ok here goes, i bought a biplane on e-bay(big mistake) all the ad said was it was a navy bipe ,no manufacturer given, and dummy me didn't ask about engine size, well i put it up on the shelf and forgot about it for about six months.so when i started to rebuild it, (oh by the way they forgot to tell me it had crashed and was half *****ed repaired, e-bay pics didn't show any damage!) i now need to guess at engine size. the plane is 36" long and has a top wing span of 48" i'm guessing it weighs 4-5 lbs maybe a little less without the engine. any ideas on motor size or how to calculate the motor size would be extremely helpful. thanks,jim

Here’s a chart that I found on the web:

Engine size (2 cycle, cubic inch) / wing area (square inch)

0.049 / 200 to 250
0.10 / 250 to 350
0.15 / 300 to 450
0.25 / 400 to 500
0.40 / 500 to 700
0.60 / 600 to 850

Also you can look at similar design and see what engine size is recommended.
Miles.