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

Cermark F16/w OS 91 DF motor

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Old 12-11-2002, 02:00 AM
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satooling
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Default Cermark F16/w OS 91 DF motor

Hey guys, try this. Put a OS 91 DF motor on a Cermark F16. Put a 12 x 6 on it to get it up to around 19500-20000. And see if you can handel it. Beaware the rudder will flutter if you dont beefen it up.
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Old 12-11-2002, 06:26 AM
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Default ?

Whoa!!

Have you done this? Flyboy Dave you out there??

I would pay to see that... My money is on the motor separating from plane within 100 ft.

james
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Old 12-11-2002, 12:32 PM
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nun45
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Default Cermark F16/w OS 91 DF motor

i would like to see a pic of the plane. i think i have one but i am not sure!---henry
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Old 12-12-2002, 01:12 AM
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Default OS 91 DF

Just wondering:
What brand of prop does one use on an engine like this?
Standard 12" APC Sport props (or any other sport prop) are not designed to do 20000 rpm I think.
Also, isn't 6" pitch a little too low for going really fast? Wouldn't a 10-8 or 10-9 be faster? Or would that be pushing a plane like the Patriot too far?
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Old 12-13-2002, 06:30 AM
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Flyboy Dave
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Default Razor....I donno man....

....I don't think the .91DF motor will turn anything
close to that with a 12 incher. At any rate,
he's gonna have his hands full trying to pass the big
block 1.08 FSR up the back straight. (heh heh heh )
Dave.
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Old 12-13-2002, 01:04 PM
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satooling
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Default F-16

I beg to differ Flyboy. Look at the HP ratings on the 91 vs. 1.08. Not even close. 91 has almost 5 Hp. The 1.08 has a lot of growing up to do before it gets in the same leage. Nice try. If you havent tried a 12" prop on one, dont guess about the RPM.
Good luck guys.
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Old 12-14-2002, 03:28 PM
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Flyboy Dave
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Default Yo, WacoNut....

....let's see a pic of your Cermark F-16 with the
Hot-Rod .90 in it....I'm waiting.....
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Old 12-14-2002, 04:35 PM
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Default Cermark F16/w OS 91 DF motor

Man O' Man....I've heard it all now.

Now, I don't know know if you're familiar with the Cermark F-16, BUT if, this was to fly the way you think it will, ya better have a hefty bag and push broom handy for when this plane comes apart.

You'd be better off with the F-20, due to the cleaner lines.

I also have to question the .91 turning that kind of RPM, with a 12" prop. Maybe with an 11X8.

My .02

Gary
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Old 12-14-2002, 05:52 PM
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Default F-16

Boys, Boys, Boys.
Just when you THINK you know everything.
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Old 12-14-2002, 07:22 PM
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Flyboy Dave
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Default Alright WacoNut....

....thanks for the pic. Good luck with the project.
Mines already at the limits of speed and indurance do
to buffeting from the fake airscoop. it looks like it's
trying to tear the wing off at full speed. (scary)
The big canopy is also restricting the speed.

As it happens....I got my F-16 from that guy "Air-Gar"
that posted above. He had an O.S. .91FX in it, and it
was such a Dog he pulled the motor out, and gave me
the plane for a repair job I did for him on his Enforcer.
I stuck a new 1.08 O.S.FSR in it, and it goes much
better than it did....however i have "hit the wall" with
the plane for speed because of the aerodynamic
limitations of the plane .

Dave.
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Old 12-14-2002, 07:26 PM
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ChuckAuger
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Default Well..I don't know everything, but..

Just a few observations..

Your pipe looks awful long to be set for 20K...

Your pressure tap is behind the widest point on the pipe...

Your prop tips are about .95 mach on the ground at 20K with a 12" prop...

I can't understand why you would want to run a 12 X 6 when something like a 10 X 10 would be so much faster, and the tip speed would be a lot lower...

Has this plane actually flown??
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Old 12-14-2002, 10:29 PM
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satooling
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Default F-16

Hey Flyboy, nice looking plane. Did you have problems with the gear. Mine were junk.



Hey ChuckAuger, yes It has been in the air several times, about 60 times. The DF motor produces so much more power over 18K, thats why I am running around 20K. The APC 10x10 ran only 14K. Remeber this is a DF motor, they like speeds. They turn a 5" fan around 22-25K.
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Old 12-14-2002, 10:58 PM
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Default Interesting way to look at it...

A 10 pitch prop is about 20 mph faster at 14K than a 6 pitch at 20K.
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Old 12-14-2002, 11:26 PM
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Default rpm

a 10x10 is alot less prop than the 12x6.If you only get 14,000 out of a 10x10, i would expect only 12500-13000 on a 12x6.
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Old 12-14-2002, 11:29 PM
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Default Yo, WacoNut.....

