Free plans? Open source plans?

oliver your innocence has hidden something important from you.

Not exactly, as I've been studying aerospace engineering for about 5
years now. I know, unfortunately that's no proof of knowledge,
experience or wisdom...

what you must have and understand for designs that you build from
anonymous sources is the design calculations.

This could easily be integrated into an open source aircraft project,
don't you think? You take the structural members of the wing, the
flaps, whichever component (I know it becomes very tricky for certain
parts), do the calcs, and if it holds up you draw up the plan. If it
doesn't, back to the design.
This way the other participants could at least theoretically verify
what one has designed. And if you have a decent number of
participants, there will hardly be any points missed. Imagine an open-
source plane flying as well as Wikipedia compares to "regular"
encyclopedias like the Enc. Britannica or the Brockhaus.

Oliver