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

GP minnow/OS91 surpass..what prop

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Old 05-17-2008, 09:36 PM
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ErikElvis
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Default GP minnow/OS91 surpass..what prop

I had one of the experienced pilots at the field take up the minnow today. It was bought used, in good shape. the engine runs strong but it really didnt seem that fast. Im just guessing but maybe 60 wide open. It was a little windy but I know it should be doing better than that. It was running a 14X6 prop. I have a 14X7 prop to throw on. Any reccomendations to make this thing haul?

oh and on the ground that prop was spinning at around 10k rpm's
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Old 05-17-2008, 10:11 PM
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Default RE: GP minnow/OS91 surpass..what prop

....12-8....you're not going anywhere with a 14-6 prop. [sm=wink_smile.gif]

FBD. [sm=regular_smile.gif]
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Old 05-18-2008, 12:03 PM
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Default RE: GP minnow/OS91 surpass..what prop

Dave, I think you mis-read this like I did......

Its a surpass 91 - 4c

Erick you may want to play with here is something more like a 13x8.
You want to get the pitch up, diameter down, and try to find the right rpm needed for the engine.
Smaller diameter means a bit less drag.
So something like the 13x8 or even a 13x10 might be worth trying. Either should keep the engine up near 9000-10000 ground rpm.
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Old 05-18-2008, 03:44 PM
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Default RE: GP minnow/OS91 surpass..what prop

....yep, I did. [sm=red_smile.gif]

....he will need a 12-9 or 12-10 to pull all the pitch he can at 10 grand on the ground.
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Old 05-18-2008, 06:02 PM
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Default RE: GP minnow/OS91 surpass..what prop

Doh! Now i have a APC 12X8. But I did buy 2 13X8's. a basic master airscrew and a wood zinger. Perhaps Ill look for a 13X9 on the web. Whats a realistic airspeed with a prop drop to a 13X8-9? Oh and the pratical rpm is up to 12,000. I could prob go up a lil with the rpms on the ground. Its still runnin a lil rich since the engine isnt that old.

Edit: Ok searched on tower hobbies and picked up a few APC 13x8,9,10 props. Also picked up a couple 10x6 powerpoints for the nexstar.... But for now Ill throw the 14x7 on there so I not overwhelmed when I do fly it.
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Old 05-18-2008, 08:05 PM
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Default RE: GP minnow/OS91 surpass..what prop

Erik, get three APC props - the 13 x 8 (10K rpm), 13 x 9 (about 9500 rpm) and the 13 x 10 (9300 rpm) and try them all. Quoted RPM figures are the static readings I've got with that engine and they will all unload in the air to a degree, especially the finer pitched of the three.

The Minnow is reasonably slick but has quite a large fuselage. I have an aircraft with a similar airspeed envelope to your minnow, also running the OS .91 Surpass, and for me, after much experimenting, the APC 13 x 10 was the best prop (176 km/h in level flight).
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Old 05-26-2008, 10:00 PM
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Default RE: GP minnow/OS91 surpass..what prop

Had the minnow up today with the 13x8 apc. Well I flew it. didnt take off or land. But it definitely was faster. I dont think it was near the 100mph mark but once I get use to the plane Ill throw the 13X10 on. It was pulling about 10,400 on the ground with the 13X8.
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Old 05-27-2008, 08:59 AM
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Default RE: GP minnow/OS91 surpass..what prop

if you are looking for speed, you will need a 140 size 4 stroke, or a 120 2 stroke. the setup you have is fine for general sport flying.
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Old 05-27-2008, 10:26 AM
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Default RE: GP minnow/OS91 surpass..what prop

100mph is great for fast sport flying. You have a very nice engine/plane set up, I say just fly the crap out of it and have a blast. I saw the toni flying at my field one day and was very impressed with how well if flew high speed aerobatics. If the minnow flies as well as the toni I know I would have a blast flying it, and looking at the design it looks like it might fly even better.
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Old 05-27-2008, 03:40 PM
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Default RE: GP minnow/OS91 surpass..what prop


That is very sound advice.....

Enjoy the plane. Take what speed you can get from it. And have fun flying it.

Its a big plane, and not "qm40" fast by any means ..... with any engine.

It does nice point rolls....

