krproton

Thinking about hitting a few Pattern contests next year. Flown some IMAC (Sportsman) over the years and thought I'd give Pattern a try. I can make it through the 2011 Intermediate sequence with my electric-powered Venus II, but only if I fly the pattern a little tight and even then with little time to spare. I'm using 3300mah batteries and could go up to 3,800 or 4,000, but don't want to go any larger than that.

So, and I'm asking this of all the guys who fly at all levels, is pretty much everybody who flies electric Pattern in the same boatlittle reserve after completing a sequence? And are there scenarios where you have to wait to land because maybe somebody else is on the runway? In IMAC sometimes you have to go into a holding pattern either before or after you fly your sequences to wait for another competitor who may be on the runway or completing their sequence in the same air space, so you definitely need extra flying time.

Well, just wondering how it works compared to IMAC.

Thanks.

Tim

Jetdesign

My Feedback: (8)

I think the Masters and FAI guys are pushing it close to battery capacity. I have never ever used 3000mah or more and can fly the Sportsman pattern at least twice with that. Haven't flown the full intermediate schedule yet, but probably still under 3000mah for me. Of course I'm running higher voltage (10S) to decrease current and run cooler.

They do fly two lines at once, so you may have to wait for runway to clear.

You should not have a problem flying the first 2 classes with 4000mah.

Mike Wiz

My Feedback: (2)

The assumption here is that you are flying 8S. Is that right? Personally, I like 5000 mah with an 8S power system. In the old days I flew TP 8S3P 6000 mah batteries. I once lost a plane due to running out of battery before I could land so I always like hauling a few extra electrons aloft... just in case.

That said, on my Reactor I fly 6S 4000 pack. If you go up in voltage, you can create the same wattage with fewer amps thereby allowing you to use a lower capacity battery. This is a big part of what made electric power so much more viable than it was back when we ran NiMh or Nicad. We could run higher voltage without making our planes weigh a ton.

krproton

Thanks guys.

Nope. I'm running 6S. 8S pushes the Amperage way up over the motor's 50/80A constant/surge current limits. I'm around 75A in flight (around 85A static). 8S pushes the Amperage up around 150A (with the same prop) if memory serves. I guess I could spin a smaller prop (running 17 x 8 now), but I don't think I want to and the RPM will also go way up possibly putting it over the RPM limit for the prop (APC).

I'm just thinking 3300mAh is a little small. Right now I have my timer set on 5 minutes (giving me about a minute in reserve). I think I need to go up to 3800 or 4000, but I really don't want to go any more than that.

Was just wondering if other guys who fly Pattern competition have to do the same math and mind their flight time too.

Mike Wiz

My Feedback: (2)

That's a lot of plane for 6S. Might try 8S and a lower KV motor. Of course, that's a pretty big change, both battery and motor. But do you see why not giving that information makes a big difference in the answers you are going to get? 3300 mah isn't a lot of capacity when your power system is drawing 75 amps. Remember, amps don't fly the plane, watts do. Amps x volts = watts. You can up the voltage and lower the current and still make the same watts. And what does lower current do? It gives you longer flight times or it allows you to run a smaller capacity battery and... and this is a big and... higher voltage is more efficient meaning your entire power system runs cooler.
 
Next time you size a power system for a plane look at going up to the next higher voltage battery and run a lower KV motor. I think you'll be pleasantly surprised at how well it works.

krproton

Part of the problem (well, it may not be a problem, it's just the confines of my motor) is this is the lowest kV motor available to me. As I work in Hobbico R&D I would prefer, if possible, to run our own Ammo motor (It's not manditory or anything, it's simply my preference). The lowest kV we have in this size is 450. That's the motor I'm running; Rimfire 1.20 (50-65-450). The next largest motor is a Rimfire 1.60 which is out of the questionit's a big step. I'm not opposed to running different motors - I've been flying my Rifle all summer with ARCs, MEGAs, Neu. I don't/didn't think I had a motor "situation" concerning the flight time with my Venus II, I was just inquiring about flight times (but of course the motor is one of the components in the whole equasion).

