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Author Topic: Electric Banshee Trimming  (Read 3224 times)

Offline Don Coe

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Electric Banshee Trimming
« on: February 14, 2015, 07:35:15 AM »
   I could use some help on trimming my electric Banshee.  My flying abilities are just past the point of not crashing every time I fly.  So trimming a plane is
something I have very very little knowledge or experience with.

   The plane has and Arrowind 2832/05 motor with 4s battery, seems like plenty of power.  Weight - 48 ozs, a little heavy.  2 1/2" was cut of the nose.  The battery box was mounted above the wing to give me a CG 1/4" forward of the CG on the plans, making it a little nose heavy.  Lap speed is 5 1/2 secs at about 85% of power.  Plane flies like a blimp with very erratic behavior.  Loops are huge.  I have redone the thrust line as that seemed a little off.  4 feet of snow prevent me from seeing if there is any difference. 

   Where do I start trimming this plane???  Any help appreciated.



     

Offline Shug Emery

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Re: Electric Banshee Trimming
« Reply #1 on: February 14, 2015, 07:52:39 AM »
This thread may help......http://stunthanger.com/smf/index.php/topic,27095.msg261749.html#msg261749
Look at post #7 for trim flow chart.
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Offline Dennis Adamisin

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Re: Electric Banshee Trimming
« Reply #2 on: February 14, 2015, 07:56:49 AM »
  I could use some help on trimming my electric Banshee.  My flying abilities are just past the point of not crashing every time I fly.  So trimming a plane is
something I have very very little knowledge or experience with.

   The plane has and Arrowind 2832/05 motor with 4s battery, seems like plenty of power.  Weight - 48 ozs, a little heavy.  2 1/2" was cut of the nose.  The battery box was mounted above the wing to give me a CG 1/4" forward of the CG on the plans, making it a little nose heavy.  Lap speed is 5 1/2 secs at about 85% of power.  Plane flies like a blimp with very erratic behavior.  Loops are huge.  I have redone the thrust line as that seemed a little off.  4 feet of snow prevent me from seeing if there is any difference.  

   Where do I start trimming this plane???  Any help appreciated.

    

The 2832 motor is actually largest/most power motors in regular use for CL - it is WAY more than you need.  If you switched to a 2815 it would take about 4 ounces off the nose - bet that would let you tighten up the loops!

The Banshee was designed to use a 10" prop, while it is tempting to use a larger diameter, the reality is that a large diameter prop can actually overpower the turning capability of the design.  The APC 10x5.8EP (LH rotation) running about 10k rpm would be in the ball park.

You did not mention what size battery you are using:  I would have tried a 4Sx2200 at about 8 0z.  As an example, if you are using a 4Sx3300 that typically weigh around 11 oz then there is a substantial weight save opportunity.

Put another way, it you could shave 4 oz off the motor and 3 oz off the pack you could reduce your RTF weight from 48 to 41 oz - the Banshee will be MUCH happier at that weight.

THEN we can start talking about more serious trim issues.  Over the past several issues of Stunt News, Paul Walker has been walking us through a very logical progression of how to trim out our stunt birds...

Can't help you with the snow - in fact we are now getting another 2-4 inches of "partly cloudy" dumped on us as I write this...  gack
Denny Adamisin
Fort Wayne, IN

As I've grown older, I've learned that pleasing everyone is impossible, but pissing everyone off is a piece of cake!

Offline Motorman

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Re: Electric Banshee Trimming
« Reply #3 on: February 14, 2015, 10:31:30 AM »
You can't put the battery completely above or below the wing. the vertical CG has to be on the thrust line. I don't know the physics but your plane will fly like a goose with a broken wing. As mentioned above if your system is too big for the plane I'd just reconfigure it for a 35 size glow and build a bigger plane for the electric stuff. Another option would be the wing box technique I used on my Banshee. http://stunthanger.com/smf/index.php/topic,35007.msg355889.html#msg355889 Beef up the spar in the wing box area and remember to put the push rod in after you have the fuselage on lol. You want about 25 degrees of elevator deflection and dumb question but the flaps move opposite of the elevator right?

MM

Offline Tim Wescott

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Re: Electric Banshee Trimming
« Reply #4 on: February 14, 2015, 02:26:31 PM »
You can't put the battery completely above or below the wing. the vertical CG has to be on the thrust line. I don't know the physics but your plane will fly like a goose with a broken wing.

The physics are pretty easy to see -- just hang the plane from the leadouts and look to see if the wing is off vertical.  Whatever it does when it thinks it's hanging straight down, that's what it's going to want to do when it's hanging off the end of the lines.

