Lap time for slow pattern

[Shorts,David]

I know there are some strategies behind flying a faster pattern.  But what is a speed at which your plane can no longer complete a pattern? That is too say, I have a plane which I flew a pattern with doing about 5.7 laps.  It flew better faster of course. 
But, and here's my question,  my new Tony can't do a pattern at 5.3.  seems like something is wrong. but inside and outsides are close to equal with a little better pull on outside.  Weight is 52 with electric. eflite 25 and castle esc.  It worked good on my chizler and oriental.  About same weight. 
Okay ... Go

[Brett Buck]

I know there are some strategies behind flying a faster pattern.  But what is a speed at which your plane can no longer complete a pattern.  That is too say, I have a plane out had a plane which I flew a pattern with doing about 5.7 laps.  It flew better faster of course. 
But, and here's my question,  my new tiny can't do a pattern at 5.3.  seems like something is wrong but inside and outside are close to equal with a little better in outside.  Weight is 52 with electric. Elite 25 and castle.  It worked good on my chizler and oriental.  About same weight. 
Okay ... Go

   Your new "tiny"? What does that mean?

  This is not exactly a stunning revelation but you almost certainly have some sort of trim issue, like inboard rudder, tail-heavy, etc. One of the hallmark characterstics of electric is that they tend to have extremely heavy line tension for their size.

     What airplane is it, what are the details, and what is it doing wrong?

       Brett

[Mark Legg]

Igor Burger did a small stunter called the Tiny.... guessing that's the one....

[Ken Culbertson]

When you say "Elite 25" are you referring to the "E-Flight Power 25"?  That is borderline for a 52 oz plane but it should still do a pattern without much effort.  What battery and timer are you using, the E-Flight is only rated to 4s.  Basically we need more details.  Trimming electric is very different from trimming IC once you are past the aerodynamic part.  When you say that it will not do a pattern are you referring to not making it to the end?  I had a 50 oz Twister with a similar sized  Cobra 2820 using 4s.  It would sag in the clover if there was no wind.  Personally, I may not be high enough up on the food chain to know the difference but every plane I have had where the thrust line and stab were above the wing C/L turned "better" outside once trimmed to turn equal.

Igor's  Tiny was a .15 size plane and weighed 19 oz. so I doubt this is what you are referring to.  If it is, then you are going to have to fly very fast at that weight and require Divine intervention past the horizontal eights. 

I am a bit surprised that the Chizzler and Oriental flew well at that weight.  I am from that era and, for that matter circle in the case of the Chizzler, and 40oz would have been considered heavy for those planes.  My own plane was 38 and far from the lightest.

Tell us more!

ken

[Shorts,David]

Hi, sorry, I made a couple typos corrections.  Warburton Tony.  Eflite 25, castle lite 50, hubin timer. 

It wont keep line tension through most maneuvers.  Run time should be fine.  Yes, my oriental and chizler had the same parts because they died.  The oriental was 54 oz and had no problem with line tension. My tony can barely do loops without going slack.
I have a fioretti timer also, but it seems like the wrong solution until something more fundamental gets resolved. 
Wings are level. I can still add more tip weight I suppose.  Lead outs are way back.  flat and level it pulls plenty good.  Maybe add more engine offset?

Battery is 4s 3300 which worked fine on my chizler (I think my Chizler was about 50oz even).  I used 5s 2200 on the oriental with a smaller prop. 

Okay, since I posted all this, I started questioning my esc settings. I got a new esc when I fried my old one (long story-lipos really burn like roman candles). I reprogrammed it but may have got a setting or two wrong. So, that is also on my list of things I'm trying for next time out.

[Ty Marcucci]

Check your wing tip weight and lead out placement.. Most slack lines are due to one of those items, but not always.. But, a good place to start ,and no two models fly the same, just seems like it.

Being the same weight as  previous models is moot,, What are their wing areas?

[Brett Buck]

I am a bit surprised that the Chizzler and Oriental flew well at that weight.  I am from that era and, for that matter circle in the case of the Chizzler, and 40oz would have been considered heavy for those planes.  My own plane was 38 and far from the lightest.

     The difference is that the power available is vastly superior. You needed to build these airplanes very light because of power, not wing loading. That is now gone, you make different compromises. 

   What was necessary 30-40 years ago is irrelevant unless you use 40-year-old power.

