thrust required to fly dominator single sit with 330kg gross weight

Agwotu

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BEEN building Dominator( single sit ), decided to power it with subaru ej 20 engine with direct drive for simplicity, then curved my own WOODEN propellers also, but managed to get 100kgs of thrust , at full throttle, my question to gyro brothers out there , ......can that thrust of (100kgs) fly gyro of ready to fly with weight of 330kg ???? my rotors are 27ft diameter ...
 

Vance

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BEEN building Dominator( single sit ), decided to power it with subaru ej 20 engine with direct drive for simplicity, then curved my own WOODEN propellers also, but managed to get 100kgs of thrust , at full throttle, my question to gyro brothers out there , ......can that thrust of (100kgs) fly gyro of ready to fly with weight of 330kg ???? my rotors are 27ft diameter ...
In my opinion a thrust of 100kg is not enough to successfully fly a 330kg takeoff weight gyroplane successfully.

The reason people use a propeller speed reduction unit is so they can use a larger more efficient propeller and still not have the tips go supersonic.

Horsepower is torque times rpm divided by 5252.

You have an engine that is supposed to turn 6,000 rpm and with a reasonable sized propeller (170cm) you probably can’t turn it more than 3,000 rpm.

In the most basic terms that suggests you might get half the rated horsepower out of it.
 

XXavier

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BEEN building Dominator( single sit ), decided to power it with subaru ej 20 engine with direct drive for simplicity, then curved my own WOODEN propellers also, but managed to get 100kgs of thrust , at full throttle, my question to gyro brothers out there , ......can that thrust of (100kgs) fly gyro of ready to fly with weight of 330kg ???? my rotors are 27ft diameter ...

The best L/D of a MTO gyro is around 4. That means that for level, non-accelerated flight, you need at least 0,25 kilogram-force of thrust for every kilogram-force of gyro weight...

Captura de pantalla 2021-10-11 a las 21.37.47.png

From 'Flight performance of lightweight gyroplanes' https://www.icas.org/ICAS_ARCHIVE/ICAS2012/PAPERS/434.PDF
 

Agwotu

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Agwotu

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You need at least 1kg of thrust for each 2kg of weight for reasonable performance, so you need about 160kg of thrust.
But the benson with that motor (culotch) engine , how did it do ? actually i see even EA81 , FLEW WITH DIRECT DRIVE , they flew, didn't they ?
 

Agwotu

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In my opinion a thrust of 100kg is not enough to successfully fly a 330kg takeoff weight gyroplane successfully.

The reason people use a propeller speed reduction unit is so they can use a larger more efficient propeller and still not have the tips go supersonic.

Horsepower is torque times rpm divided by 5252.

You have an engine that is supposed to turn 6,000 rpm and with a reasonable sized propeller (170cm) you probably can’t turn it more than 3,000 rpm.

In the most basic terms that suggests you might get half the rated horsepower out of it.
Thank you very much Sir,

what bothers me, the EA 81, FLEW direct drive, they did fly, didn't they ? yes they did... mark you , its 1.8litre engine, what did they do that i , don't know...... ?

But this EJ20 is 2.0litre, ANY WAY 330kg gross weight gyro, worries me though, but 27 ft of rotor, would let me fly some how i might be wrong or right, i don't know or do i need to curve larger prop, the one i use is 56inch with 28inches of pitch , but the 60inches prop i made lowered the rpm ..... eemmh makingn the engine not to make enough power for flight, all in all 56 ich prop, proved to give me about 60-70% of throttle
 

XXavier

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0.25kg of thrust to every kilo of weight, !!!! meaning 330kgs /0.25kg you get 82kg of thrust . right ? will i be able to get airborne ?

Probably not, because overcoming rolling resistance during takeoff run and then climbing would require extra thrust. Those 82 kg-f will be –always in theory– barely enough for level, unaccelerated flight at the favorable L/D of 4. In practice, for climbing and other maneuvering, you'd need much more...
 

Kevin_Richey

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The EA-81 in direct drive mode was only able to carry a lightweight pilot IN A GYRO.
4-stroke engines such as a VW or Subaru are quite heavy for their output in DD mode.
Anyone over 180# (82kg) was disappointed as they were attempting to use it for flying around in a directly-driven engine IN A GYRO.
The tiger came out when a reduction drive was mated to it. Then you have a screaming engine that is almost as high rpms as a comparable output 2-stroke one...which requires a reduction drive!
The Yamaha converted from snowmobile use for flying still requires a reduction drive, as their rpms are really up there (6K-9K) to get their huge amount of power out of them.
 

