ORIGINAL: DaveL322
Tim,
Another approach -
The reason you are not getting a really specific answer is because there is substantial variability in the answer. You will find guys flying Masters on 10S 5000s that are only using 3000 mah for a flight....and you will find guys routinely exceeding 4000. A lot depends on flying style, how well the airframe is matched to the flying style, and how well matched the motor/prop is for the flying style/plane. You can also find substantial variation (as much as 10%) depending on how the mah are measured.....ie, Eagletree, ICE log, charger, etc.
The majority of 10S pattern stuff is between 75 and 95 amps static on the ground, and depending on motor type (geared inrunner, or direct drive outrunner), and heavily loaded, the peak amps in the air will drop 5 - 15%. Average amp draw from takeoff to landing is typically 25 - 35 amps......so figure about 40% of static peak is what you will see for pattern flying. I've found this 40% number to be generally valid on my smaller 3, 4, and 5s pattern/sport planes when flying pattern. Obviously, most of the pattern stuff is 10S, and for your case, if the drop in cell count is roughly equivalent to reduction in airframe size, mass, drag, then you could expect the 40% number to hold up. My gut feel is that your 6S setup is probably being pushed harder than the average 10S setup in Masters, but you are also looking at flying a shorter sequence (initially at least), so I think you'll be fine for Sportsman, Intermediate, and possibly Advanced.
At 7750 RPM.....consider trying some of the APC glow props....you may find them to be more efficient at the relatively high RPM.
Regards,
Hmm, thanks Dave.
Yea, no way I can use 10S on my Rimfire motor. 8S is also out of the question (unless I really prop down which would no longer be a pattern setup). I had the Eagle Tree setup in another Pattern plane with the same exact setup as in the Venus II and the
average current in flight was 40A, so your 40% rule is pretty close. Similarly, on my little speed plane (Rifle), I've noted a 32% drop in current from static readings vs. in-flight (again, with Eagle Tree). This was very consistent for all motors/props in the variety I tested.
I think part of the problem is the current limitations of my motor (50A constant, 80A surge), but I'm not certain. Also, I'm using a smallish battery at 3,300mAh.
I'd hate to have to resort to a glow prop, but worth testing. Also possibly dropping down to a 16 x 8 E as a few others have suggested.
As a side note, this is the kind of stuff that glow proponents, or more accurately, electric haters, dislike. Yes, all this experimentation can be a bit of a nuisance, but I still think it's worth it and a little bit a part of the fun. Besides, glow/gas isn't always a walk in the park either! Finally, once you get a good setup, you can share it with everybody else.
Thanks again.
Tim