DennisFetters
Super Member
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Dennis, iv been tinkern with this same stuff.
Im not go'n to argue your numbers, coz im not that smart, but in the lift columb, for 200rrpm you have 50.
50 wut?.
And iv found if you set the AOA at bout -3.5 degrees ona 8H12, youll have 0 lift.
Theres still go'n to be more drag than a symetrical section, but no lift.
The problem is at that degrees the blades produces the same amount of drag as they do at zero when the lift is creating the drag. So there is no real benefit to pitching the blades that far down, unless your propeller is producing so much thrust you can't hold back with that lift load off the wheels during braking.
But what unit of measure is it Dennis? 50.4? Is it pounds?That is how much lift the rotorsystem will produce at 200 RPM's.
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That's not quite accurate. Although the parasitic drag remains about the same, the induced drag resulting from producing lift is eleminated.
But what unit of measure is it Dennis? 50.4? Is it pounds?
I went back and read it again to assure I had not miss-read.Thats what I said.
How is the lift so low? even at 350 rpm the lift is only about 150 pounds. What rpm do the blades have to spin at to get enough lift to fly? If my gyro flies at 320 rpm, isn't my lift going to be the gross weight of my gyro with me in it? like 500 pounds?
It seems like the HP required numbers on the right would be for about 50 rpms less than what is shown on the left. 150 rpm to 300 instead of 200-350.
Whoever did the rotor calculations that Dennis posted got the trends correct but the numbers are overly optimistic..
Here is the calculated profile drag of a 7” chord x 23’ diameter rotor at zero lift using a realistic drag coefficient:
100 rpm----------0.17 hp
200 rpm----------1.35 hp
300 rpm----------4.6 hp
400 rpm----------10.92 hp
500 rpm----------21.32 hp
Dennis I understood your numbers, and solved some unanswered guestion for me and I also understand the lift coefficient due to the fact the blades are not yet under load, the lift factor will increase greatly once the aircraft is moving and the blades inter the collious effect. Is this correct thinking.
Dan