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help me ww1 big cowl use long prop - 7/7/2008 7:16:02 PM   
avionette


 

Posts: 154
Joined: 12/3/2005
From: Palermoitaly, ITALY
Status: offline 		hello

i have busa 1/6 scale sopwhit pup I'm putting os 46 ax .
i see that these ww1 models (fokker triplane, pup ,nieuport )has big engine cowl , with these models have i to use long propeller ? because i think the air flow must move the model for the fly without turbolence around the fuselage; or no matter what i thinking? could you help me based on your experience
thanks a lot in advance
       Post #: 1

RE: help me ww1 big cowl use long prop - 7/7/2008 10:04:19 PM   
caribefoto


 

Posts: 65
Joined: 8/2/2004
From: Lake Wales, FL, USA
Status: offline 		Typically, 75% of lift (thrust) of a prop is generated by the outermost 25% of blade length, so the prop doesn't have to be that much larger in diameter than the cowl. Depending on prop speed (RPM), pitch and other variables, an even greater percentage of lift may be generated by the outer 25%............John

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RE: help me ww1 big cowl use long prop - 7/7/2008 10:15:28 PM   
avionette


 

Posts: 154
Joined: 12/3/2005
From: Palermoitaly, ITALY
Status: offline
quote:

ORIGINAL: caribefoto

Typically, 75% of lift (thrust) of a prop is generated by the outermost 25% of blade length, so the prop doesn't have to be that much larger in diameter than the cowl. Depending on prop speed (RPM), pitch and other variables, an even greater percentage of lift may be generated by the outer 25%............John


Hi caribefoto
If tomorrow i'll show you cowl+prop size fotos can you advice me based on your theory ?
regards!

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       Post #: 3

RE: help me ww1 big cowl use long prop - 7/7/2008 11:25:20 PM   
TFF


 

Posts: 743
Joined: 10/30/2006
From: Memphis, TN, USA
Status: online 		On my Fokker DVIII 1/6 scale, OS .40 FP I run a 13X4 or 5 which gets the prop outside the cowl but does not load it up too much. I would use either a 12 or 13 in prop and 4-5 in pitch. You will have to experiment and get some of each to test as one will end up the best for your experience.

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       Post #: 4

RE: help me ww1 big cowl use long prop - 7/7/2008 11:47:38 PM   
vertical grimmace


 

Posts: 1145
Joined: 3/13/2004
From: ft collins , CO, USA
Status: offline 		I agree with the large diameter and low pitch. These aircraft perform better with this type of prop anyway and that should be a good size range for your engine. For the .46 look at the APC 12.378 x 3.75 size. Great prop.

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       Post #: 5

RE: help me ww1 big cowl use long prop - 7/8/2008 10:39:02 AM   
avionette


 

Posts: 154
Joined: 12/3/2005
From: Palermoitaly, ITALY
Status: offline 		ok i give you picture the prop in fotos is 11x5 tell me if i can do the first flyght the prop go out from cowl 60 mm

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RE: help me ww1 big cowl use long prop - 7/8/2008 1:19:52 PM   
TLH101



Posts: 5513
Joined: 12/27/2001
From: Corpus Christi, TX, USA
Status: offline 		The size of cowl has absolutly nothing to do with prop diameter. Props are "tractor", they pull thru the air. Adrian Page proved this several years ago when he flew a Gee Bee, with a prop that was the same diameter as the cowl.

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       Post #: 7

RE: help me ww1 big cowl use long prop - 7/8/2008 1:25:56 PM   
MajorTomski



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From: Oklahoma City, OK, USA
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quote:

ORIGINAL: TLH101

The size of cowl has absolutly nothing to do with prop diameter. Props are "tractor", they pull thru the air. Adrian Page proved this several years ago when he flew a Gee Bee, with a prop that was the same diameter as the cowl.



A little expansion on this. Remember that the propeller is a wing that is generating lift. The thrust or propwash you feel behind it realy doesn't contribute to the pulling power of the propeller. So as stated it really doesn't matter if the prop sticks outside the cowl

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       Post #: 8

RE: help me ww1 big cowl use long prop - 7/8/2008 3:30:39 PM   
TFF


 

Posts: 743
Joined: 10/30/2006
From: Memphis, TN, USA
Status: online 		The prop sticks out ok, but an 11x5 is a little small for an OS46 AX. 11X6 or 12X5 would be better.

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       Post #: 9

RE: help me ww1 big cowl use long prop - 7/8/2008 3:51:32 PM   
CanDo


 

Posts: 80
Joined: 2/23/2006
From: Ventura, CA, USA
Status: offline 		FYI, my GB R2 has a 14x7 prop in front of a 12" cowl and it has plenty of thrust. In fact, the designer (Adrian Page) put a 12" prop on his and it flew just fine.

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RE: help me ww1 big cowl use long prop - 7/9/2008 10:24:06 AM   
avionette


 

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From: Palermoitaly, ITALY
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quote:

ORIGINAL: CanDo

FYI, my GB R2 has a 14x7 prop in front of a 12" cowl and it has plenty of thrust. In fact, the designer (Adrian Page) put a 12" prop on his and it flew just fine.


thank you for your post because my fokker dr1 cowl size is 11" so your gee bee has good power and fly great whit 14x7?

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       Post #: 11

RE: help me ww1 big cowl use long prop - 7/9/2008 3:52:55 PM   
TLH101



Posts: 5513
Joined: 12/27/2001
From: Corpus Christi, TX, USA
Status: offline 		You need to use the correct prop for you engine/airframe combo. A 14x7 is not anywhere the correct prop for you WWI model powered with a 46AX. What some of the posters have tried to impart here, is that you need to use a low pitch prop of an acceptable size for you model. Old WWI biplanes are very draggy, so props with larger diameter and less pitch will usually do well. As someone maybe a 12x5 would be a good choice.

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       Post #: 12

RE: help me ww1 big cowl use long prop - 7/9/2008 5:39:42 PM   
Prop Nut



Posts: 1558
Joined: 5/4/2004
From: Coral, MI, USA
Status: offline 		Avionette, just use the proper size prop for your engine size (as others have mentioned). The large cowl behind the prop doesnt make much of a difference in this case. I have a Beaver (OS40) 10x7 that just barely clears the cowl, it works fine. I also have a couple other small planes with large cowls that also work just fine. You should have no trouble. By the way, I am going to be taking the train down there this weekend (From Germany) out of curiosity, whereabouts do you live?

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RE: help me ww1 big cowl use long prop - 7/9/2008 5:44:46 PM   
Prop Nut



Posts: 1558
Joined: 5/4/2004
From: Coral, MI, USA
Status: offline 		ahh, I see...you typed palermoitaly, Italy and you live in Palermo, Italy.

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Scope? Listerine? Or Prop Wash?

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       Post #: 14

RE: help me ww1 big cowl use long prop - 7/9/2008 7:41:23 PM   
avionette


 

Posts: 154
Joined: 12/3/2005
From: Palermoitaly, ITALY
Status: offline
quote:

ORIGINAL: avionette


quote:

ORIGINAL: CanDo

FYI, my GB R2 has a 14x7 prop in front of a 12" cowl and it has plenty of thrust. In fact, the designer (Adrian Page) put a 12" prop on his and it flew just fine.


thank you for your post because my fokker<