What is the biggest prop you ever ran on your engines?
For a year ago there was some complaining about some of my engines being loud [] so I started with large props to keep the noise down and discovered the huge static thrust as a bonus[sm=thumbs_up.gif]

I was amazed today how well my 13 years old Super tiger S90K turned the APC 17x8@7800rpm with a quiet pipe and perry VP-30.
Irvine 72 on the same setup is turning a APC 16x6@8600rpm, on a shorter pipe lenght it did 9100rpm but was more difficult to setup.
All the figures are on 10% nitro and at sea level.

Man you guys in Sweden sure have a thing about big props and being quite. Is your whole country a quite zone ? Your animals and pets must need mufflers on their butts in case they fart !!!!!!!!!

I have a Super Tiger 51 that I have just installed a 12X6 and was amazed that it will spin it with authority. I am going to try a 13X6 on it next.

With the torque these Super Tigers have I would not be surprised if you couldn't spin an 18X6 with that 90. It is clear that Super Tiger tuned for torque with their engines, but don't be mistaken, they will spin up with the best of them.

We actually do not have to be that quiet 84dba at 7meters are the noise limits. Sadly I was part of this noise trouble at our flying site with my engines turning @ 18000-20000rpm almost every sunday so I had to do some radical changes and I am glad I did it and as mentioned discovered the huge thrust our little engines can produce with a larger and more efficient prop.

And you know "when a neighbour complains he/she complains" and we can not ignore them or we will be forced to fly only very well muffled and quiet fourstrokes or electrics

Now the guys telling me how quiet my twostrokes engines are and the neighbours are happy again[sm=thumbs_up.gif].

I also think it would spin a APC18x6W within 200-300rpm from the 17x8. This same engine used to turn a APC 13x8 or the 15x4W @12000rpm on a shorter pipe length so it sure has good all round power and behavior.

The tallest prop I have run on an S90K was a Zinger 15x8... stock muffler, no nitro, 2% acetone... it was a dog, over heating all the way! The biggest I managed on my fuel was a 15x6. Sweet running engine, awesome thrust... but no speed!

Largest prop I've run on my .90 4 stroke is an 18 x 12. It's quite a sight but a bit unnerving to work around and would cause ground clearance issues, so for normal flying I use a 15.5 x 12 4 blade. Oh, this is on my RCV 90SP.

Scott

Buzz Put whatever prop you like on your 51 and 90 but you will miss the boat.The ST 90 and 51 will shine if you keep WOT at 12,000 RPM. You will have full use and proportional control of your throttle. By over proping you will lose throttle control at about 70% open. Move it farther open and you can't tell the difference. Read Bax he likes RPM.

We aren't talking about optimum prop here, just the largest one it will fly with. The 51 will fly with a 12X6 with good rpms especially in the air. It might over-rev a little in the air with the 12X6. I haven't figured out the 90 yet but I have seen one fly with a 13X8 and it was turning some serious rpms.

Hey scott what nitro level are you running and do you have a tach reading? Im thinking of running a 15x7 3 blade MAS on my saito 100 powered H9 Corsair, would love to go bigger if the engine supports it using 30 nitro.

cheers

Buzz, my .51 has always had a 12x6 Graupner when run as a glow engine, when running it as a Diesel I change to a 12x6 3 blade, same rpm either way about 10,300.

Hobbsy, what did you do to convert to diesel? I have been thinking of trying it but have no experience with diesels and didn't want to invest a lot of money.

Buzzingb...
Go to here: http://www.davisdieseldevelopment.com/ . The dieselengine are more powerful, quitere and economical than the glowplug engine, they are allways running with larger propeller for same rpm.

Jens Eirik

I run a 68" 3 blade on my Rotax 503, I'd estimate around 300lbs of static thrust at sea level..

I had an OS 1.40 RX on a fun fly plane a while back which I ran an 18x8 wood prop and it gave pretty much unlimited vertical performance, that was a pretty wowie performing motor (fell victim to bearing rust tho).

One day if I get another plane and radio, I still have a NIB 1.60FX that I'd like to run, I think it'll swing an 18" pretty well....

LS

Read here[X(]: the people at PAW once put a huge 18-6 prop on a PAW 35 engine and started it. It could turn only 3500 rpm, but it ran for <five> hours straight with no damage to the engine! The test was stopped just because the people wanted to go home.

The text are from the link: http://www.antiquemodeler.org/Engines/diesels.htm

Jens Eirik

Buz, here is my SuperTigre .51 turning a 12x6 3 blade at 10,100 rpm. Note head and fuel lines.

How well does the 51 run on diesel. I have always thought about diesel as being a lot of trouble but others tell me that it isn't. I also wonder about the effect of the extra compression on piston, ring, rod, and crank/bearings. Understand that I have never seen a diesel glow engine run.

There is no extra compression, the fuel has ether in it to reduce the required compression, that .51 has been a Diesel since 1992, some glow engines have too much compression for Diesel operation, a High Compression Saito .80 for example. A Diesel will run nearly twice as long on a tank of fuel. With a Diesel you throw HP figures out the window and just watch it fly your plane better than you thought possible.