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Old Mar 29, 2009, 08:50 AM
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powder springs georgia
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On the amp thing I did some ciffering and this is what I came up with
If you draw 60 amps, that 1 amp. per min. ,the battery is 4.5 amps, so at that rate you would get 4.5 min. flight ...with no charge left
If you draw 50 amps thats .83 amps per min. The battery is 4.5 amps, divide .83 into 4.5 and you get about 5.43 minutes for total discharge, which you would never get.. I know that there are other factors but generally this might be right. I did the figures on my edf and it was pretty close.
If you draw 40 amps, thats .66 amps per min. which equals about 7 min.time.
So depending on how you fly I would say 3-8 min. flight times.
Don't get too tech. on me hear , just a general idea that I think is right.
Of course how long you fly and what you put back in is the real deal.
Throttle management is the key, you take off wide open , then throttle back.
You might go as low as 25 amps and up again. Also static measurement is always higher than flight ..If you put in a reader to give you in flight amps. it would give you the real draw...
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Old Apr 09, 2009, 09:55 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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It is with great sadness I must report the death of my S-71. I launched it and it immediately rolled upside down, I gave full down but it was not going fast enough yet and it hit and cartwheeled All I could say was "What the hell?"

Don
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Old Apr 09, 2009, 10:43 PM
Tweaker
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Corona Del Mar
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Hey, I give you credit for going with the full down, it would have been an awesome save! Sorry for the loss
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Old Apr 09, 2009, 10:52 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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I learned that from a flying wing I had and every time I tried the "pizza toss" it would flip over so I use to push down and climb out.

Don
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Old May 20, 2009, 09:46 AM
On the Edge of Space
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Exit 4, South Jersey, USA
Joined Dec 2007
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Anyone try lower kV and single LiPo SR-71?

I need to build a slower, lighter version of this. Our field is small, about 400 X 200 yards and boxed in by tall trees. I have 3600 kV 64mm fan motors, supposed to push 14 oz each and draw 13A each. Plan to use single 2200 3S 30C. Any guesses whether this will work? Any suggestions or lessons learned through first hand experience gladly received. Thanks for the thread Don. Hope you build another. I mean a Blackbird, how do you top that?
PS - Any consensus on CG location?
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Old May 20, 2009, 11:59 AM
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United States, FL, Sebring
Joined Feb 2006
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Quote:
Originally Posted by The Don
It is with great sadness I must report the death of my S-71. I launched it and it immediately rolled upside down, I gave full down but it was not going fast enough yet and it hit and cartwheeled All I could say was "What the hell?"

Don
That's happened to a few of mine. it's always a sad moment.
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Old Jun 14, 2009, 05:24 AM
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Melbourne Australia
Joined Apr 2009
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So sad to hear the end of the sr 71. Getting mine in the post soon. Looking forward to flying it stock standard with one 3s2200. Taking careful note of all comments in this excellent thread. Will post details as they come along. Safe flying to all...

PS it would be interesting to know the cause of the take-off crash, could it be that one fan stopped???
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Old Jun 17, 2009, 09:49 AM
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Uppsala, Sweden
Joined Sep 2007
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Ordering one today from China...
New set up now:
4s lipo and 3600kv motors...
2.4Ghz tr.
Anyone hear something about this?
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Old Jun 17, 2009, 10:51 PM
On the Edge of Space
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Exit 4, South Jersey, USA
Joined Dec 2007
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This one is about 65% assembled, it has 3600 Kv motors and 3S 2200 mAH 30C battery. Hope to launch this weekend or next.
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Old Jun 17, 2009, 10:56 PM
Wonderfully Wicked
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Willoughby, Ohio
Joined Jan 2002
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Not sure whose version you have but I hope they have at least 400 watts total power to make it fly reasonably well.

Don
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Old Jun 19, 2009, 07:29 AM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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This is airframe only with separate purchased components. Going for light & slow due to small field. If the published fan motor specs are correct it should have .9/1 thrust to weight and 145W/LB. In theory, that should at least fly, right? So far no one admits trying this configuration. If it does prove overweight/underpowered I know this place that sells these wicked motors . Then I'll have to spend $60 to join the club with the bigger field.
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Old Jul 08, 2009, 11:57 AM
On the Edge of Space
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Exit 4, South Jersey, USA
Joined Dec 2007
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Ok, it flew, but it was REAL slow, maybe 30 or 40 mph. Flew it into a tree, not enough roll throw to turn in the area of our field, which is fully ringed by trees. Re-glued, removed landing gear, turned up aileron throw, re-flew. Slow bird confirmed. (Good duration though). Gots to kick it up a notch. OK Don, you told me so. Thinking of copying fh lucky's setup. If you're listening lucky, what fans are you using?
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Old Jul 08, 2009, 05:20 PM
Ginger or MaryAnn ??
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United States, TX, Garland
Joined May 2005
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56mm 3 bladed fans ,from phase 3 F-16 and make some thrust tubes...its a hoot to fly...
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Old Jul 09, 2009, 06:53 AM
On the Edge of Space
dLdV's Avatar
Exit 4, South Jersey, USA
Joined Dec 2007
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Thanks Lucky, I'll see if I can get my nosepickers on a pair of those. Why did you decide to go with smaller fans, just using what you had or some other reason?
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Old Jul 09, 2009, 08:01 AM
Ginger or MaryAnn ??
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United States, TX, Garland
Joined May 2005
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I was just trying something different from what everybody else was trying,and it happened to turn out great... I figure I am only person to run that setup in it,and it lets Don see how different setups work in different applications.I have Wicked motors in everything 64mm and smaller.Now I have his new BI 3600 70mm motor,and I am REAL inpressed with it. Joe
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