer than the a comparable RV8 with a CS propeller. At 64 KIAS over the fence, I can touchdown before the1000 ft marker. In calm air, I can stop before the 1800 foot distance with slight braking. With no braking, I can exit the runway at the 2400 foot distance. With moderate headwind, I can easily exit the runway at the 1400 foot distance because the flap adds a lot of drags at the 3-point landing attitude.

Emergency on Takeoff: with the excellent climb performance my RV8 in the current configuration, I can easily turn back to the 3000ft runway at 500 AGL or greater in an emergency. Plus I have to do bleed off energy or else I will land at the opposite end of the airport.

Having a light weight propeller is nice, it is a great propeller for local flying and long XC. I can definitely extract more performance with a light weight Hartzell CS composite propeller but I am not sure want to spend the money on it at the stage of my flying.
 
brad walton said:
Keep the climb prop. At 2500 rpm each, you and a cs RV-8 with same hp will be side by side. And no one wants less climb rate. CS will out perform fp for the first minute or less, but over 120 knots both will have very similar rate of climb.
Click to expand...
What would the differences in cruise look like. I plan on a lot of cross-country flying
 
TheNewGuy said:
Hi all. I pick up my RV8 next week. it is a FP IO-360 180HP with a Catto 3-Blade Wood Core Propeller. Looking at the specs I see it has a Diameter of 68" and 74" Pitch. How ideal is this for an 8? The prop its almost 20 years old so I am unsure if this was standard at the time, Catto since adjusting their options.

I don't know too much about Prop choices. Is this more of a climb, cruise, or all-arounder. Wondering if it's something I should pull, sell, and replace. Would be doing various styles of flight, primarily cross-country flying
Click to expand...
The absolute best prop for a RV8 is the one that achieves your mission profile and there isn't a better one out there.
 
My take is short. I’m in a group that does primarily formation.

CS accelerates faster.
CS gets off the ground faster.
CS climbs faster.
CS accelerates and stops faster for formation.
CS stops quicker on landing.
CS costs more.

Depends on your mission. If you truly are interested in formation it does make your life a lot easier. Can you do formation with fixed…yes. But here’s what I tell other people. Over the last 8 years I’ve been with the group, we’ve had a fee people join with fix pitch props, off those only one guy didn’t eventually install a CS prop….and he ended up buying a 7 to replace his 6. He’s been swooning ever since.

It all depends on your mission. A fix pitch prop is amazing, but a CS is more versatile just by its nature and of course that’s gonna be more expensive.

#1 enjoy your plane!
 
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I appreciate it all. I’m thankful to join the community at the end of the day. Coming from slower certified aircraft, I’m 100% sure I’ll have the RV Grin on my face no matter which prop is mounted.
 
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