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Author Topic: Tom Dixon Tutor Too - electrified!  (Read 2624 times)

Online Steve Berry

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Tom Dixon Tutor Too - electrified!
« on: April 25, 2021, 06:09:42 PM »
Ok, I just mentioned it over on the finishing board. I'm going to finally build & finish a plane, after many false starts due to loss of building space. I've chose one of the Tom Dixon Tutor Too quick build profile kits. I'll be converting it to electric, and it'll be my first electric plane, so starting from scratch. I don't have a whole lot of specs on the plane just yet, but I believe it would be happy with a .46LA or ST G-51, so electric equivalent of that.

I could use some suggestions for:
motor size, either Cobra or Badass
battery
ESC
timer
programmers
charger

Stuff I'm pretty sure about:
3D-printed motor mount from Okie Air
control system from Okie Air, but could use suggestions on bellcrank size (3" or 4"?), standard control horns, or the surface mount Dubro-style, etc.
handle & lines from Okie Air, as well

Once everything arrives, I'll start a build thread on it. I'm also thinking of doing a short video series on it, in the style of Windy (minus the mundane day-to-day life stuff).

One other thing - I'm currently considering doing an Ultracote finish with fiberglass reinforcement on the wing under the covering. Will Ultracote actually stick to a fiberglassed surface, and will the weave show through?
Oh, and the colors I'm considering are cream for the bulk of the airframe, with flaps, elevators, and rudder green or red. Should be pretty sharp when finished. Hope it lives long enough to wear out.

Steve

Online Dennis Nunes

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Re: Tom Dixon Tutor Too - electrified!
« Reply #1 on: April 25, 2021, 08:01:29 PM »
Hi Steve,

You might be interested in reading an article that I wrote about "Turning to the Darkside - The Building of Circulas 46 IIe - An Electric Profile". This article can be downloaded from the flyinglines.org website at http://flyinglines.org/nunes.circulas46lle.html

The article is about my decisions, issues, design and construction of my first electric plane.


Enjoy,

Dennis




Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #2 on: April 26, 2021, 08:29:42 AM »
Funny you should mention that. I was pouring over your build last week. That's part of what motivated me to get it. From what I can tell, they are about the same size, so I may simply flatter you and steal your setup for my plane. I'm not expecting it to be a world-beater. Shoot, I'm not even really expecting it to last more than about a year (I'm still trying to come back from about a 16 year layoff from flying). I do want it to be about the best that I can do at the moment, though.

Online Dennis Nunes

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Re: Tom Dixon Tutor Too - electrified!
« Reply #3 on: April 26, 2021, 09:40:44 AM »
Funny you should mention that. I was pouring over your build last week. That's part of what motivated me to get it. From what I can tell, they are about the same size, so I may simply flatter you and steal your setup for my plane. I'm not expecting it to be a world-beater. Shoot, I'm not even really expecting it to last more than about a year (I'm still trying to come back from about a 16 year layoff from flying). I do want it to be about the best that I can do at the moment, though.
Take whatever you like, there is no patent on anything on this plane! Most of what I used was stolen borrowed from someone else.  ;D

Dennis

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #4 on: April 26, 2021, 11:31:46 AM »
What's the wing area on the Tutor

Well, it's supposed to be based on the TopFlite Tutor II ARF, which according the 'net is about a 54" span and something like 594 sq. in. Per the ad, it calls for a .40-.51 size engine.

Online John Rist

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Re: Tom Dixon Tutor Too - electrified!
« Reply #5 on: April 26, 2021, 12:16:55 PM »
The way I pick an electric motor for a gas to electric conversion is make note of prop size and RPMs for the original gas engine.  I then go to the Cobra web sight and look at the prop data charts for possible electric motor choices.  Keep in mind that if running in the governed rpm mode you will be running the motor at less then max RPMs and max current draw so a prop just outside the "safe" range will probably be OK.  SO I pick a motor/cell count that will turn a prop size and RPM similar to the original gas setup.  For instance the setup I am using on my S1 Ringmaster is:

Motor,   Cobra 2221/10 KV 1500
Battery,  Hyperion 3S 1600 70C
ESC<  Trunigy Plush 30 amp
Prop APC 9x6 EP
Timer, KR.  Initial RPMs set to 9500

According to the prop chart the Cobra 2221/10 on a 3 cell LiPo will turn a APC 9x6-E @ 11,378 RPMs.  It is in the yellow category meaning   "The prop can be used, but full throttle should be kept to short bursts. (80 to 100% power)"  So with the RPMs set at 9.5K and lots of cooling (profile ship mount) it has worked well.  I picked this motor on the fact that a Fox 35 turns a 9x6 prop at around 9 to 10K.   y1   
John Rist
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Teodorico Terry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #6 on: April 27, 2021, 06:22:11 PM »
Steve,

I have been thinking about this model as well but my approach might be a little different; generally speaking, electric motors do a better job generating torque than a glow engine (4-Strokes included).  With this in mind, I don't shy away from using a somewhat larger prop.  The increased diameter can eat up power very quickly if you try to spin it too fast; the answer is to increase the pitch.  I know that this goes against the current wisdom.

