Hi, Ken...
 KE> was in particular on my PT-40.  I have a GS-40 on it and was running
 KE> a 10 X 6 on it.  After a few flights I had some pilots ask what size
 KE> prop I was using and they said I should use a 10 X 8.  I tried it and
 KE> did not really notice much of a difference.  I noticed even in the
 KE> Tower Hobbies catalog it gives two or three different sizes for each
 You have probably received a post-reply from Kevin Kline about why
 several different size props can be used on an engine - Kevin really knows
 what he's talking about so his advice is very good.  As to using a 10x6
 vs. a 10x8 prop on a GS-40...the ST line of engines are ALL very good,
 well-made, and very powerful.  The GS-40 will pull the 10x8 very easily
 without overloading the engine - you see, overloading is EXACTLY what we
 must avoid because it doesn't allow the engine to reach its normal RPM,
 stresses the metal due to overheating, and quickly will ruin the engine.
 A powerful engine can use the largest prop in the range but a weak engine
 (like the OS-40HP, the Thunder Tiger, and some others) will suffer badly,
 they will have to use the lowest dia/pitch prop in the size category.
 Many modelers will experiment with a range of props with their engines to
 find what works best - but always after the engine is well broken in and
 usually the testing is done with a tachometer.  Good luck and TTYL - Roger
... Catch the Blue Wave!
--- Blue Wave/RA v2.12 [NR]
---------------