Agwotu

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just made propeller with wider blade and low pitch , i see 136kg , of thrust. that test was done with no exhaust silencer .... which i think if exhaust put will make me 140kgs of thrust
 

Agwotu

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just made propeller with wider blades and low pitch , i see 136kg , of thrust. that test was done with no exhaust silencer .... which i think if exhaust put will make me 140kgs of thrust.

will 140kgs of thrust make me fly ??????? , by the way i am with altitude of 3600 above sea level
 

Vance

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Thank you very much Sir,

what bothers me, the EA 81, FLEW direct drive, they did fly, didn't they ? yes they did... mark you , its 1.8litre engine, what did they do that i , don't know...... ?

But this EJ20 is 2.0litre, ANY WAY 330kg gross weight gyro, worries me though, but 27 ft of rotor, would let me fly some how i might be wrong or right, i don't know or do i need to curve larger prop, the one i use is 56inch with 28inches of pitch , but the 60inches prop i made lowered the rpm ..... eemmh makingn the engine not to make enough power for flight, all in all 56 ich prop, proved to give me about 60-70% of throttle
An EA 81 is a much lighter engine than an EJ 20 leading to a much lower takeoff weight.

In my opinion based on not enough information to make a precise judgment 140 kilograms of static thrust will not be enough thrust to fly a 330 kilogram gyroplane safely.

You may be able to take off but climb out will be ponderous at best.

Your 3,600 foot altitude requires more power to fly than sea level and temperature will also affect the performance.

I recommend you get flight instruction from a qualified flight instructor and have him test fly the gyroplane to help you understand the limitations of your aircraft.
 

j4flyer

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The EA-81 direct drive is probably 50-60 HP. I had one on my Barnett. Mine had a redrive and was marginal. I liked the engine as it burned 3 gallons per hour at cruise. I had a 3 blade precision propeller, ground adjustable. I switched to a Lycoming o-235. I had increased HP and no cooling issues from an over worked engine. There is no substitute for HP.
 

Jean Claude

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Several things to know:
1) Propeller thrust in forward flight is always lower than static thrust.

2) The best L/D ratio of a "Dominator" is about 3, and this ratio becomes even worse with the low forward speed of takeoff.

3) Thus, the thrust required is related to the weight to be lifted (Bensen B8M weighed less than 400 pounds and your Dominator weighs 680 pounds)

4) The takeoff occurs when the rotor rpm is still accelerating. Its drag is then stronger than when the rpm rotor is steady

5) The takeoff assumes a positive rate of climb which requires additional thrust to that necessary for level flight
 
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XXavier

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Several things to know:

1) Propeller thrust in forward flight is always lower than static thrust.

(...)


Well, I'd say 'usually'... An adjustable-pitch prop can be set at a very high pitch, so that the thrust is very low while stationary, with the blades stalled, but the AoA of those blades decreases gradually during takeoff, the blades start working better, and thrust reaches an optimal value at cruise.

Sure it's not relevant for slow aircraft like gyros, but in high-speed planes that can be important. An extreme example are the fixed-pitch contra-rotating propellers of the fastest floatplane in history, the Macchi MC-72:

Captura de pantalla 2021-11-12 a las 14.15.47.png
 

Gyro28866

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Short answer -- NO!
The old rule of thumb, was the ALL UP WEIGHT divided by 2 equals the minimum THRUST for average/marginal flight.
330kg = 727 pounds
727 / 2 = 363 pounds of thrust needed
330kg / 2 = 165kg of thrust, minimum
And then you have to add in for Density Altitude
 

Jean Claude

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An adjustable-pitch prop can be set at a very high pitch, so that the thrust is very low while stationary, with the blades stalled, but the AoA of those blades decreases gradually during takeoff, the blades start working better, and thrust reaches an optimal value at cruise.
Despite the large propeller pitch required for the highest climb speeds ever hoped for a gyrocopter, stall the blades does not give a significant decrease in static thrust compared to the thrust in fast flight.

Here are the thrusts calculated by JavaProp.

Sans titre.png
 
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