Skytwister Helicopter Plans Part 1

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

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

• HTD Cog Drive Pulleys: Blower Drive services

• 70 Tooth Chain Sprocket: Sprocket Specialists

---

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.

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 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

---

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.