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Old Apr 18, 2012, 06:46 PM
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white lake michigan
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inlet lip radius

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Old Apr 18, 2012, 07:22 PM
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best would be about the size of your little finger ..but somewhere @1/4" to 3/8" would work too . look at the BVM sport jets they had really good inlet duct radii.
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Old Apr 18, 2012, 08:29 PM
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Old Apr 19, 2012, 01:33 AM
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Old Apr 19, 2012, 02:25 AM
TeamSiam
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Originally Posted by Aethertek View Post
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Hi, please remember that the drawing is only valid for a VDE-Inlet lip, used on the test bench to be comparable with other tests from other brands.

The tip to use around 5mm radii at an inlet at the fuse is right.

The drawing above is also not good for an OPEN DUCT SYSTEM (no place for it in the fuses). Here you can use an laying ellipsoid shape, 10mm and 15mm radii.

BR, Rainer
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Old Apr 19, 2012, 09:13 AM
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upland CA
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its easy just make the lip as big as you can and still make it look good. the real truth is air can only bend around a curve of a given size depending on the speed it is moving. and no model will have a intake lip radia that will work at max power in most cases..so just make it as nice and round as you can and live with it...it really only makes a big diff for take off run once your flying there will be little speed loss. infact if done correctly the sharp intake will be faster as high speed
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Old Apr 19, 2012, 11:22 AM
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Make it as big as is practical and scale. A sport model designed from the ground up may very well have 1/4" plus radius on the inlet lips. I have flown 90mm size rigs with as little as 1/16" radius. The smaller radius will get you more noise and turbulence at lower speeds. One you get up to flying speed this goes away. But it will return as the jets forward speed is reduced and then power is applied. You will lose some take off thrust with the sharper inlets also. I try to go a minimum of 1/8" radius on my scale 90mm stuff.
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Old Apr 19, 2012, 10:34 PM
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Old Apr 20, 2012, 09:40 AM
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if your after speed you need to remove the cut out infront of the intake(naca shape) it will cause too much turbulance intering the duct
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Old Apr 20, 2012, 01:56 PM
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So, let's see ~
A large radius is best for low speed acceleration. A sharp or small radius is good for high speed.
Electra has a short radius on the outside of the inlet, that grows to a larger radius as it goes towards the inside diameter. Best of both worlds??
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Old Apr 20, 2012, 02:05 PM
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You are describing an elliptical shape. That is the ideal cross section shape of the intake lip. But i have done plenty with just a circular shape with a certain radius. Fairly easy to do if you are just filling and sanding.
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Old Apr 20, 2012, 02:11 PM
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Yes on elliptical shape.
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Old Apr 20, 2012, 06:50 PM
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Quote:
Originally Posted by turbonut View Post
if your after speed you need to remove the cut out infront of the intake(naca shape) it will cause too much turbulance intering the duct
I don't agree with this statement at all. not trying to start anything, I just do not agree with this and neither would the designer of it. the whole idea of the NACA inlet is to take advantage of almost zero losses due to the physical design. the whole idea of the NACA inlet, is that the walls of the duct and the ramp angle create a swirling vortex that discard the sluggish and turbulent boundary layer. this allows better quality air to be drawn in and allow pressure recovery inside the duct. the reason I designed them into the Chimera was for two reasons. firstly, it decreases total frontal area by having some of the inlet area to be depressed into the fuselage. secondly and most importantly, it is for pressure recovery. as you know, there are two types of inlet. pitot style and NACA style. pitot style recover energy ahead of the intake lip, which is why a properly shaped inlet lip is so important. the NACA inlet recovers its energy inside the inlet, by using generated vortex to draw in a higher energy column of air. this has a sort of ram effect. this hybrid inlet was designed to get the best of both worlds. good ram pressure of the pitot inlet, with boundary layer ejection for high speed flight.

the whole thought of this inlet drawing in turbulent air goes against everything the designer of the inlet intended as its purpose. it was designed to do exactly the oppposite.

Rich
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Old Apr 20, 2012, 07:02 PM
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Rich, can you post a drawing of a pitot inlet Vs. a equivalvent NACA inlet please?
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Old Apr 20, 2012, 07:05 PM
turbonut's Avatar
upland CA
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Yes but that is not a NACA duct..they were tried on inlets for full size and it did not work then with real naca designers doing the work....
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