Prop selection, .91FX on Vortex  
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All Forums >> RC Airplanes >> Extreme Speed Prop Planes >> Prop selection, .91FX on Vortex
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Prop selection, .91FX on Vortex - 5/22/2008 12:57:18 PM   
Lomcevak Duck



Posts: 970
Joined: 2/22/2004
From: Warner Robins, GA, USA
Status: offline 		I'm finishing my BTE Delta Vortex in the next few days and I'm hoping to fly it this weekend sometime. Power is an OS .91FX and I'm not overly familiar with the engine so I'm asking for some prop recomendations for the engine/airframe combo. I know this isn't a true speed plane, but I've seen several guys in here had one.

I'm not really seeking max top speed or 3D capability, just a good middle ground that'll make the engine happy. I've got a three blade 12x6 (looks great on this triangle airframe) and some wood 14x4s, master airscrew 12x8s APC 13x4 sport and 15x4 wide blade (worried about ground clearance with this one). Anything other recomendations?

Thanks, Steve

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RE: Prop selection, .91FX on Vortex - 5/22/2008 1:54:54 PM   
freakingfast


 

Posts: 800
Joined: 1/3/2005
From: mather, CA, USA
Status: offline 		If that’s a 12X6 Master Airscrew 3 blade, go with it. It will have a bit less top speed than the right two blade, but some other fun factors can make up for it. Three blades typically pull harder in climbs, re-accelerate faster after hard turns, better air braking and not having about trimming the blades at landing is definitely a plus in your case. Think about an 11X 8 (3 blade) if your plane’s not too dirty.

< Message edited by freakingfast -- 5/22/2008 2:11:18 PM >

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RE: Prop selection, .91FX on Vortex - 5/22/2008 4:14:57 PM   
bob27s



Posts: 4821
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: online 		Id try the 12x8 2 blade.

The Vortex is a bit big. You are ok up to about a 13" prop.


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RE: Prop selection, .91FX on Vortex - 5/22/2008 6:51:56 PM   
MJD


 

Posts: 1683
Joined: 5/27/2003
From: Orangeville, ON, CANADA
Status: offline
quote:

ORIGINAL: Lomcevak Duck

I'm finishing my BTE Delta Vortex in the next few days and I'm hoping to fly it this weekend sometime. Power is an OS .91FX and I'm not overly familiar with the engine so I'm asking for some prop recomendations for the engine/airframe combo. I know this isn't a true speed plane, but I've seen several guys in here had one.

I'm not really seeking max top speed or 3D capability, just a good middle ground that'll make the engine happy. I've got a three blade 12x6 (looks great on this triangle airframe) and some wood 14x4s, master airscrew 12x8s APC 13x4 sport and 15x4 wide blade (worried about ground clearance with this one). Anything other recomendations?

Thanks, Steve


Forget about your 4" pitch props with this bird. Go with the other suggestions.

(in reply to Lomcevak Duck)
       Post #: 4

RE: Prop selection, .91FX on Vortex - 5/23/2008 1:29:55 AM   
Flyboy Dave



Posts: 13448
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		.....I use a 12-7 on mine at 12,900 RPM using a clone engine on 5% nitro.
The plane is surprisingly fast for how thick it is. A 12" prop is about as big
as you can go on the Vortex.

FBD.

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An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
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       Post #: 5

RE: Prop selection, .91FX on Vortex - 5/23/2008 1:37:42 PM   
Lomcevak Duck



Posts: 970
Joined: 2/22/2004
From: Warner Robins, GA, USA
Status: offline 		Thanks guys, I'll try to snap a couple of picks and let you know how it goes with the maiden. I don't expect any troubles.

FBD- Is that the old ARF version? I like the cowl.

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When someone loses a plane in the pits, you do a lomcevak duck.
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       Post #: 6

RE: Prop selection, .91FX on Vortex - 5/23/2008 1:52:04 PM   
evan-RCU



Posts: 2674
Joined: 2/4/2002
From: Charlotte, NC, USA
Status: offline
quote:

ORIGINAL: Flyboy Dave

.....I use a 12-7 on mine at 12,900 RPM using a clone engine on 5% nitro.
The plane is surprisingly fast for how thick it is. A 12" prop is about as big
as you can go on the Vortex.

FBD.


That's a 13X7 in the picture Dave, did you try that too?

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Revver #125, Pico Owners Club #3
R/C Anonymous. My name is Evan and I have not flown for 14 hours.

(in reply to Flyboy Dave)
       Post #: 7

RE: Prop selection, .91FX on Vortex - 5/23/2008 3:54:58 PM   
Flyboy Dave



Posts: 13448
Joined: 3/20/2002
From: San Bernardino County, CA, USA
Status: offline 		....whoops....yes, that is the original prop I tried on the plane....too big.
The engine detonated with it. I had too much nitro in it as well 15% in
the clone ASP engine which is a high compression European engine. I
blew two plugs on the first two runs, a Fox Miracle plug, and it blew a
cold Rossi plug. I went to 5% and it was OK. I didn't fly it with the 13" prop.

Any of the 12 inchers should work fine, the 7 pitch gives better than expected
performance....I suspect the 3 blader would work Ok too. A 12-8 would be
a good bet too in a Zinger.

Yes, that is the ARF version. I have the rudders rigged up to work as air
brakes using the retract switch....pretty cool.

FBD.

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_____________________________

An engineer says.... "That won''t work".
A mechanic says..."Oh yeah, watch this".
"Old Age, and Treachery will overcome youth and skill".
Revver Bro #4.

(in reply to evan-RCU)
       Post #: 8

RE: Prop selection, .91FX on Vortex - 6/9/2008 2:31:54 AM   
ArtW



Posts: 69
Joined: 2/16/2003
From: San Rafael, CA, USA
Status: offline 		I flew a Delta Vortex for 4 or 5 years with an O.S. 91 FX running 13*8 or 14*6 props. It was a wonderful airplane. It is not a high speed plane. Bruce Tharpe designed it to fly well not to go exceptionally fast. The one trick I have learned recently about it is in landing in high wind watch out with increasing angles of attack as the induced drag will slow the plane rapidly with lift increasing slightly causing it to drop suddenly. It will suddenly loose lift on landing in a high wind. All deltas do this with high angle of attack. Despite this minor ideosyncracy, it is a wonderful plane, but it is not a speed plane.

(in reply to Flyboy Dave)
       Post #: 9

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