I'm having a hard time understanding the ready set power systems for a .15 sized airplane. It seems the 3s 2200 is a common battery size for a .15? That sounds pretty big to me. An average 3s 2200 is around 6.5 oz, whereas a fox 15x is 3.5oz. Then you have a motor, esc and timer? Even a fox 35 is only 7oz. Am i missing something? Please help.
I want to make an akromaster with lights in the wings. It's getting dark early! Thanks guys

I'm not an expert on electric set ups but most of my models fly with relatively small motors for the size of the model. The Acromaster will fly well with a Norvel 074 so why would you even consider using an E flite 15 or equivalent motor. It's too much for that aircraft. Think smaller. the motor designation is grossly misleading about its potential. It is more potent than an equivalent sport 15 glow as far as it's ability to develop power or turn a larger or higher pitched prop.

I'm having a hard time understanding the ready set power systems for a .15 sized airplane. It seems the 3s 2200 is a common battery size for a .15? That sounds pretty big to me. An average 3s 2200 is around 6.5 oz, whereas a fox 15x is 3.5oz. Then you have a motor, esc and timer? Even a fox 35 is only 7oz. Am i missing something? Please help.
I want to make an akromaster with lights in the wings. It's getting dark early! Thanks guys

You are right, weight is everything in this size range!

I fly a 1/2A Pathfinder & a Wee Duper Zilch with 3Sx1300 packs, using about 1000mah.  These airplanes are the same size as the Akro, and both are outstanding flyers.  The PF finished off at 15 oz, the WDZ at 13 oz which is also a good target weight for the Akro.  Both of these are excellent stunt models.  I demo'd then passed around the PF at the Brodak Fly-In a few years ago and people really enjoyed it.  It is amazing how deep you can go into a corner with a 15oz airplane!  The WDZ is OTS legal but I only fly modern patterns with it - seems a shame to hold it back to the Old Time Pattern.  Using .012 x 50' lines (eye to eye), but will soon be flying on Spiderwire which should be just a smidgen better:

Prop: APC 7x5EP
Motor: Arrowind 2210 kv=1560
ESC : Arrowind 18A
Pack: 3Sx1300
Timer: Hubin FM-0c

BTW, the Arrowind motor sizes are based on internal dimensions (like AXI Cobra or Scorpion) If you use a Turnigy (outside dimensions) then the equivalent size would be about a 28-28 or so.  Also key is that the kv be at least 1500 - need to spin it up.

On birds this size the enemy is WEIGHT!  Andy Borgogna built a PF using this power system (I think he changed the motor out later on) and reported here on SH that he was able to save around 1 oz by eliminating the bullet connectors, shortening the wires and soldering the motor wires directly to the ESC.  I did not do this but if I ever got around to a re-build I probably would.  BTW Andy also use the KR timer system.

There is probably a lighter battery connection than the Deans Ultra plugs too but these are handy (to me) for other reasons.  Should also mention that these are a few years old & Lipo technology has progress.  I'd bet you could find either lighter 1300's or the similar size/weight packs at 1500 mah or so.


For a hotter set-up, I also have a Jr Flite Streak that I "motored up" to use an 8x6EP prop and 3Sx1800.  It really scoots on .012 x 50' lines - like a Flite Streak should!  This one is 15.8oz.  Several folks flew this at the 2014 Brodak Fly-in and it produced instant smiles...

Prop: APC 8x6EP
Motor: Arrowind 2215 kv=1180
ESC : Arrowind 18A
Pack: 3Sx1800
Timer: Hubin FM-0c

I'm not an electric expert either, but i would definitely not use an eflite 15 on this tiny plane!

If you have an eFlight "X" motor, then they don't mean "this motor will replace a 50 year old "X" engine on 5% nitro".  They mean "this motor will replace the hottest "X" engine you can buy, running on 35% nitro or more".

Keith, excellent info there! In fact, I'm thinking that and what Dennis said proves i need to be thinking smaller. Dennis is right, an 074 would fly this thing. Maybe like Frank and Denny said, look into more of the 1/2a - .09 type power.
Excellent info everyone!

I'm thinking in the 2215 size. I'll see what brodak has. I love arrowind products. Already got plenty of timers and esc's

Outstanding Keith. Thank you for your help. I think i can get away with a little less power than the plane shown in your thread. It looks like yours is a little bigger physically than the akromaster?
My goal is to practise the pattern at night. Plus, if I'm wrong and it's not enough power, or flight time or whatever, my daughter will take it and fly it anyway! Putting the lights inside and having an electric plane is the main focus. If it can complete the pattern, bonus!

Sorry for the delay, wanted to get back with specifics.  This all goes back to your original thoughts about the weight of the system.  In my first reply I reference my 1/2A Pathfinder being similar sized to the Akro. Here's a tale of the tape:

                                              Akromaster                       1/2A Pathfinder
Span                                             34"                                       35"
Area                                           250 in2                                 236 in2
Fuse length                                  20.5"                                      23"
  (nose to rudder post)
Recommended Engines                15-25                                  .049-.07

Not much difference in structural weights, the Akro uses a "log" LE & TE but it also uses a 2-wheel gear.  My read is that these two are pretty much the same except for the engine recommendation.  Now if I was out to replace a 25 I would be looking at something that would turn a 9" prop and probably use something like a 3Sx2200 (or 4Sx1800) pack.  However if I was looking to replace a .049 - .07 then I would size the power system to drive a 6"-7" prop.

The difference in perception yields huge differences in weight!  In your original post you mentioned that a 3Sx2200 pack would weigh about 6.5 oz.  The complete power system I described weighs 7.1 oz.

