Basic Rule of Thumb

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RC design

Transcript

  • By

    S. M. Anwarul Aziz Lecturer AIB. PRO Runway 32.

  • Outline

    Components of an Aircraft

    Basic Definitions

    Rules of Thumb for RC Aircrafts (Method-1)

    Rules of Thumb for RC Aircrafts (Method-2)

    Rules of Thumb for RC Aircrafts (Method-3)

    Additional Considerations 2

  • Components of an aircraft

    3

  • Basic Definitions

    Aspect Ratio, AR

    AR =

    =

    Glider = 7 - 10

    Trainer = 5 - 7

    Fighter = 3 - 5 4

  • Basic Definitions (cont) Wing Loading

    Weight of the aircraft divided by the area of the wing.

    e.g. Boeing 787 : Weight = 228,000 kg

    Wing Area = 325 m2

    Wing Loading =

    = 701.54 kg/m2

    = 70.154 gm/cm2

    Thrust to Weight Ratio

    Thrust provided by powerplant divided by weight of the aircraft

    e.g. Boeing 787 : Max Thrust = 57,084.6 kg

    Weight = 228,000 kg

    T/W Ratio = 0.25 5

  • Rules of Thumb (Method 1)

    1. Estimating Weight

    2. Wing Loading Calculations

    3. Wing Area and Other Wing Parameters

    4. Empennage Design

    5. Fuse Length

    6. Wing and Empennage Position

    7. Control Surface Sizing

    8. Required Thrust 6

  • 1. Estimating Weight

    Estimate a weight for your RC.

    As a beginner, it is a good idea to start with a low weight.

    e.g. Model Weight, W = 900 grams

    7

  • 2. Wing Loading Calculations

    Pick a Wing Loading for your Aircraft type:

    Glider = 10 oz/ft2 = 3.05 kg/m2= 0.305 gm/cm2

    Trainer = 15 oz/ft2 = 4.58 kg/m2 = 0.458 gm/cm2

    Fighter = 20 oz/ft2 = 6.10 kg/m2 = 0.610 gm/cm2

    ** We will go for a Trainer in this session. 8

  • 3. Wing Area and Other Wing Parameters

    Get Wing AREA (S) from Model Weight (W) and Wing Loading (/)

    Choose Aspect Ratio (AR) according to your Aircraft type [i.e. Glider, Trainer, Fighter]

    Get Wing SPAN (b) and Wing CHORD (C) from Aspect Ratio (AR) and Wing AREA (S)

    9

  • 3. Wing Area and Other Wing Parameters (cont) Model Weight, W = 900 grams

    Wing Loading (/) = 0.458 gm/cm2

    So, Wing Area, S = 900

    0.458 = 1965.07 cm2

    Let, AR = 6 [as, AR for Trainer = 5 7]

    =

    = 6

    Wing Span, b = 6 1965.07 = 108.58 cm

    Wing Chord, C =

    =

    1965.07

    108.58 = 18.10 cm

    10

  • 4. Empennage Design

    Get Horizontal Tail AREA (SHT) and Vertical Tail AREA (SVT) from the following approximations:

    Horizontal Tail AREA, SHT = 20 25% of Wing AREA (S)

    Take Aspect Ratio (AR) 3 or 4

    Get Horizontal Tail SPAN (bHT) and Horizontal Tail CHORD (CHT) from Aspect Ratio (AR) and AREA (SHT)

    Vertical Tail AREA, SVT = 7 11% of Wing AREA (S)

    11

  • 4. Empennage Design (cont)

    Wing Area, S = 1965.07 cm2

    So, SHT = 22% of S [SHT = 20 25% of S] SHT = 1965.07 x 22% = 432.32 cm

    2

    Let, AR = 3

    =

    = 3

    HT Span, bHT = 3 432.32 = 32.01 cm

    HT Chord, CHT =

    =

    432.32

    32.01 = 13.51 cm

    And, SVT = 9% of S [SHT = 7 11% of S] SVT = 1965.07 x 9% = 176.86 cm

    2

    12

  • 5. Fuse Length

    Calculate Fuse Length from the following approximation:

    Fuse Length = 75% of Wing SPAN (b)

    Fuse Height = 10 15% of Fuse Length

    e.g. Wing Span, b = 108.58 cm

    So, Fuse Length = 75% of b

    Fuse Length = 108.58 x 75% = 81.44 cm

    13

  • 6. Wing and Empennage Position

    Wing position and Horizontal Tail position may be found from the following approximations:

    Wing leading edge to Propeller or,

    The NOSE LENGTH = 1 1.5 times the Wing Chord (C)

    Wing trailing edge to the Elevator = 2 3 times the Wing Chord (C)

    14

  • 6. Wing and Empennage Position (cont)

    Wing Chord, C = 18.10 cm

    Wing leading edge to Propeller or,

    The NOSE LENGTH = 1 X 18.10 cm = 18.10 cm

    Wing trailing edge to the Elevator

    = 2 X 18.10 cm = 36.20 cm

    15

  • 16

    Sum

    min

    g U

    p

  • Summing Up

    17

  • 7. Control Surface Sizing

    Calculate Control Surface Area as follows:

    Aileron Area= 2 x

    of Wing Area

    Elevator Area =

    of HT Area

    18

  • 8. Required Thrust

    Get a Motor based on Estimated weight of your RC and your Aircraft type.

    Assume motor efficiency = 80 90%

    So, Thrust Required for a:

    Trainer type = 1.10 X Estimated weight of RC

    Fighter type = 2.30 X Estimated weight of RC

    e.g. Model Weight = 900 grams

    Motor Required = 1.10 x 900 = 990 grams 19

  • Additional Considerations

    Powerplant should be placed as such that, we get

    2 3o Right Thrust

    2 3o Down Thrust

    Better to place the wing at a 3 4o incident.

    20

  • Rules of Thumb (Method 2)

    1. Available Thrust

    2. Estimating Weight

    3. Wing Loading Calculations

    4. Wing Area and Other Wing Parameters

    5. Empennage Design

    6. Fuse Length

    7. Wing and Empennage Position

    8. Control Surface Sizing 21

  • Summing Up

    Thrust for Trainer type = 1.10 X Est. Weight of RC

    Pick a Wing Loading for your Aircraft type: Trainer = 0.458 gm/cm2

    Choose Aspect Ratio (AR) according to your Aircraft type [i.e. Glider, Trainer, Fighter]

    Get Wing SPAN (b) and Wing CHORD (C) from Aspect Ratio (AR) and Wing AREA (S)

    Horizontal Tail AREA, SHT = 20 25% of Wing AREA (S) 22

  • Summing Up

    Take Aspect Ratio (AR) 3 or 4

    Get HT SPAN (bHT) and HT CHORD (CHT) from AR and SHT

    Vertical Tail AREA, SVT = 7 11% of Wing AREA (S)

    Fuse Length = 75% of Wing SPAN (b)

    The NOSE LENGTH = 1 1.5 times the Wing Chord (C)

    Wing trailing edge to Elevator = 2 3 times the Wing Chord (C)

    Aileron Area = 1/16 of Wing Area

    Elevator Area = 1/4 of HT Area

    23

  • Rules of Thumb (Method 3)

    Download full plans from Internet.

    http://www.parkjets.com/free-plans

    http://www.flyelectric.ukgateway.net/

    http://www.flitetest.com/

    24