Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Need prop suggestions

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Old 07-28-2007, 05:34 PM
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UkerDuker
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Default Need prop suggestions

I rebuilt my H9 Ultrastick after a failed introduction with a tree. I put an os50SX on it with a Macs tuned pipe. I shortened the header pipe 3/4" and improved the RPMs from 13500 to 14600. I'm spining a 10x9 APC prop.

This is my first fun with a tuned pipe. SHould I continue cutting on the header pipe or should I switch to a different prop?

Thanks for any suggestions.

Mike



BTW, the tuned pipe mount is not is the same position now, ITs closer to the end of the pipe, since I shortened the header.
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Old 07-28-2007, 06:10 PM
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Default RE: Need prop suggestions

Tricky question...Once you have the prop. you want to go with you keep cutting the header until there is not RPM increase, but a 10x9 is a bit unusual for that engine. I probably would not go bigger than a 10x8 for speed, 12.25x 3.75 for 3D ( i ran a 13x4 Zinger on my OS-50SX) or 11x6 for sport flying on the 50. The challenge happens when at some point you want to move the engine to another airframe that might desire a different prop. size--

Great looking install by the way, I bet it hauls the mail! I love U-Sticks! So versatile

P.S. You can search for threads that cover, "Tuned pipes" as I recall Bob27 posted a great guide to that effect
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Old 07-28-2007, 07:08 PM
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Default RE: Need prop suggestions

For all around flyability I liked the 11x5 or 11x6 with the STICK / .50 combo. I tried a pipe with the Webra .50 but went back to the muffler for more linear throttle control. A 10x9 is a speed prop for a .90.
If you want to go with a pipe get a baseline rpm with open header [and the best working prop, like maybe a 10x6 or 11x6, do your homework here first], then couple up the pipe and take note of the rpm. Slide the pipe and header apart some and take note of what happens then. This test will verify that the system is either too long or already too short. It can also point to whether or not you are using the correct size pipe for the job. If you note improvement with coupling the pipe up as short as possible, then start taking 1/4" lengths off the header until you notice little or no improvement, then go fly. Don't be surprised if the engine starts blowing plugs after you have "supercharged" the engine, lower the compression if need be and always make sure the mixture is rich enough and that there is plenty of lube in the fuel [I don't care what anyone says, I run some castor].
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Old 07-28-2007, 08:47 PM
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Default RE: Need prop suggestions

OK, I guess I need to test a few more props. I will try a 10x8 and 10x7 to see how the RPM are affected. Normally I would just have a stock pipe with an 11x7 prop. But I want to see if I can tear the wings off this plane. (Figuratively speaking)

What kind RPM ahould I expect to see when I get the right prop and pipe length? Will it be anywhere close to the 17000 that OS claims?

Mike
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Old 07-28-2007, 08:55 PM
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Default RE: Need prop suggestions

UD, It should be at least that or the extra expense of the pipe system will have been a waste.
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Old 07-28-2007, 09:34 PM
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Default RE: Need prop suggestions

One other issue I thought about....

Would upping the nitro content from 15% to 20% make a big difference? What about changing to a different Glow plug? Currently I am using the stock the OS #8. If I went up to 20% nitro, would using an OS A5 plug be better?

Eventually, I will explore most of these options. Right now I;m just brainstorming and asking the people who fly fast prop planes.

Mike
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Old 07-28-2007, 11:01 PM
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Default RE: Need prop suggestions

You won't find any improvements there as dramatic as doing your homework with props and drag reduction.
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Old 07-28-2007, 11:24 PM
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Default RE: Need prop suggestions

you could try some ofthe APC pylon props from performance specialties www.pspec.com I run an 8.87x8.75 with an ultathrust muffler on my OS50sx I get oruond 17k on the ground

Howard
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Old 07-29-2007, 03:01 AM
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Default RE: Need prop suggestions

I would run the 12.25x 3.75 APC or a cleaned & balanced Pro Zinger 12X4 on your stick. That tuned pipe may not be the right choice for 3-D. I would run a Mac's Quiet pipe. This pipe has a broad smooth power band due to it's multi disk reflector design. Some other tuned pipes/muffers tend to be either on or off and hard to feather the power. Inspect the plastic wing screws that came with your plane, some have been very loose/undersize and could strip out. Install new plastic screws if they look stretched, have white marks or you had a bad landing, it's cheap insurance. Watch for notch wear on the two wood pins on the front of the wing (it looks like friction burns). If it's not deep, fix it with a drop of CA.

Enjoy the Stick!
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