Michigan State University Helicopters

Division B 2014

Event Supervisor Thomas Baumann

Coaches Workshop

Presentation Overview

•  Helicopter design rules •  Steps to a successful competition:

–  design selection –  construction –  experimental evaluation

•  Resources •  Appendix

Rules

Read and understand the rules.

Helicopter History

One-bladed helicopter (Germany, 1962)

Helicopter Dimensions

Rotor Diameter

This is too big!

Design Selection

•  There are few kits available on the internet. Make sure they comply with the rules or adjust accordingly.

•  Plans should have two key elements: –  drawing of plan showing dimensions and arrangement of all parts –  bill of materials (often missing, you probably will have to make it

yourself)

•  There is still plenty of room for experimentation! –  Remember, the purpose is to test, collect data, and adjust.

Construction Tools •  Must have:

–  flat building board (e.g. foam insulation board) –  wax paper –  sharp knives and spare blades (e.g. X-acto, scalpels, razor blades) –  metal edge rule or straight edge –  pins & scrap balsa blocks –  scale accurate to 0.01 g (inexpensive ones can be found used on the

internet) –  wire cutters, pliers, tweezers

Construction Tools •  Nice to have:

–  balsa stripper (simple one can be built from Al sheets and razor blades)

–  matting board, foam board, or ¼ inch balsa for jigs –  many other tools can be home built (like glue applicator, pitch

gauge, deflection meter… )

Construction Materials

•  Complete kit –  easy way to get all needed materials (except glue) –  more costly, especially if you want to build more than just one or

two helicopters, and you can’t pick balsa densities/grain.

•  “Bulk” material –  balsa: 1/32, 1/16, and 1/4 inch thick sheets, or suitable width sticks,

select appropriate grain and light to medium density. –  covering: indoor mylar, tissue, grocery store bags –  glue: superglue (cyanoacrylate or CA) or white (aliphatic) glue –  if using CA, instant setter –  wire 0.020 inch diameter –  prop hanger

Construction Steps •  Gather and prepare materials.

–  Use bill of materials to determine weight of each component. –  Weight is the key parameter!

•  Make jigs. –  Jigs will help you to build consistently and efficiently.

•  Make rotor frames. –  Select proper balsa –  Cut many ribs/blades and select by weight (rotors should be

balanced).

•  Cover rotors and assemble/balance. •  Make motor stick/tube. •  Attach lower rotor to motor stick/tube, depending on

design.

Flying Materials •  Necessary:

–  rubber: FAI TAN Sport or preferably Super Sport, various thicknesses, but 1/8 inch may be a good starting point; need spare rubber!

–  o-rings (e.g. teflon tube slices) –  winder (the rubber needs hundreds of turns!) –  stop watch –  flight log –  sturdy carrying/storage box (models are very fragile)

•  Nice to have: –  stand to hold the fragile helicopter –  anchor to wind motors off the helicopter –  torque meter –  repair kit (CA, setter, knife, spare covering, spare balsa)

Experimental Evaluation •  Expect to spend a lot of time testing and flying!

–  Try different rotor designs if possible.

–  Select variables you plan to explore.

–  Keep detailed records and organize your experiments to test alternatives effectively.

–  Measure and analyze results, find out what the key variables for improvement are.

–  Run multiple trials to minimize errors.

Flying the helicopter

Competition •  Flight duration may be different due to ceiling height!

–  Keep in mind that most helicopters will hover under the ceiling. –  Height of last year’s gym is 21 feet.

•  Have the students be ready for quick repairs:

–  snapped motors –  broken rotor blades

Resources •  http://soinc.org/helicopters_b

National Science Olympiad Helicopters homepage with links to other online resources.

•  http://scioly.org/ The Science Olympiad Student Center. Also see http://scioly.org/wiki/index.php/Helicopters

•  http://www.indoorduration.com/ “The ultimate resource for the indoor rubber-powered model airplane flier”

•  http://www.indoormodelsupply.com/ “Store for Tru-Weight Indoor Balsa, and competition grade supplies as well as a huge selection of free flight kits and accessories.”

