I see that all pattern planes run really high pitch props. There is so much talk about constant speed and down line braking that I figured you would need a big diameter low pitch prop. Why is it that no one uses this type of prop?

I ordered a CA Model Epsilon with a OX FX 91 to get started in pattern with. The manufacturer tested it with this setup and an APC 14x8 prop. A few guys complained and said that the .91 wasn't enough when you go over the top of a square loop. I would imagine that a 14x6 turning a few hundred more rpm and putting out a couple more pounds of thrust would resolve this. However the wide open flight speed would be 10mph slower (~75mph with the 14x8 down to ~65mph with the 14x6) . Would that be a problem?

ound is one reason...Also the 10-11-12 pitches on the props tend to be better and energy management. On fun fly stuff and 3D models the chopping of the throttle usually results in a serious Braking effect and the model will slow and wallow...When flying near a stalled condition this is OK....but when you are trying to manage your energy so that you are using it for the sequence and not constantly adding and reducing throttle to get the desired pace and flight characteristics...the big flat pitch props are not really the best.

The pattern models are not out flopping around at low speed and with low energy like some of the flippy flop 3D stuff...as a result the higher pitch props tend to work a little better for many situations.

When we chop the throttle we don’t want the model to immediately decelerate.....we want it to semi coast a bit....the big flat props act like parachutes and make energy management very very tough.

I know that many of the TOC guys used to change their props from Competition to Freestyle setups. Many also added large amounts of tail weight too....The reason is again form fits function the flat props will accelerate quicker but to a lower total speed...But they will tend to spool up quicker and be a little more responsive in the lower throttle ranges flying slow doing the High alpha and 3D stuff....

I don’t have much experience with the OS 91FX but my thinking is on a 90 sized model like the Epsilon if setup properly the 91 should be more than enough power. Maybe the ones in question were built a little heavy or maybe they are not running the motor at its full potential. Stick some Nitro in it…. Setup the mixture right and perhaps even add a pipe…In reality stick a YS 110 on it and you’ll have gobs of power. That is what I would do. That YS 110 will walk circles around any OS 91FX I have seen.

Happy Flying

Troy Newman

On my Alliance I have tried both a 16x12 and a 17x10. I would use the 16x12 over the 17x10 any day. The extra speed it gives the plane means it locks in better and in fact the vertical performance seems better with it too (which is counter intuitive to my mind but still).

Scale it down a bit for a 90 size plane but the principles are the same. With the coarser pitch props the power "flows" better. Don't confuse constant speed with slow speed!

Thanks for the info. I guess this is why pattern guys need the engines with all those ponies. I will run the 14x8 and go up on nitro if I have to. I run 30% in all my Saitos already so it no big deal. Maybe split the diffrence and run 20/20 as 30% might be too much for my 2 strokes.