      Brett

[Brett Buck]

It wont keep line tension through most maneuvers.  Run time should be fine.  Yes, my oriental and chizler had the same parts because they died.  The oriental was 54 oz and had no problem with line tension. My tony can barely do loops without going slack.

     Is it drastically slowing down in the maneuvers?  Make sure you set everything as plain-vanilla as you can, and it should run at a constant RPM no matter what you are doing. If it is doing that, then, again, you have some massive trim problem.   

     I am disturbed at your comment:

Wings are level. I can still add more tip weight I suppose.  Lead outs are way back.  flat and level it pulls plenty good. 

   If the leadouts are too far aft, and the wings are level, that suggests you have something akin to "Twister Disease", where you are compensating for a large yaw angle by taking out tip weight, to get the wings level in level flight. As soon as you touch the controls, that is going to swing the nose in at you, as the crab angle goes away, it also rolls in at you, and all your line tension goes away. My strong suggestion is to *remove any rudder offset*, *move the leadouts forward* to about an inch behind the CG, add about 3/4 ounce of tipweight. Then fly it again using a baseline trim. The 3/4 ounce is probably way too much, but if your situation is as I imagine, just removeing the other things you will find you have way too little as it is, and you have to get it safely off the ground and do a flight.

     I am curious what inspired you to move the leadouts far aft because that is definitely not a baseline trim situation.

          Of course, if there is some misalignment somewhere, that is also a possible issue. So my suggestion is to go do a proper bench trim. Once you get it generally OK and flying acceptably in the maneuvers, then you might find a better trim solution that has the leadouts further aft than traditionally needed, but you aren't anywhere close to that.

    The fact that it is fine in level flight and loses it in the maneuvers is either the motor giving up, or, much more likely given the description, massive trim issues. Trying to fly at large yaw angles with the wings level in level flight  is certainly going to cause problems with no line tension in the maneuvers, the higher it goes on the circle, the worse it will get.

      Brett


     

[Ken Culbertson]

Okay, since I posted all this, I started questioning my esc settings.

I think you may have hit on the exact problem.  The Castle does not come from the factory set for us to use and with a Hubin timer you are not going to get any help.  I had the same problem when an esc failed and Castle replaced it. On factory settings it did almost exactly what you are experiencing.  It was a windy day so I had me some fun doing slow motion squares and the like. It was 4 years ago and I can't remember what the wrong settings were but fortunately I had saved the old configuration on my computer and uploaded it to the new ESC.   The timer was told to give me 9800 RPM and it was delivering about 7500. None of the other trim stuff matters till that is fixed.  I am also curious why the aft leadout position?

Ken

[EddyR]

In the 1980's I flew my Juno at 5.8 sec lap.  Most said it was the smoothest plane they had seen fly including Windy. I never used offset  in anything.  It weighted 50 ounces and was powered by a ST51 packed into a ST 40 case.
EdddyR

[Ken Culbertson]

 What was necessary 30-40 years ago is irrelevant unless you use 40-year-old power.

      Brett

Brett, we are dealing with 40 year old power here. The Power 25 is a small motor for a 52 ounce plane.  It is the rough equivalent of a glow .15 to 25. It could be made to act like a .35 but it is not designed to and certainly not on a Hubin timer.  I am probably wrong, but I think the original Tony was powered by a Merco 35.  Still, I do not think that available power is the issue here.  It is the ESC and trim.

Ken

[Brett Buck]

Brett, we are dealing with 40 year old power here. The Power 25 is a small motor for a 52 ounce plane.  It is the rough equivalent of a glow .15 to 25. It could be made to act like a .35 but it is not designed to and certainly not on a Hubin timer.  I am probably wrong, but I think the original Tony was powered by a Merco 35.  Still, I do not think that available power is the issue here.  It is the ESC and trim.

      You can certainly get more "power" than a Merco 35! Even if the power is less, the effectiveness is far higher. If it is able to govern the RPM without hitting some current limit, it's already going 5.3 second laps so it will be the same power in the maneuvers.  Maybe it will burn up the motor at some point, but otherwise it should keep going until it does.

     I think, from the description, I can guess the problem, as usual, trim. Starting over with a sound baseline should at least get it to the point of functional.

      Brett

[Shorts,David]

Okay, major break through. I had the esc programmed backward so that it never increased any power at any time. It still isn't programmed the way it used to be because now, as Ken said, my 11,000 rpm setting was delivering 8.5 second laps. I made some more changes and for the first time this plane did vertical and overhead 8s. So, I'm thinking this 10 month old plane will finally see its first pattern this coming week.

