benjuken

I taught myself to fly with 3 years of fun on a few Fire Flite's and several RC simulators.

I have a wattage cap 232 with a super cobalt 400 running on 7 Cell Cp1300. I use 3 Cirrus CS-21 BB servo's ($11.95 each from global) and a Futaba RJ.. 8 channel receiver. I have a Futaba T6XA transmitter and a Wattage Park .. charger. I hand launched it for my very first trainer flight and nosed right into a broken motor mount and firewall. After replacing them 3 times and a few patch jobs, I finally got in a good flight around 20 acres and landed with no power. The next flight I went around a few times and nose dived into a split banana'd front fuselage.

I stepped down to the wattage lightning. I have 40+ flights on my wattage lightning with 380 geared drive and the standard wattage 5/4 AAA pack.

I've snapped my wattage lightning fuselage in half 4 times and have replaced every piece they sell and want through stripping several gears. The IC30 without the BEC did the trick to prevent stripping gears. I put it through some serious hell. It epoxy's right back together each time. I'm sure I'll have this fuselage for life. It's well worth it! I finally stripped a gear from usage rather than from error. It lasted me about 35+ flights. I've got good control of it these days and try to fly every chance I get.

I was feeling the need and so I rebuilt my front fuselage of my wattage cap 232. I even bought an extra one on sale for $100. I got a good 5 minute flight and lost a wheel on takeoff (no boots) and still managed to land unharmed without rolling over. It's heavy though. It stalls easy and each roll loses major altitude. A high speed landing is a must. The 7 Cell CP1300 is just so heavy. It will climb at a steep angle and goes vertical for a second or so. It's so fast it's screaming and heart pounding. I would like to be able to hover and go vertical out of site, but I'm a bit more interested in longer flight times and soaring....but only just a bit. It won't soar with the CP1300 pack and bringing in on no power is a staircase of quick 5-10 ft drops. I'm considering rebalancing CG and moving the battery back, but I don't believe it will satisfy me. I've been reading many complaints on the super cobalt as well.

OK OK, sorry to bore you. It's not my sob story, I enjoyed every step of the way.

I have to land between a few tree lines in a field that's pretty rough. I do like speed and I think I can handle the 7 Cell CP1300, I would just like a slower - glide in - landing....butIwannahover2...ya...ehuh...ya.

I've got my wallet out and I'm so close I'm trying to stop myself, but it's inevitable---I'm Go'N *brushless* man. I've already told my girl and all too. It'sss serious.

I definitely plan on getting a Phoenix 35 and TP3S1P 2100 and a Triton charger with temp control set at 100 and speed control cutoff at 9v. Not scared of using dual rates in fast flight with my Futaba T6xa either.

I guess I've limited my problems to the motor. Ya riiiight! I'm sure you see a lot more than I knowingly wrote.

I've read too much about the Mega 16/15/7 or 16/15/4. 7 or 4 turns, I'm not sure of what turns are is or the difference to be honest, but the reviews and threads are overwhelming. I'm also wondering about putting these lipo packs in a parallel for more flight time or maybe go with a larger pack, but I am scared of the weight, but also 11 minutes just won't do for $300+.

I would appreciate a suggestion of prop and motor combination considering the above characteristics of my illnesses.

Famouse RC-Universe quotes:

Gerns-RCU, your Wattage Ultimate will rock with the following setup:

Motor: Mega 16/15/4(KV2300)- Max. 25 amps
ESC: Castle Creations Phoenix 35
Prop: APC-E 7 X 4 -- amp draw 24 amps
Battery Pack: Thunder Power TP3S1P 2100
Watts Per Lb.: 119 watts per lb.
Thrust: 27 oz. of Thrust for a Plane which weighs 28 oz.
Cruise Time: 11 minutes

If you change the prop to 7 X 3, Amp draw drops to 21 amps, Watts per lb.
drops to 107 - Cruise Time goes up about 1 minute.

Matt Kirsch

My Feedback: (21)

Lots of stuff to cover. Please forgive me if I don't get through it all. As far as being overwhelmed, don't try to take it all in at once. Go in small bites. Search on one aspect of your project, read only about that aspect, but only a little bit, then let it digest.

Okay to start off with, mAh is duration. The more mAh you have, the longer you can fly. But this comes with a price by the name of WEIGHT. You have to trade off weight for flight time. Heavier plane and more flight time, or lighter plane and less flight time. Then there's the point where the plane gets too heavy, and flight time starts to drop off again because you have to fly at higher power levels. Eventually you get so heavy that the plane won't fly at all. With LiPolys, it's very easy to increase flight time; you simply add packs in parallel. Because LiPoly packs are about 1/5 the weight of the same capacity NiCd, you're not adding that much weight to the plane.

If you're going to go with LiPoly batteries, you need to understand their special handling needs. One of the more important ones is, if you want them to last more than one flight you can't overdraw from them. LiPoly batteries have a discharge rating that's given in terms of "C" or the total capacity of the pack (including all parallel packs). Thunder Power 2100 cells have a C rating of 6C if I'm not mistaken. For a ?S1P 2100mAh pack, that means you can draw 12.6 Amps without damaging the pack.

Now, read your little excerpt. You're planning on drawing 24 Amps from a pack that can only deliver 12.6 Amps? No, you need to stack multiple packs in parallel until their total capacity equals or exceeds the draw from the motor. Adding a second pack in parallel gives you a total capacity of 4200 mAh, which at 6C gives you a maximum draw of 25.2 Amps. This will be adequate to run the motor as listed above.

