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XB-70 Valkyrie, 24" Span

Old 01-13-2010, 07:29 PM
  #1  
Octavius
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Default XB-70 Valkyrie, 24" Span

After what I'd like to think of as a success on a 20" version, I've decided to build a larger one. This one is a slightly perverted XB-70 since I've changed some stuff. Mainly the engine ducking is much smaller and no intakes. One thing that's important to me is to have a scale length fuselage.

Span: 24"
Length: 41"
Motor: Turnigy 2836 3700kv
Battery: 1750 mah 4S 30/40C
ESC: 60 A
Prop: APC 4.2x2 or 4.1x4.1 (possibly cut down)

After this I'd like to make an even larger one on twin pushers and have working wing tips that drop and completely scale.

Last picture is my previous XB-70 at 20" span.
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Old 01-13-2010, 08:03 PM
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Billmanak
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Looks great. This has always been on my wish list.
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Old 01-14-2010, 03:28 AM
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Dr Kiwi
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Just a question... can you really use all the speed generated by that very high Kv motor on 3s/4s with a toothpick prop... would it not be better to use a slightly lower Kv motor and a somewhat larger prop for greater thrust and efficiency??

3700Kv @ 14v and 80% of Kv x V must get you >40000rpm... that's over 160mph pitch speed. Even 3s will get you 130mph pitch speed... what do you reckon the max. airspeed of the plane could be?
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Old 01-14-2010, 05:15 AM
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Octavius
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This setup is popular with some of the speed guys, and I've tested it on 3S on the plane below. Crashed before getting to try 4S.

Even though the real XB-70 is mach 3 normally I wouldn't push a scale plane this hard. I'd just like to see what's it's capable of. I have a more reasonable motor/battery combo I might switch to after I test this. But I almost might just move to the next, larger version of the plane which is my end goal.

I'd like to get this one to 100 mph.

End goal version might roughly look like a twin setup:
30" span
50" length
2836 2300kv (2X)
1750mha 3S (2X)
30A ESC (2X)
APC 6x4E and 6x4EP
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Old 01-14-2010, 07:54 AM
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Didn't have much time tonight so I only built the canard. It turns out it's only 13.75 sq in and the moving part is 1/3 of that. It's quite small.
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Old 04-10-2012, 01:02 AM
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heartbreakfatty
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Default XB-70 Canard

You will find that you have to increase the moving part(elevator)to about 2/3 of the canard. 1/3 is not enough. In fact elevons are the best solution to this. I have a foamie that uses elevons and it works fine. In fact. if I was building a scratch XB-70, I would set it up so the entire canard wing moved. This aircraft has been my favorite model of all time.
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