I currently fly a SIG Fazer which I built as a C/L model.  The original model has a very short and stubby wing so I increased the span slightly by adding rounded tip and went with a narrower cord flap.  I also increased the tail moment by 3 inches.  In the end, the model came in at 56-58 oz ready to fly.  The wing area is north of 600 squares but I do not remember the exact number.  It is electric powered and with everything hanging out and the fat wing the model is quite draggy.  Once the motor is off it will not glide very far unless you whip it.

I did quite a bit of experimentation with props and RPM settings.  The smallest prop I tried was a 12x7 and the largest was a 13x10.  In the end, I discovered that the reverse rotation prop provided better line tension but is also limited my choice of props.  The most efficient prop was the 13x10 but I settled on a 13x8 since I could not find a reverse rotation 13x10.

For the motor, I am using a Hacker A10XL with a Kv of 900.  Power is provided by a 4S pack of 2600 mah capacity.  The ESC is a Castle set-up to run on governor mode and the timer came from Brodak.  With the 13x8 prop I set the RMP in the 7200-7300 range which is quite low for proper governing but it seems to work reasonably well.  On the ground, the current draw is in the 24 amp range while in flight it can peak at around 30-31 amps.  The only thing I would do differently is use a pack of larger capacity, probably in the 3000 mah range.  Even with the larger prop the plane will corner reasonably well (given my lack of skill).

For the Tutor I think that an Eflite 25; the one with a Kv of 870 is a reasonable choice.  Given its Kv you will probably want to stay with a 4S pack.  For props you could go with the popular 11x5.5 and opt for high RMP or maybe try a 12x8 at lower RPM.  The Hacker has a somewhat larger outer can (diameter, larger diameter -> better torque) than the E-flite; I am not too sure that the Eflite would like the 13x8 prop.  The thing to keep in mind with electrics is that some experimentation might be needed to find the set-up that works best.  That is part of the fun.

Good luck,

Teo

PD  I have been flying electric R/C since 2007 which probably skews my thinking away from what is common practice in C/L.  I fly pattern for the most part (rather poorly I might add) and I am getting back into C/L after a 25 year break.  Electric off course.

Offline Dwayne Donnelly

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Re: Tom Dixon Tutor Too - electrified!
« Reply #7 on: April 28, 2021, 06:41:29 AM »
I can't remember who posted it here but a simple formula to figure out what size motor you need is 150 watts per pound of plane, so say you are shooting for a 52 oz. plane rtf = 3.25 lbs = 487.5 watts of motor.
Hope this helps ;D
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Teodorico Terry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #8 on: April 28, 2021, 05:31:06 PM »
Hello,

I have seen the 150 w/lb rule posted before, I think that the initial recommendation was for 100 w/lb and as systems got better the numbers went up.  In my experience, the power required is actually more of a function of the speed you would like to fly at and the prop you intend to use for a given motor and battery combination.

For the Fazer I fly, the nominal power is in the 370W range in level flight.  This propels the plane at about 53.5 mph which on 65ft lines gives you a relatively slow lap speed  of 5.8 sec or so.  When I pull into a wingover, the current draw goes up to 31 amps or so (ESC has data logging) which means that the power has gone up to 460W or so.  That is almost a 25% boost in power due to the governor trying to keep the RPM constant.   The model weighs 56oz or 3.5lbs which means that in level flight I am at 105 W/lb and 131 W/lb while performing a wingover.  I would agree that I am slightly under powered but mostly due to the fact that the plane is so draggy and it could have been lighter.  This is using a Hacker A30-10LX, CC ESC, 13x8 prop and 4S 2600 mah pack.   

While trying to set-up the model, I played with different props trying to reduce the lap time to about 5.5 sec.  What I found out was rather interesting, generally speaking, to get the same lap time, the power requirement was roughly the same.  The larger diameter prop was about 5% more efficient than the smaller prop of the same pitch. Also, for the same pitch, the smaller diameter prop had to spin a little faster (makes sense if the level flight power was the same for a given lap time).  The difference became more noticeable when maneuvering, the larger diameter prop did not appear to lose as much speed in a corner and it appeared to recover the speed more quickly.  This is just an observation. 

