UMX FrankenDelta

It all started with my JAS-39 Gripon (retired).

After a serious nose-in, it’s nothing more than a twisted hulk of foam that I trip over occasionally. But I noticed the wings were still in pretty good shape. What if, I wondered, I pried them off and stuck them together? Could I stick a motor in the back and make a tiny flying wing?

I actually thought it looked super-cool. I chopped the elevons up to make room for a propeller. Then chopped them up some more. Then decided that this should really be a tractor delta, rather than a pusher wing, so I had to glue them all back together again.

The wings didn’t quite fit together, as they have some raised ‘tabs’ that originally fit into holes in the fuselage. I decided to retain the space in the middle to mount my equipment in. I a bamboo skewer through each set of tabs to hold everything in alignment and create some internal spars.

I made a firewall out of some plywood and stuck it in the front, then mounted a Turnigy 2730-3000 outrunner (from a destroyed Adrenaline Rush) to it. I didn’t want the servos dragging on the ground, and the 6 gram servos I’m using didn’t fit the original pockets anyway, so I cut new holes in the wing and mounted the servos vertically in them.


Here’s a top view where you can see the round ‘tabs,’ and the empty center space they create, pretty well.

I used blue fanfold foam to fill the gap in the bottom of the wing. You can see the little 6gram servos sitting in their giant, empty pockets as well.IMG_1634

This gets covered up with tape, along with the empty servo sockets.


The receiver sits up front, behind the firewall. IMG_1637

The ESC sits in the backIMG_1638  I made winglets for the rear of the wing. They are modeled on the original Gripon’s canards, but made of blue fanfold foam.IMG_1640I ran two strips of “Velcro” down the gap on the top, to temporarily mount my battery while I try to work out the best CG for the plane.IMG_1636

With a 17″ wingspan, it weighs 4.4 ounces without a battery. AUW with an 850mAh 2-cell is 6.2 ounces. With a 5×3 prop, it develops 12.2 ounces of thrust and goes in the neighborhood of 50MPH. It will roll at a ridonculous 200 RPM. maiden01


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