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Sep 08, 2009, 07:28 PM
just Some Useless Geek
Build Log

An Alternative Smart Dart -- the Smarty Pants


AUW: 180 grams
Battery: Turnigy 500 mAH 2S 20C
Motor: Turnigy 2204-14T with a GWS 8x4.3 prop
ESC: 8/10A Super Simple
Servos: hexTronik HXT500 (x2)

I had to play with the Smart Dart configuration to see what I could get away with. The result was the Smarty Pants. Very slow flight, very stable, really easy to fly. My maiden flight I sent it up and down the street under the overhanging trees. Really, really easy to fly -- did I mention that?

I made the wings pretty wide, put some asymmetrical trail in there (trying to move the CL back), and added a KFm2 to it. The fuselage started out as three layer sandwich. Now I make it with 10 mm Depron and a 1/8" square birch or spruce spar along the bottom edge. This prevents the fuse from cracking during really high G maneuvers, of which this plane is plenty capable.

I use CA in some places, but mostly yellow Gorilla Glue. GG is fast becoming my adhesive of choice, since it can be made to cover a multitude of sins. Heh.


Numbers in the drawing are millimeters. Rather than try to put a V notch in the top of the fuse I use a couple pieces of balsa angled trailing edge material slitted to the right size. The KFm2 upper panels are dimensioned off of the main wing. I didn't bother with calculating exactly how much narrower in span the KF panels are; I just used TLAR with a visual approach. The wing roots need to be angled so that the assembled wing is at about 165 degrees or so. This plane doesn't require a whole lot of dihedral, so go easy here.

The front of the wing assembly is even with the front of the fuselage. I grind the whole assembly flat after the GG has cured so that the motor mount base plate has a flat surface that encompasses both the fuse and the wings. A piece of light ply forms the motor mount base plate on the airframe side.

A nice piece of EPP makes an impact-resistant motor mount pad. The motor should mount to a flat plate of light airplane ply, and that attaches to the EPP block. Very smooth. I also used EPP for the little winglets that hang below and stick above the wingtips. EPP "tip plates" out here help to prevent crash damage as well as adding some vertical stability during prop hangs.

The vertical stab is notched out to rest on top of the rear portion of the wing assembly. The stab can just butt up to the fuselage. A good CA or Gorilla Glue bond there will hold the stab against any impact that the fuse can survive. This I know for a fact! The horizontal stab lays up against the bottom of the fuselage, with its trailing edge even with the back of the fuse. The elevator hangs out behind that. The rudder is a rectangular piece coming off the back of the vertical stabilizer and should be around 35-40mm. The elevator should be the same size so that the plane can rest on these edges for vertical takeoffs. (For more phun you can increase these to 70mm or so. Try it -- you'll like it!)

Anybody with a grain of brains can put this thing together and prolly do a better job than me. CA and GG are the adhesives of choice, but I mount the EPP winglets and motor mount block with hot glue so that they can be replaced easily later on.

Flight Tests

The Smarty Pants is hard to beat as an acrobatic/trainer three channel slow flyer. It flies slowly because of the low wing loading and the KFm2 airfoil creating all kindsa lift, but the steering characteristics are nice like the GWS Tiger Moth. It has a harder time in the wind than something like the Yardarm, but it can still fly acceptably even in a 5-10 MPH breeze.

As a trainer the Smarty Pants acts like a good dihedral plane. You let go of the flightstick and it corrects itself. Nice. As a violently twisting acrobatic plane the Smarty Pants flops and spins all over the place. (More video to come.)

See it fly
Last edited by A Useless Geek; Aug 23, 2011 at 02:07 PM. Reason: Notes for stupidly abrupt performance
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