Design Challenge: around the world from east to west or pole to pole

[Scott Kenny]

All those wires WILL vibrate. The more tension on them, the higher the frequency of vibration (see violin strings)

 

[Nicknick]

The trick is, keeping the Eigenfrequencies below the aerodynamic excitations. There might be some damping involved too. Please note, that the oval shaped wires don't vibrate in yacht rigging, unlike the conventional round wires.

 

[Scott Kenny]

The trick is, keeping the Eigenfrequencies below the aerodynamic excitations. There might be some damping involved too. Please note, that the oval shaped wires don't vibrate in yacht rigging, unlike the conventional round wires.

Doubt that, but I bet they need much higher windspeeds to start vibrating compared to round wires.

But an airplane is going to have ~100knot relative winds on those wires, when a yacht is pushing maybe 30knot relative winds.

 

[Nicknick]

The oval cross section avoids producing Karmansche wake vortexes, which is a clear advantage, but I agree, any flexible structure moving through the air is prone to vibration. On the other hand, making everything as stiff and light as possible doesn’t always help, the 747 e.g. has its outer engines quite far out to prevent resonancy. It is often the better solution to keep the Eigenfrequencies far below the excitations, this will be true for the rigging as well as for the 747 wing.

View: https://www.youtube.com/watch?v=N3383AN9sMY&ab_channel=FutureFibres


Keep in mind that damping it also an option, it could be done at the endings of the wires, or even in between, e.g. by hollow bodies fixed to the struts which are partially filled with a liquid or with a liquid plus a loose body moving around in the fluid.

Note that Burt Rutan’s also suffered from vibrations.

 

[publiusr]

All those wires WILL vibrate. The more tension on them, the higher the frequency of vibration (see violin strings)

The lay-out is almost a fuselage using sails as wings...

I wonder..

 

[Nicknick]

Basically yes, but with a fixed wing made of carbon fiber instead of fabric sail. This concept allows the use of an extreme wide wing span without high bending loads in the wing. The structure can be very light and aerodynamic efficient. We don’t need a tail, possible no controls surfaces in the wings (steering by gravity shift) and the fuselage can also be very light (no bending moments from any wing) and optimized for laminar flow.

The main difficulty lies in getting it into the air.