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  #11  
Old 10-22-2007, 03:14 AM
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dan dan is offline
 
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Yeah, but what's the biggest heading change they have to accomplish on a turn?




The original question asked about the optimum way to produce a 120 degree change in heading.

I've been thinking more about this and I stand by my "lazy 4" analogy. Anything more than about 120 degrees and I'd be looking at that 3rd dimension VERY seriously. Go out and test it. I plan to.
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Last edited by dan : 10-22-2007 at 03:17 AM.
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  #12  
Old 10-22-2007, 03:26 AM
Chappyd Chappyd is offline
 
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This may or may not be relative. I used to race model planes. Little F-1 models that went 200 mph, had about 3 hp and turned props at about 25,000 rpm. Smoother is faster. Yank and banks will slow your airplane. Any control surface deflection creates drag.

From a minature perspective, but physics are physics.
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  #13  
Old 10-22-2007, 03:37 AM
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Quote:
Originally Posted by Chappyd View Post
physics are physics.
Yep, they sure is.

Think about it. If you just bank hard and then haul on the Gs, as others have noted you would end up exiting the turn having bled off some of your energy. Now you're going to WASTE precious time accelerating back up to full straight & level max speed. As we all know, that last few% of the speed band takes the longest amount of time to achieve.

So DON'T GIVE AWAY that last bit of speed.

If you add vertical to the mix, yes, you will slow down in the process, but you EXIT at the SAME airspeed you entered. NO TIME WASTED. Yes, you slowed down during the maneuver, but you change heading JUST AS QUICKLY and you don't sacrifice one bit of the top end speed on exit. I'm not talking about going straight up. I'm not talking about abrupt maneuvering. I'm just talking about adding a dimension to the maneuver on sharp heading changes.

Am I the only one smoking this crack pipe?!

Groucho, Kahuna, somebody out there who understands a HI YO-YO in the context of energy management, chime in.
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Last edited by dan : 10-22-2007 at 03:43 AM.
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  #14  
Old 10-22-2007, 05:18 AM
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Quote:
Originally Posted by dan View Post
How about a half lazy 8 style turn? You'd exit the turn at the same altitude & airspeed at which you entered it, and you'd seriously "cut the corner." Just a thought from a NON EXPERT.
When I raced my RV at Mesquite several years ago, (it may have been back in the 20th century) they did not allow us to change altitude in the turn. I wanted to do what you say but they would disqualify you if you did.
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  #15  
Old 10-22-2007, 06:54 AM
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Nuisance Nuisance is offline
 
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If you look at the Reno diagram Sharpie posted, the red lines are the "deadlines". The penalty for cutting a pylon is a few seconds, but if you cross the deadline you are DQ'd. So, the near 90 degree angles you see at Reno are required by the course and the speeds.

In the late 1920s Jimmy Doolittle developed a technique where he would fairly gradually climb before the corner, then dive as he went through the corner to take some of the g-load off the plane and keep the speed up into the next straightaway. Soon all the racers were doing it.

The altitude change is not illegal in our racing, but it does increase the possibility of a mid-air. Mostly we are racing single-file, but if someone doesn't give his correct speed to the race boss then some passing may happen. So it is important to have your head on a swivel.

My technique has been to fly a line that is about 1/2 mile outside of the direct point-to-point course. Then I can hold a 45 degree turn and cross over the turn spot, and hopefully not lose too much speed, and not travel too much extra distance.

Good luck, John
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  #16  
Old 10-22-2007, 06:56 AM
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Kahuna Kahuna is offline
 
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Quote:
Originally Posted by dan View Post
Yep, they sure is.

Think about it. If you just bank hard and then haul on the Gs, as others have noted you would end up exiting the turn having bled off some of your energy. Now you're going to WASTE precious time accelerating back up to full straight & level max speed. As we all know, that last few% of the speed band takes the longest amount of time to achieve.

So DON'T GIVE AWAY that last bit of speed.

If you add vertical to the mix, yes, you will slow down in the process, but you EXIT at the SAME airspeed you entered. NO TIME WASTED. Yes, you slowed down during the maneuver, but you change heading JUST AS QUICKLY and you don't sacrifice one bit of the top end speed on exit. I'm not talking about going straight up. I'm not talking about abrupt maneuvering. I'm just talking about adding a dimension to the maneuver on sharp heading changes.

