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Old Jun 24, 2015, 07:27 PM
SeanOKeefe is offline
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P51 conversion to Electric

Hi All,

I am new to the forum, and this is my first post, so be gentle...

I did some searching in this group, but the P51 conversions are for the 0.60" class planes.

I have a Hangar 9 P51 model # HAN4425 that I would like to convert to electric, probably using HobbyKing parts. I have never run it as a Nitro...

http://www.hangar-9.com/Products/Def...ProdId=HAN4425

The motor on it is not the original, but an OS 46AX (not the 46AX II), and it was swinging a Master Airscrew 11x6 2-blade prop. That motor lists 1.6HP at max RPM (~1100W), but the reviews say that it is probably running in the 800-900W range for practical RPM's. I am open to putting a 3-blade prop on it.

With a model AUW of just about 3kg (6.5 lbs), 100-120W/pound puts it at the low end of that power category. I am planning on using at least 4s batteries. The fuel tank opening is 50x60mm(x >170mm long) so nearly any battery would fit.

I have been using eCalc.ch and it looks like a reasonable motor for the same prop would be a HobbyKing G42480650kV or the G46-670kV

http://www.hobbyking.com/hobbyking/s...arehouse_.html

http://hobbyking.com/hobbyking/store...?strSearch=g46

There is only ~2.3kg of thrust with 5s on the G46.
How close to 1:1 should I be for a warbird?


EDIT: The eFlite .46" equivalent motor is similar in performance, but 3x to 4x the price. 730 watts at 4s power.

Thank you,
Sean
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Last edited by SeanOKeefe; Jun 24, 2015 at 08:19 PM. Reason: added new motor option
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Old Jun 24, 2015, 10:18 PM
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For scale flight, a warbird should not have anything like 1:1 or greater thrust:weight. But most model airplanes are overpowered (power/weight) compared to scale. You can always fly at a lower throttle setting.

An 11x6 is kind of a small prop for that plane, I think. For comparison, my 1450mm FMS Mustang foamy (which I expect is a bit lighter than your H9 but is otherwise about the same size) spins a 14x8 four blade prop on a 4S. It's spec'd to fly with a 4S but people fly them with 5S all the time. 4S flies longer and more scale like, 5S gives unlimited vertical and quite a bit of additional speed.
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Old Jun 25, 2015, 05:56 AM
SeanOKeefe is offline
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Thanks Rocket.

I fly on a grass strip, so I am limited a bit by how large of a prop I can use, but I'll go measure....

When my plane on the landing gear and is level to the ground, the axle of the prop is 10" from the ground. So, in theory if the grass is 2-3" high then a 14" prop would JUST work.

I'll run some slightly bigger prop more numbers through eCalc.

Sean
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Old Jun 25, 2015, 02:37 PM
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I'm flying my FMS off grass, too. It's not so much the grass height you need to worry about as the dirt that's under the grass. Until the prop hits dirt, it's a weedwacker. The grass doesn't slow it down much and even less once the plane is moving. The thing I worry about most is landing and taxiing. The FMS gear has a simulated oleo strut that compresses about 3/4", which is all the margin the prop has relative to the ground...
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Old Jun 25, 2015, 04:03 PM
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I've used the Turnigy G46 (420kV) very successfully on a glow - electric conversion on a 2.5kg 3D aircraft. Originally had a Saito .72 four stroke fitted.

With a 3000mAh 5S battery and 14x10 prop it performs very well with great vertical - should be ample performance for a less demanding (albeit heavier) warbird - but I wouldn't be expecting out-of-sight vertical performance.

Thread here http://www.rcgroups.com/forums/showt...t#post22160230
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Old Jun 25, 2015, 06:39 PM
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Yeah. But the OP chose a 650 and a 670KV motor, which is much too high for a 4 bladed prop. He should see how much more he can bump up his 11x6, but if he wants to go to a 4 blade he needs a lower KV then the ones he's selected.
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Old Jun 25, 2015, 07:27 PM
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Old Jun 25, 2015, 09:12 PM
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Hi Casey,
Thanks for the info and the link to the other thread.
The simple motor mount is a great K.I.S.S.-approved design.
I sort of like the idea of staying with a 4S battery. I think that my next electric will be 6S (I have a 6' Cap231 with a 0.90 nitro on it, that I would like to convert)
But, in the meantime, I think that there may be a lot of fun to be had with 4S-size planes. (Spacewalker, etc...)

There are a lot of prop options that work with both 4S and 5S. I think I just need to jump in...

The 670 keeps things viable at 4S. (11x7 or 12x8 work well) (it says 11x6 has a low pitch speed and 12x8 is max current)
670kv w/ 5S gives lots of power with the props at or slightly smaller than listed above.

The 500 is pushing me to 5s and bigger props.

I think that G46 670kv and couple 4S and one 5S battery might be the plan.

Time to think seriously about an order.

Thank you,
Sean
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