well with a 890 Kv motor, and a 4s pack, its going to end up being most likely something with a 6" pitch to turn the right rpm,, as to diameter, I dont know the motor,, but I would wonder unless its a small plane drag wise, probably the 12 x 6

OK guys here's the deal.  If you had, lets say, a Scorpion 3020-890 890Kv motor and, lets says, a 4S 3400mah battery, and you were going to put it in, lets say, a 50 ounce stunter on, lets say, 60 foot lines eye to eye and want lap times of, lets say, 5.2-5.4 seconds.  What kind of a set up would you use and why?

Hey I know a guy who is having a great time flying a set-up just like that!   

Option 1: do nothing but fly it.  Trim and improve the airplane to the best of its abilities.  Learn how to "camapign" an ECL for a season of CLPA wars. The motor and battery should be under little stress.  If the bird flies JUST FLY IT

Option 1A:   For 50 oz on 570 squares it might be better to keep the airspeed up AND give the bird a little more room to breathe.  If I wanted 5.4 lap times I would also opt for 63' lines.

Option 2:  Change parameters and re-optimize.  Achieve weight savings by downsizing the motor and battery to just fit the needs of the bird.  I think the bird that size does not need any mopre than an 11" prop.  That with governor braking should be plenty.  Do ONLY if you can achieve a 4 oz weight savings (including potential re-ballasting) which should let you slow down your lap times and keep the 60' lines.

Option 3: new bird to match the capabilities of the power system.  Kick the wing area up to 630-650 squares (i'd do it all in wing SPAN  ) The larger bird will let you exploit the big prop/big power reality of your most excellent power system.


...but that's just me!

Alan, Everybody,
Not a trick question at all.  From my previous posts you all know what 'tack' I'm taking with my setup.  I got some interesting feedback and wanted to know what other people would do if they had the same setup as I do.  I admit, I don't know all that much about electric CL as most others here on the Forum.  I do appreciate the feedback from you guys and it has made me think a little about what I doing.  I will continue along the lines of what I stated earlier.  In reality, the Xoar 12x6 prop is working very well and I suspect that I won't stray very far from it.  I might go to 2 foot longer lines and some minor changes in rpm and such.  I do have a lot of power to play with.  What I really need to do is what Dennis says, fly the airplane and campaign ECL.

Mark,
The 12 x 5 Xoar prop needed 10,600 rpm to generate a lap time that was usuable.  Perhaps it would work if I went with a higher KV motor.  Hmmmm...

The point isnt to make the prop work, its to get a setup that works the way you want. the High rpm low pitch setup is a philosophy about power delivery. Its about the drive and recovery from manuevers, as well as the braking effect coming downhill. My believe is that flatter pitch props get more benefits from the advantage that the govenor gives us in those situations. So its not about making the $5 prop work, its about making the setup work. I have two 120 $ motors for my setup so that I can experiment, but then I also have way more than that in props,, all of which are wood, different brands, sizes, and pitchs. I think its an addiction,,,

Hello, my name is Mark, I am a propellor addict. This week I only bought one dozen propellors,,,

T=One of the cool things about electric is that you do have more flexibility to experiment with this sort of thing. compare a 75 $ motor to a $350 PA 40,, ah well, it works for me anyway,, lol

Yup, Mark is right.  It's the package that I'm working on, not just the props. I flew with the Xoar 12x5 prop and I needed 10,600 rpm to fly a 5.4 lap.  I only used 1942mah for that flight.  I wanted to be around 9600 rpm so I switched to a 12x6 prop.  The 12x5 flew very well but I thought the rpm was a little too high for the KV of my motor.  I do have some 13x5 Xoar props that I need to try.  I'll probably have to cut them down but if they give me a good lap time at around 10K then I might be on to something.  Many possibilities for props and rpm's.  At least I have a lot of overhead in the battery to try different combos.  I'm sure there is a setup out there that will make me happy and get the peformance the plane/ECL setup has to offer.

