Thursday, January 21, 2010

Control Surfaces, Dihedral & Winglets

The prototype wing is coming together well. Last night's activities:

  • Trimmed trailing edge of wing to square it up and bring it to a uniform thickness

  • Cut out elevons and prop hole

  • Mitre cut wing root to add 0.5" of dihedral

  • Glued wing halves together (using 5 minute epoxy)

  • Attached winglets (using 5 minute epoxy)
I've deviated from the original design. This prototype is going to be built up as a lightweight floater, just to test the wing geometry, construction techniques, etc before I put together the final high speed wing. The elevon size, motor location and winglets were all eyeballed- no calculations used. This may prove a mistake, but it will be interesting to see how it flies. Since it is so lightweight it should be durable enough to try several different thrust angles and motor offsets. I also extended the elevons behind the prop to give some measure of vectored thrust to try and improve extreme slow speed maneuverability.

The resulting glued up fusalage is darn lightweight- only 95.6 grams.

Major Component Weights
  • Wing, Wingtips & elevons, no cutouts 95.6g
  • Turnigy plush 18A ESC 25.4g
  • Esky 1000 mAh 3cell LIPO battery 87.5g
  • Emax CF2822 1200kV motor, prop adapter, & APC 9x6 67g
  • 2x Parkzone DSV130M Servos 31g
 total: 306.5 grams
 Using the WebOcalc calculator:
  • estimated stall speed: 9.8 mph
  • maximum speed: 50.9 mph (pitch speed)
  • 3:1 Thrust to weight ratio
  • 910mAh 3 cell 20c minimum battery
So far, looks good. The Esky 1000mAh batteries I have are total junk, so I'll try to fly this with the 500mAh 3 cells or 800mAh 2 cell batteries until the Rhino 1000mAh's arrive. I may also cut out the wing enough to allow trying the 2200mAh 3cells.

The next steps are to find some of the fancy 3M double reinforced packing tape for "spar" reinforcement and wrapping the elevons, plus some colored packing tape to cover the wing. I may also insert some balsa into the elevons behind the prop to stiffen them up.

 Top view, components arranged before cutting elevons or gluing wing cores together

Dry fit components, including pilot

Components epoxied together & drying (notice sweet painter's tape clamps)

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