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Old 04-01-2014, 01:36 AM   #1
MidwestRSX
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Default Tell me what to buy!

Hey everyone,

I just ordered a NitroPlanes Aerosky B60 kit. I am looking for recommendations as to which motors, ESC's, batteries and chargers I should buy. My goal with the plane is longer flight times, not necessarily more power. I'd like to charge two batteries at once in closer to 30 minutes than an hour. Here are the specs:

Two 4011 OutRunner Brushless 900KV, Two 45amp Brushless Electronics Speed Controller, 14.8v 3600mah 25c Li-Po.

With the goal in mind of longer flight times, what would you guys recommend?

Also, this plane does not have counter-rotating props. I would prefer it did, and since I'm starting from scratch I figured I could make that happen.. I'm assuming they make spinners and props cut in both directions..

Thanks for all your help!
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Old 04-01-2014, 02:27 AM   #2
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To get longer flight times, you would need a higher mah battery. The issue is, weight goes up, so you have to experiment with finding what actually increases flight times, and at what point you don't gain or even lose flight time. Are you sure it isn't counter rotating prop, it would be achieved by a pusher prop on one motor and having it turn the opposite direction. I can't recall whether it is better to have the props turn from the bottom of the fuse to the top (with looking at plane, left side would turn counter, right would be clockwise) or from top to bottom (left side is clockwise, right is counter), I read about it in a thread on here. I know someone would certainly know better than me, all I fly, as of now, is single prop tail draggers.
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Old 04-01-2014, 04:40 AM   #3
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The ARF is not counter-rotating. The kit I bought doesn't come with any electronics, so I can do it however. Would a pusher prop function correctly acting as a puller prop?
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Old 04-01-2014, 05:36 AM   #4
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"pusher" is actually a bad name for the prop... they should be labeled as Right hand vs Left hand rotation. (or clockwise vs counter-clockwize)

Full scale SU-26 uses the opposed rotation for the prop vs most conventional single engine aircraft. Works fine.


The labeling of props as "pusher" type comes from the common glow engines being hard (or impossible) to make operate "backwards." and so when setting up an aircraft that uses a pusher configuration you had to get the "reverse rotation" style prop.
(Cox's venerable .049 runs equally well forward or backward...)

**************

To reverse the rotation of a common electric motor (brushed or brushless) just swap 2 wires between the ESC and motor. There are only 2 available to swap with brushed... any 2 of the 3 will work for brushless.
So for electric there is no need for a "pusher" prop" (when setting up a pusher style aircraft).... and use of a "pusher" prop on one side with a conventional prop on the other is the correct way to counter-rotate.

The real problem is getting a MATCHED (except reversed pitch) set of props for counter-rotation. There is a much better selection of "normal" vs "pusher" props.

***********

For the vast majority of aircraft... top of prop moves toward the fuselage for counter-rotation. This is so the torque of the operating engine opposed the yaw of imbalanced power if one engine fails.
Full scale P-38 is a known case where its top away from the fuselage. This is due to some strange interaction of the swirling propwash and the P-38's tail causing instability (crashed a prototype, cured issue by swapping engines right vs left). Some models of the P-38 exhibit this, some don't.
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Old 04-01-2014, 05:42 AM   #5
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Yes, it would I believe, from what I know. Any prop spun the opposite way creates the opposite airflow. Lets say you use a tractor and want it to be a pusher, you would essentially turn make it turn the opposite way. A pusher actually works with the motor turning the same way, just the blades are reversed, resulting in a direction of airflow away from the motor. Reverse motor direction and you have a pusher. It isn't quite this easy however, as props like APC are designed for one direction, and lose efficiency in the other. This means you would either have to flip an apc prop so it cuts the same as it would in it's designed rotation, but even with this you would still have a difference. The result is that you need a prop that has symmetrical blades, and has the same efficiency in both directions. I may be wrong, but Master Airscrew should be like this and would be a good choice for this setup.
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Old 04-01-2014, 05:52 AM   #6
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The prop "only cares" that the face of the blade is forward. A prop blade is just a rotating airfoil, much like a helicopter blade.

The helicopter blades are commonly symmetrical so reversing pitch will reverse the direction of "lift" which is EXACTLY like making it into a "pusher' prop when you go from +5 deg pitch to -5 deg pitch.

The fixed pitch props we commonly use have a flat or concave back side and a convex front side. Put the flat to the back and turn it the correct way... it will work fine every time. Put the flat to the front, but rotate it the motor the same way and you get 30% to 70% less thrust depending on the prop design.

