Espritmodel.com Telemetry Radio
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Old Jul 08, 2010, 08:33 PM
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Originally Posted by gtfreeflyer View Post
Vic, you are making me get Otter fever again. I may just have to get to work on Otter #2 this weekend, lol.

By the way, where are you located?
I'm on the East coast near Baltimore MD. We had a pretty bad winter and now we are having a heat wave - 100+ temps.
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Old Jul 09, 2010, 01:02 PM
Put a bigger motor on it!
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Alright, I started working on the Otter last night. I remade the engine pods that came severly warped from day one. I just retraced all the parts and cut them with my scroll saw. They are all glued together now and will be installed on the wing next.

I also had to replace the battery hatch's latch since it didn't slide back very easily. It worked perfectly on my first Otter, but was just not manufactured well for this new Otter. Lucky for me, I had about 10 latches laying around, so I'm just using one of those (see pics).
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Old Jul 09, 2010, 03:33 PM
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Hatch Latch

I already bashed the hatch latch in another post. However, I have a couple of the latches like you showed and will look into replacing the paperclip hatch that came with the kit. Thanks for the idea...
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Old Jul 10, 2010, 01:44 PM
Put a bigger motor on it!
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I'm making a ton of progress. Nacelles are on the wings with the motors and ESCs mounted. I've strung the wiring for the lights. I'm about to go shoot the landing gear with some paint. I can't decide whether or not to paint the wheel rims white as well. I don't know how the metal paint will stick to plastic. I also need to solder together a few y-adapters for the servos and also a parallel adapter for the motors. Almost there...
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Old Jul 10, 2010, 04:00 PM
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Dang GT, you will certainly get your bird in the air before me at the rate you are going. I build very slowly to avoid mistakes - I still make some.

I'm still not sure how to wire the motors and ESCs. I saw that you had fabricated a connector for your other model. I'd like to keep it simple.
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Old Jul 10, 2010, 06:48 PM
Put a bigger motor on it!
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I'm not fabricating any special connectors for Otter #2. I'm also keeping it as simple as I can. I'm sticking with the setup I show in post #54, except that I'll be plugging each ESC into a separate channel rather than using a Y-harness.

I also build very slow. I should have been done long ago, but I'm still going at it. The majority of the remaining work I have left to do is soldering and radio programming.
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Old Jul 10, 2010, 11:03 PM
Put a bigger motor on it!
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I have another rant...
The 4 holes in the main landing gear did not at all line up with the 4 holes drilled in the fuselage. I wish they didn't drill the holes in the fuselage so that I could match-drill them myself. I can't redrill new holes because the new holes would hit the side of the existing holes. I don't know where they copied the hole pattern from but oh well. I got it to work anyway by forcing the screws at a sharp angle. I don't like it, but it works.
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Old Jul 11, 2010, 06:08 AM
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Originally Posted by gtfreeflyer View Post
I have another rant...
The 4 holes in the main landing gear did not at all line up with the 4 holes drilled in the fuselage. I wish they didn't drill the holes in the fuselage so that I could match-drill them myself. I can't redrill new holes because the new holes would hit the side of the existing holes. I don't know where they copied the hole pattern from but oh well. I got it to work anyway by forcing the screws at a sharp angle. I don't like it, but it works.
As I have said numerous times, this ARF is poorly designed and built. The price should reflect this. $169.00 is way too much for what you get with the plane. Hopefully, other modelers will read this thread and at least be aware of the deficiencies associated with the kit. Then the choice will be theirs to pay the high cost or go for a different model.
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Old Jul 11, 2010, 03:03 PM
Put a bigger motor on it!
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Well, I got the wiring done today. It's all in, zip-tied, and looks great. Check out the pic below. Is that a crazy looking connector or what? I ran out of plug on the Rx so I had to make this. The connector on the upper right combines all the gyro gain control channels (so I can turn on/off the stabilization system) and the connector on the upper left takes the power from the BEC.

I'm almost done after about 8 hours of work between Fri, Sat and today.
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Old Jul 11, 2010, 07:44 PM
Put a bigger motor on it!
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For the life of me, I can not remember how I mixed the two motor channels so they would work together, and have the option of killing one motor in flight. Sounds so easy right? I've tried everything over the past 2 hours. I'm only blogging this because I know I'll figure it out once I share it, lol.
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Old Jul 11, 2010, 08:20 PM
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Originally Posted by gtfreeflyer View Post
I'm not fabricating any special connectors for Otter #2. I'm also keeping it as simple as I can. I'm sticking with the setup I show in post #54, except that I'll be plugging each ESC into a separate channel rather than using a Y-harness.

