The rotors turn at 600 rpm. The blades crossover each other 4 times per revolution [4P]. There is therefore the potential for vibrations at 40 cycles per second, or 20 per second if alternate crossings resonate.

The port rotor rotates CCW and the starboard rotor rotates CW. This means that the crossover location moves forward. Both directions of rotation have been tried and perhaps the outside forward rotation results in greater vibration during forward flight since the crossover location would be moving aft along with the flow of free air. This might result in an accumulating of the downwash, from one rotor to the other.

Three blades per rotor will decrease the vibration by increasing its frequency. ABC with outside forward rotation may increase the vibration.

The port rotor rotates CCW and the starboard rotor rotates CW. Therefore ahead of the masts the roots of the blades cross first (like scissors), whereas behind the masts the tip cross first. If there were to be blade-blade contact it would be a stropping action ahead of the mast and an interlocking action behind the mast.

There are 4 critical locations in respect to clearance between the blades of the two rotors. Two are at the front where the blades are leaving each other and any contact would result in a "stropping" action. The other two are at the back, where the blades are coming together and any contact here would result in interlocking.

The locations are;

Near side rotor: Azimuths = 180 +/- 50.9521 degrees; Radius 82.5177"

Far side rotor: Azimuths = 90 +/- 39.0731 degrees; Radius 104"

If one were to segment the air into adjacent vertical columns, then ahead of the masts the air columns near the root would start their decent from the upper blade to the lower blade before the air columns near the tips. Behind the masts the air columns near the tip would start their decent first.

In summation; in front of the masts the "root" air starts first, moves slower and has a shorter distance to go. Behind the masts, the "tip" air starts first, moves faster and has a longer distance to go.

Note: The differences in the speed of the air flow at different elements along the span of the blade appears to not vary much when the .66 degrees per foot of twist is put in to the blade.

The following is from the drawing 0419. This plan view displays the disks as true circles not as the ellipses that they should be shown as because of the 12.5 degrees of slope on each disk. The following calculations should be close enough; for now at least.

The blade tips on the upper blades will be above one of the other rotor's blades at azimuths of 51 and 129 degrees.

The 80% radius point on the lower blades will be below one of the other rotor's blade's tips at azimuths of 219 and 321 degrees.

The tip speed is 544 feet per second.

Half a SynchroLite. See Helicopter TESTING #1 [item 0036].

SynchroLite

The same argument should apply to the "vacuum" on the upper blade created by the passing of the lower blade; I think.

With forward velocity the blade interaction locations will change.

Consider crazy idea of swashplate with cam follower and 4 relocateable "humps" within the 360 degrees.

The Flettner-282 and the Kaman composite blade both have the NACA 230 series profile.

center of pressure at 30% of chord with angle of attack of 14 deg.

center of pressure at 27% of chord with angle of attack of 1 deg.

whereas the NACA 0012 airfoil has a;

center of pressure at 26% of chord from 1 through 14 degrees.

On the synchropter the blade's angle of attack must be subject to some change as it passes through the down wash of the upper blade. This means that the center of pressure must change also, which in turn will probably subject both the cyclic stick and the blade to vibratory forces.

The VR7b-2 airfoil, that is proposed for the SynchroLite, is even worse than the NACA230 series since it has a;

center of pressure at 33% of chord with angle of attack of 14 deg.

center of pressure at 27% of chord with angle of attack of 1 deg.

May want to consider initially using the 0012 airfoil (Vortech extruded aluminum) then adding stiffness, the adding anhedral tip then manufacturing composite VR-7b.

Oct 30, 2001 ~ The rigidity of the carbon blade in combination with the inertia of a heavy tip weight may reduce the flapping of the blades as they momentarily pass through the downwash of the other rotor's blades.