That's not to say the above motor configuration is ideal. For my tastes, the prop is too big and the motor is being pushed too hard. Here's where turns come in. Turns is simply the number of times the wire inside the motor is wound around each pole of the stator in the case of brushless motors.

Fewer turns reduces the strength of the electromagnetic fields, so the motor spins faster on a given voltage, but gives up some torque. The wire can be thicker because there's not as much of it taking up the limited space in the motor, so the motor can handle higher currents.

More turns increases the strength of the electromagnetic fields generated, so the motor has more torque, but it spins slower on a given voltage. Because thinner wire must be used to fit more turns in the motor, it can't handle as much current as a lower turn motor.

Using turns as a comparison only works on motors of the exact same design, like the Mega 16/15 series.

benjuken

That's defintely a start in the right direction. I appreciate it. I see what you mean- pulling too many amps from the pack I see there is much more reading and comparisons to do and changing the prop and battery will change the motor recommendation. I'm afraid that adding a second pack in a parallel is going to come close to the 7 cell cp1300 and I'm back to my weight problem.

Would you recommend a completely different setup? brushless-prop-lipo-esc for the Wattage Cap 232.

Or how about this quote:
I found that the Mega 16/15.....3-4-5 turns will draw 20-25-30 amps.

Quoted in each purchasing spec here:
http://www.atlantahobby.com/shopdisp...Mega+Brushless

I see when adding a 5x5 prop on 3 turns and 7x4 prop on 4 and 5 turns...it changes the amps to 19-24-16. Adding the 3:1 gearbox, changes the amps to 21-15-7.

Quoted in the "Examples of uses:" for the 3-4-5 turn Mega at the bottom here:
http://www.hobby-lobby.com/mega_brushless.htm

TP3S2P (4200mah total) would be 8oz (4oz per pack)
That is 1 ounce less than the 7 Cell CP-1300 that I consider too heavy.

Is TP2S2P a step in the wrong direction. Is lowering the volts from 11.1 to 7.2 going to lower the amps.

Yet, both the 3S and the 2S are 6C rated. I'm not sure I get it, but I'm thinking now that 2S or 3S having 2 of them in parellel is going to be 25.2 amps Max draw because they are both 6C rated packs and 2 in parallel is 4200mah total

The Mega 16/15/4 draws 20-25 AMPS with the 7x3 or 7X4 APC prop according to the excerpt in my last thread you talked about. I see you are saying the 7x4 and 7x3 props are both too big for this motor... especially with the batteries I'm considering. Because my interests are weight, I think I need to start with the bettery and go from those specs to decide the motor and prop.

If TP3S2P 2100 mah (4200 mah total) is my weight limit of 8 oz and I want something lighter to last longer or just as long .......is it possible?

Say I went to an extreme here to understand this. For instance TP2S3P 1320mah (1.95oz). 2S is 7.2 Volts and 3P is 3 packs in a parallel x 1320mah. That's 3960mah in 5.85oz. This is about the max weight I'm looking for. It's still 6C rated and will provide 36.3amps per your calculations I beleive, but I think this is going to be less speed with only 7.2v. Please correct me if I'm wrong. I'm still considering just using the TP3S1P 2100mah at 4oz. or looking for a larger capacity.

This is a lot of variables and I know they rely heavily on my wing area and plane weight and many more. Which I might get to investigating more.

7 turns with the Mega?

Mega 16/15/7 direct drive
AeroNaut 10x7 black carbon prop
draws 16-17 amps
From post 7 here:
http://www.rcuniverse.com/forum/m_15...tm.htm#1577174

Ahhh.....Considering now the Mega 16/15/6 and a 7x4 prop draws 11 amps I could use a 6C battery. The TP3S1P.

(the 11amps is from this URL at the bottom:http://www.hobby-lobby.com/mega_brushless.htm)

I just need to find the median between the 16/15/7 and the 16/15/6 with the correct prop combination but also need to learn about the effects on these when changing from an 11.1v to 7.2v.

Sorry this is so long of a thread, but I here this is a life long decision and I think I was mislead by some of the other posts.

My research conclusions on the Mega:

16/15/7 with AeroNaut 10x7 black carbon prop draws 17 amps
16/15/6 with 7x4 prop draws 11 amps
16/15/5 with 7x4 prop draws 16 amps
16/15/4 with 7x4 propdraws 20-25 AMPS

These are with load as well and I'm sure the load will change with the number of cells too. There's not much info available there so my research only leads to the 16/15/6. How can I learn about props and how the battery will change the amps? I'd liked to have experienced people with people's experiences such as my last reply rather than just trying to figure out a chart on my own.

Oh also, if a 7x4 prop is too big for that 4 turn, but will it suffice for the 6 turn? Is 5x5 too small for both?

Much ablidged for any assistance you all can provide.

phat742

the first setup i had on my cap was the mega 16/15/6 with a 7x4 prop and a 2100 mah 3s1p lipo. it only pulled 11 1/2 amps. the performance was great. definately an excellent pattern plane that was pretty quick as well. the setup i have now is a mega 16/15/4 on a 7x4 with a 3s2p 4200 mah lipo pack. it is a little heavier but the speed is just ballistic. the pack didn't fit inside the plane so i had to make a harness for it on the bottom of the plane. it looks like it's carrying a bomb on the bottom of it.