I''ve been looking at what some of the 3D guys are using for prop selections and I''m a little perplexed. The pitch of these things seems far too low compared to mfg''s suggested prop sizes. In particular, I''ve seen where guys are putting 17x4 on an O.S. 1.20! I would think that might cause damage to the engine by not providing enough resistance compared to a 17x6-7 for the RPM range of this monster. Can someone enlighten me on the use of these low pitch props? It seems to go against what I thought I knew.

Lower pitch and bigger diameter, it evens out you know. A 17-4 APC is marked "w" meaning wide and gives about the same load as a normal 17-6 so the engine will not tell the difference.

A bigger diameter prop with smaller pitch will pull better than a smaller diameter prop with more pitch, that`s exactly what is needed for 3-D. The rpm on the engine itself will stay about the same

Thanks. I thought my question sounded kind of stupid when I posted it, but I really didn''t know. For all the years I''ve spent reading magazine articles and building/flying models, I should be better educated.[sm=red_smile.gif]

It didn''t sound stupid at all. Glad you found out what you were looking for.