Dave,

The best climb angle is about 60% cruise speed at full throttle. This gets you higher, quicker than any other angle, unless your thrust to weight ratio is greater than 1.
You cannot put a fixed angle on the best climb rate. Put a full scale Cessna at 55 degrees for long and it will end up back at the recycling plant, but put a F-15 at that angle, and it will go until it is out of sight.
Best climb angle is also determined by the density of the air, so the same plane with the same load may climb better at a shallower angle in the summer than in the winter.

While not having read that book, if the author is stating that the optimal angle for climb of a specific model in indoor flight is 55 degrees, he may be absolutely correct. If he is making a general statement about all models, I would regard anything it that book as highly as if Snoopy told me personally. [sm=71_71.gif]

Oh, and remember that logic is the art of going wrong with confidence.

Bob