The other thing is the current draw I provided. Maybe I should clarify; 75A is the max current draw at full - throttle, which in sport flying I don't use much anyway (I have about 225W/lb!) and when flying the sequence I try to use sparingly (and don't need much again). I don't have the figure for the averge current draw in my head, but it's back at work in my Eagle Tree data. Probably around 50A.

This kind of beggs the question then; Where within a motor's constant/surge Amp ratings are other Pattern flyers when they go to full-throttle? Me, we already established, I'm up there - I'm pulling 75A in - flight at full - throttle and the motor is rated for 50A constant/80A surge. Are you telling most guys aren't nearing the motor's limitations at full - throttle?

Given the same kV motor, the way to facilitate an increase in Voltage AND lower the current is go with a smaller propeller - a much smaller prop! Then this wouldn't be a Pattern setup. So the best way to higher Voltage and lower current is, as you said, a lower kV motor. What motor do guys like on an 8.5 lb pattern/sort plane such as the Venus II? Maybe I'll do a search my self. Now that I think about it though, going from 6S to 8S would be a significantly heavier battery which I don't want, unless I go down in capacity. What? An 8S 2,000mAh battery? That doesn't sound right.

Mike Wiz

My Feedback: (2)

There is a lot in that last post, Tim and I want to address everything properly. When I get a little time, I'll give you a more comprehensive response. The short reaponse for now is, you need to convince the guys making the rimfire motors to make their 1.20 sized motor in a couple of different windings. For instance, take a look at the Hacker A50 series. In particular their A50-16L is a good example. It's design is perfect for flying 90-110 size pattern planes on 8S.

It would be nice to have a more complete lineup of Rimfire motors for us to choose from. There are a lot of gaps between the offerings that could be filled by just offering different windings.

krproton

First off Mike, I neglected to thank you in my previous post for taking the time to write a reply.

Second, yes, they "paired down" the Rimfire lineup a while ago. I agree with what you are saying. I don't know what goes into the decision making, but surely it was sales related. It would be nice to have a more extensive lienup, but if they aren't moving the numbers they need...

Maybe I need to look at a different brand motor which I'm not opposed to doing. However, back to my original issue, I think the easiest solution would just be to go to a 3800 or 4000 battery. Another guy at work is flying his EP Venus II with the same exact setup as I, but is using a 5000 mAh battery. I tried it once or twice and really didn't like it. I can really "flick" mine around with the lighter setup. It's like a feather.

Well, thanks again Mike and looking forward to your response.

And my question still remains for everybody else: Is flight time a concern when flying the sequences in Pattern competition, or do most of you have plenty in reserve?


Tim

Jetdesign

My Feedback: (8)

If you could borrow his 5000mah battery and put it in your plane, it would help. You may have been feeling things like different throws, different trim setup, different CG, etc.

The Venus is built pretty heavy, but it seems to handle the weight very well. I would not hesitate to go w/5000mah. It would be good to compare the weight of a 6S 5000mah pack to an 8S, 4000 mah setup.



I have plenty in reserve. I have not even come close to using up a whole charge. Batteries do better/last longer if you are not fully draining them all the time.

Mike Wiz

My Feedback: (2)

Tim,

I'm trying to nail down your existing setup in Motocalc so that when I plug in possible changes I'm going get answers that will be very close to reality.
I got the motor constants for that particular Rimfire motor plugged in. And I've plugged in the airframe. At this point I don't know what prop you are using nor do I know your all up weight.

For what it's worth, I'd love it if Great Planes offered a world class lineup of motors. If guys can manage to get Andrew using a Rimfire in his winning pattern planes the sales numbers will knock your socks off. But you gotta have a motor that is worthy first. It's a chicken and egg thing. But I'm sure I'm not telling you anything you don't already know.