But, I will try sliding my lead outs back forward and see what happens. I'm confident this plane is not straight, just because I built it, so I'll see what I can do with the trimming as well. 

[Ken Culbertson]

      You can certainly get more "power" than a Merco 35! Even if the power is less, the effectiveness is far higher. If it is able to govern the RPM without hitting some current limit, it's already going 5.3 second laps so it will be the same power in the maneuvers.  Maybe it will burn up the motor at some point, but otherwise it should keep going until it does.

I think we are saying the same thing in different ways.  If the ESC is not set up right you are not going to get the power the timer is asking for.  I have had that exact problem on the same ESC and timer he is using.  The timer was set to deliver 9500 RPM which would be constant with most Hubin timers.  The ESC translated that to 7500.  If you don't TAC your rpms on every flight like you do with an IC you probably would not notice that the ESC was the problem.  Once that problem is confirmed and corrected or not confirmed, then we can move on to trim.  He must have the RPM's really cranked up to get a 5.3 if the ESC is not right.  It should still deliver the same RPM's that give you the 5.3 as you illuded to.  He must also be hitting some limits in the ESC or it is not reading the actual RPM's correctly and drooping in maneuvers.  The Castle Edge 50 has telemetry, but I wonder if it is accurate if the settings do not match the motor and intended use.  In my case the number of poles on a replacement ESC I got from Castle was set wrong.  The default is 14 and I never suspected I would get one from them set to anything other than that, but I did.

Ken

[Ken Culbertson]

 

Okay, major break through. I had the esc programmed backward so that it never increased any power at any time. It still isn't programmed the way it used to be because now, as Ken said, my 11,000 rpm setting was delivering 8.5 second laps. I made some more changes and for the first time this plane did vertical and overhead 8s. So, I'm thinking this 10 month old plane will finally see its first pattern this coming week.

But, I will try sliding my lead outs back forward and see what happens. I'm confident this plane is not straight, just because I built it, so I'll see what I can do with the trimming as well. 

 

Now you can start trimming!  Let us know how it turns out.  Curiosity had me go look into that version of the Tony and it looks like a real winner.  The lines and airfoil should do well using electric.  Must look nice without that cylinder head ruining the shape of the nose.

Ken

[Bill Schluckbier]

Hello,

One of the things that seems to be left out on a regular basis when talking about electrics is the prop being used, how the ESC is set, and the desired RPM.  I have used an Eflite 25 on a 54 oz model and it could fly the sequence; however, it was probably not the best set-up.  Knowing what I know now, I probably would have set it up differently and it would probably be just fine.

At any rate, I use the same simple Hubin timers; however, I only use them as an on-off switch for the power system. I just set the start delay and duration while adjusting the throttle signal to 100%.  I spend my time programing the ESC which for a CC is basically setting it up to run in governor mode (motor Kv, battery voltage, gear ratio), adjusting the gain, power ramp up and setting the PMW frequency (the switching frequency, I believe I use 12).  For the CC, if you set the over current limit to very sensitive it will generally shutoff the motor in case of a prop strike. It will not re-start even if the prop is free to spin again.  It is a useful feature.

If you are using the version of the motor with a Kv of 870, assuming an operating voltage of 3.7 volts, the motor can only generate a peak RPM of about 12,876 (870 x 3.7 x 4) under load.  If you are asking for 11,000 RPM, you may not have enough overhead (meaning the difference between the 12,876 and 11,000) for the ESC to govern the motor properly.  The max permissible RPM is probably closer to 10,300 (~80% of the 12.876K). That might be one of the reasons why the power system seems to behave oddly.

I would be curious to know what prop you are using and my suggestion would be to increase the cell count to 5S.  Choosing the right prop is also important; APCs are OK but there are better options out there (I use a lot of Xoars).  The model that I mentioned earlier ended up with a Brodak 12x5 prop (no longer made).  Although the prop was supposed to have a 5" pitch, given the deep airfoil it used it behaved more like a 6" or even 7" pitched prop.  Badass props are worth a look as well.  Light props and spinners will make it easier to govern the motor RPM as well.

Finally. the voltage limit on motor is more a function of the RPM limit before the magnets fly off.  The current limit is probably closer to being an actual limit.

Good luck

[Brett Buck]

Okay, major break through. I had the esc programmed backward so that it never increased any power at any time. It still isn't programmed the way it used to be because now, as Ken said, my 11,000 rpm setting was delivering 8.5 second laps.

