[stegl]

Originally Posted by davidmc36

Yeah that is a MAS. The two lipos are 2.7lbs

OK what you are saying is you have two 5 cell lipos of 5000 mah each ; setup in parallel ? One battery of 5S 5000mah will be more than enough unless you fly wide open all the time . Also no weight needed in the tail.

[davidmc36]

Originally Posted by stegl

OK what you are saying is you have two 5 cell lipos of 5000 mah each ; setup in parallel ? One battery of 5S 5000mah will be more than enough unless you fly wide open all the time . Also no weight needed in the tail.

Exactly, just what I am debating.

Let's see: remove the tail weight at a moment of 88 and remove one battery with a moment of 113, a difference of 25. So about 2.25 oz on the motor mount (or even a bit less if I take apart the round part and put it even farther FWD).

With 64 amps available for 4.7 minutes it would be a fine length flight at normal cruising throttle. And I would save over a pound and a quarter, also eliminating the parallel harness, one less failure point.

And with the batteries I have I get four nice flights instead of two that would likely just get monotonous near the end.

I think you talked me in to it.

[stegl]

I keep my flights arround 6 minutes and use up about 20% of the battery ( 4500 mah)

[davidmc36]

I just may be good to go. Sits at 4 1/4 with one battery and nothing for ballast in the nose. Maybe will put an oz of stick on lead on the motor mount for the first flight.

[davidmc36]

Originally Posted by davidmc36

I just may be good to go. Sits at 4 1/4 with one battery and nothing for ballast in the nose. Maybe will put an oz of stick on lead on the motor mount for the first flight.

And as an added bonus I can now shift the battery a hair to the left to trim out lateral balance.

[davidmc36]

Originally Posted by davidmc36

....I think you talked me in to it.

Battery tray is all set for single battery, just waiting for G-Glue to set.

[stegl]

Originally Posted by davidmc36

I just may be good to go. Sits at 4 1/4 with one battery and nothing for ballast in the nose. Maybe will put an oz of stick on lead on the motor mount for the first flight.

If you have the time to do it use my idea if you want. I didn't copywrite my installation .

Where I bolted the square led weight I groved front to back slots were the bolts are and that way I can slide the lead weight back or foreward when I want to move the C of G back and that way don't have to worry about stickons dropping off.

[davidmc36]

Well with a few small things added and the second battery removed I am sitting at 11lb 6 oz now. Balances at 4 1/4 inches with no ballast.

Weather looking poor for here tomorrow but Tuesday is a maybe and Wednesday looks good for sure.

[stegl]

If that is the all up weight with lipo then that s light.

[davidmc36]

Originally Posted by stegl

If that is the all up weight with lipo then that s light.

I don't have the interior in it just now other than the sidewalls which are glued in so that would add another 7 ounces or so. Gonna see how I like flying it and maybe get a new one this winter. Original is a little rough.

I wonder how accurate Prop Calc is. When I put in my RPM and voltage/apmerage values it comes out to 1248 watts into power system and 1245 watts absorbed by the prop. If it is anything close to that I am running upwards of 100 watts per pound.

I am thinking it may be a bit high since I got 9lb 2oz measured static thrust at 53 amps and the calc is estimating nearly 11lbs. I guess you would need to put some more accurate numbers into the prop type fields. I just left it at custom and 1 for Kt and Kp.

If you play with the constants and bring the static thrust down to around 9.5lbs it is more like 850 watts absorbed by the prop. I think that may be a bit more realistic, more like 75 watts per pound.