I also build very slow. I should have been done long ago, but I'm still going at it. The majority of the remaining work I have left to do is soldering and radio programming.
Did you disable one of the BECs or leave both active?
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Old Jul 11, 2010, 08:40 PM
Put a bigger motor on it!
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Both BECs are disabled. I have an external Castle 10A BEC. I got it figured out. Actually, I didn't figure it out, but I just switched the programming over to heli mode and it works great. Now I just need to adjust the throttle/pitch curves, which in this case is Motor1/Motor2 curves. I'll have the extra options of gyro gain control thru the gyro menu and also a throttle kill switch.
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Old Jul 12, 2010, 03:56 PM
Put a bigger motor on it!
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I just did some more radio programing. All I have to say is wow! I wish I had programmed all my planes in heli mode in the past. It is so much better. I was just so intimidated by heli programming I never tried it, but over the past few months I got into RC helis and saw the benefits that the programming offered that can be used for planes. I'll try to make a video tonight and show my setup. I'm stoked to get this plane in the air! This plane is going to kick
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Old Jul 12, 2010, 08:24 PM
Put a bigger motor on it!
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Here's the video. Check it out

VMAR Twin Otter Motor Mixing (1 min 26 sec)


Here's how I set it up:
The radio is in helicopter mode.
Ch1= Ailerons on a Y-Harness, connected thru a headlock gyro.
Ch2= Elevator, connected thru a rate gyro.
Ch3= Left motor/ESC.
Ch4= Rudder, connected thru a rate gyro.
Ch5= All 3 gyro gain control channels combine into here.
Ch6= Right motor/ESC.
Ch7= Steering servo, mixed as a slave to the rudder. This gives me individual trim without having to mess with the linkage.

The motors mixing can be fine tuned by adjusting the throttle and pitch curves (heli lingo), but in this case the right motor is plugged into the collective pitch channel so I have individual 5 point curves for motor 1 and motor 2.

3 idle-up modes give me three different throttle curves for each motor, controlled by the 3-way switch as seen in the video.

I'm using all 3 custom programmable mixes:
Mix 1 is the rudder to nosewheel mix.
Mix 2 is the rudder to left motor mix, and the mix is only active when the rudder stick is pushed to the left (kills the left motor). No mixing occurs when the stick is pushed to the right.
Mix 3 is the rudder to right motor mix, and the mix is only active when the rudder stick is pushed to the right (kills the right motor). No mixing occurs when the stick is pushed to the left.

Throttle hold switch kills both motors regardless of which idle-up mode I'm in or where the throttle stick is.

Gyro gain switch turns on/off all 3 gyros.

Rudder/steering on their own dual rate and expo switch.

Aileron and elevator on the same dual rate and expo switch.
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Last edited by gtfreeflyer; Jul 12, 2010 at 08:44 PM.
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Old Jul 12, 2010, 08:56 PM
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Wow!!! That is absolutely Amazing.

Well, I am just in the beginning stages of programing with my Futaba 9CAP. I just started out simple with the motors in parallel and one of the BECs from the ESCs disabled by pulling the center lead on the connector. I just used a 3S 3300mah battery with a nearly full charge for the initial test. Here is what I got on the bench test:
Props: 8 x6E Master Airscrew 3-blade
Battery: 3S 3300mah
Volts: 11.26
Amps: 28.3
Watts: 319

These readings are for both motors running in parallel. So I am only drawing about 14 Amps through each of the 25A ESCs and about 160 Watts from each motor. That is right at the max watt rating for these motors so I will have to check them after the maiden. The truth is that I will not be running WOT throughout the flights so this should be a safe setup.

Just a note that the motor mounts torqued during the test and moved noticeably as power was applied. The horizontal stabilizer flexed up and down (fluttered) at 2/3 to full power. This is not what I call a "sturdy" plane. I will be sure to do the maiden without any spectators - for their safety in case she does not hang together.

I am not comfortable with the construction of this plane and have doubts that it will have along life without some mechanical or structural failure. May the gods be with us...
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Last edited by Iflyrc_vic; Jul 12, 2010 at 09:20 PM.
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