Upthrust Question...?  
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Upthrust Question...? - 12/31/2002 7:15:16 AM   
Ernie Misner


 

Posts: 3166
Joined: 7/5/2002
From: Tacoma, WA, USA
Status: offline 		Greetings,

I am assembling a World Models ARF called a Super Stunts, 40 size. This is a high wing "stick" type of plane.

It appears that there is a degree or two of upthrust built into the firewall. I am wondering if this is a mistake and I should shim it out of there. I thought I high wing plane would have downthrust if anything....

Thanks for any help!

Ernie
       Post #: 1

Upthrust Question...? - 12/31/2002 10:00:37 AM   
BMatthews



Posts: 9052
Joined: 10/4/2002
From: Burnaby, BC, CANADA
Status: offline 		It'll depend on what angle the wing is to the firewall rather than what the firewall is to the center line. If there's a LOT of incidence in the wing relative to the centerline then there is probably still some downthrust.

Or it could just be another assemby line boo boo.....

_____________________________

Witty saying to be plagarized shortly.....

(in reply to Ernie Misner)
       Post #: 2

Upthrust Question...? - 12/31/2002 7:25:12 PM   
Tattoo



Posts: 2124
Joined: 2/10/2002
From: Wichita, KS,
Status: offline 		I've encountered two Global ARF Superfly's that were almost unflyable due to the factory produced upthrust of the engine rails. Once corrected with washers under the rear engine mount holes, the planes flew as advertised...so yes...the ARF's are not perfect, and if you know basic aerodynamics and suspect something wrong with your plane...I'm betting it probably is!

(in reply to Ernie Misner)
       Post #: 3

Thanks - 1/1/2003 1:32:36 AM   
Ernie Misner


 

Posts: 3166
Joined: 7/5/2002
From: Tacoma, WA, USA
Status: offline 		Thanks for the replies!

The stab is installed flat to the straight bottom line of the fuselage, and the chord line of the wing (symetrical wing) appears to be on the fuse straight with no built in incidence changes whatsoever.

World Models usually build a true and straight ARF. I am thinking that perhaps with a bit of upthrust it would fly more "trainer like" and that is what their intention was. For my purposes though I want it to be more of a neutral flier and have (so far) installed an Ernst 1 degree shim behind the motor mount. It still might have a tiny bit of upthrust and I might go to the 2 degree shim later. These Ernst shims are neat.... I have another one in there giving me a little right thrust also.

Ernie

(in reply to Ernie Misner)
       Post #: 4

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