#### NoWingsAttached

##### Unobtainium Member

- Joined
- May 21, 2006

- Messages
- 4,897

- Location
- Columbia, SC

- Aircraft
- Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp

- Total Flight Time
- >350

Please note the change in thread title, after careful consideration of the thoughtful comments and suggestions below.

Please find here a table for the ZeCA (explained below) Ratio for known (and some estimated) gyrocopter types with their respective power plants.

The list will be edited and added to as folks report in, and is arranged in no specific order.

The higher the ZeCA value the better the expected take-off and climb ability.

AC = Air Command

RFD = Dominator

SC = Sport Copter

MB = Monarch

TG = Tango Gyro

Playing around with numbers, I realized that the first successful Yamaha Genesis 4-cylinder powered aircraft, affectionately known as "The Wicked", my beloved Air Command tandem that I purchased in flying condition from Ora Cook for $4,500 (it was Ora's gift to me back at Bensen Days 2011 after he met my 7-yr-old while we were RV camped next to each other and spent hours chatting), produced 600# thrust and yet only weighed 595# dry. Round up the weight a tick and that is an interesting 1:1 ratio.

SO I trotted out my trusty trig excel spreadsheet and started pluggin in other gyrocopter dry weights and thrust numbers that I knew off the top of my head and arrived at an amusing ratio that is great for overall comparison of ALL gyrocopters ever built. All ya gotta know is your dry weight and your maximum reliable thrust (from a properly done test, of course. No fair cheating with "spiked" test results from hitting the throttle fast and hard. The thrust must reflect steady state thrust after at least three full seconds of waiting for the pull numbers to settle in.)

The basic trig equation is

tan Ø = opp/adj

My excel sheet converts tangent to radians, and then degrees (I couldn't figure out a way 5 years ago to build the thing to go straight from the equation to a degrees output, so it takes three steps. I still dont' know any other way to do it with Excel, to be honest.) You just plug in your weight and your thrust, and read the output angle.

I'm calling it the Zero Climb Angle, or ZeCA for short.

So the higher the thrust, and/or lower the weight, the higher (and better) the ZeCA value.

My Wicked has a perfect ZeCA of 45°, and my Blue Bee at 300# tested with a 60 HP Hirth producing 285# thrust has a ZeCA of 43.53°

An 800# gyro would need to produce a whopping 800# of thrust to hit 45 ZeCA degrees, but I think the best we can expect from a 160HP engine is just this side of 700# (from my most recent tests using Geoff Resney's YG4 EXUP, which I have nicknamed Godzilla). A Subaru 2.5 producing 670# thrust, in a heavier enclosed SxS gyrocopter weighing 850# will have a ZeCA value of 38.25°, and the same gyro producing 700# of thrust on a dry, cool day will have a 39.47 ZeCA.

Geoff Resney's MAC YG4 EXUP Air Command weighs 630# and produces 670-700# thrust, and so the ZeCA value of "Godzilla" is an INCREDIBLE 45.87 - 47.12 ZeCA !!!

Wow. And I'm betting there is at least one MAC 90 Bensen out there that can one up us here. Where is it, and can anyone provide cold, hard facts and data for it?

In 2015 I finished Kurt Carleson's single place Air Command MAC YG4 (I nicknamed that one "Viper") which pushes 600# no matter what day of the year it is, for some reason. It weighed 565# at the time, though it has put on some weight with many alterations and add-ons since. Kurt's ZeCA number, as-built, was 46.97.

Godzilla is my new MAC-built WWF Heavyweight Champeeeen.

The Wicked remains at 45.24° ZeCA these days, dropping to third place behind Godzilla and Viper.

If anyone wants a free copy of the MAC ZeCA Excel spreadsheet, write to me at

[email protected].

I would absolutely LOVE to hear from ANY of you with your numbers so we can rank your hot-rod gyrocopter in an (un) official listing using the ZeCA formula. No cheating, it's no fun if you pad the numbers. There are no prizes, no trophies, just a friendly and fair comparison.

Hope to see you at Mentone 2020, God willing and the creek don't rise.

Yours truly,

Gerg the Monster Maker.

Please find here a table for the ZeCA (explained below) Ratio for known (and some estimated) gyrocopter types with their respective power plants.

The list will be edited and added to as folks report in, and is arranged in no specific order.

The higher the ZeCA value the better the expected take-off and climb ability.

