Originally Posted by Erik v. Schaik

You cannot use an 2s A123 pack+ regulator because the regulator will brown out. You cannot use 3s A123 pack + regulator because the regulator will overheat, reduce current limits and shut down on thermal.

NiCd=1.2V
NiMh=1.1V
Voltage will be reduced under load like Lipolly.

I'm going to run two castle creations 10amp BECs in parallel operating off of a 2S 1320 lipo pack. And I'm planning on 'Y'ing one of the BECs together with the one digital on the elevator, and the other BEC into the battery port on the rx. Whatcha think?

-Joshua

As long as you connect the mass together it is possible.

Originally Posted by Paulofthenorth

I'm seriously considering building a plane similar to yours in a 90 mm fan size. I've looked at the basic dimensions you give in the Spatha thread and am scaling them up to about a 45 inch span.

Would you be willing to share the c of g location of the Spatha or the Charger?

Any help would be appreciated.

Paul,

The CG of the Spatha is 42% of the chord from the leading edge at the root. So, its a 12" chord at the root, and its 5 inches back from the leading edge. See the photo.

I would say that this is the near the foward limit of the CG range. Some times I run a lighter battery, moves the CG back about 3/16" and it still flies fine. The long tail moment and large tail really make this design super stable.

If you have any more questions or need a photo I'll do my best to help you out.

-Joshua

Paul,

A couple more things to consider on your dsign:

If your nacell/exhaust is going to be in the same place as our jets, consider about 2 degrees of down thrust (point the nozzle down 2 degrees). The little Spaha flies around with about 1/32" of down elevator for level flight. In high power, low speed situations the little jet pitches up pretty hard. Dad added down thrust on the Charger, made a huge difference.

If you are planning on flying at high density altitudes or on a short runway I would highly recomend an aerodynamic brake of some sort. Whether its dual flaps, a singe flap (if trailing edge it straight) split flaps, or an airbrake like the Comp ARF Spark, any of which will help control speed on approach. The Spatha is easy to fly but an absolute pain in the butt to land. It's so clean that it refuses to slow down, However, its flight controlls are a little slugish at approach speed. So I end up landing at at about 1.5x stall speed. The Charger is outfitted with large laps that make a huge difference, and more generous flight controll area for better controll authority up to and through a stall. The Charger flies like a trainer.

-Joshua

Joshua,

Thanks very much for the info. Much appreciated!

Paul