Going back to the original question, I would probably follow what others have done (i.e. Circulas 46) as a starting point keeping in mind that some experimentation might be needed.

Good luck

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #9 on: May 09, 2021, 01:22:44 PM »
My kit finally came in (post office was slow this time). Now I have a feel for just how big this one is. I would say at least the size of the Forerunner, and the plans confirm the area to be 599in^2. I think if it was glow, the perfect engine would probably be either the .46LA or a ST G-51. Since I'm going electric....

This one is meant to be quick to build and get me back to flying, in a hurry. With that being the case, I'm very seriously considering either the RSM Sport or Competition glow .46 equivalent system, as opposed to building my own system. Everything is already done, and all I have to do is just mount & fly. I believe, given the size, the competition system may be better since it appears to have the stronger motor. Only other things to worry about would be a charger and spare batteries. It should be a good starting point for me so I can get familiar with the electrons. From there I can play & experiment with other components to have the confidence to build my own system.

What are y'alls thoughts on which system to go with, and which charger should I go with? The cost difference between the 2 systems isn't an issue, so I think it comes down to quality of components and how easy is it to tinker with later (switching to a different motor, adjusting timer & RPMs, playing with props, etc). I don't want to go cheap on the charger - since I'll be using it for years, a quality charger is in order. I just need to know which one, and if it needs a power supply.

Oh, before I forget. For those that have the experience, should I go with one of the 3D-printed mounts from Okie Air (leaning that way) or the BH-2022 Universal “E” Electric Conversion (for Profile Fuselages & Front Mounted Motors) by Brodak? Cost is the same, installation looks to be about the same. I personally think the printed mounted to be the cleaner looking installation (looking at you Dennis Nunes and your Circulas 46 IIe), but I'm welcoming any and all input on this matter.

Steve

Online Ken Culbertson

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Re: Tom Dixon Tutor Too - electrified!
« Reply #10 on: May 09, 2021, 09:37:37 PM »
Oh, before I forget. For those that have the experience, should I go with one of the 3D-printed mounts from Okie Air (leaning that way) or the BH-2022 Universal “E” Electric Conversion (for Profile Fuselages & Front Mounted Motors) by Brodak? Cost is the same, installation looks to be about the same. I personally think the printed mounted to be the cleaner looking installation (looking at you Dennis Nunes and your Circulas 46 IIe), but I'm welcoming any and all input on this matter.

Steve
Haven't used the BH-2022 but I have used the Okie Air. Really easy and the spinner shape is perfect.  I flared mine in and it looks great.
My fuselage (Sandpiper Trifecta) is built up and I used dowels to anchor the mount to the fuselage.  I ordered another one for my built up Endgame II.

Ken
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Online Dennis Nunes

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Re: Tom Dixon Tutor Too - electrified!
« Reply #11 on: May 09, 2021, 11:55:57 PM »
...I personally think the printed mounted to be the cleaner looking installation (looking at you Dennis Nunes and your Circulas 46 IIe) ...
If you want to get an idea of how Circulas 46 IIe flies you can take a look at a video I made of David Fitzgerald flying Circulas 46 IIe for the first time and putting it through what he calls his "torture pattern". It survived! The video is located on YouTube at:




Enjoy,
Dennis

Teodorico Terry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #12 on: May 10, 2021, 08:03:46 AM »
Hi -

I did order a copy of the Brodak mount and in the end I did not use it.  It seemed rather heavy and there was only enough room for the motor and battery; the ESC and timer would just have to sit outside.  On my next profile build I would either make the mount on my own or use one of the ones offered by Okie. 

Regarding the power system I think that if you wanted to go with something that came ready to use from RSM it would be reasonable.  I took a look at it and the only thing I was wondering about was if it included the little stick needed to program the Kr timer.  Other than that it seemed complete.  Keep in mind that at the end of the day you will likely want to play around with the settings but for those initial flights it might be O.K.  A word of caution; the initial flights should be short so that you can get a sense of the power consumption and then adjust the flight time accordingly.

I have been thinking about getting one of those kits, do you think that you could post a photo or two?  I would like to know what it looks like.

Thanks and good luck,

Teo

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #13 on: May 10, 2021, 08:26:26 AM »

I have been thinking about getting one of those kits, do you think that you could post a photo or two?  I would like to know what it looks like.

Teo

Well, since info on the kits seems to be in short supply, I was planning on doing a build log of some sort. I'd love to do a vlog on it, showing everything step by step. But I've never done that before. So, at least for this one, I may just do a regular build log with photos.  Everything seems very well thought out, and most everything is included except for the control system.

