Help! Vincent Unrau C-130 plan downscaling

[Flying.Nevs]

Hello,

I thought about building this plane (because I really vibe with multi-engine planes, also not the first build) but downscaling the plans to 75% or 65% so I can still transport it relatively well. My question now is a) has anybody built according to these plans and can potentially give me some information on the expected flight characteristics and b) what factor would be better: 65% or 75% (both fit for transport purposes)?
Also, how would I go about determining the CG of the plane if there is no information given by the original designer?

Best regards

 

[Merv]

Hello,

... what factor would be better: 65% or 75% (both fit for transport purposes)?...

If both transport equally well then look at power systems. Example: All of my planes fly on a 2200 3S battery. So I would prefer any new plane fly on that battery. All else being equal.

Bigger planes always fly better. But they don't store or transport as easy and take more power.

Also, how would I go about determining the CG of the plane if there is no information given by the original designer?

If there is a CG mark, the CG mark scales with the plans.

If no CG mark, start with the CG at 25% of the wing area, that is 25% of the MAC.
I prefer to model a wing half in a CAD program which ever one you prefer. Make an area about the size of the wing looking down form the top. Let the program calculate the size of area, then guess at a line that is 25% of that area. Let's say your guess is 2 inches or 50 mm from the leading edge. Then adjust you guess until your line until 25% of the wing area is in front of that line. While you are at it make a 30% line. There is your CG range. I usually get it the the nearest 1/4 inch or 5mm for a standard size FT plane that is within the 25-30% range.

If your aileron or flap follow the air foil shape, include them in your CAD or manual calculation. If they are flat, that is, a single sheet of foam like most FT wings, don't include them in the CAD model. They don't add to lift.

Here is an article how to do it manually if you prefer.

Aerodynamics Simplified: Wing Chords

This week in the Aerodynamics Simplified series, we're looking at wings and what the Mean Aerodynamic Chord is.

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