AC = Air Command

RFD = Dominator

SC = Sport Copter

MB = Monarch

TG = Tango Gyro

Gyrocopter ID & Seating | Engine | Thrust | Calculated HP @~4.3:1 Thrust: HP) | Dry Weight | ZeCA @ TOW (Dry Wt +225#) |
---|---|---|---|---|---|

the Wicked, MAC AC II | MAC Yamaha YG4 140 | 600 | 140 | 595 | 36.19 |

Godzilla, MAC AC II | MAC Yamaha YG4 160 | 680 | 158 | 630 | 38.5 |

Blue Bee, Hirth Honey Bee 1 | Hirth 2606 | 285 | 66 | 305 | 28.27 |

Kurtsey, MAC AC, 1 | MAC Yamaha YG4 140 | 600 | 66 | 575 | 36.87 |

SC II, IO-360 210, 2 | Lyco IO-360 Special | 900 | 210 | 1100 | 34.19 |

Predator, IO-320 160, 2 | Lyco IO-320 | 690 (calculated) | 160 (listed) | 1100 | 27.85 |

TG YG3 120, 2 | Yamaha Vector 120 | 515 (calculated) | 120 (listed) | 600 (est) | 31.97 |

TG YG3 135, 2 | Yamaha Nytro 135 (EFI) | 575 (calculated) | 135 (listed) | 600 (est) | 34.88 |

Bensen Mac,1 | Maculloch 70 | 305 (est) | 71 | 254 (est) | 32.49 |

Jazzenjohn, 1 | Hirth | 320 | 74 | 277 | 32.52 |

MTO 912, 2 | Rotax 912 100 | 430 (calculated) | 100 (listed) | 600 (est) | 27.53 |

Cavalon | Rotax 914 | 495 (calculated) | 115 (listed) | 630 (est) | 30.07 |

Magni | Rotax 915 | 580 (calculated) | 135 (listed) | 600 (est) | 35.11 |

AC Subaru, 2 | Subaru 2.2 | 560 (calculated) | 130 (listed) | 750 | 29.87 |

Sparrowhawk, 2 | Subaru 2.5 | 690 (calculated) | 160 (listed) | 900 (est) | 31.52 |

Playing around with numbers, I realized that the first successful Yamaha Genesis 4-cylinder powered aircraft, affectionately known as "The Wicked", my beloved Air Command tandem that I purchased in flying condition from Ora Cook for $4,500 (it was Ora's gift to me back at Bensen Days 2011 after he met my 7-yr-old while we were RV camped next to each other and spent hours chatting), produced 600# thrust and yet only weighed 595# dry. Round up the weight a tick and that is an interesting 1:1 ratio.

SO I trotted out my trusty trig excel spreadsheet and started pluggin in other gyrocopter dry weights and thrust numbers that I knew off the top of my head and arrived at an amusing ratio that is great for overall comparison of ALL gyrocopters ever built. All ya gotta know is your dry weight and your maximum reliable thrust (from a properly done test, of course. No fair cheating with "spiked" test results from hitting the throttle fast and hard. The thrust must reflect steady state thrust after at least three full seconds of waiting for the pull numbers to settle in.)

The basic trig equation is

tan Ø = opp/adj

My excel sheet converts tangent to radians, and then degrees (I couldn't figure out a way 5 years ago to build the thing to go straight from the equation to a degrees output, so it takes three steps. I still dont' know any other way to do it with Excel, to be honest.) You just plug in your weight and your thrust, and read the output angle.

I'm calling it the Zero Climb Angle, or ZeCA for short.

So the higher the thrust, and/or lower the weight, the higher (and better) the ZeCA value.

My Wicked has a perfect ZeCA of 45°, and my Blue Bee at 300# tested with a 60 HP Hirth producing 285# thrust has a ZeCA of 43.53°

An 800# gyro would need to produce a whopping 800# of thrust to hit 45 ZeCA degrees, but I think the best we can expect from a 160HP engine is just this side of 700# (from my most recent tests using Geoff Resney's YG4 EXUP, which I have nicknamed Godzilla). A Subaru 2.5 producing 670# thrust, in a heavier enclosed SxS gyrocopter weighing 850# will have a ZeCA value of 38.25°, and the same gyro producing 700# of thrust on a dry, cool day will have a 39.47 ZeCA.

Geoff Resney's MAC YG4 EXUP Air Command weighs 630# and produces 670-700# thrust, and so the ZeCA value of "Godzilla" is an INCREDIBLE 45.87 - 47.12 ZeCA !!!

Wow. And I'm betting there is at least one MAC 90 Bensen out there that can one up us here. Where is it, and can anyone provide cold, hard facts and data for it?

In 2015 I finished Kurt Carleson's single place Air Command MAC YG4 (I nicknamed that one "Viper") which pushes 600# no matter what day of the year it is, for some reason. It weighed 565# at the time, though it has put on some weight with many alterations and add-ons since. Kurt's ZeCA number, as-built, was 46.97.

Godzilla is my new MAC-built WWF Heavyweight Champeeeen.

The Wicked remains at 45.24° ZeCA these days, dropping to third place behind Godzilla and Viper.

If anyone wants a free copy of the MAC ZeCA Excel spreadsheet, write to me at

[email protected].

I would absolutely LOVE to hear from ANY of you with your numbers so we can rank your hot-rod gyrocopter in an (un) official listing using the ZeCA formula. No cheating, it's no fun if you pad the numbers. There are no prizes, no trophies, just a friendly and fair comparison.

Hope to see you at Mentone 2020, God willing and the creek don't rise.

Yours truly,

Gerg the Monster Maker.

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