Prop comparisons are always a good subject here so here goes some figures obtained last week at our flying field.
Engine--Stock g-62 with bennett muffler
Plane---T-F P-51 ARF
Altitude-5,000 feet
Temp.---55 degrees and humidity ~50%
all props tested using 87 octane gas with 40 to 1 Honda oil

Bamboola 22/8 -----6800
Zinger std 22/8------7100
Zinger std 22/6/10---7100
Zinger std 20/8/14---7100
XOAR 22/8-------7200
APC 20/10-----8500

An unscientific pull test showed that the XOAR seemed to pull best, closely followed by the Zinger 22/8 and the 20/8/14, the
Bamboola pulled worst.

Plane was flown with the Zinger 22/8 and flew quite well, good speed and pull and sounded great.
Did not fly with other props, Wanted to test XOAR but would not fit spinner cut outs. Have flown plane with a Menz 22/8, same RPM as Zinger 22/8, Seemed to pull and fly very similar. Remember , THIS IS A WARBIRD! IT DOES NOT FLY LIKE A 3D PLANE! I don't want to hear that a DA50 or a Briillili would fly better! Also, we fly at a mile high, This means we have to go down a prop size to get the RPM's into the power band, take that into consideration. Have flown the TF p-47 with same combo, and aTF Corsair with a Sachs 4.2.
I think that given all factors the APC would probably fly these planes the best but I am leary about using them on the Sachs. I do know that the G-62 turned the APC the most effortlessly. Have not tried that prop on the plane in the air yet. For comparison a friend of mine had a TF-P51, stock G-62 set up the same, flying with a Mejelik 20/10 carbon fiber prop at the Denver Warbirds meet two years ago.
This prop let the engine wind up in the air into the high 8,000 or low 9,000 range and wow was it ever impressive. The plane would blow past ZDZ 80 powered p-51's like they were standing still. The only thing faster were a couple of jets. When RCIGN says a Zenoah likes to rev up believe him! Only disadvantage was a marginal take off and you had to "get the engine up on the pipe" that's an old formula one term guys, all us warbird fliers in Pueblo used to fly pylon! I would not recommend using the Mejelik only because the take off was so marginal but for performance it would be hard to beat.

Larry

Larry, thanks for the data. Some work for me to check out prop power relationships and prop constants in [link=http://mvvs.nl/prop-power-calculator.xls]my calculator[/link].

The prop that brings highest rpm static need not be the best one in flight. Slightly reduced static rpm may very well be the ticket home, and a lazy start may just mean that the exhaust system needs to be adjusted, not the prop. Even maybe not change any, and enjoy the power envellope in flight.

I think you will be plesantly surprised when you get a chance to fly it with the Xoar I hear nothing but great things about them. I have only used NX, MSC, Mej, and Menz, and PT... I can tell you that the difference between Zinger / APC and NX / Mej is night and day so I can only imagine the Xoar since it's suppose to pull as hard or harder than an Mej.

Have actually compared Xoar 22/8 and Menz 22/8 both flying at the same time on TF p-51's, both with g-62's set up identically. Menz seemed to be slightly faster, engine sounded like it unloaded a little more. Xoar was right in the same ballpark. Interestingly the same p-51 with the Menz flew quite well with a std Zinger 22/8. It is really hard to compare props by RPM, Pull, Sound as it is such a subjective determination. I have had planes which flew better with a prop which no way would you expect the results you get. Example, my TF-Corsair flew better with a wood Master Airscrew clunky prop than it did with a fancy shmancey carbon fiber prop. Sometimes perception and reality don't match. I used to get the late lamented English magazine RC Scale Intl. and always got a kick out of the pictures from English and international scale contests, especially when they would show some top scale modeler flying his world class plane with a MA black plastic prop. I guess that is where the saying "different horses for different courses" comes from. Some times I think that this forum gets too caught up in what is considered the ultimate prop, or engine and forgets what just works well. I am reminded of another of my favorite sayings. This is attributed to a Russian admiral, he said, " sometimes perfect is the enemy of good enough" I know that engine X or prop Y aren't the ultimate but you know what? They do the job. Watching some poor slob mess with his "perfect" engine while I enjoy flying my " good enough" engine until it wears out gives me a perverse satisfaction.