Mark,
Laps times I'm shooting for are 5.2 to 5.4.  Yeah, I'm going to try the stock 13x5 at 10600rpm and see what happens.  And yeah my gear is made to deal with a 13 inch prop.   

Did you say you had meds left over?

Hi Gang,
   Dean

P.S.

Part of the fun to watch evolution is when folks stop speaking of "the setup" as when copying one of the benchmark setups, and then start speaking of dialing "my" setup to suit me and my airplane.

Well I now have 39 flights on the Resolve.  I flew it in the Polk City contest this past weekend.  The plane flew very well and has a very nice corner.  The set up is very strong and I got several compliments on how well it flew.  I'm still using the Xoar 12x6 prop launching at either 9600 or 9700 rpm.  On average I draw 2450mah per flight.  Over the next month or so I'll finr tune the set up including the reverse rotation 12x6 seeing it has less pitch than the standard 12x6.  I'm a happy camper! 

The plane still needs some trimming but I will continue to fly it to build some handle time.

Just keep flying!

Did some more flying tonight.  I tried an APCE 12 x 6 pusher prop. ..... <snip>.... With the standard prop that I was using there were some bobbles, bumps, jerks, etc during the stunts.......<snip>

So you're saying, a pusher prop gets rid of the jerks? Have to try that.  Oh yea, does it get rid of the jerks on both sides of the line?

Very funny Alan!

In a couple of weeks you'll see what I mean.

Crist,
Yes and you can probably imagine how smug I am that after dallying with poser props, you have come back to the "one true" APC 12-6 prop---even if there are two versions of it!

Update on props and such.  I'm now using an APCE 12.5 x 3.5 Pusher prop.  It started out as an 13x6.5P.  You can get these at Tower Hobbies.  I repitched it to 3.5 on my reverse pitch gauge.  I run it at 9200 rpm and draw about 2450mah for a full flight with a lap time of 5.1 sec.  I have more on order and will go to a 3 pitch to see if I can get closer to 9600 rpm.  Also, I plan on using the full 13 inches.  I'll keep you posted as to what I find out.  Those of you who are using the 12x6P should try this prop out even if you cut it down to 12.  The blade is a little wider than a stock 12 incher.  The reason I need to go to 3 on the pitch gauge is because these props are undercambered.  Remember, you heard it here first!

If you go to any lower pitch, you will have to reverse the rotation, and so a pusher will become a tractor and vice versa!

At some point go to 0!

Then I'll be down to where your anemic current draws are!   

on a "serious" note, I cannot believe that zero pitch is optimal --so there must be an optimal pitch.

So what do I mean by that.

Well there is efficiency, and there is thrust vs airspeed. I know that efficiency goes up with pitch (to a limit of course) and my fooling around with prop calculations indicate that lower pitch seems to increase the slope of thrust vs airspeed (a good effect).

Now to optimize, you need to consider the extra weight you carry around to be able to waste watts on level flight, and this will subtract (in some way) from the extra thrust you may get in the climb as the airspeed drops (which is a function of weight).

Braking enters into it too, but again, with our governors, I have a constant lower rpm with higher pitch than you have with a higher rpm and lower pitch. I think you are winning, but I do not really know by how much. Again, total plane weight matters too. At this point, I have not felt my setup is lacking anything---at least compared to previous glow setups.

But that is the great thing--my guess is that the "optimum" is a broad peak with respect to all these variables and there is no big advantage to anyone at this point.

At some point we begin to "argue" about minor details.

My main point is that you don't have to spend a fortune of state of the art equipment to make a setup that favorably compares to a glow setup in cost and weight and far supercedes it in user friendliness. My setup for example is really consistent every flight and offers incredible advantages compared to the typical LA40 Nobler setup. That is what I am trying to get across (outside of this forum!). And the cost isn't outrageous.

Finally (climbing down from my soapbox---actually maybe I am climbing up), I think glow is on its way out. As RC abandons methanol (and the general energy picture), the cost of glow fuel, not to mention its availabilty is just going to skyrocket. And the glow engines will begin to slowly disappear. It will be soon be like 1/2A is right now.

