Method of stabilizing articulated rotor blade

A rotor blade for a rotary wing aircraft, the rotor blade comprising:

• a spar comprising:
• an upper portion comprising an upper forward portion having a first thickness, an upper aft portion having a second thickness smaller than the first thickness, and an upper tapered portion positioned between the upper forward portion and the upper aft portion, the upper tapered portion tapering from the first thickness to the second thickness, the tapering beginning at a position between about 55% and about 65% of the distance to an aft end of the spar measured from a forward end of the spar and ending at a position between about 65% and about 75% of the distance to the aft end of the spar measured from the forward end of the spar;
• and
• a lower portion comprising a lower forward portion having a third thickness, a lower aft portion having a fourth thickness smaller than the third thickness, and a lower tapered portion positioned between the lower forward portion and the lower aft portion, the lower tapered portion tapering from the third thickness to the fourth thickness, the tapering beginning at a position between about 55% and about 65% of the distance to the aft end of the spar measured from the forward end of the spar and ending at a position between about 65% and about 75% of the distance to the aft end of the spar measured from the forward end of the spar,
• wherein the spar is made from a multifilament graphite material with a tensile modulus of approximately 38,000,000 to approximately 42,000,000 psi and a filament tensile strength of approximately 660,000 psi.