Actualy banktoturn I have no problems with spars breaking what so ever.I am just curious to find out something I can not figure out myself.
I did learn something from all these discussions : if there is a force that can make my wing break it will most likely be during the launch. Since my plane is electric I really do not need to worry about that. It is just my German urge for perfection that makes me build things 150% when 90% would be more than enough.

As to testing: it is not hard to build parts and break them. But how do you ensure that you use the same force in each situation? How do you measure that? How do you know that what you measure is a rule and not just a coincidence where forces come into play that you are not aware of?

The only acceptable test would be one that can be repeated by anyone else and would lead to the same results every time you do it with the same equipment. Impossible in a private environment.

I am not a big fan of learning by trial and error because it is inefficient. But that is the only option we have I guess.

Like I said before, someone who is really proficient in physics can answer that question. It is as far as I remember simply a matter of vectors. What is the result of a force in that direction and how is it distributed in which situataion. Beginner stuf for a physics major.

Steff