Offline ericrule

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Re: Tom Dixon Tutor Too - electrified!
« Reply #14 on: May 10, 2021, 05:08:18 PM »
Mike at RSM Distribution (951-678-1406) has a full electric package available (prop, motor, ESC, KR Governor Flight Manager, battery) that would work very well in the Tutor 2. The RSM 46 electric power package comes ready to bolt in the model, flip the switch and fly. Everything fully assembled and tested. If you're a first time electric guy this should really do the job for you.

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #15 on: May 10, 2021, 05:10:45 PM »
Mike at RSM Distribution (951-678-1406) has a full electric package available (prop, motor, ESC, KR Governor Flight Manager, battery) that would work very well in the Tutor 2. The RSM 46 electric power package comes ready to bolt in the model, flip the switch and fly. Everything fully assembled and tested. If you're a first time electric guy this should really do the job for you.

Exactly the man and the answer I was looking for! Thank you - that makes for a very easy decision. I'll be getting my order put in this week.

Steve

Edit: Forgot to ask, would a programmer of any sort be needed for the timer or ESC in order to adjust a few parameters (flight time, RPM, etc - the sort of thing you play with at the field)?

Online John Rist

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Re: Tom Dixon Tutor Too - electrified!
« Reply #16 on: May 10, 2021, 05:41:29 PM »
Exactly the man and the answer I was looking for! Thank you - that makes for a very easy decision. I'll be getting my order put in this week.

Steve

Edit: Forgot to ask, would a programmer of any sort be needed for the timer or ESC in order to adjust a few parameters (flight time, RPM, etc - the sort of thing you play with at the field)?
Package includes the program stick for the timer.  You can set start delay, run time, RPM, and control aggressiveness at home or at the field.  Does not require a computer to control. Does require a tack to set RPM.  Don't know about the ESC.  I don't use the same one that comes in the RSM package.   D>K

You may also want to read How my KR Timer Works:

 https://stunthanger.com/smf/gettin-all-amp'ed-up!/how-my-kr-timer-works/msg566404/#msg566404
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Offline ericrule

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Re: Tom Dixon Tutor Too - electrified!
« Reply #17 on: May 11, 2021, 10:51:31 AM »
Thanks for the "catch" John. I completely forgot about the program stick.

Now that I am retired I guess this just goes to show that Mike Griffin is correct and I am starting to show early onset "old timers disease". Now if I can only remember how to turn off my computer all will be well  LL~ LL~ LL~

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #18 on: May 12, 2021, 08:28:08 AM »
Can anyone tell me the size of the x-mount bolt pattern for the Black Tiger 3548C? I'm designing up a custom 3D-printed mount that can handle both it and the BadAss 3515/710 and comparable Cobra motors. The BadAss & Cobra have the same 25mm diagonal spacing on the motor frame, while the Black Tiger has 2@25mm and 2@19mm. I was thinking of just using the cross mount for the motors, but all I have the dimensions on is the one that comes with the BadAss and Cobra motors.

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #19 on: May 14, 2021, 04:50:41 PM »
Can anyone tell me the size of the x-mount bolt pattern for the Black Tiger 3548C?

Thanks, Eric Rule for helping out on that.

Online Steve Berry

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Re: Tom Dixon Tutor Too - electrified!
« Reply #20 on: May 17, 2021, 04:37:57 PM »
Rats!

Got an email from Mike today saying he can't put together the system for me due to supply shortages. So, looks like I need to piece together my own system. Back to researching...

Motor: Cobra 3515/18 OR BadAss 3515-740
ESC: BadAss Rebel Series Brushless ESC, 45A w/ BadAss Rebel Series Brushless ESC LED Programmer OR YEP 60A (2~6S) SBEC Brushless Speed Controller w/ YEP ESC Programming Card
Timer: Hubin FM-9 with start button & programmer (Brodak only source?) OR KR Compact Governor Flight Manager (RSM only source?)
Battery: 5S 25C 2800mAh (brand not determined, yet)
Prop: APC 11x5.5e Thin Electric Prop
Charger: Unknown, still need suggestions
Connectors: unknown qty and type - seriously could use help here; I think bullet connectors from motor to ESC, and XT60 connectors from battery to ESC, but feel free to correct me here.

The adventure continues.
Steve

Offline Dwayne Donnelly

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Re: Tom Dixon Tutor Too - electrified!
« Reply #21 on: May 17, 2021, 06:57:00 PM »
Good place to start is right here, give Okie Air Models a call.
My purpose in life is to serve as a warning to others.


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