5Two Overall Components Helicopter(s) up to 2 in competitionFlight Log
6Construction Parameters RotorsMaximum Rotor Diameter – 25.0 cmAny number of bladesNo chord size maximumStudents must construct rotorsMinimum Overall Weight – 3.0 gNo Boron Filaments on helicopterAny other Material may be used -Glue, wire, clay for ballast, plastic, tape, etc.
7Construction Parameters cont’d Rubber Poweredrubber weight doesn’t contribute to overall weightNo mass or size limit on the rubber itselfRubber lubed before or after check inFlat Balsa Wood Disc – upper most part of helicopterDesign - May use published plans, kits, and/or student designsHelicopter must be Labeled
8Flight Log Minimum of 10 Entries Minimum of 6 Data Points Motor size before windupany of these - Mass, width, length, etc.Number of turns before flightFlight TimeAny three otherMost important part of practice and competition!
9Competition Flight Period for Official Flights – 8 minutes Starts with 1st Official FlightOfficial Flights – up to 2 using 1 or 2 helicoptersAll flights within a Team’s Flight Period are official unless declared a trim flight prior to launch.
10Timing Start – when helicopter leaves student’s hand End - Any part of the helicopter touches the floor (including pieces that break off)Rotors no longer support the weight of the helicopterJudges determine the flight to be over
11Scoring Longest single flight aloft (+/- Bonus or Penalties) wins Ties broken by longest non-scored flightBonus – Each single-bladed rotor assembly (up to 3) receives a 10% bonus added to that helicopter flight time (max 30%)Penalties -10% flight time deduction for incomplete log, 30% deduction for none (off of each flight)Construction & Competition violations for a helicopter are ranked below all other teams
12Flying - Basics Wind rubber motor Attach one end to each hook Pay attention to winding direction!Attach one end to each hookCheck the ceilingMake sure you launch in a clean/clear spotLet Go of Helicopter!Record Data!Be prepared for repairsDon’t grab a flying helicopter from the air
13Flying – More Advanced Critical Parameters affecting duration Turns on motorTorque of motorPitch and Diameter of rotorsWeight of overall helicopter (motor and airframe)DragRubber Motor is the most easily adjustable factorThicknessLengthBatch
14Flying – Torque More advanced Torque can be fairly converted to ThrustTorque is the rotational form of force, if you apply more force on something, it will move faster. If you have more torque on your rubber band, the rotors will turn faster and you’ll have more thrust.Thus, knowing how much Torque the motor outputs, you essentially know how much Thrust the helicopter has.A Torque Meter is the most essential tool to increasing flight times.
16Creating a Torque Curve Wind a thick motor with one end attached to the torque meterInitially the meter will quickly jump several numbersMeter will hold steady for a period of timeMeter will quickly jump until the motor breaksCounting the winds, record at each interval:Number of windsNumber on the torque meterPlot on the graphRepeat the process with a thin motor
18Using the Torque Curves Make a flight with the thick motor wound until just before it breaks (or close)At end of flight, take motor off and check remaining torque on the meterMark that spot on the Torque Curve for that motorAny winds left on the motor are wasted turns (always will have some left)Idea is to find the correct combination of motor size to each helicopter that gives you the least number of winds left at the end of the flight.
19More Torque infoThrust is needed to counter the weight of the HelicopterThrust > Mass = ClimbingThrust = Mass = HoveringThrust < Mass = DescentFor Helicopters, it is important to be powered for the whole flightBuilding a Torque Meter - ed_files/torqueMeter.pdf
20Construction – General Tips Anticipate building many helicopters throughout the yearPriorities1 - Build quality/trueness/straightness2 - Strength3 - Weight4 - (and a distant number 4) Design
22Adjusting Basic Template Rotor Pitch – Increase pitch by lengthening the fold up triangle flaps at the ends of the templateRotor Diameter – Increase or Decrease the width of the template
23Supplies Balsa Music Wire – One 36” piece of 0.020” music wire Four sticks of ~40 cm long 1/16” x 1/16” (rotors)(can be stripped from sheet stock)One 1/8” x ¼” x ~15” balsa (motor stick)One ~3”(wide) x 1/16” sheet balsa (ribs & disc)Music Wire – One 36” piece of ” music wireCovering Material (condenser paper, mylar, tissue)Glue (Titebond, use superglue extremely sparingly), 3M 77 spray adhesiveTools (templates, razor blades, rulers, pliers, etc.)
26Trim long sticks to required length for spars (longitudinal supports). Mark spars in 6 equal lengths with marker (rib locations)
27Using curved template (can be cut from soda cans, French Curves, sheet metal), slice curved balsa ribs from 1/16” sheet stock
28Lightly tape spars to template (I use drafting tape)
29LIGHTLY dip one end of rib in a small puddle of glue LIGHTLY dip one end of rib in a small puddle of glue. Just enough dipping to cover the tip (I can’t emphasize how much glue is overused).Place the glued end on the lower spars, resting the rib on the top spar.- Do not use curved spars for center posts, use a piece of 1/16” x 1/16” stick
30Allow the lower glue to dry (it should not be long if you are using the right amount). Cut the scrap end of the ribs off at the spar to miter the joint. Apply a similarly small amount of glue, using a scrap piece of wood as a brush.
31Once dry, you have a completed rotor frame! If covering with paper, cut a piece a bit larger than the section to be covered.
32LIGHTLY dust the area to be covered on the frame with 3M Super 77. Roll frame on covering to firmly attach paper.Trim excess with a brand new razor blade(the sharpest you can find).
33Cut a piece of music wire ~4” long for the motor hook. Bend a complete circle on one end.Bend base of circle back to make the rotation symmetrical.Bend a small flare on the end of the wire loop to allow motors to attach (not pictured)
34Cut two pieces of ~1/8” square to 3 cm long. Mark the center.Pierce the pieces with the motor hooksBend the wire as shown to latch onto the stickGlue the sticks and wire to the center of the spars (the top spar for the bottom rotor, the bottom spar for the top rotor).
35Cut a stick of 1/16” x 1/16” x ~2” long balsa Cut a stick of 1/16” x 1/16” x ~2” long balsa. Attach a disc larger than a dime atop.Glue assembly to top rotor.
36Thrust Bearing (Pigtail) – Cut two pieces of hardened music wire in order to make a thrust bearing. Follow directions at:
37Attaching the Thrust Bearing to the Fuselage - Cut the 1/8” x ¼” piece of wood to ~15” (this is something to play with a lot)Cut a notch in each endGlue the thrust bearings into the notches(make sure the center thrust line is perfectly straight on each side!)