HI for what it's worth this is my explanation - An object having mass has a force exerted on it by another (larger) object also having mass- ie gravity. In the case of the earth this force will act directly toward it's centre ie centre of gravity. The only way that this force (weight) could be changed is if due to the rotory motion of the blades an additional component was generated. It is simply a vector addition. Therefore the centripetal force (which generates the equal and opposite centrifugal force)which acts in a different geometric plane will generally not affect the downward force (weight) of the blades unless an additional component is generated.
Think of the forces acting in two entirely different planes which don't bear any relationship ( as long as they act with right angles between them - that is the main point- as soon as a right angle is lost between the vectors then we have a dynamic mass since there will be addional components)
I hope this makes more sense to you than me - it's been 6 yrs since I studied it.
Steven
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Doors to Automatic