Now you can be sad (I am a bit because I like mechanical things), but still if you like the smell of castor in the morning, enjoy it while you can.

Ok, off the box!

Good thing this is in the electric forum!

First a personal perspective, as much as I beleive in electric, I cant see myself doing a classic ship with electric just yet anyway, around here that would likely get you tarred and feathered! lol,,

now, as for your comments Alan about "wasting " energy with a high pitch setup. I dont get where that comes from, perhaps if you use your same motor and wind it up you might, but if you get a different motor with a higher KV and run a high rpm low pitch setup, it will be just the same efficiency as the low rpm high pitch? to put it in another light. If you use the same diameter prop, but with a flatter pitch, it will move the same column of air ( spaure inches of prop area) with more thrust, even at flight speeds. but it will take the same power to spin the flat pitch prop at a higher rpm because there is less drag per revolution of the blades, IOW they are taking a smaller bite of the air each time they rotate so it takes less watts to rotate it per rpm. This is my take on it,, FWIW. I also believe that a high rpm setup all else being equal, will generate a much better airspeed to rpm ratio, and breaking affectivness than a high pitch setup will. My target is somewhere around Crist, though a bit higher, I want to spin about 10000 to 10500 rpm with a 4 pitch prop or thats where my "calculations" put me. that will be with a Hacker A30-8XL that is capable of over 650 watts, though I dont plan on using all of it. regretably, it will likely be this fall before my new testbed takes the air. I have to finish the Avenger, and the 109 profile, (Crist this is the one you cut cores for quite a while back) and Jessica wants to finish her plane too,, sigh,,

I got some more 13x6.5P today.  I repitched one to 3 at station 10.  It is the full 13 inches in diameter.  We'll see what happens this weekend.

Crist
ANOTHER great set of data.  Geez what a difference a year makes.  You gone a LONG way from the Barnstormer with the 13x8(?) or what ever it was you were flying last summer!

Crist,
thanks for sharing, great information!
good luck flying now, have a great season

"Wind up" or "whip up" is when the airplane gains speed when doing stunts on the down wind side of the circle.  Most noticable when doing the 3 inside circles.  It's like having a kite doing loops that get faster and faster and eventually you will run out of elevater and can cause crashes when it is at its most.

OK, I get it. I assume one of the PA goals is to fly a constant ground speed around the circle, regardless of the wind. So you have two cross-wind portions, one headwind, one tailwind, and the transitions between. The governor will then be trying to keep the air flow through the prop constant as it loads and unloads in the transitions.  Would I be right in thinking the transitions are the important parts where the governor is working hardest to keep the RPM stable?

I have the gain in my CC PHX 45 set to medium. Does the RPM stability benefit from setting the gain to high ( not too high!). I would think high is where to run it as long as the speed doesn't hunt. CC doesn't say much about the control algorithm or give one much in the way of options to modify it. Since it is a consumer product, there won't be many people using it that have the understanding necessary to fine tune the control anyway.

Good stuff, guys.

John

Alan, I was using airflow through the prop as a euphemism for airspeed, but I see your point. No way to keep a constant groundspeed without some kind of reference.

So do you have any info about what the CC software means relative to response times for the  governor gain, for instance is low to med to high an order of magnitude each time, or a doubling, or some nonlinear factor?

I'm scheduled to fly Saturday AM, so I think I'll take my laptop and try changing the gain and see how it works.

Interesting that a lot of E-flyers are interested in numbers and numeric modeling. I think that might be because we can get the info. A glow engine is hard to compute.

John

IIRC my gain is set fairly high. cant say for sure just how high, but its in the upper range of the available settings. have not looked at it for awhile though.

I should note that I base my "gain" observations primarily on my data recorder rpm measurements. So I say that I am satisfied because I don't see any apparent sags or surges of the rpm level during a pattern flight.

