fanman Posted December 2, 2009 Share Posted December 2, 2009 Stop press, just dug out some info I got from Rick at GSC which gives their recommended settings for the CorsAir Black Devil... 44" diameter prop: 2 blade - 13.5 degrees 3 blade - 11 degrees 45" diameter prop: 2 blade - 13 degrees 3 blade - 10.5 degrees 46" diameter prop: 2 blade - 12.5 degrees 3 blade - 10 degrees 47" diameter prop: 2 blade - 12 degrees 3 blade - 9.5 degrees 48" diameter prop: 2 blade - 11.5 degrees 3 blade - 9 degrees Quote Link to comment Share on other sites More sharing options...
edwardc Posted December 2, 2009 Share Posted December 2, 2009 Fanman Thanks for the info, you have been a great help and I will let you know how it goes when this weather lets me try it out! Eddie Quote Link to comment Share on other sites More sharing options...
spigot Posted December 2, 2009 Share Posted December 2, 2009 Fanman, You wouldn't happen to know which reduction drive those settings are based on would you? Colin B Quote Link to comment Share on other sites More sharing options...
fanman Posted December 2, 2009 Share Posted December 2, 2009 I think you should find that those settings are a good enough starter for both 2.5:1 and 2.6:1 redrives as having set the basic settings you then want to do a sustained static test to see what rpm you can maintain (measured on a tinytach or similar) before making minor adjustment to suit your individual machine, ie if the rpm is slightly too low then fine the pitch angle down a bit and vice versa. The 2.2:1 redrive is not very common but if you do have one then you should be looking at going slightly finer as the prop will be turning faster. The BD was originally designed to run close to 10,000rpm but then set up to achieve 7,500rpm max. Consequently a lot of people in the States set their pitch to give a max of 7,800rpm which works very nicely. Quote Link to comment Share on other sites More sharing options...
spigot Posted December 2, 2009 Share Posted December 2, 2009 Nice one... So if I've got my maths right... Running 2.49:1 reduction, 39inch 3 blade prop, I need a pitch of 13.5 deg Anyone know the pitch of a the standard Parajet compact blade? I ( ) temporarily adjusted the pitch of my blades for a couple of flights yesterday and it made a hell of a difference, (sustained full power for much longer). Just want to know the ideal pitch before I make the change permanent. Quote Link to comment Share on other sites More sharing options...
fanman Posted December 2, 2009 Share Posted December 2, 2009 ...but those pitches are only valid when using a GSC pitch tool on a GSC ground adjustable prop on a Black Devil motor. Pitch expressed as degrees is variable along the blade whereas pitch measured in distance should be roughly even at any point along the span. Pitch distance can be calculated if the pitch (in degrees) is known at a known point along the span (2 x pi x r x tan blade angle). Quote Link to comment Share on other sites More sharing options...
spigot Posted December 2, 2009 Share Posted December 2, 2009 bugger Quote Link to comment Share on other sites More sharing options...
fanman Posted December 2, 2009 Share Posted December 2, 2009 ... and that is why pitch distance is a much more useful measure than blade angle. Quote Link to comment Share on other sites More sharing options...
spigot Posted December 2, 2009 Share Posted December 2, 2009 The other option I guess is to fit the smaller 50mm pulley to my motor. anyone got a spare one to try? Quote Link to comment Share on other sites More sharing options...
longwing Posted June 18, 2010 Share Posted June 18, 2010 I've just been going through the archives and came across this thread. What were the results of the GA props, did they solve the problems, and how do they compare to the fixed pitch? Are they expensive? What is the reccmended pitch for a 122cm 1:2.6 reduction. Thanks Quote Link to comment Share on other sites More sharing options...
Guest Posted November 8, 2015 Share Posted November 8, 2015 Bump. SW Quote Link to comment Share on other sites More sharing options...
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