     You earlier said it was unable to do a pattern at 5.3 seconds, now it is going 8.5?

     Brett

[Pat Johnston]

One little thought about lap times.
For me, I find that a classic 35-40 sized plane is a lot happier flying at 4.9 to 5.0 second lap times. It seems that centrifugal force is a major factor in good line tension. I also agree on setting the middle of the leadouts 1” back from the CG. Basic bench trimming 101. Also, level the plane on the bench and slide a scale under the right wing to see exactly what the overall tip weight is doing. 3/4 to 1 ounce would be a good starting point for the Tony. I suppose erring on the slightly heavy side allows for easy removal after the initial flight.
Your scale is also handy for measuring the tail weight. Get the plane dead level and measure the tail weight. It should be about 10% of the weight of the plane. Adjust the sweep of the main landing gear to hit this setting. This formula will be a good starting point for getting smooth landings.
That’s everything I know.
Pat Johnston
Idaho Skunk Works

[Brett Buck]

It seems that centrifugal force is a major factor in good line tension.

   Have you been taking lessons in deadpan humor from Howard?

     Brett

[Pat Johnston]

I love Howard’s sense of humor. He is my hero.
Pat

[RC Storick]

You needed to build these airplanes very light because of power, not wing loading. That is now gone, you make different compromises. 


      Brett

Humm will a tank turn faster than a Porsche?  And the tank has way more power. I know this will trigger Brett.  If you would like you can fly my 52oz 730 SQIN Viper this year and let me know how it turns

[Brett Buck]

Humm will a tank turn faster than a Porsche?  And the tank has way more power. I know this will trigger Brett.  If you would like you can fly my 52oz 730 SQIN Viper this year and let me know how it turns

     We will also see how it scores.

      Brett

[RC Storick]

     We will also see how it scores.

      Brett

How it scores has nothing to do with how it flys. No matter how I fly it it will never score as good as you.

[Brett Buck]

How it scores has nothing to do with how it flys. No matter how I fly it it will never score as good as you.

   Maybe, maybe not. That's 5 months from now, that is potentially 1000 flights. But that's wasn't the point. I have seen plenty of competently-built airplanes that light and a few much lighter (like Scott Bairs 46-sized "Stuntfire" at about 700ish and 48 ounces and Larry Robertson's "Golden Bantam" at 42 ounces and 720) and they were not particularly good, and certainly not better than many other airplanes from the same people - picking on Larry, his first "Revolution" was about the same airplane and was, I think, 60 ounces, flew *far better*.

    Of course, for further "triggering", the infamous Tucker Special experiment, where two highly competent pilots found that going from 38 ounces to 46 ounces with absolutely no other changes and the same physical airplane *tremendously improved* the performance. As always I never said making it heavier always makes it better, we have all seen lead sleds, but it does unequivocally prove that lighter isn't always better.

    But, for sake of argument, presume you are right and, I am going to get a better score. Doesn't that mean you might want to at least *consider* that I (and by extension a lot of other people) who might be more accomplished *actually what gets you better scores" instead of immediately naysaying it on philosophical/religious grounds?

     Obviously do as you wish, but you might at least consider that some of the rest of us know what we are doing, too.

    Brett

     

[RC Storick]

 
     Obviously do as you wish, but you might at least consider that some of the rest of us know what we are doing, too.

    Brett

   

I guess we could always ask Billy if he would like to add 10 ounces to his 53 oz Thunderbolt

[Brett Buck]

I guess we could always ask Billy if he would like to add 10 ounces to his 53 oz Thunderbolt

    Oh no, now you are going to tell on me to Billy! Absolutely do that!

     I am 100% sure that after Bubba sent Robbie over to ask me about the Tucker experiment, they all know about it! Probably had a good laugh.

      Brett

[RC Storick]

    Oh no, now you are going to tell on me to Billy! Absolutely do that!

     I am 100% sure that after Bubba sent Robbie over to ask me about the Tucker experiment, they all know about it! Probably had a good laugh.

      Brett

Will do. 

[GERALD WIMMER]

Hello
 
I remember my first large stunter with a new ST 60 and painfully slow 7 second lap times.
Then made the mistake of giving up on it and selling it before sorting it.
I should have run the ST60 in longer and played with pitch and nitro to try get into the high 5's

Regards Gerald

[Brett Buck]

Hello
 
I remember my first large stunter with a new ST 60 and painfully slow 7 second lap times.
Then made the mistake of giving up on it and selling it before sorting it.
I should have run the ST60 in longer and played with pitch and nitro to try get into the high 5's

Regards Gerald

   Some things just aren't going to work no matter how light or how much "power" you have, 7 second laps are among those things.

