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Old Jul 20, 2001, 01:52 PM
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Santa Clara, CA, USA
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Question for LS's prop motor gb 8x270mah experts

LS's prop motor gb 8x270mah experts,

Now that quite a few of you all has successfully flown LS stock and modified LS, here is my question for you experts.

How can I drain my 8x270mAH battery effectively to extend my duration?

Using stock prop/mot/gb and 8x270mah battery, I get 20min flight time.

Add 3oz camera payload and now my flight time is reduced to 8 mins. Battery is only half drained.

What will you recommend for extending the flight duration and burn the rest of the battery juice? Increase prop-pitch? Increase prop-diameter? Or is this (8 min) the best I can do with the setup?

Any kind of help is appreciated,
Charles
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Old Jul 20, 2001, 02:21 PM
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Tell us a couple more things about your setup.
1. What prop/gear ratio motor are you using
( I assume you mean 10x4.7 IPS-A)
2. what esc are you using
3. what servos are you using

Also is your flight time limited by motor shutting off or by lack of thrust?

[This message has been edited by mattk17 (edited 07-20-2001).]
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Old Jul 20, 2001, 02:43 PM
"Simplify, then add lightness"
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I used an APC 10x7 prop on my lite stik, and the extra pitch seemed to help a lot when running with the 9v Rayovac NIMH batteries. I have also twisted some more pitch into the stock GWS 10x4.7 props. GWS also makes a 10x8 prop that you might try. If you increase the pitch or the size of the prop, be careful with full throttle when the battery is fully charged or you may burn up the motor. A heat sink might be a good idea.
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Old Jul 20, 2001, 02:48 PM
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Jeff,

How long does your rayovac 9v run with the apc 9x7? I'm getting about 5 minutes of actual air time on my rayovacs with the gws 9x7. My only problem is the gws 9x7 prop is fragile compared to their 10x4.7.
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Old Jul 20, 2001, 03:21 PM
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Hi JasQfix. EXPERT. ex=hasbeen and Spurt is a drip under pressure! At 8 minutes I'm guessing that the drive is mostly at full power for the run? The combination of that and 8 cells is overvolt and closing on at the limit of the motor's performance with heat build up on a carbon brush motor. Any duration past that will drastically reduce motor life with my experience. I'm hoping you can tell me where your Firebird's cg was for best performance abd do you still fly it? Best Regards
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Old Jul 20, 2001, 03:26 PM
"Simplify, then add lightness"
Raleigh,NC
Joined Nov 2000
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Matt,
My lite stik is in pieces, and I don't use the 9v Rayovac's much any more, but I think I got about 5 minutes with the APC 10x7. Never really timed it. I fly my Tiger Moth with an APC 9x6 that I have twisted a little to try to get more pitch. It seems to fly as well as the GWS 9x7 and is much stronger. The APC 10x7 worked better, but I burned up a motor on the Moth with it, so I dropped back to the twisted APC 9x6.
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Old Jul 20, 2001, 05:28 PM
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mattk17,
Yes my stock setup is 10x4.7 Ips-A, Pixie7 ESC and 2xHS50 servos. I have never seen the BEC cutting off. There are plenty of juice left in the battery. Just that the prop/motor/gb combo is not giving enough thrust after about 8 min of full throttle and about 25% glide time.

jeffs555,
Thanks for the full throttle motor burn warning after a full battery charge using a higher pitch prop like 10x7.

Bleriot,
I still fly my FB like a v-tailed mini zagi with ailerons and zero dihedral. The CG is still around 50mm behind the leading edge of the wing. The FB camera mount is nice because the pusher prop does not get in the way.

I will try the 10x7 or 10x8 prop and try to program my Tx to make sure I don't accidentally go full throttle the first 5 mins of the flight.

Lesson is NIHM battery, after the first half of their discharge cycle has drop voltage to a point that, it needs a higher pitch or higher diameter propeller to increase thrust just to match the thrust output during the first half.

Thanks,
Charles
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Old Jul 23, 2001, 01:40 PM
Master of the Wind
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yea try 6cells with a 1145
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Old Jul 23, 2001, 01:44 PM
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Hello Charles, sorry to get off topic but does the Firebird have elevator too? Thanks Best Regards
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Old Jul 23, 2001, 03:15 PM
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Bleriot,
No elev on FB. Fly just like a zagi with a training wheel on.
Charles
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Old Jul 23, 2001, 03:41 PM
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AIR MOVER,
Are you suggesting that I try 11" x 4.5" APC prop with a 6 cell nicad or nihm? Nihm 6 cell might be way under power. Is that right?
Charles
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Old Jul 23, 2001, 05:06 PM
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Charles,

You might try a 9x7 prop and see how that one does. I'd think a 10x7 would be too much but if you are careful about throttle management early in the flight it could work.

Bottom line: 3 ounce camera is alot of extra weight for such a small plane to freight around. 8 or 9 minutes might be as good as you can do without going to bigger batteries which of course add more weight and stress to an already rather delicate airframe.
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Old Jul 23, 2001, 06:31 PM
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mattk17,

Thanks for the sanity check. I know the 8mins to 9mins is plenty for my flight experience. The thing that troubles poor me is that the battery charger keeps telling me these batteries are not completely drained. In fact most of the time it is only half drained.

Thanks in any case,
Charles
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Old Jul 24, 2001, 12:17 AM
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Finally got an APC 10x7 for my LS. My crude amp meter jumps from 1.6amp on stock 10x4.7 to 1.8amp on the new APC 10x7 prop. Several flight statistics show a little improvement in flight time (~ +10%). Is that what I can expect from going to a higher pitch prop? I have been more careful in full throttle with the new prop. I only go full throttle after half way into a fresh battery flight.

Is there anything I can try next?

Thanks,
Charles
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