We'll still mount those mock-up motors by identical means, and to do so I've removed the seating plinth and inverted the airframe so as to apply a pair of six-inch brackets.
These are oriented face-down, so that they essentially reinforce the perimeter tubing in resisting the upthrust. In many ways this is a more satisfactory engineering solution, because a rear-mounted motor and propeller for instance can't so easily separate as one up front ~ mainly because of the aircraft in the way. I knew someone take off in an ARV not-so-Super2, whose propeller parted company soon after.
The only difference here however is at the leading edge of the perimeter frame, where angle alloy already supports the safety grille and provides for the same role in part.
The U15 includes four 4mm (or four 5mm) threaded inserts around a circle two inches in diameter: these tally nicely, such that two bolts pass through the tubing and one through each bracket.
