Hyjinx

Hello. In it's simplest form please. How do I correctly calculate what size engine will produce the right amount of thrust to correctly fly my 1/3 scale Balsa USA Stearman biplane?

mkjohnston

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what does the plans or instruction call for? If you look here, https://shop.balsausa.com/product_p/460.htm. It says this airplane requires a 70cc to 120 cc engine for proper flight.
good luck
Michael

Hyjinx

Thanks for the reply Micheal.I may have framed the question wrong. A new hypothetical, closer to a subject plane I am setting up. Example. I have an existing airframe that is a biplane.
I have an engine that is capable of creating 32 pounds of thrust at it's most efficient propeller and rpm range. The wing surface can be measured and the auw calculated less the motor. The engine exists and can be weighed.
How do I determine if this engine will safely fly the plane with with 32 pounds of thrust?
The Stearman example is not hypothetical. A 257 Moki it is set up on it. The engine was purchased new. The retailer opined that the motor would fly the BUSA Stearman based on his experience with similar other set ups buyers asked the question of. My simple question is this. How did he know this engine would be a successful powerplant for for this plane. Experience aside, what is the math?
Thank you. Respectfully. Aaron

kmeyers

You want me to believe that a 257 Moki only makes 32 pounds of thrust? You must have something wrong here, these engines are swinging props in the 28 - 34 inch range. My guess would be that this engine easily makes 90 pounds of thrust. If the plans say use an engine in the range of 30 - 50 pounds, I think you still need to reframe the question.
The math is cross sectional drag aah never mind, here open this:

Hyjinx

I don't ask any one to believe anything. And with withdraw both of the written questions I asked in this thread.
Thank you to all who responded to my inquiries. My question (s) were scientifically answered by another party last week.
Respectfully
Aaron Hubbard.
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