Am I the only one smoking this crack pipe?!

Groucho, Kahuna, somebody out there who understands a HI YO-YO in the context of energy management, chime in.
G is a turn speed killer. Unlike a power boat which can jump back to speed in an instant, our medium takes too long.

As for using the vertical, while you might enter and exit at the same speed, you will not have covered the same distance due to g, angle of attack drag, and so forth. Since a race is about distance to target, forget the vertical for the turn.

Vertical in the yo yo is about displacement into another plane(dimentional plane) and gaining an advantage of position, timing, and sight picture against a target. Used to fix a potential overshoot by decreasing closure rates and gain advantage out of plane. Too complicate for me to type.

Also I do not think the formulas are useful because if you look at the factors affecting entry and exit speeds for a turn, weight, power, prop, and other factors play big in this game. I do not have a clue what the answer is, but I suspect gentle is better than yank.

my 2 cents,
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  #17  
Old 10-22-2007, 07:53 AM
Christopher Murphy Christopher Murphy is offline
 
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Thumbs up race turns

Quote:
Originally Posted by rv969wf View Post
Anyone needing advise, go to the RENO air races and watch the PRO'S.... I went this year and when they flew,,,, they were taking large radius turns around the pilons and keeping there elevation the same. Most of the pilots were not banked more than 30-40 degrees. Take this for what its worth. Been there, seen it, etc.
The above technique is the best I have found. Keep the rpms up and make a nice smooth turn around the pylon. The most critical point is to make sure you roll out on the correct course to the next turn. You will loose much time if you have to bracket the direct course. When your plane is totally stock, no aftermarket plenum,wing tips,cowling,etc one must use every trick in the book to go fast. Precise flying will make up for some of these handicaps.

RACE 34 ( still working to get to MEM 100)
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  #18  
Old 10-22-2007, 08:31 AM
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Quote:
Originally Posted by dan View Post
So DON'T GIVE AWAY that last bit of speed.

Groucho, Kahuna, somebody out there who understands a HI YO-YO in the context of energy management, chime in.
A Yo-Yo/whifferdill is certainly one way to get your turn rate up, but like Kahuna said, there are many other variables you throw in there too. I can't say for sure which way would be faster, but, IMHO, I think you could get within a second of the no-kidding fastest race turn by just varying g to figure out what gets you pointed the right way & at full speed the fastest.

The math does matter in this, but only once you start to get close to the best solution. A good technique was mentioned...offset pylon by whatever your turn radius is (plus a margin so you don't cut it), then pull however many g's through the turn you planned on (2, 3, whatever).

Over a cross country race, there are many, many other things that can matter more. If you start on the runway & have to climb to altitude, what climb airspeed to you use? If the finish line is back at runway level, when do you start decending? What altitude do you fly? Lots of other things to think about too.

FWIW, I sat at Pylon 1 during an unlimited race in 2006 & they were probably close to 70 deg/bank...which matches the 500mph spec on the course layout. Cross country races are different than Reno though...tons more time in the straights.

Alright, where's the next race near SoCal? I'm in.
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  #19  
Old 10-22-2007, 08:32 AM
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Ron Lee Ron Lee is offline
 
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Default Memphis 100 race course

~ 100 nm, Relatively equal legs. The start is while airborne.

Details here: http://www.sportairrace.org/id132.html

Since this will be my first race, I am clueless about many things. I am assuming that they want you to fly right over the turn point for timing purposes. If not, then being a bit outside during a turn like John does won't matter.

I know that I won't be first. Maybe not even second or third. But I need to beat the person whose posts motivated me to enter the race.

Last edited by Ron Lee : 10-22-2007 at 08:34 AM.
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  #20  
Old 10-22-2007, 08:40 AM
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az_gila az_gila is offline
 
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Smile Offset your track...

Quote:
Originally Posted by Nuisance View Post
......
My technique has been to fly a line that is about 1/2 mile outside of the direct point-to-point course. Then I can hold a 45 degree turn and cross over the turn spot, and hopefully not lose too much speed, and not travel too much extra distance.

Good luck, John
Hey... that's what I said earlier....... but John put it better describing the offset in your course to the actual turn point.

I think some of the previous posters assumptions are that a ground track is required with a "sharp" corner of the 120 degrees at the turn point...

A smooth turn with minimum losses and low control deflections will win....

gil A
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