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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Glow Engines >> Prop Determination
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Prop Determination - 11/18/2009 4:31 PM   
stevenmax50


 

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From: ft payne, AL, USA
Status: offline 		I am getting a magnum 91 4 stroke for xmas.  I know that the MFR gives a prop range for the engine but I wonder how you determine which prop is the most suitable for your particular A/C. 
Which prop gives more power?  An 11, or 12, or 13? 
And what does changing the pitch from 6 to 7 or 8 do for me? 
My current model runs an OS 65 LA and I can run either an 11-7 up to a 12-8. 
I would assume that length bites more air thus giving more thrust.  Am I full of dodo? 
And I have no idea what pitch changes add or take away. 
BTW, I will be putting that Magnum on a Tiger 60.  My flying skills are minimal so I am still very much in a learning phase.  No advanced aerobatics from me yet.  A basic loop and roll give me all the thrill I can handle right now.  I hope the Tiger helps me advance some in my flying skills and I believe the magnum will power me into, and out of, whatever trouble I feel squirelly enough go for. 
I hope ya'll can understand what I am asking. 
12 more days until my Tiger shows up!!!
Oh YA....I just saw both the Magnum and the Airtronics at the Hobby People website for 40 to 60 bucks LESS the Tower.  Backorder but what the heck.  90 bucks between radio and engine.  I can buy a reciever batt and servos for that.

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RE: Prop Determination - 11/18/2009 5:50 PM   
w8ye



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Status: offline 		Use a 13 X 8 on your Magnum FS91 for the Tiger 60.  You will like it


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RE: Prop Determination - 11/18/2009 9:02 PM   
j.duncker



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From: North SoundBVI, VIRGIN ISLANDS (BRITISH)
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quote:

Which prop gives more power? An 11, or 12, or 13?

I need to guess what you mean by power. Your engine will turn an 11x10 a 12x8 and a 13 x6 at approximately the same RPM therefor producing the same ENGINE BHP = power

quote:


And what does changing the pitch from 6 to 7 or 8 do for me?

On an 11x10 you will notice that the MODEL will be slower to accelerate to take off speed and may not climb out well. With a 13x6 It will accelerate more quickly on the ground and climb out at a steeper angle.

I am assuming it is a TT Tiger 60. a 13x8 will do just fine on a magnum 91 4 stroke but if you want to play around with props a try a 13x6 or a 14x6 and see if you notice a difference.

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RE: Prop Determination - 11/19/2009 12:18 PM   
cymaz



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Status: offline 		Try this....

http://www.flyingsites.co.uk/howto/propchoice.htm

Works for me

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RE: Prop Determination - 11/19/2009 7:25 PM   
jaka


 

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From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
The most suitable props for a .91 four stroke are 14x6 or 13x8! These props work best for 80% of all airplanes.
For planes like a "You -Can-Do .60" , 3D models , a 15x4W or 15x6 or even 16x4 APC might work better.

< Message edited by jaka -- 11/24/2009 12:55 PM >

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RE: Prop Determination - 11/21/2009 3:57 AM   
jeffie8696



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From: Muscatine, IA, USA
Status: offline 		Big prop shallow pitch means low top speed and lots of thrust.
Smaller prop and pigger pitch equals less thrust but more top speed. I have been told to just get a nice variety and fly them and choose.


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RE: Prop Determination - 11/21/2009 12:58 PM   
PARKER10527


 

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From: gaffney, SC, USA
Status: offline 		Dude i have a 91 magnum on a 46 size decathlon seagull i run 16x4 wide my plane hovers great im turning 9300 rpm running wildcat 10% 2@4 18% oil

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RE: Prop Determination - 11/22/2009 3:44 AM   
jimmyjames213



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Status: offline 		i WOULDNT go smaller than a 13x8 or 14x6. mine is turning those in the 11 grand range (must have gotten a good engine as this thing makes some serious power)

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RE: Prop Determination - 11/22/2009 4:04 AM   
w8ye



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From: Taylortown, OH, USA
Status: offline 		11,000 with a ACP 14X6 is right on the money


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RE: Prop Determination - 11/23/2009 9:09 PM   
mike early



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Status: offline 		13x8 seems smallish for a .91. I use a TF Powerpoint 13x8 on my Saito .72. I've tried a bunch. It's perfect for my GP Revolver.

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RE: Prop Determination - 11/23/2009 9:51 PM   
w8ye



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From: Taylortown, OH, USA
Status: offline 		He was talking about ground clearance


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