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  #41  
Old 07-09-2020, 02:40 PM
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Saville Saville is offline
 
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Originally Posted by sandifer View Post
Entry speed is whatever allows you to get to vertical without stalling or falling out. You could do this from 100mph or from Vne, it doesn't matter. Entry speeds don't matter for the basic figures. Low cruise works for anything in an RV. Regarding when to kick, airspeed indication is not a good way to learn to do a good pivot, since airspeed will be dead by the time you need to pivot. If you're using airspeed as an indicator, you're going to be kicking early, and 'flying' over, meaning a large radius rather than the ideal minimal radius pivot.
Ok then if not airspeed then what do you use for the decision?

I was taught to do hammerheads in a Super Decathlon. There, I was told to wait until the corkscrew slip stream of the prop slaps against the fuselage - you feel a wobble, or vibration. Then kick.

So what's the signal for the hammerhead kick on an RV-8?
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  #42  
Old 07-09-2020, 05:19 PM
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Gash Gash is offline
 
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Originally Posted by Saville View Post
Ok then if not airspeed then what do you use for the decision?

I was taught to do hammerheads in a Super Decathlon. There, I was told to wait until the corkscrew slip stream of the prop slaps against the fuselage - you feel a wobble, or vibration. Then kick.

So what's the signal for the hammerhead kick on an RV-8?
Here are two techniques you can try for hammerheads in the RV-8. These both worked fine for me while flying in contests, and I never had any problems "flying over".

1. When flying the upline, as you decelerate, you'll eventually need aileron to counter the tendency to torque roll. Looking down your left wing, when you see aileron starting to go up, kick the rudder. This technique is a little subtle, so you can always fall back on 2. below:

2. It's true that airspeed is not a great crutch to use, but it does work once you find the right number for your airplane and you get some feedback from somebody watching on the ground. On my RV-8, as soon as I saw 40 KIAS, I would kick the rudder. I got high scores with this.

Some math here. By the time you're well into your hammerhead pivot, you will have decelerated to something less than 40 KIAS. Let's conservatively estimate that you're now down to 30 KIAS (although you're probably slower). At 30 KIAS, you're traveling 50.6 feet per second. You're not going to "fly over" 2x your wingspan at this velocity as long as you keep the pivot turn going until you're vertical down.
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Last edited by Gash : 07-09-2020 at 05:33 PM.
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  #43  
Old 07-10-2020, 03:53 AM
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ronschreck ronschreck is offline
 
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Originally Posted by Saville View Post
Since we're talking aerobatic technique:

What entry speed and rudder-kick speeds do the aerobats here suggest for hammerheads in the RV-8?
I tried the string on the wingtip but that didn't work well.

I observe the airspeed indicator and count two potato after the needle passes 40 knots then kick rudder. With practice you will discover how many potatoes your airplane requires.

Eric Sandifer has already discussed entry speed.
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Last edited by ronschreck : 07-10-2020 at 03:54 AM. Reason: typo
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  #44  
Old 07-10-2020, 07:45 AM
sandifer sandifer is offline
 
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Originally Posted by ronschreck View Post
I observe the airspeed indicator and count two potato after the needle passes 40 knots then kick rudder. With practice you will discover how many potatoes your airplane requires.
The secrets are now coming out! I take back the ASI comment for RV hammers based on Bill and Karl's feedback.

Saville, the clues available for pivot timing vary a bit between aircraft types, and it's whatever consistent method you can find that works. As Karl mentions, some airplanes will start to torque roll as you slow to the pivot, and you use aileron input as a gauge. This is also the most useful method in a Pitts. Some airplanes produce a slight airframe or tail buffet as the prop slipstream tightens at or near the pivot point. The drumming belly fabric is the classic method in the Super D, as you've already learned. You can also tie a string to the sight gauge and observe the flicker pattern as you reach the proper point. This works better for some than others, also depending on aircraft type, as Ron observed. Increasing right rudder is required to control yaw as the airplane slows and could possibly be used as well. I believe Bill McLean said at one point he gauges right rudder deflection in his RV-4.

Besides airspeed indication, those are all the methods that I'm aware of. It seems ASI can be a tool for the RV. The usefulnesss of airspeed indication depends on how slow the airplane can get before pivoting. High power-to-weight ratio ships with powerful rudders (Extra/Pitts types) can practically come to a stop at the pivot. Airspeed cannot be used here. It could be an aid for planes that must begin pivoting with more airspeed. If you can find a way to do it consistently with your eyeballs outside the cockpit the whole time, that's ideal. Ground coaching is needed if you really want to learn to pivot with the tightest radius, but it doesn't matter of course for funnin' around acro.
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