•  http://www.faimodelsupply.com/ “Home of World Champion Tan Super Sport Rubber”

Appendix by Jeff Anderson

Rotor Construction Three basic approaches: •  Straight, offset, twisted spars with ribs connecting, covered by light material, what I’ll be showing today. •  Formed props, possibly most efficient, solid or built up, attached to a center spar see: http://www.indoorduration.com/INAVHobbyShopper.htm or http://www.indoorduration.com/F1DPropConstruction.htm a simplified version of this prop can use flat paddle blades. •  Carved Rotors, see: http://www.gryffinaero.com/models/ffpages/tips/propcarve.html or http://www.hbrf.org.nz/joomla/index.php?option=com_content&view=article&id=101:carving-a-balsa-propeller-35&catid=40:general-articles&Itemid=59

Appendix by Jeff Anderson

Bill of Materials

Part Name qty length width thicknessvolume (in3)

rec density (lb/ft3) wt (grams)

spars 4 15.66929 0.0625 0.0625 0.244833 12 0.772ribs outer 4 4.58939 0.0625 0.0625 0.071709 7 0.132ribs outer less 1 4 3.75 0.0625 0.0625 0.058594 7 0.108ribs outer less 2 4 3.010399 0.0625 0.0625 0.047037 7 0.087ribs outer less 3 4 2.462214 0.0625 0.0625 0.038472 7 0.071Upper Rotor, center rib 3 1.5 0.0625 0.0625 0.017578 10 0.046Upper Rotor Wire 1 2 0.02 0.000628 489.6 0.081Covering 4 5.905512 3.525802 20.82167 9 0.1209Motor Stick 1 12 0.375 0.25 1.125 7 2.069Prop hanger 1 0.1tail wire 1 0.75 0.02 0.000236 489.6 0.030misc glue, etc 0.25

3.866

PLANNING DATA, 6 inch tips span, 1.5 inches tall, store bag covering

Appendix by Jeff Anderson

Prepare materials • Select straight parts from your sticks or strip your own from sheet to match plan, make sure you check weight against the bill of materials, stiff and straight, cut slightly long.

• Cut ribs, lots, select the best that weigh the bill of materials amount.

• Cut covering with a one inch margin. • Cut multiple motor sticks, select the best, stiffest, to weight on bill of materials.

• If building on plan, tape to building board, cover with wax paper, otherwise just cover board with wax paper.

• Have glue, pins, scrap blocks to hand.

Cutting Ribs

Appendix by Jeff Anderson

Build rotor frame • Pin spars to plan or jig. Don’t pin through balsa! • Dry fit ribs in position. • Check rib position for accuracy. • Glue with CA using micro applicator. • Let dry or apply accelerator. • Remove from building board.

Cover Rotor (airplane wing shown as example)

Smooth down one edge

Roll down Trim, use a fresh, sharp knife

While example is tissue, this approach works for any covering

Any spray glue works

Once you drop it, don’t try to move it!

Appendix by Jeff Anderson

Make up Motor Stick (example from plane)

Flying Session Date:

Room Size: Ceiling Ht: Temperature: Air:

Flight Number

Wing setting

Tail setting

Propellor Pitch

Motor Size

Max Turns

Backoff Turns

Max Torque

Backoff Torque

Max Height

Turn Diameter

Flight Time

Flight Behavior

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Airplane being tested, brief description

2009 Wright Stuff Div BFlight Log

Thoughts on optimizing the design For my design, variables to explore: • Area • Pitch • Differential pitch

Appendix by Jeff Anderson

Flying, misc. hints/tips Rubber motor. • Lube your motors • WIND THEM! A 2 g 3/32 motor will take well over 1200 turns before breaking. I fly my 0.075 motors on 1800 turns!

• BREAK A MOTOR OR TWO to know when it breaks! • Pre Flight (develop a checklist, use it every flight) • Assemble helicopter • Check settings, use plan recommendation as start point. • Check for anything broken, fix it. • Set plane in stooge. Winding • Wind off the helicopter using a hook, put the knot by the hook • Stretch 3-4 times length, start winding stretched, about 500 to 600 turns start coming in to end at motor stick length with 1000 plus turns

• Transfer the motor to the helicopter –  Have one partner hold the plane, lock the propellor and present it to the winding partner, watch the tail! –  Winding partner, without touching plane (much) take motor off winder, put it on prop hook. –  Then take other end of motor off anchor and put it on tail hook.