Skytwister Helicopter Plans Part 1

skytwister helicopter

Ben Showers Brilliant Little One Seat Helicopter

Here we will present a series of articles presenting to SkyTwister helicopter as per the original hand-drawn plans by Ben Showers.

ABOVE: Australian builder flies Rotax 583 powered SkyTwister (EDITOR – I always though of these style DIY helicopters as paddock hoppers, here’s why).

From YouTube….

Darren Andrew Mitchell

Published on Aug 19, 2017

Experimental helicopter fun 2004, This was my little helicopter. I flew it for about 16 hrs and I just new it was going to kill me if I flew it at higher altitude. And at 10 hrs my suspicions were confirmed. A tail rotor blade decided to let go entirely and embed its self into the ground. lucky for me It was on start up and I was on the ground.


Part 1: Skytwister Helicopter General Information

The reason the Skytwister off sets it’s main rotor shaft


DRIFT

Thrust produced by the tail rotor of a single rotor helicopter will cause the helicopter to drift. To compensate for this drift, some helicopters have their main rotor mast rigged slightly away from the vertical position. This offset gives the lift produced by the main rotor a slight horizontal component.

This addresses:

  • YAW

  • DRIFT

  • TORQUE

The tendency of a helicopter to drift in the direction of tail rotor thrust during a hover is called:

  • Coriolis Force

  • Translating Tendency

  • Transverse Flow Effect

rotorhead parts

Rotor blade data as flown on the Skytwister Light Helicopter

  1. Rotor Disc Area: 362.86 square feet

  2. Rotor Disc Loading: 580 pounds per square foot

  3. Rotor Blade Loading: 3.51 lbs


Skytwister Helicopter Parts Supply


Recommended Skytwister Helicopter Engines (Use 12 lbs/hp Ratio)

  • Rotax 55-65hp (503 DC)

  • Hirth 55 – 65hp

  • Cuyuna – 460L-50hp 2SI (2 Stroke International)

Option to use the Hirth reduction drive with integrated Behlen Centrifugal Clutch for automatic rotor engagement like the Mini 500 helicopter.

rotorhead pin detail

Overrun Clutch

ORIGINAL PART: MR 300A Cross Morse Sprag Freewheeling Clutch (original specification)

EDITOR: Please note, later it was recommended to use the next size up clutch after a few failures. The original was hand made from automatic transmission parts by Ben. But there was an issue with the hardening of the shaft and it failed in a low hover causing him to crash land – and walk away (sporting a broken rib and crushed vertebra).


Skytwister Helicopter Optional Drives

  • O-Ring Motorcycle Racing Chain Drive – Chain and Sprocket

  • HTD Cog Drive System – Cog Belt and Cog Pulley (Aluminum)

  • Alternatives – Motorcycle Cog Belt Final Drive – Pulleys and Belts


Rotor blade data as flown on the SkyTwister Light Helicopter

1. rotor disc area – – D = 21′ 5″ = 21.5

FORMULA: F = D2 x Π / 4 = 462.25 x 3.14 / 4 = 1451.46 / 4 = 362.86sq ft area

2. rotor disc loading – – R (580 lb / sq ft)

FORMULA: R = G / F = 580 / 362.86 = 1.59

3. blade loading – – B (580 / 362.87)

FORMULA:B = G / Z x F1 = 580 / 2 x 82.5 = 580 / 165 = 3.51 lbs / 36287

skytwister helicopter rotor head

Skytwister Light Helicopter Helicopter Worksheet
Empty Weight 252lbs
Place Capacity 1 Person
Pilot Weight 200lbs
Main Rotor Diameter 19.5ft
Main Rotor RPM 450
Number Of Blades 2
Weight Of Single Main Rotor Blade 15lbs
Main Rotor Blade Length 9ft
Main Rotorhead Diameter 18in
Main Blade Width 6.75in
Main Rotor Blade Area 5.06sq/ft
Main Rotor Speed 459.46 ft/sec
Co-Efficient Of lift 0.57
Swept Area 298.65 sq/ft
Fuel Capacity 5 gal.
Density Of Air 0.00238 slgs/ft
Transmission Efficiency 95%
Tail Rotor Diameter 3.20ft
Tail Rotor RPM 2700
Number Of Tail Rotor Blades 2
Weight Of Single Tail Rotor Blade 1lb
Distance To Tail Rotor Hub 9.33ft
Total Weight 482lbs
Lift/Drag Ratio 18.38
Vertical Air Velocity 23.02ft/sec
Lift HP 20.17
Profile Drag 204.56ft-lbs
Main Drag Horsepower 17.53
Total Main Torque 463.14ft-lbs
Total Main HP 39.68
Tail Rotor Pull 49.64lbs
All Computer Generated Specifications

skytwister rotor head plans


DO NOT USE GMAIL OR YAHOO ACCOUNTS TO ORDER THESE PLANS! – 1. Gmail and Yahoo blocks our server, why? we do not know. 2. Gmail and Yahoo limits the size of the download, so we cannot send it manually! 3. Gmail and Yahoo blocks our email address or places it in your spam folder – so we have NO WAY of communicating with you or responding to your emails.

Summary
Skytwister Helicopter Plans Part 1
Article Name
Skytwister Helicopter Plans Part 1
Description
Ben Showers SkyTwister Helicopter was a spin off from the original Adams Wilson "Choppy" design plans built helicopter. Unlike Doug Schwochert's AW95 rendition of the helicopter, Ben took a more modern, yet complex approach to the design.
Author
Publisher Name
Redback Aviation
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