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  #11  
Old 06-05-2018, 04:54 AM
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ronschreck ronschreck is offline
 
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Default +1 for Sandifer

Ditto, everything Eric Sandifer said except I find that ROUND loops require more like 4 to 4.5 Gs on the initial pull in order to have enough speed on the top to ease back to a quarter G to float it over the top and make the loop round. Ground critiquing is absolutely required to develop the finesse required to make a loop truly ROUND and pulling off power is not necessary or desired.
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  #12  
Old 06-05-2018, 06:44 AM
sandifer sandifer is offline
 
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Originally Posted by ronschreck View Post
Ditto, everything Eric Sandifer said except I find that ROUND loops require more like 4 to 4.5 Gs on the initial pull in order to have enough speed on the top...
Absolutely Ron! I mentioned that an actual round loop will require more than the 3-3.5G he was pulling, but not to sweat it prior to getting ground critiquing since it's almost pointless to try for perfect round ones until then.
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  #13  
Old 06-05-2018, 07:57 AM
precession precession is offline
 
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Originally Posted by sandifer View Post
There's a degree of gyroscopic yaw to the right any time you pitch toward the canopy in an airplane with a Lycoming turning motor. But the amount of precession of course depends on RPM, prop mass, pitch rate, and prop to airframe weight. Even with a metal prop, it's such a small effect in an RV that there's nearly negligible need to correct for it with left rudder. With a wood/composite prop, forget it. Even in something like a Pitts S-1 turning a big metal prop at 3000+ RPM and pulling 6G into a loop, the effect was very small. Before I switched to a composite prop in the Pitts, all I really told my left foot to do was breathe on the left rudder for hard pulls to vertical. Hardly even a real movement. Keep in mind that as soon as you pull, there's a degree of P-factor working in the opposite direction of the gyrocsopic yaw. Both are small forces.

Bottom line, I wouldn't bother trying to make a correction here. Just enter the loop ball in center, and do whatever it takes with the rudder to keep it there...which will likely be nothing, or virtually so. ... But for a loop, airflow is so high, and pitch rates so low that it's not much of a factor.
Okay, well that (as now seconded by Ronschreck, I see) seems to nail my question about as perfectly as I could ask for, so thanks again (to both) for the very excellent info.

Since I'm flying a composite fixed-pitch prop, I am going to stop throwing in that (guess-work) left rudder on the pulls, unless/until I definitely see something on either my sight picture or the ball that indicates it's needed. If not, that will give me one less input to worry about (or possibly screw things up with), which will be nice. In fact, as an experiment next time I'm out I think I'll do a few 4-4.5G pulls at loop entry speed and just look at the ball to see if it's moving at all. (Don't recall ever having looked at it at that point.)
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Last edited by precession : 06-05-2018 at 08:10 AM.
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  #14  
Old 06-05-2018, 08:01 AM
precession precession is offline
 
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Originally Posted by ronschreck View Post
Ditto, everything Eric Sandifer said except I find that ROUND loops require more like 4 to 4.5 Gs on the initial pull in order to have enough speed on the top to ease back to a quarter G to float it over the top and make the loop round.
Thanks, can you give an idea of what entry speed range you'd be looking for if you were practicing to make good loops with this amount of pull in the RV-8?
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Last edited by precession : 06-05-2018 at 08:13 AM.
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  #15  
Old 06-05-2018, 09:26 AM
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ronschreck ronschreck is offline
 
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Thanks, can you give an idea of what entry speed range you'd be looking for if you were practicing to make good loops with this amount of pull in the RV-8?
Anywhere between 160 and 190 knots works best for me.
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  #16  
Old 06-05-2018, 10:14 AM
precession precession is offline
 
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Anywhere between 160 and 190 knots works best for me.
Thanks. I know RVs have the speed, but 184 mph on the low end is more than I expected.
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  #17  
Old 06-05-2018, 10:28 AM
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ronschreck ronschreck is offline
 
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Thanks. I know RVs have the speed, but 184 mph on the low end is more than I expected.
Note that we are talking about ROUND competition style loops here. If you are just doing loops for the fun of it then you can enter at a lower speed. Your loops will probably look more like a cursive "L" in that case. Do be careful that you have sufficient speed and G loading to make it over the top with airspeed to spare.

Falling out of a loop or any other aerobatic maneuver can lead to an out-of-control situation. Before trying any aerobatics it would be wise to get some instruction that covers spin and unusual attitude recovery. Training does not need to be done in an RV. Aerobatic training is done in certified aircraft such as the Decathlon or Extra but the basics of recovery training transfer to the RV series and will make you more confident that you can handle any misstep that may occur. The IAC web site has a long list of aerobatic schools. If you are determined to try IAC aerobatic competition you would benefit from ground critiquing. Your local IAC chapter is a great resource.
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