- Joined
- Jan 12, 2017
- Messages
- 747
One key advantage of Mignet's Flying Fleas is that the wings fold (both of them) over the top. Already small planes, this allows them to fit easily into a garage.
The plans for Mignet's HM290 (& Rodolphe Grunberg's "modernized" HM293) call for the male side of the forward spar hinge to be fabricated from 4mm sheet steel, simply butt welded to a bushing tube.
Even recognizing that this is thick material (4mm = 0.160") and that we are talking about the top hinge, while the flying loads will be carried primarily by the bottom locking mechanism, to me this still would mean putting an awful lot of faith in that weld.
The alternative I am exploring (and hoping you folks will respond with comments about) is this:
How about .080 4130 welded to 1/2" bushing tube and wrapped by .040 4130 (with perimeter welding all around), enclosing not only the .080 sheet but also the tube, as shown below? Total thickness of the 3 metal sheets = 0.16 = 4.06mm.
The plans for Mignet's HM290 (& Rodolphe Grunberg's "modernized" HM293) call for the male side of the forward spar hinge to be fabricated from 4mm sheet steel, simply butt welded to a bushing tube.
Even recognizing that this is thick material (4mm = 0.160") and that we are talking about the top hinge, while the flying loads will be carried primarily by the bottom locking mechanism, to me this still would mean putting an awful lot of faith in that weld.
The alternative I am exploring (and hoping you folks will respond with comments about) is this:
How about .080 4130 welded to 1/2" bushing tube and wrapped by .040 4130 (with perimeter welding all around), enclosing not only the .080 sheet but also the tube, as shown below? Total thickness of the 3 metal sheets = 0.16 = 4.06mm.