Cheers,

Wiz

krproton

Hey Wis,

here's my setup:


Venus II ARF (converted to electric):

Battery: Turnigy 6S 30C 3,300mAh
Prop: APC 17 x 8 E
Motor: 50-65-450kV (Rimfire 1.20)
ESC: Phoenix 85 HV

Amps: 85.5 (max/full - throttle, static) 75A (max/full - throttle, in-flight)
Watts: 1914 (static)
RPM: 7,750

RTF weight (w/battery): 8.5lbs (136 oz)
Wing area: 866 sq. in.
Wing loading: 22.6 oz/sq.ft
Watts/lb: 225

Jetdesign

My Feedback: (8)

Try a 16x8. I flew the VII with a 16x8 and 15x10 (glow) and was satisfied with the performance. It would save you some of those precious mah's and not cost much to do

Jetdesign

My Feedback: (8)

You should do a poll. People like polls.[sm=thumbs_up.gif]

nonstoprc

My Feedback: (90)

To allow extra reserve in battery probably is always good idea, especially flying in a windy day.

In pattern or imac competitions, I noticed very few instances of planes being requested to be in the holding pattern in the air. The exception is to allow emergency landing (e.g. dead stick).

Options I see possible to improve your situation is

1. use of a lighter battery pack
2. reduce plane's weight

If you can fly slow, it probably is OK to fly it tight Otherwise, you may not have enough time to set things up. You may just try it and see.

rcpattern

My Feedback: (45)

With the new sequences, I don't think anyone in Masters or FAI are regularly going over 4000. Even on a windy day I can fly HUGE with my Wind S Pro and still only use about 3900 on the new sequence, usually its about 3400. I think the FAI guys are in the same general area.

Arch

Mastertech

My Feedback: (31)

Arch flys as big as anyone I've watched and when he lands his batts are barely warm.

Masters takes about 6 1/2 minutes or so, Advance takes 5 1/2 for me and I fly big with long turn arounds.

I use every inch of the box I can.

We were discussing this at Green Sea, Masters "can" be flown with 4000's but the airplane was designed for 5,000's to make weight, Seems there's a consensus that Electric airplanes fly best between 10.5 and 11 pounds for the wing loading by design. I think that is correct.

Tim

smcharg

My Feedback: (1)

I fly a Passport with 4900's and the NEU-F3A motor.  The plane is right at 10 lbs 14ozs.  In the Advanced sequence, I'm using about 3000-3200 mAh for the sequence.  It's really all about learning throttle control.  You don't have to fly maneuver to maneuver at full throttle.  Slow down baby....it gives you more time to plan out what's next.  I see so many Sportsman and Intermediate pilots only pulling their throttle back on the down lines of maneuvers.  Try coming out of one maneuver and flying at 1/2 throttle to the next.

There are a few times where every pattern pilot has had to "go-around" because the other line was landing at a contest or taking off.  Usually you may need to make one 360 coming upwind and turning mid-field and at the most two.  Other than that, you won't really have to "hold".

Throttle management is the key in electric pattern.  If you don't have that, it's hard to make it through any of the sequences, especially on a lower capacity battery.

krproton

This is what I was thinking (though I welcome all suggestions for motor/battery options); If you're using around 3,200 for your sequences, it makes sense then that my Venus II has little reserve as I am using a 3,300 mAh battery. I can fly the Intermediate sequence okay, but I do have to keep it slightly tighter than I would prefer. Yes, reserving full-throttle only for uplines is the way to go I do know. I know from flying IMAC (I'm not a pro, just Sportsman in IMAC) you want to fly deliberately and with patience - not "jet" through the whole thing. Plus, if you fly fast you're back on the ground before you know it and it's all over.

Well, I'll keep checking back for more replies.

Thanks guys.

DaveL322

Tim,

Another approach -

The reason you are not getting a really specific answer is because there is substantial variability in the answer. You will find guys flying Masters on 10S 5000s that are only using 3000 mah for a flight....and you will find guys routinely exceeding 4000. A lot depends on flying style, how well the airframe is matched to the flying style, and how well matched the motor/prop is for the flying style/plane. You can also find substantial variation (as much as 10%) depending on how the mah are measured.....ie, Eagletree, ICE log, charger, etc.

