ORIGINAL: Ram Jet
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I'm breaking-in on a light 7 x 6 APC prop. Wow, this little devil will pull from a 9 x 6 to a 10 x 4? Torquey little engine or what! Top Flight recommends a max of 9 x 4. I guess I have a-lot to learn. Keep posting please.
My comments about bigger props - 9.5x6, etc. where specific to the model 4004 19-IV.
The later .19s - model 4005 19-V and model 4006 19-VI are timed differently and are better off propped smaller - 9x4 or so seems to be ideal.
For comparison, my model 4004 19-IV manages around 11,500 on a Taipan 9x4, where my model 4005 19-V happily reaches 12,000 or more. Put a 9.5x6 Bolly Clubman on, and the 19-IV digs in and does 10,500 - 10,600, whereas the newer 19-V dies can't even do 10,000. Furthermore, on the big prop, the older 19-IV becomes far less "cranky", where on the 9x4 it is quite snappy. I tried it on an 8.5x4 and it was just plain evil.
cheers,
Colin