If I didn't have this data, I guess I would play more with the gain setting since the main feedback (as far as I know) is when you overdue the gain setting and can hear the overshooting and undershooting (prop noise) during the maneuvering---like I heard with my Super CLown when I apparently overdid the setting.

Of course it is painful to make these ESC changes if the PC is back home, and not at the field. But as they say, no pain, no gain!

John,
You sound as confused as I was when I was trying to figure out how i was suppose to setup the governor. It took some time and patience from the guys here on the forum to talk me though it (a belated thanks!).

Anyway here is the way to look at it. First lets look at normal governor mode:

In "normal" mode, the ESC is looking at the pulse coming out of the timer/throttle (the Ztron in your case). The timer puts out a 1-2ms pulse at a 50Hz rate. A 1ms pulse is interpreted as throttle "off", and a 2ms pulse is throttle "full on" =wide open throttle or WOT. So lets say you set your Ztron dip switch for a "25" setting---which I think is right in the middle of the throttle range. Then the Ztron would put out a 1.5ms pulse. This is nominally equivalent to the throttle channel output on a RC receiver.

ok, so far, so good. Now the trick is how the ESC interprets this signal. What it does is map the Ztron output into a rpm range. Now you should know, the ESC doesn't really measure rpm directly, but it is counting the signal that the permanent magnets make as they spin around the stator. A typical motor that we are using has 14 magnets. I think Dean Pappas once gave us the conversion between the Ztron pulse output and the rpm level. Anyway the Ztron output maps onto a rpm and it is a little trial and error to figure it out. When I use to use this mode, I would replace the normal propeller with a small 2"diameter disc that had alternating dark and light quadrants. My tach could read the rpm of the motor this way, without worrying about a dangerous 9000 rpm prop whurling around. By playing with the timer, I could map out the rpm as a function of the timer setting. A little tedious, but it worked.

If you are still with me, once the throttle setting is made, the governor will try and keep that rpm setting, as long as the throttle setting stays the same. So if the load goes up (like in a climb) the ESC governor will increase power to the motor, and take it away as the load goes down. As a result the rpm stays constant. The only limitation is that the rpm itself must be attainable by your particular motor and battery. That typically means that we fly our level laps at ~75% throttle. If the power needs go up, the ESC can draw on that remaining 25% to increase the throttle. Now it isn't completely clear what 75% actually means to everyone--to me it means that the ESC is outputting a PWM pulse that is on 75% or the time and off 25%. That actually translates into less than 75 % power (I think).

There is a small wrinkle called "high" and "low" governor mode--and that is because you may want a higher target rpm range than what is considered "normal" (normal was defined for helicopter pilots).

The advantage of the above type of governor mode is that if one day you think you need a little bit more "oompf", then simply increase the Ztrin throttle setting a click or two higher, and the rpm will increase some too. Last I recall each click is in the 100 rpm range--but I forget because...

I use the set rpm mode. I was tired of the back and forth setting stuff, and knew where I wanted to fly. In Set RPM mode you can set 3 target rpms. The first value is for timer throttle settings above 0 and less than 50%, the second above 50% and below 99%, and the 3rd is for 100% throttle. I set the first value to be 7500 rpm, the second to be 7950 rpm, and the third also to be 7950 rpm. I then use my timer so that when I take off, the throttle value is ~45%. This gives me 7500 rpm for a nice calm takeoff. I then set the timer to ramp the throttle from the 45% value up to 100%. Now this took a few trials and errors, but right now, my timer passes the 50% point about 1.5 laps before the wingover--so when the ESC sees the 50% value, it ramps the rpm to 7950, and holds it there the rest of the flight.

But the disadvantage, at least the way I am using it with the reduced takeoff power, is that I am locked into a flying rpm, and can't change it unless I bring a laptop to the field. If I didn't care about the takeoff power, I could set a windy weather rpm and a calm day rpm, and then just adjust the timer to one of the desired rpms. Or if I had 3 timers already setup, I could just change timers.

Well this was another long winded post. I hope it isn't confusing you.