Having said that -- I don't think that's at all the problem here.  Yes, it's something to address, but Don has bigger fish to fry at the moment.

Don, in addition to everyone's comments about generally lightening the plane and getting the CG back to the location shown on the plan, are you sure that your control system moves freely?  Ideally the individual hinges should be so light that without the control rods in place they should just flop down.  Once everything is put together, you should be able to move the controls through their range without any discernible force.  If the controls are stiff, or worse, if the controls have sticky spots or bumps (or whatever they come across feeling like) it'll mess you up in the air.

Do the test and report back.  If you have someone to hold the plane, test it again while pulling on the lines -- there are bellcrank and leadout mounting errors that can make the thing bind under tension but not when things are loose.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Tim Wescott

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Re: Electric Banshee Trimming
« Reply #5 on: February 14, 2015, 02:28:29 PM »
And while you're messing around, get the controls at full range in one direction or another and measure the angle of the elevator vs. the angle of the flaps.  The flap/elevator ratio should be 1:1 or less; if the flaps are moving more than the elevators it would make the plane sluggish even with the CG in the right spot.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Don Coe

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Re: Electric Banshee Trimming
« Reply #6 on: February 15, 2015, 05:10:55 AM »
Much thanks for all the information from everyone.  So much info it's going to take me a while to wade through it. Winter weather will delay any trimming and testing for a month or so, which will give me the time to digest some of this information.  I'm sure I'll have more questions.  Again, thanks to all.  H^^

Offline Tim Wescott

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Re: Electric Banshee Trimming
« Reply #7 on: February 15, 2015, 09:23:32 AM »
The checks that I suggested can be done in the shop, and if it's a sticky control system or if the flap to elevator ratio is too high you want to start fixing it now, when you can look out the window and console yourself with the fact that you weren't going to fly anyway.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Brett Buck

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Re: Electric Banshee Trimming
« Reply #8 on: February 15, 2015, 02:12:31 PM »
   I could use some help on trimming my electric Banshee.  My flying abilities are just past the point of not crashing every time I fly.  So trimming a plane is
something I have very very little knowledge or experience with.

   The plane has and Arrowind 2832/05 motor with 4s battery, seems like plenty of power.  Weight - 48 ozs, a little heavy.  2 1/2" was cut of the nose.  The battery box was mounted above the wing to give me a CG 1/4" forward of the CG on the plans, making it a little nose heavy.  Lap speed is 5 1/2 secs at about 85% of power.  Plane flies like a blimp with very erratic behavior.  Loops are huge.  I have redone the thrust line as that seemed a little off.  4 feet of snow prevent me from seeing if there is any difference. 

   Where do I start trimming this plane???  Any help appreciated.

   5.5 second laps seems pretty slow for a 48 ounce Banshee.

    I wouldn't worry about minutia like the vertical CG. I have managed to go about 40 years without really ever considering it.

    The fore-aft CG, however, seems like a place to start. With stock Banshee parts, I would guess that the CG should be about 1 3/8" or so behind the LE of the wing to start with. Normal handle movement should give you about +- 30 degrees of control motion. I don't know what you are using for a pushrod, but if it is a conventional wire pushrod, as supplied, it *must* have a fairlead about halfway between the flap and elevator. Otherwise, it will bow out on inside corners and make the turns massive.

   The center point of the leadouts should be about 1" to 1 1/4" behind the CG, and very close together.

   The elevator should have the same motion as the flap, i.e. 1:1 ratio. That means that the pushrod must enter the flap and elevator horns at the same height from the hinge line. Make sure that the controls move freely throughout their travel from end to end.  If you used pinned hinges, you should also seal the elevator and flap hinge lines with Scotch Crystal Clear tape.

   While you are at it, double-check that the fuselage is square to the wing in all three dimensions, that the stabilizer is absolutely parallel to the wing in all dimensions. Measure from the flap hinge gap to the tail hinge gap at each stab tip and make sure that it is the same to as close as you can measure. Then site along the rear to make sure the wing and the stab are both in the same plane.  Make sure the flap and elevator are both neutral at the same time and neutral from side to side with respect to each other.
Also check for any visible warps by sighting from behind. Look at the root, center the TE between the top and bottom of the wing surface, and then slide your gaze out to the tip. It should be centered there, too, if it isn't you have a warp. Correct it with a heat gun or the towels and boiling water trick.

   Remove any rudder offset, or leave just enough to make sure it is not inboard. I forget what it shows on the plans but it's almost certainly too much. Install about 1 ounce of tip weight.

   Start with 0.015x62 foot lines, eyelet to eyelet. Cut them down from "70'" lines, which are really supposed to be about 68 feet in the package.