    Not that you should "target" particular lap times, do it by feel, but there are limits to everything.

      Brett

[RC Storick]

The absolute slowest lap time I have seen and would not recommend them is 6.1 by Mike McHenry. You would swear it was not going to make it over the top. A good slow lap time I shoot for is 5.5 and I think it is too slow. But some people make it work. Just go as fast or slow as the airplane needs to go, on full line length. The engine's RPM should be happy and times adjusted by pitch or line length on RPM. Good luck

[Brett Buck]

The absolute slowest lap time I have seen and would not recommend them is 6.1 by Mike McHenry. You would swear it was not going to make it over the top. A good slow lap time I shoot for is 5.5 and I think it is too slow. But some people make it work. Just go as fast or slow as the airplane needs to go, on full line length. The engine's RPM should be happy and times adjusted by pitch or line length on RPM. Good luck

  The aforementioned Scott Bair airplanes were routinely around 6 seconds, as I recall (from 45ish years ago) and there wasn't a lot of doubt it would make it. That was an extraordinary case.  I have flown in the upper 5s on rare occasions, 6.1 at the 1997 NATs, as I recall. It was the high score on the circle for that round, but I sped it up later because it was too nerve racking.

   The only really competitive guy flying anywhere near 6 seconds is our 2012 National Champion, Doug Moon, who is routinely 5.7-5.8.

     Brett

[Matt Colan]

  The aforementioned Scott Bair airplanes were routinely around 6 seconds, as I recall (from 45ish years ago) and there wasn't a lot of doubt it would make it. That was an extraordinary case.  I have flown in the upper 5s on rare occasions, 6.1 at the 1997 NATs, as I recall. It was the high score on the circle for that round, but I sped it up later because it was too nerve racking.

   The only really competitive guy flying anywhere near 6 seconds is our 2012 National Champion, Doug Moon, who is routinely 5.7-5.8.

     Brett

I’ve flown with Doug a lot over the last few years! I still have no idea how he does it! I can only get to 5.5-5.6 lap times and still feel competitive!

[Ken Culbertson]

A 6.1 is not unreasonable. Electric gives you the ability to fly much slower and still maintain control.  With the proper timer settings you don't need as much entry speed because you don't loose as much in the maneuver.     It depends a lot on your style.  I am a fan of tracing imaginary maneuvers.  It is easier flying slow.  Recently I have been flying around 5.4 and I think my squares are suffering from it.  Maybe *I* need to slow down.   

Ken

[Dan McEntee]

  Todd Lee can get really up there in the lap times also. Anywhere from 5.6 to 6.0 from my experiences watching him. And he does it no matter what the wind looks like either. I still remember watching him put in the winning flights in some serious wind at a '92 NATS in Lawrenceville and I think he was still a Senior class flyer.
  Type at you later,
    Dan McEntee

[Bill Schluckbier]

I agree with Ken based on my personal observation regarding electrics.  Properly set-up you do not need to carry as much speed in level flight to make up for the loss in speed once you pull the nose up and gravity starts to act against the thrust produced by the prop. Either the ESC or timer (if using an active one) will increase the output power when the load is increased.  But I think that he left something out and that is the choice of prop; both in diameter and pitch. Maybe pitch is not as important when using an active timers but prop diameter does matter in my opinion. The way I look at it is that to generate the additional thrust needed to overcome the additional "drag" a small diameter prop will have to increase the velocity of the air it moves more significantly than a larger diameter prop. As a result I believe that the larger diameter prop will help reduce the speed variation while maneuvering (at least when the nose is pointed up).  Low pitch can help reduce the speed gain when the nose is pointed down.

I fly a profile Oriental with clipped wings (52in) which weighs 42oz on 58' lines.  From the center of the circle to the fuselage centerline I imagine that the model is actually flying in a 62'-63' circle.  The model will fly the sequence reasonably well in winds of up to 10 mph while keeping a 5.4 sec lap time.  Assuming the 63' circle that means that the airplane is flying at 50 mph which isn't blazingly fast. The model flies behind a 12x4 prop spinning at 10,450 RPM.  In my case, the lower speed seems to be a good match for my skill level.