Even though my structure books are still in the mail, I'm beginning to think about doing structural design on my first part, just to see how little I know. I'm going to start with the winglets. Interestingly, my winglets are all-flying and deflected by electronic actuators, so at some level I get to choose the max load "arbitrarily"; if I'm approaching limit loads, I can simply refuse to deflect (or stop deflecting) the surface. Indeed, since I'm likely to use a direct drive torque motor, this is as simple as limiting amperage (and providing safety factors).
I've decided that I want to be able to support max slip rate (11.5°β) at speeds up to Va (which is approximately twice Vs for this design, I think). At lower speeds, β will still be limited in the control system to this value, but symmetric deflection (airbraking) becomes available. Airbraking will be limited based on loads on the winglets as described above, so in a no-slip condition it will be possible at speeds at and above Va. At speeds above Va, slipping will be permitted up to the load limit. I may or may not choose to allow max-rate slips at some speeds above Va by allowing "negative airbraking" (symmetric inward deflection) of the winglets, which can provide a huge reduction on winglet loads within the limits of geometric concerns.
It looks like total load on the critical winglet (which is the forward-moving outer winglet) at the critical condition (Va 11.5°β) is around 111 lbs.
Would it be reasonable to design to 166 lbs limit / 250 lbs ultimate, then? Am I missing other critical conditions?
I've decided that I want to be able to support max slip rate (11.5°β) at speeds up to Va (which is approximately twice Vs for this design, I think). At lower speeds, β will still be limited in the control system to this value, but symmetric deflection (airbraking) becomes available. Airbraking will be limited based on loads on the winglets as described above, so in a no-slip condition it will be possible at speeds at and above Va. At speeds above Va, slipping will be permitted up to the load limit. I may or may not choose to allow max-rate slips at some speeds above Va by allowing "negative airbraking" (symmetric inward deflection) of the winglets, which can provide a huge reduction on winglet loads within the limits of geometric concerns.
It looks like total load on the critical winglet (which is the forward-moving outer winglet) at the critical condition (Va 11.5°β) is around 111 lbs.
Would it be reasonable to design to 166 lbs limit / 250 lbs ultimate, then? Am I missing other critical conditions?
