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So there are lots of rules of thumb and calculators on the internet. Another rule stated that the thrust to weight ratio should be at least 0.5 for flight. My T/W is about .35. A little further research (Wikipedia) shows that many, many aircraft fully loaded have a T/W ratio worse than me. So this rule seems a bit conservative. Basically I will not have an acrobatic airplane. Low and slow as expected. In summary I think the numbers are adding up acceptably now.

Yet another rule states that a good prop ratio of pitch to diameter is 0.5.
I am at 39/74 which equals .527. So I choose well for the new prop. Note the old prop was 44/80 = .55. You would think a good choice but it had too much inertia to turn easily. So this factor assumes that you have the horsepower to turn the prop.

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