Enjoy it for what its worth [&:]
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Old 05-28-2008, 12:01 AM
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Default RE: GP minnow/OS91 surpass..what prop

Its a real solid plane/engine combo. I dont plan on swapping the motor out. Im just trying to get what I can out of it. I need to find someone with a radar. Id be happy to get 100mph out of it. I think ill stick with the 13in prop and just keep upping the pitch. I have 13X8-11's to try.
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Old 05-28-2008, 12:04 AM
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Default RE: GP minnow/OS91 surpass..what prop

by the way i went from a tad over 10k with a 14X6 to about 10,400rpm with the 13X8. I figure the engine is plenty safe at 10,500 on the ground. It still is a lil rich as it isnt that old. Think 10,500 is a good ground rpm for say a 13X10 prop? The engine should safely pull over 11 in the air.
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Old 06-03-2008, 06:15 PM
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Default RE: GP minnow/OS91 surpass..what prop

ORIGINAL: ErikElvis

by the way i went from a tad over 10k with a 14X6 to about 10,400rpm with the 13X8. I figure the engine is plenty safe at 10,500 on the ground. It still is a lil rich as it isnt that old. Think 10,500 is a good ground rpm for say a 13X10 prop? The engine should safely pull over 11 in the air.
Erik, I reckon you'll get between 9200 and 9400 static with the 13 x 10 and will get at least as much speed as you got with the 13 x 8. The OS .91 Surpass is virtually indestructable so it won't mind running at those rpm figures you quoted for the 13 x 8 at all. Let us know what you find.

Edited to add: If your minnow is set up nicely, you should get over 100 mph with the right prop.
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Old 06-04-2008, 01:26 AM
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Default RE: GP minnow/OS91 surpass..what prop

I actually took off and landed the plane the last 2 days. My first day went well. I was expecting a fast fall out and kept a couple clicks up on throttle right until I was about to land. then I would cut down to idle. Today I was pulling her in far out and cuting the throtle way before the spot I actually wanted to touch down. This didnt work so well as the control surfaces wouldnt respond if I was too slow. Gonna go back to the couple clicks up on throttle and completely cut to idle at or right b4 touchdown.
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Old 06-08-2008, 01:38 PM
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Default RE: GP minnow/OS91 surpass..what prop

Well Ive been having problems with the tuning, or so i thought, on the minnow. I took the prop and cowl off. Inspected all the fuel lines and modified a tad. And I went to turn the engine by hand and noticed the drive washer was just spinning. Somehow the key disappeared. Im wondering if the up and down throttle at full throttle was just the engine spinning faster than the prop. It flew ok at half throttle. Of course the LHS doesnt carry just the key so I guess I gotta wait a few more days to get it fixed. And it definitely didnt fall out when I pulled the drive washer off. I would have heard it on the table. I was having trouble completely tightening the prop before this. Well now Ill get this thing movin.
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Old 06-12-2008, 01:34 AM
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Default RE: GP minnow/OS91 surpass..what prop

Ok the key is in and she's on the charger now. Today I will take her up with the 13X9 and hopefully she doesnt try to show me whos boss again... [:@] I also lowered the expo on my high and low settings. I had the D/R and expo at 75%/75% on high and 50%/50% on low. I switched high to 75/50 and low to 50/30. The plane was just to mushy with all that expo.
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Old 06-15-2008, 01:36 AM
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Default RE: GP minnow/OS91 surpass..what prop

Harry you are right. Im pulling about 9600 with the 13x9. But im not sure the engine really likes the prop. Think trying a 12X10-11 would do any harm?
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Old 06-15-2008, 01:39 AM
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Default RE: GP minnow/OS91 surpass..what prop


ORIGINAL: ErikElvis

Harry you are right. Im pulling about 9600 with the 13x9. But im not sure the engine really likes the prop. Think trying a 12X10-11 would do any harm?
Ps I know people are viewing this thread and input is welcome. I am running a OS91 4stroke surpass.
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Old 06-16-2008, 01:13 AM
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Default RE: GP minnow/OS91 surpass..what prop


ORIGINAL: ErikElvis

Harry you are right. Im pulling about 9600 with the 13x9. But im not sure the engine really likes the prop. Think trying a 12X10-11 would do any harm?
Erik, 9600 static is a good zone for the .91 surpass to be. Did you fly her with this prop? It should unload quite a bit (maybe 800 - 1000 rpm?) once airborne and on-song if the airframe is reasonably slick, which I would imagine is the case with the Minnow.

A 12 x 11 of 12 x 12 won't do any harm either and should be tried at least. As long as the static rpm are around 9300 thru about 10K you'll be fine. The Surpass .91 is a very forgiving, adaptable powerplant.
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Old 06-16-2008, 01:46 AM
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Default RE: GP minnow/OS91 surpass..what prop

I did fly with the 13X9 and it was a hell of a lot better than the original 14X6 but I think Ill pick up a 12X11 and see what happens. Hope the LHS has one.
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