....thanks. Look closer at the front gear on my F-16.
Yes, all the gear is junk on the Cermarks. The front
gear was so weak with the extra weight of the 1.08
I couldn't even taxi the plane. It just flopped around
like a wet noodle LOL. That's a rigid gear on there....
it doesn't retract. The stock mains have to be
straightened after every flight. I got Robarts for it
but they sent me the 85 deg. ones, instead of the
90's.

Dave.
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Old 12-14-2002, 11:37 PM
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Default Cermark F16/w OS 91 DF motor

Rpm x pitch x .00095 gives theoretical top speed the 6 inch pitch won't do much 114 mph.
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Old 12-15-2002, 04:34 AM
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Default Cermark F16/w OS 91 DF motor

JEEZ, you guys and all the technical stuff!

Fly the friggin' thing and then judge. I doubt that this has flown "60" times, and IS flying over 120MPH....IF THAT...., however, lets give him the "benefit of the doubt".

We need details....

Gary
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Old 12-15-2002, 04:43 AM
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Default Cermark F16/w OS 91 DF motor

Just with a 91 up front it could be so much more
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Old 12-15-2002, 10:40 AM
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Default Cermark F16/w OS 91 DF motor

Have you really reached 19500 rpm with a 12x6? Watch out that the prop doesn't break.

By the way, in a review of the OS91 in RC Jets, the engine reached 5.9 hp at 21000 rpm, with only 10% nitro. About 1 hp more than OS suggests.

Vincent
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Old 12-15-2002, 02:47 PM
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Default cermark f16

just a question
is there a way to modify that scoop so that it is flow through ducting. maybe that might help with speed. also, how does this plane do with a 60 size motor?
i really like the looks of the plane. i am happy with speeds of 80 to 100
dave
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Old 12-15-2002, 03:34 PM
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Default Cermark F16/w OS 91 DF motor

i have flown mine with an os 91fx,( dog), asp 108 was super fast but extremely nose heavy, an old os61 that flies it pretty good but the engine is old and as it gets hot it dies out. now i have a new kraft 61 that i will try just for grins. i will also run the 10x9 that i have on the os 61.---henry
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Old 12-15-2002, 05:27 PM
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Default F-16

Hey Vincent, thanks for your possitive words. These guys on here just think they can do some calculations of RPM and pitch and think they can come up with a speed. There are so many variables to consider, weight, drag just to name the main two.
Yes this plane has flown over 60 times. Just because it is in one piece, is that your question?
And yes the planes has been over 160-170. I had several people clock it. Two of they guys hold records at the nats on speed divisions.
Good flying.
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Old 12-15-2002, 06:19 PM
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Default calculations

these calculations are just estimates. they are probably on the high side. to get 160 mph you need at least 28,000 rpm on that 6 inch pitch. that prop aint staying together. so you draw your own conclusions.
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Old 12-15-2002, 09:29 PM
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Default Cermark F16/w OS 91 DF motor

Thats why these are theoretical numbers at 100% efficiency so subtract from there.
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Old 12-20-2002, 04:42 PM
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Default Re: Cermark F16/w OS 91 DF motor

Originally posted by WacoNut
Hey guys, try this. Put a OS 91 DF motor on a Cermark F16. Put a 12 x 6 on it to get it up to around 19500-20000. And see if you can handel it. Beaware the rudder will flutter if you dont beefen it up.
I've been considering using the 91 DF to spin a prop as well, but in a 40 size warbird. I know where your coming from regarding the higher horse power at 20,000 rpm with the 12x6 vs the 10x10 at only 14,000. I was just wondering if you tried flying the 10x10.

In most high speed applications static rpm is a poor measurement of flight speed. Thats because a fast plane will allow a fast engine to unload considerably in the air, up to 25% more RPM. So there is a chance that a slower spinning static prop will actually move a plane faster in the air than the higher spinning statically measure prop. I've notice this on several of my airplanes. My guess is that if your 12x6 is turning 20,000 on the ground, its turning about 23,000 in the air, or about 130mph pitch speed. If the 10 x10 does 14,000 rpm on the ground its probably doing about 16,100 rpm in the air, or about 152mph pitch speed in the air. These are only guesses assuming that the engine will unload by 15% in the air. It can unload more or less and is also dependent on the available horse power at the unloaded rpm.

By any chance do you have any idea what the flight speed is with your 12x6?

Thanks for reading,

Rudy (Aerowolf)
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