Prop advice to Lyc O-235 L2C

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monclerjacket · Post by **monclerjacket** » Wed Aug 21, 2024 8:45 am

monclerjacket · Post by **monclerjacket** » Sun Apr 28, 2024 11:01 am

JimParker256 · Post by **JimParker256** » Thu Oct 19, 2017 11:17 am

at7000ft wrote:Concerning a 3 blade prop on a Panther. Is it true that only advantage over a 2 blade is that it looks real cool?

Aviation Consumer did a feature article on this a few years ago, using several different airplanes and props. Their conclusion was that the 3-blade props generally provided slightly faster climb rates (roughly 5%), at the expense of a few (2-5) knots lost in cruise speed. The 3-blade props were definitely smoother (they measured vibration levels at various power settings), and almost all of the participants and observers thought the 3-blade props were substantially less noisy than the 2-blade. The 3-blade props also provided more 'braking effect' when power was pulled off. But overall, the 2-blade props were slightly more efficient in cruise, where we spend most of our time.

Interestingly enough, when they actually used a decibel meter to measure the prop noise (both on the ground and in "flyover" mode), the 3-blade props were actually louder than the 2-blade props. Apparently, the difference was the frequency of the noise changed so that it occurred in a range that is less "objectionable" to human ears.

But the "ultimate" quality that won the day for the 3-blade props in the Aviation Consumer review was the "cool factor"... Everyone agreed that the 3-blade props just looked better, and made the airplanes look fast just sitting on the ramp.

One other thing to consider if you're going to be flying a lot of aerobatics... The gyroscopic effects of a 3-blade prop (generally heavier than their 2-blade counterpart) will be greater, and will thus transmit more loads/stresses to the engine, engine mount, and airframe during aerobatic. Just food for thought, as I have no aerobatic flight experience and am not a load stress engineer.

at7000ft · Post by **at7000ft** » Thu Oct 19, 2017 9:42 am

Concerning a 3 blade prop on a Panther. Is it true that only advantage over a 2 blade is that it looks real cool?

muehlberg · Post by **muehlberg** » Wed Oct 18, 2017 11:09 pm

Les,

Thank you for the information. I understand it is based on only 4 hours, but it helps me a lot. What Sean and you are indicating between 3000 and 3500 feet msl (understanding that the temps were likely different) is what I was hoping to achieve with my Panther. I'm sure both of you would have a true air speeds in the 160 mph range at 7,500 ft or so. Not bad for an O-235 burning around 6 gph. The fact you are flying without wheel pants makes your speed at of 133 knots (about 153 mph) at 2520 even more impressive to me. Thanks to both of you for posting you data. I look forward to hearing more as your test flight envelopes expands.

Thank you again,

Eric Muehlberg
S/N 11 Panther LS

LesBoatright · Post by **LesBoatright** » Wed Oct 18, 2017 8:16 pm

Hi Eric,

To be quite honest, I have less than 4 hrs of flight time on the plane at this point. So, I think any data I give you is purely qualitative. With my job, and with the weather we've had the last coupla weeks, I haven’t flown enough to do a full set of flight tests, or to repeat tests and verify consistency. And I've spent much of my flight time so far at the low speed end of things, checking engine cooling and learning about our Panther's handling and stall characteristics.

I do believe our Static and In-Flight RPM values are still running about 100-150 RPM lower than what Dan predicted. But I'm not ready to change props after only 4 hrs! I'm happy with the performance so far, and we were never looking for absolute speed anyway. That wasn't our main mission.

For Static ground runs, we see about 2150 to 2200 RPM.
Dan says we should see about 2300 Static RPM with this prop/engine combo.
In flight, Wide-Open at about 3,000 feet, I saw around 2520 RPM and about 133 KNOTS indicated.
But that's a single data point, it was a very brief run (maybe 1 minute), and we don't have wheel pants installed.
I’ve checked our RPM against a hand-held optical unit to verify the EFIS RPM reading is accurate. And it seems to be.

Just for the record, we have the Sensenich WC68PM-65 prop that Dan recommended for our engine.
(2-blade, Fixed-pitch, wood core with Carbon Fiber overwrap)
It’s lightweight, and is a beautifully made prop! It was also easy to install with the Saber extension.
Our Lycoming O-235-C2C is a low compression engine.
The book says it's rated at 108 hp at 2700 RPM continuous, and like yours, it's supposed to make 115 hp at 2800 RPM (but limited to 5 mins at 2800).

We still have a lot of Phase-1 testing to go, so we'll fly more and collect more data when we can.
Les

muehlberg · Post by **muehlberg** » Mon Oct 16, 2017 1:57 pm

Les,

As I'm using basically the same engine as you (O-235 C1B, 115 hp @ 2800), I'm really interested to hear how the prop preformed once you got everything worked out. Both static and max (full throttle in flight) RPMs and what speeds/altitudes you were indicating compared to Sean and his 118 HP. I need to order my prop but really wanted to hear what some of you with the O-235 engines are seeing before I do. Thanks in advance for any information you can provide.

Eric Muehlberg
S/N 11 Panther LS

LesBoatright · Post by **LesBoatright** » Mon Jul 17, 2017 9:52 pm

Thanks Again Dan!
That sounds good, and we're putting together a set of specific troubleshooting steps this week, starting with the simple stuff first, like verifying the tach with the TruTach optical reader.

I did some more research and found these great EAA Hints for Homebuilder's clips on Carb maintenance and adjustment.
Since we have not touched the Carb on our used engine since we got it, it makes sense that it may be out of adjustment.

Checking the Carb Inlet Screen for debris or blockage should be an easy item to check off. (we have the smaller MA-3 on our O-235)
http://bcove.me/155hkxzj
http://bcove.me/ls8yrrkx

The rest of our fuel system is new, clean and has been flushed out thoroughly to verify good. That Carb screen is the last filter element, and has not been checked yet. So we will.

Carb Adjustment (To me, this seems to be a very KEY piece of information for us)
http://bcove.me/cwz0zl0w

I think our idle RPM is a bit too high at around 750-775, with the lever pulled back to the closed position. It really should be closer to 700. Likewise, based on the engine roughness I felt at the lower RPM, I think we may be set a bit too Lean when the Mixture lever is sitting at the Full Forward/Rich position. IF we are indeed lean-of-peak when the Mixture handle is Full Rich, then we're surely losing some of our RPM there. So that's another item we will check and adjust as needed.

Sorry if I'm hijacking Sean's thread on the Prop type & Size. Hopefully this information can be helpful to others who might read this.

For Education & Recreation right???

Les Boatright
Panther Co-Builder
SN 083

Post by **danweseman** » Sun Jul 16, 2017 7:19 pm

Les
That certainly seems substantially low RPM your engine and prop. In very general terms the different HP rating of the 0-235 series are mainly due the compression ratio and RPM rating of the engines. If you research the power curves Your 108 HP engine should make a similar power to a 115 hp at the same RPM. but its peak rpm and HP will both be higher.
#1. verify the tach.
#2. if the rpm dosent change when doing a mag check it may be a wiring or switch issue that is only allowing one mag to operate at a time. This could drop 50-75 rpm? Dont know how yours is wired etc ,or if this is even possible.
#3. Do compression check, check engine timing etc etc. could be alot of things .
Your engine should spin that prop inth low 2300 rpm "range".

Your engine shouldnt vary by 60 RPM in a 1 minute run. We typically see less than 20 RPM variation in a 1 minute full throttle static run?

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