The majority of 10S pattern stuff is between 75 and 95 amps static on the ground, and depending on motor type (geared inrunner, or direct drive outrunner), and heavily loaded, the peak amps in the air will drop 5 - 15%. Average amp draw from takeoff to landing is typically 25 - 35 amps......so figure about 40% of static peak is what you will see for pattern flying. I've found this 40% number to be generally valid on my smaller 3, 4, and 5s pattern/sport planes when flying pattern. Obviously, most of the pattern stuff is 10S, and for your case, if the drop in cell count is roughly equivalent to reduction in airframe size, mass, drag, then you could expect the 40% number to hold up. My gut feel is that your 6S setup is probably being pushed harder than the average 10S setup in Masters, but you are also looking at flying a shorter sequence (initially at least), so I think you'll be fine for Sportsman, Intermediate, and possibly Advanced.

At 7750 RPM.....consider trying some of the APC glow props....you may find them to be more efficient at the relatively high RPM.

Regards,

Jetdesign

My Feedback: (8)

I still say try a 16x8. You will use less current and increase your flying time. Plus it's a cheap experiment.

viva_peru

I would have suggested using a 16x10 instead. The load will be similar to the 17x8, but it might give you better top end speed which means that you can probably cruise in between manuevers at a lower power setting. The vertical might suffer a little however.

Good luck,

Teo

krproton

Hmm, thanks Dave.

Yea, no way I can use 10S on my Rimfire motor. 8S is also out of the question (unless I really prop down which would no longer be a pattern setup). I had the Eagle Tree setup in another Pattern plane with the same exact setup as in the Venus II and the average current in flight was 40A, so your 40% rule is pretty close. Similarly, on my little speed plane (Rifle), I've noted a 32% drop in current from static readings vs. in-flight (again, with Eagle Tree). This was very consistent for all motors/props in the variety I tested.

I think part of the problem is the current limitations of my motor (50A constant, 80A surge), but I'm not certain. Also, I'm using a smallish battery at 3,300mAh.

I'd hate to have to resort to a glow prop, but worth testing. Also possibly dropping down to a 16 x 8 E as a few others have suggested.

As a side note, this is the kind of stuff that glow proponents, or more accurately, electric haters, dislike. Yes, all this experimentation can be a bit of a nuisance, but I still think it's worth it and a little bit a part of the fun. Besides, glow/gas isn't always a walk in the park either! Finally, once you get a good setup, you can share it with everybody else.

Thanks again.

Tim

Jetdesign

My Feedback: (8)

I'm sure there was plenty of experimentation when glow was getting popular a billion years ago.

Electric is nice, there is a lot of flexibility in the systems. I experimented with my plane, a little, and have unlimited power and 11 minute flight times by increasing volts and decreasing current but maintaining power.

dreadnaut

My Feedback: (5)

Own design Focus Sport Clone-9lb
Scorpion 4035-330
Castle Ice 100
APC 17-8
Zippy 8s-4000

Gets me through the intermediate with little reserve, but if I do have to go around, who orbits at full power? One turn of the pattern pretty much pushes the batteries to the limit with out going over. Thanks to the weight savings of the smaller batteries I don't have to go full throttle on some vertical maneuvers, like stall turns.

greg_m

Hi Guys - motor manufacturers!

For years we flew pattern with an OS 140. Now the motor manufacturers come up with equivalent outrunners motors of size 120 or 160 = refer to post #7 above. WHY WHY WHY?

I recently converted to the dark side - Otop. The 160 outrunner is to big, too powerfull and way to heavy . The 120 outrunner is not powerfull enough although size and weight are good. Most guys here in SA using the power160 outrunner love it but say they only using half throttle most of the time.

Why is there no 250kV 140 equivalent size outrunner out there that can take a 10S battery setup?????????????

I am current weighing in at 5.2kg in my Otop with a 120 size equivalent motor (63x56 can), 10S 4400 15C lipos and 100A HV speed controller all from a cheap source because it was purely experimental for me. Averaging about 2800 mAh per intermediate flight ... max amps of about 60A and average around 35 - 45 Amps for the flight. running a 17x10 APC-E prop.

the cheap motor is heavy - if there was an equivalent 140 size outrunner from a reputable manufacturer that weighed the same or less I would go for it like a shot...