WhoDaMan

My Feedback: (164)

Hi Guy's
Any one know th best 3 blade prop for a Zenoah GT-80

Thank you
Dave

Antique

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I THINK the JR/Horizon guys used a 25-12 Mejzlik....

WhoDaMan

My Feedback: (164)

Thank you, I am have heard of them using a 24x10 also I need it to pull a 1/5 scale T-34

pe reivers

The 80 will love a 22x10 or 22x12 three blade prop. A 24x10x3 will be courting the engine's limits.
The power demand of a 22x10x3 Mejzlik at 7500 rpm (engine peak HP with standard muffs) is about 8 horsepower. The engine however delivers just 5.5hp at 7500 rpm, so it will turn (much) slower than that with a 22x10 prop.
It is nice to dream. I like numbers better.
A 25x12x3 prop at 6000 rpm would take an engine with 9 hp @ 6000. The zenoah 80 has it's sweet spot at or above 7500, so that is not going to happen.

edit:
Made a small mistake. Peak torque is at 7500, hp at 10,000 is 4.5, all on standard mufflers. With these numbers a 22x10x3 would probably be the largest prop the engine can handle well, rpm will be about 6000.

Antique

My Feedback: (4)

Good info, the three blade on the Gt80 was one I saw at a race a few years ago, the JR guys were demonstrating an airplane...CRS, the prop was probably smaller...

WhoDaMan

My Feedback: (164)

Hi Pe,,,, thank you for the info great numbers, I will look at the 22-10

pe reivers

Ralph, you run the engines open exhaust. What are your props/rpm? (static)

Antique

My Feedback: (4)

The first 445 about 10 years ago turned a Zinger 22-10 7000...7000 feet altitude, 1 quart oil and 4 quarts with 87 octane gas...
Open exhaust should get about 500 stronger, don't fly enough any more to know what works best...
OLD age..[]

STUKA BARRY

I run 22X10 three blade Mezjliks on my G-62's. I'm sure thats too small for a GT-80. I'd thry the 24 or 25X10 myself.

pe reivers

Powerwise, the 80 and the 62 are about the same with the 80 having the edge by 10%. Even the sweet spot rpm of both engines match quite closely. (this is based on Zenoah published data)
Some muffler experiments may yield surprising results though. The 25x10x3 or 25x12x3 will be good props for a modern, powerful 100+cc engine.

PS,
I dug up some more data from my files:
Suitable propellers are the Menz-S-two blade 22x12, 24x10, 24x12, 26x8 and 26x10. From the Menz-S three blade propellers you can use the 21x12, 22x10 and 22x12
Power:
With Tuned Pipe: 7,0 hp
Open Exhaust: 6,0 hp
Standard Silencer 5,4 hp
Weight: 2870 g
Our GT80 race twins turn a 19-18 about 11,500 on methanol (Ralph C, open exhaust)

Ralph, I understand you are still THE engine judge of the standard Zenoah 80 racing class?

Aeronut04

My Feedback: (185)

A Good friend is flying a 16 ft. Flying Boxcar, 100 pounds pair of GT-80s, Bennitt mufflers, Mejzlik 24-10 3 blade props turning 6100 on the ground, flys it very well, I am most likely going to try the 23-10, 3 blade.
I agree 22-10 3 blade is for G-62s, I have run 18-10 3 blades on Q-42s, and G-38s with great success.
Usually what ever 2 blade an engine will run, the Mezlik 3 blade in the same dia. and pitch has always worked just fine.

Pelle Gris

A friend runs a 22x12 3-blade Mejzlik on a GT-80 powered tug. ItĀ“s equipped with a single tuned pipe, and spins the prop a little under 7K as far as I remember.
Tows 50lb half scale gliders like thereĀ“s no tomorrow....:-)
On standard mufflers lower rpm is to be expected, or a slightly smaller prop must be used to keep the rpmĀ“s up.
Personally I would try a 23 to 24x10 3-blade myself.

Peter_OZ

My Feedback: (1)

thoughts on 2 blade prop to go in GT-80 with standard mufflers going into a warbird. I would like RPM around 7500

Idea is to get the engine to unload when it is coming downhill.

As for G62 I have had good succces with 21x12 Mezlik getting 7000 rpm on Jtech exhaust and with RCXL electronic igntion and 90 degree carb bend. Fitted to 42lb Seafury

GT-80 will replace the G62.