Max Weight of Non Lift Producing Components

On Friday, December 1, 2017 at 3:44:44 AM UTC-8, Kiwi User wrote:
On Thu, 30 Nov 2017 10:07:57 -0800, phouchg278 wrote:

Does anyone know, how exceeding that non-lifting weight influences the
flutter of the wing?

Its more a structural thing than load related.


For the non engineers that might read this..... a loading illustration
using two examples:

Use a (really long)tongue depressor and white glue to glue a hollowed out eggshell to the half span point. Let it dry. Take a wing tip and do anything you like to shake the egg off the stick. Not enough mass in the eggshell to part it from the stick. Safe scenario = under max non-lifting parts weight.

The worst case scenario is the same eggshell full of heavy stuff. Mercury would be great - but its impractical. Imagine it. Load that egg (fiberglass shell) to the max, and then introduce a bunch of G's via centrifical or gust(rotor flight)force. The eggshell will rip off the stick(spar). Or, the stuff inside the shell will rupture it and leave the scene - think an over-max-payload person attached to max 242 lb. (110 kg) seat belt attaching points.

There are recurring discussions about how much margin designers provide for protection from this and that (max non lifting, Vne, gust loads, seatpan loads). My response is always - do you know the life history of this pretty fiberglass? The controlrod end play? The hingepoint tightness? How many times someone flew it how close to/over Vne due to an antique instrument or partially plugged pitot line? I am not in favor of flying beyond manufacturer's limits for anything.....
thanks for the many contributors to good info on this thread.

Cindy B

On Friday, December 1, 2017 at 10:00:14 AM UTC-8, CindyB wrote:

There are recurring discussions about how much margin
designers provide for protection from this and that...

One of the more high-profile examples is this RV-10 airplane for which the amateur builder arbitrarily increased the gross weight by a hundred pounds. Designer Dick Vangrunsven rightfully took issue with this practice:

https://www.facebook.com/notes/vans-...37594966250883

...I am not in favor of flying beyond manufacturer's limits for anything...

That's the best plan!

--Bob K.