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Oct 27, 2002, 08:26 AM
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Far4nugn's Avatar

Best AR for RG-15 at 500 in2? (Q-500)

I want to scratch-build a Q-500 pylon plane and plan to use a foam core/sheeted/glassed wing. I need to stick to 500 in2 and would like to know if a span of longer than 50" would be appreciably faster on a pylon course.

Also, I've noticed the V-tail trend is to mount the stabs from the bottom of the fuse rather than the top, thus leaving the tail end of the fuse 'inside' the "V". What is the advantage to this? Are the acute angles formed at that point on the top less draggy than the "Y" style intersection?

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Oct 27, 2002, 09:22 AM
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Q500 pylon rules normally state that the span has to be between 48" and 52" (I think) at constant chord. This prevents high aspect ratio models or any kind of design that might be considered pretty.

As for the V tail positioning. I've not seen any of the low mounted ones but I don't imaginé there's much if any aerodynamic advantage.

I'm going to move this to the gas high performance discussion, leaving a link here.
Oct 27, 2002, 10:09 AM
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Far4nugn's Avatar
Dave, thanks. I intentionally left out any 'dirty' words because I figured I'd get better response over here.

As for the V-tail mounting, the Vixen is one notable:

Photo from: Matney Models web site.
Oct 28, 2002, 01:35 AM
Speed Demon
GregG's Avatar
After looking at the picture, could they be doing this to enclose the linkage? That would help decrease drag.
Oct 28, 2002, 06:14 AM
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Far4nugn's Avatar

Another reason I like this design is that the servo is pulling to give up elevator. I've had pushrod flex problems before that have almost wrecked my plane because I couldnt pull out of a high speed dive.
Nov 06, 2002, 01:57 PM
Registered User
Those little "V" shaped junctions do cause drag, and having two of them like that is worse than having one on top with a less acute angle. I bet that GregG is right, and this configuration is used to hide the control horn. I would guess that the exposed horn would cause more drag than the acute junctions, but it's only a guess.


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