Keith R made a very pertinent point about flying at altitude.  Out there in "Lost Wages" my GUESS is that you will have to tip the nitro uhh, I mean turn the RPM up some to compensate.  While that normally increases battery drain you are really only restoring lift & drag to levels comparable to what I see here in FTW - I think you would still be OK.

I also fly the PF at about 4.3 sec lap times and it is timed to fly the pattern with a few laps left over. That should work for the Akro too but if you were seeking to fly faster then you might want to look at a little more battery then the 1300.

BTW I designed a conversion kit for this size power system & profiles - see Brodak #BH-1935.  It should work well for the Akro and maybe save you a little fabricating time...

Ok, thank you very much Denny. I am ordering the eMotor mount set of that part number. I'm really leaning towards the 2215 just because of the idea of weight. I do believe my SIG kit wood is going to come out heavier than your path finder. I think you've seen a few of my Monokote ringmasters, and know i build pretty light, but I'm just building a box stock kit. Thank you for the part numbers.I'll be placing the order today

I think based on this discussion, I'm shooting for the .09 type power on this project

Not a bad plan at all!  The 2215 will actually turn an 8x6 if you want to go that far - of course that may push you into the 3Sx1800 pack.

I have an Akro started also (since 3 years ago!) but mine has all really good wood.  The log LE & TE are pretty good and the fuselage is weightless!  I am planning on the same set-up as the PF and am optimistic about achieving a similar weight.

BTW, one thing the PF has that the Akro does not: the PF is designed to use a 3" bellcrank, the Akro is designed to use a 2".  It really improves the control system if you can use the larger crank, but you have to open up the ribs to make that possible.

Yes I have admired your fabulous Ringmaster builds & 'coting methodology.  What covering will you use on the Akro to keep it light and electron-proof?

Wow, NICE job on the double bellcrank - a Ringer never had it so good!

What will the lites in the Akro weigh? Sounds more & more like a little power up may be a plan.  Also check out the Akro plan, the instructions call on cutting the LE & TE to length, but if you leave them full you can gain another 1.5" or so of extra wing span & area for negligible weight gain- might come in handy

Right on right on!!
Got my order in from brodak. The new motor mount conversion set up and arrow wind motor. I'm pretty excited! This should be wicked fun!

Thank you rex, very cool planes. This will be my second Akromaster. The first was not a great build... I'll admit that! Lol

I like the peacemaker. It's on my bucket list. My friend George built one, and i really liked it. But I've never flown one.

This is my third attempt at electric. The first didn't work out too good.... Lol

No promises Chris, but at least it will look pretty!! lol
Heres a quick video clip of prepping the akromaster for the Brodak EPS-10 system conversion

I guess this could turn into somewhat of a build thread. Mostly just to keep me on track and hurry up! Lol.
So the wing came out with an additional inch on each side. So 2 inch more wingspan. Thanks Denny. Unfortunately, i did something wrong or don't understand something... I ended up having to make two more ribs for the wing tips. It shows 13 on the plans, but i ended up needing 15. They are however, evenly spaced.

Pic one shows the notches that were there, and i just notched the end on the scroll saw

Pic two is just rib spacing.
Pic three is the sheeting almost done. Gotta cut the push rod exit

Heres a quick video on monokote covering the little akromaster fuse.

I got the wing in, and the flaps on / extended. The box says 34" wing, i ended up at 38.5"
 The wiring for the lights is almost done. I couldn't find red for my nav lights so pink was close enough.

Thanks for keeping us informed.  Keep going!

I spent a little time truing up the elevator halves after joining them. Took some slight shimming, trimming and sanding. Then i rounded the corners and tapered the elevators. Just for aesthetics.

I think i want to cut down the fin and rudder a little, just for looks also

A little at a time. It's surprising how little time can be dedicated to building a kit, but it still progresses. The kids aren't interested in building every day, so 15 to 30 mins is about all i get! Lol

Getting there!

I finally took a look at this thread.   I am amazed at what you are doing to the little bird.   Need to get my daughters plane off the hook and clean it up.   By the way this old man says there is never enough hinges,  I even put in extra DuBro hinges, especially a second one out on the ends of the flaps.

Everything is looking real good Dane.  I have been using the over/under hinges too and really like them.  I usually make them 1" wide and use them full span until I run out of surface.  Happy the CG is looking good too.

Ok, wings and fuse done. It took a little longer to order in the transparent white. I ordered some lettering and graphics from cfc graphics. Thanks Charles. As soon as those come in, I'll plaster them on.

Here's the lights done. Looks neat through the transparent white. Not much work left. Just some finish up and the bench trimming.

I want to SEE a night flight.
(Road trip to Vegas this spring!)
Looks great, Dane. No pun intended (mostly).
Br,
Chris

Thanks guys. I'll be alone tonight! That means this thing will get done. Just gotta cover the wings and hook up the remainder of the electronics. Like i said, the cg seems really good as a starting point. I just used the lead out positioning on the kit. It's stamped into the wing tip. I don't remember having any issues with that before.

Duke, do you fly free flight? Was that you i saw in the ama mag? I always flip to the back to check for control line and FF articles.

Hey Dane
Yes that was me in the back of the AMA, if you have the E-version you can see the launch video.  Chuck showed up to the contest in Oregon and I spend the last day with him on the flight line.

The plane looks Great!

Well, unfortunate news. We tried to fly the little Akromaster tonight. The bell crank actually broke in half pretty quick. I've never seen this happen. My last akromaster was built with the box hardware. I flew it many many times and ended up giving it away. So the repairs are almost done. At least it looked cool for a few seconds...