   That's all stuff you can do sitting in the workshop, and it's very important.

When you get a chance to fly, first fly around level upright, and inverted, and watch what happens to the Roll angle. Ideally, the wing should stay aligned with the lines all the time. What is likely is that the outboard wing will be higher than the inboard and different from upright and inverted. Also check the lap speed carefully (or get your flying buddy to do it). Adjust the speed until it is about 5.0-5.1 seconds a lap, which should give you lots of tension.

 If the outboard wing is low upright and inverted, add tip weight. If it is high upright and inverted, don't do any maneuvering, and after the flight, add tip weight. If the outboard wing is higher upright than inverted, bend the outboard flap up with respect to the inboard, by twisting the flap near the flap horn to bend the flap horn. If the outboard wing is lower upright than inverted, bend the outboard flap down.

    Then, try doing round loops. Two things to note - on inside loops, look and see if you see the top or bottom of the wing. If you see the top, add tip weight 1/4 ounce at a time, until it stays straight with the lines. Same with outside loops, check the same thing, if you see the bottom of the wing, add 1/4 ounce of tip weight at a time until that stops.
 
   Also, see if it takes a lot of force to keep the loops going around, or if the loops tend to come out lower than you started. If so, add 1/4 of weight to the tail and try again.

  The point of this is to experimentally determine the tip weight, and remove any residual warp or flap misalignment, and to get the fore-aft CG correct. The next step is to try some harder corners, and look for similar effects to refine the tip weight better. At some point, you will want to play the CG location against the handle spacing to get the best response, but just getting it close is where you have to start.

    Brett

Offline Don Coe

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Re: Electric Banshee Trimming
« Reply #9 on: February 20, 2015, 05:46:12 PM »
Reporting back after going thru some of the information you all were kind enough to supply.  I appreciate it.  H^^

Moved the battery in line with the thrust line. The 3300 4s battery just fits between the rear of the motor and the leading edge of the wing.  It's moved my CG to 1/2" behind the leading edge.  So nose heavy but better than I thought.  A smaller/lighter motor will be installed if need be.   The plane has a 3/32 pushrod but does have a fairlead 1/2 way.  I've got 1 oz in the wing tip now and more or less can be added.  Lap speed can be increased by turning up the motor.  I'm running a 10" prop.  Flaps & elevator run smooth and free.  Looks to be equal movement between flaps & elevator.  Studied the flow chart for trimming.  That's about it till I can get it flying.  Again, thanks all.

Don

Online Brett Buck

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Re: Electric Banshee Trimming
« Reply #10 on: February 20, 2015, 06:57:10 PM »
Reporting back after going thru some of the information you all were kind enough to supply.  I appreciate it.  H^^

Moved the battery in line with the thrust line. The 3300 4s battery just fits between the rear of the motor and the leading edge of the wing.  It's moved my CG to 1/2" behind the leading edge.  So nose heavy but better than I thought.  A smaller/lighter motor will be installed if need be. 

   I think putting on a lighter motor will likely be a good idea, but that's not way off. Since its electric, and you are doing the equivalent of measuring the CG with a full tank of fuel, you have to set it further forward than you would with a conventional engine and empty tank.

     Brett

Online Howard Rush

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Re: Electric Banshee Trimming
« Reply #11 on: February 20, 2015, 07:21:24 PM »
Since its electric, and you are doing the equivalent of measuring the CG with a full tank of fuel, you have to set it further forward than you would with a conventional engine and empty tank.

And electrics tend to be happier with the CG even farther forward than with a "conventional" engine with a full tank.
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Offline Motorman

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Re: Electric Banshee Trimming
« Reply #12 on: March 28, 2015, 10:31:59 PM »
Moved the battery in line with the thrust line.

Would like to know how this turned out since I made a big effort to put my battery in the wing on my Banshee.


MM

Offline Don Coe

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Re: Electric Banshee Trimming
« Reply #13 on: March 29, 2015, 06:01:36 AM »
Would like to know how this turned out since I made a big effort to put my battery in the wing on my Banshee.


MM

We still have feet of snow on the ground, so no test flights yet.  Summer is supposed to be on a Tuesday this year (hope it doesn't rain).   LL~

I'll report when I get a chance to get out.  I'm awaiting to hear how your test flight went.

Offline Motorman

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Re: Electric Banshee Trimming
« Reply #14 on: March 29, 2015, 09:13:56 AM »
No snow down here but still freezing temps and rain. I did get out once to make sure the prop turns the right way. Had to switch the wires to the motor but it's ok now.

MM


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