Cox used to recommend that beginners put the prop on backward, but start the engine normally to reduce the max speed of the model while learning to fly.
This wasn't really a good thing to do. Generally it made their overweight plastic airplane act like a slow underpowered car.
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Old 04-01-2014, 02:34 PM   #7
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But wouldn't you need to turn the prop around on the motor. Suppose it would work on an apc as long as there is not spinner backplate. On a tractor (I have no experience with pushers) the blade curves extend past the hub, so it would not work against a backplate. Without one I guess it would be fine. With a symmetrical blade design it could be mounted in the opposite side easily.
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Old 04-01-2014, 04:23 PM   #8
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Please continue hashing out this counter-rotating prop issue. It will be easy to reverse motor direction obviously, but my main concern is the props/spinners.
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Old 04-01-2014, 04:43 PM   #9
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On a pusher prop, the front of the prop faces the motor. To turn it into a pusher you would flip the motor around, reverse motor rotation and the prop itself, to face the correct way would have to be reverse on the motor shaft (the prop itself would face the same way as when a pusher, but motor would be behind the prop now). What I am thinking is that something like an apc prop can be mounted okay, but a spinner may pose an issue, but maybe not. I have never looked at a pusher, but I assume the leading edge of the blades go past the hub. As long has the hub of the prop can rest against the backplate and not have the blades pushing into the backplate, it will be fine. I was a bit confused before, sorry. I was mentioning symmetrical props, like Master Airscrew because it is a simpler design and will let the hub rest against the backplate, whether you want to turn a tractor into a pusher or vice versa. For a pusher APC there shouldn't be an issue though, as pusher planes don't have spinner, so likely the same design is kept, but with a reversal of the pitch. The rear of the prop should still be flush with the hub and allow you to use it as a pusher in a counter rotating manner.

Oh and one other issue with spinners is the blade angle they are setup for...and I don't know if you can find spinners designed for counter rotation. I presume some companies will sell them that have their own counter rotating setups I suppose. There are probably prop and spinner combos out there that let you just install on the plane, both matching.

http://www.wattflyer.com/forums/showthread.php?t=60499

Just found this quickly, it is available.
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Old 04-01-2014, 04:48 PM   #10
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What you see "transforming" in this thread is a very good example of what transpires on any forum when an "open-ended" help statement is posted like "Tell Me What to Buy!"...........

99%, of the time, you will be "told" any number of un-related "here's what I know" suggestions that will spin for days and provide the OP with little value related to the real intent of the thread.................just an experienced observation. Duplication of the same thread generally makes the matter even more inviting to those who are trying "very hard" to be helpful as well........

AMA 928214
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Old 04-01-2014, 04:55 PM   #11
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Lol, two threads doesn't help. I made a mistake before/didn't make myself clear. I was thinking about the situation incorrectly before, not thinking about the obvious fact that the prop just has to be fitting in the same orientation to the plane, but reversed on the shaft due to the motor physically facing the opposite direction. Sorry about the confusion. If you don't wish to use spinners, its just a quick install of the pusher, change motor direction and you are good to go.
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Old 04-01-2014, 05:16 PM   #12
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How do Turnigy brushless outrunners compare to E-flite/Rimfire?
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Old 04-01-2014, 06:29 PM   #13
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Can't go wrong with turnigy in my opinion. Never used rimfire, but I find eflite too much for what you get. Currently I have a huge turnigy motor in my mini switch, unlimited vertical, insane speeds, at least insane for what the plane is. 300W in a 34 inch wingspan plane.
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Old 04-01-2014, 07:53 PM   #14
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Re getting spinner.. there are spinners with very little (or none) of the slot cut to suit the prop. These can easily be cut to work with either a normal prop or a counter-rotating prop.

Just as there is a limited selection of the counter-rotation props... there is less selection in spinners that will have a neat appearance when cut for them. An example (not cheap...) is this carbon fibre spinner that has no slots for the blades... cut your own to fit any prop.
http://www.r2hobbies.com/51mm-2-inch...r-spinner.html

High end spinner suppliers will often cut the slots for you... for a fee.

We don't have enough info on what you are doing (including budget) to be sure we are making the best recommendations.
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Old 04-01-2014, 09:41 PM   #15
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What other info do you need? I'm looking for long flight times over more power. Probably going to go for a 3600 - 4000 mah 25 - 35 C batt.
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Old 04-02-2014, 02:32 AM   #16
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Please lock and direct further posts to: http://www.wattflyer.com/forums/showthread.php?t=73470
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