Thanks Dean,

Your formula worked out great. I determined that my desired RPm was approx 9000.
I bench tested at 8970 RPM with my Zigras 2 timer.I got steady bench runs with my set up,as follows:

   2 Motors-E-flite 480 -910kv
   2 CC-35 ESC
   1 Zigras 2 timer with new pot.
   1 14.8v, 4270 mah evo-lite battery
   2  APCe 9x6 props( repitched to 6.2-6.3") inbd one is pusher.
   Static bench runs: 34.1amps 505watts at start RPM 8970-9000 steady
   
   I flew 3 flights with this set -up. Power was good lap speed was 5.03 --5.04
   on 64'- 6'' lines .018" dia. Wind was 6-10 mph ,Temp 65 F.
  After getting wings level aqnd handle adjusted to even out inside&Outside loops,
  I flew the full pattern on the third flight. All flights had same lap speed even though
  their voltage was not the same. I was really surprised since I had never flown with
  Heli-high gov. mode before.When I recharged my batteries They only required 2.17AH
  to 2.19AH for full charge. This tells me (I think) that I can use less MAH in the
    Battery. I had planned on using my TP4000 4s2p 14.8v batteries that I had used
  in my GEMINI twin last year,but when I bench tested them with my set up they
  did not have enough power to hold a steady 8970rpm. The evo lite battery added
  2 ounces to my planned weight. I would like to try a 12oz battery . Evo 30 14.8v
  3200mah but I am not shure if it has enough mah to hold constant RPM for a full
  6 minutes.
    Has anybody tried this battery with 2.2AH usage? That is using only 69% of
  advertised capacity,BUT I don't trust all ADVERTISED numbers.

   Looking for some advice!
     
   Walt Brownell

 

   Mike
Thanks for the input. I just weighed my Evo30 premium battery that I bought last summer from Tower. It weighs 12.25 OZ. with Deans connector. I saw that new ones
are listed as weighing more. I am puzzled by the TP battery weight. I have been
flying with 5- TP 4000mah14.8v 4S2P batteries since May 2005. They all weigh
12.5 OZ with Deans connector.The reason I am not using one is that on my bench
tests they did not have enough "headroom" for the twin set-up, in static runs.
Maybe they will work in actual flight conditions. They also don't fit my battery envelop without structural mods. Evo battery does. I will hold off as you suggested
and fly in warmer conditions before making any battery changes. 
   If there are lighter (11.25oz)TP batteries please let me know how to get these.

  Walt
 

Hi Walt,
That's great. Like Mike says, hold off on any dramatic nattery changes. To begin with, the EVO battery has much lower cell resistance than the 4000 mAH battery you are comparing it to. You will actually get more voltage and more watt-hours out of the same mAH draw. This is not because of different chemistry but because thinner insulator materials and better electrode plate manufacturing methods allow them to pack mnore surface area in for a given weight of the all important electrolyte. This is the direction the market is going in. The TP 4200 Pro-Lites may represent a better compromise of cell resistance and weight for Stunt. A few of us in Pattern are working on the folks at TP to create a new series of batteries with the same Pro-Lite-like tradeoff, rather than the EVO characteristic which is aimed at greater than 15C discharge. We average 7C (or less!) in Stunt, with peaks at 10C.

Most 3300 batteries aren't much lighter, so you might make your choice based on $$$.
 

Since you are only using ~50% of your battery capacity, you might try adding a little more prop diameter, if you have the room. That will add maneuver power and only slightly add consumption. You could up your consumption by 10% and still safely use 3300s.

Mike,
You are dropping off the governor? Are the batteries at end of life or are you just using too little pitch and a few too many RPM?

later Friends,
Dean

Hi Dean,
   The batteries are tired. This will be their 5th season if I continue to fly them.

Mike

Walt,
As I pointed out, you are drawing about 22 A on the average if you pull out 2.2AHr in 6 minutes (0.1hour--so 22A*0.1hr=2.2AHr). You said that on the bench you are pulling 34A. So when you fly, at a fixed rpm, you are using about 2/3 the power (watts) that you are seeing on the bench. The reason for the "about" is that the voltage in flight is a little higher since the current is less, so wattage is probably a little more than 2/3, but that is the ballpark. So 2/3 of 500 watts is ~330Watts.
My E-nobler flies at ~270Watts, so things sound about right.

Hi Dean,
   The batteries are tired. This will be their 5th season if I continue to fly them.

Mike

Wow, Mike!
 4 whole seasons!
How many flights per pack do you figure? This is a payoff number for so many would-be E flyers.

Dean

Mike,
Give us a guess fer cryin' out loud!
Dean