I picked up a Ringmaster ARF and I have an Arrowind motor same as in the Brodak power package. I've looked through the setups thread and only found one picture of battery placement. Also in the setups thread I saw a few references to different batteries in use, both 3S and 4S and capacities from 2200 to 3300mah. I have several 3S 2200 packs I use on my 450  helis. These packs would fit nicely right behind the motor, forward of the wing but may make it too noseheavy.
What's the hot setup for lightest weight and best performance?

Thanks, Matt

Hi Matt
I an the one who set-up the electric Ringmaster for Brodak.  The intended motor is an Arrowind 2810, with kv=1100.  The ARF was designed to accept a 4S x 2200 pack, you can go as small as a 4Sx1800 with a little care on RPM and flight time management.  The Brodak power package also includes a simple 40A ESC and the Hubin FM-0c Timer which adds throttle over the course of the flight  as the battery discharges to maintain airspeed.

The battery box is integrated with the motor mount, fuselage and wing leading edge.  The battery is installed from the inboard side, slip the end without the wires into the front of the battery box, then rotate the end with the connectors into the back of the box (at the wing) then rotate into position.  Centrifugal force, and a Velcro strap keeps the pack in place.  I have seen a lot of other profile installations, frankly few are as secure as this.  I do not like battery retention systems that rely solely on Velcro (call those "bombers"!) nor do I like those that compromise the structure or airfoil of the wing.

The recommended power system drives an APC 9x4.5E prop, with the RPM set around 10,800.  That delivers a 4.8 - 4.9 second lap time on 58' lines which is a good speed if you want to take the Ringer through a complete pattern.  BTW the power system will turn a 10" prop but my experience with Ringers indicate they fly better with a 9" anyway.

My Ringmaster was the prototype for the electric conversion for the ARF build.  Mine turned out pretty light (29 oz RTF), so it is a little nose heavy.  Sometime in its second summer I added a 1/2 oz of lead to the tail to improve the triangles.  The ARFs do not have shaped fuselages (mine is an oval) and reports are they balance pretty well.



If you want to use a 3S pack you will have to find a different motor with a kv in the range of 1300-1500.  A 3Sx2500 should roughly match the 4Sx1800 for power density and should provide enough power & duration to fly the pattern.  A 3Sx3000 would be needed to equates to the 4Sx2200, but you will have some trouble finding one in the correct form factor.  The pack must also be approx. 35mm x 35mm x 105mm and cannot be one of the longer wider thinner "wafer" packs.  If you use a 3Sx2200 you will have to shorten the flight duration some.



 

I got sidetracked on this project a bit but back on it now. I got the Brodak E conversion kit and found the leading edge brace. Stripping the wing covering wasn't really in my plans! Any chance the brace is already installed in the ARF wing? I'm guessing not installing it is a bad idea also? Almost takes the fun out of making it electric. I have a decent running OS 25 FP sitting here that would simplify things but I really wanted to make it electric. 


Thanks, Matt