Larry

hello all these small industrial engines develop their max torque and horsepower at 7500 (torque) and 8000 (horsepower). unmuffled, have a test paper on a homelite 2.5 cubic inch. dyno figures for this engine. regards to all ----- jack strickland

hello again forgot the horspower was 2.6. on the 2.5 homelite emgine, it became the magnum 2 by contempo enterprises. a very strong engine, but had a 600 rpm requirement to develop spark. very few modelers could flip it fast enough. and a fellow in sacramento ca. developed the first spring starter. this was circa 1982.

Hopefully, thats a new engine and not leaned out yet. [X(]

I'm an avid G-62 user, as you may well know Larry. I don't have a single one ( I have 3 right now) that won't turn most 22-10 props over 7100RPM. Only one that slows my G-62 engines down is the Bambula 22-10. I get about 6300RPM out of those, if memory serves me correctly.

NX 22-10 are up in the 7200--7300RPM range
APC 22-10 is pushing 7500RPM
MSC 22-10 is about 7100--7200RPM
Pro Zinger 22-10 7200--7300RPM

Mine are basically stock. C&H ignition of RCIGN1 ignition units. Pitts style muffler. 40:1 Husky oil and 87 octane gas. Needles tweaked for max and then fattend up about the thickness of the adjustment slot in the top of the screw. Maybe 1/10th or 1/8th turn rich.

I'm up at 5973' elevation right now.

The engines actually should turn the same RPM as sea level. Air is less dense, so prop resistance is less. We get same RPM as the guys at sea level--but we're actually giving up about 20% thrust because of the thinner air.

Say Hi to the Italian Air Force for me. I'm sure they miss me.

Larry,

I have tried many different props and did RPM and pull tests on them. APC props do spin the fastest in the big 22" sizes, but actually pulled far less than say a Xoar or a Mejzlik. I found that in the smaller sizes like say a 16x8, then an APC would do better. The APC just gets so thin in the larger sizes like a 22x8. I have also flown all 3 mentioned 22x8's and the Xoar and Mejzlike flew the plane the best. It was a GP Christen Eagle. You should try the Xoar in flight. They seem to do a great job and on the stand pull a little harder than even a CF Mejzlik. The G62 will pull like a bear with a Xoar 23x8

Scott

I didn't want to post anything about thrust numbers because I don't have a fish scale and rope to actually test the props. I just have a tach to report RPM.

I do concur with poco242 on the APC props. They might perform well in the smaller sizes, but the big ones just turn a lot of RPM and make noise. They don't actually pull worth a hoot. I can tell by the way my plane flies. My 80" Patty will hover easily at about 5/8 throttle with an NX or MSC 22-10. With the APC prop--RPM is up by 200-300, but it won't even hover at full throttle. Lots of noise--not much go.

Thanks for the info, that old Zinger 20x8-14 was popular before 3D became the normal mode of operation. If it still works well enough, the price is exceptional.

which is exactly my experience with APC in the larger sizes. Lots of rpm, but no thrust to match. That probably is due to the very narrow blade. Wide wings can carry more load.

Actually the cost of a Zinger is the same or more than an NX, Xoar, or other prop like that. Zingers are just easier to get at your LHS.
Here is a list of costs I found.

Pro Zinger 20x10 (Tower) - $23.99
Xoar 20x10 (Chief) - $22.00
NX 20x10 (Airwild) - $19.00

Just a couple examples. I have done some pull testing with Zinger as well. I do not rmrmber actuall numbers, but I do remember the Zinger turned lower numbers while also pulling less. It all comes down to what flies the plane best. RPM and thrust measurments do not allways translate into better flying. Seems like every plane/engine combo like a different prop.

Can anyone tell me what the bennifit of the Zinger type variable pitch props is? I allways wondered about that. It seems like at lower speeds the higher pitch part of the prop would create more drag and at higher speeds the lower pitch would do the same. It seems like you would never see the true bennifit of either ends of the pitch range.

Just curious.