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Old 12-17-2015, 07:32 PM   #11
4stripes
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Re: LX SU47 twin 70mm build


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The stock gear is several inches behind the CG which will cause poor ground handling and require more effort to rotate. The BH plane will rotate thanks to thrust vectoring but correct placement of the gear is an easy fix at this stage of building.
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Old 12-17-2015, 07:46 PM   #12
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Re: LX SU47 twin 70mm build

Here are the gear components. Be advised we drilled the main trunions to take 5mm wires to fit the alloy legs and made retract mounting plates to screw to the other side of the retract and are not supplied with the medium retracts. The plates can be fabricated from some other material like PC board or aluminum.
http://www.hobbyking.com/hobbyking/s...dproduct=23483
http://www.hobbyking.com/hobbyking/s...dproduct=23875
http://www.hobbyking.com/hobbyking/s...dproduct=34842
http://www.hobbyking.com/hobbyking/s...dproduct=23481
http://www.hobbyking.com/hobbyking/s...dproduct=45229
Here is the large retract that came with the plastic plate for mounting on the other side of the retract. I drilled new holes to match the medium retract.
http://www.hobbyking.com/hobbyking/s...dproduct=14838
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Old 12-17-2015, 09:11 PM   #13
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Re: LX SU47 twin 70mm build

Didn't think of that, guess the thrust vectoring dose have its advantages. I'm not using their, looks so non-scale and the ones I got bind. I might design my own, not that hard to do.
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Old 12-17-2015, 09:17 PM   #14
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Re: LX SU47 twin 70mm build

Spent some time figuring out servo placement and movements. Due to the canards there needs to be two reversed elevator servos so I will use one AUX channel to mix with the regular elevator channel to control those two. The thrust vector needs mixed elevator and aileron for two servos and one extra rudder servo for yaw. The elevator/aileron mixing will be done with a small servo mixer from HK
http://www.hobbyking.com/hobbyking/s...tra_small.html
It will be connected via Y harness to the elevator and aileron channels but I will only set up minimum TV travel as it doesn't take much to get a reaction based on my previous TV models. It will be full time so I do not want to over control the first flights!
The 13 servos and wires creates quite a pile on the work bench and the wiring in the plane will take some planning to keep neat and out of the ducts. In some ways I think the HXT900 servos would have been a better choice as they are easy to reverse whereas the 9018mg are not and require electronic reversal.
I forgot there is already one more servo on the nose wheel bay for steering bringing the total to 14!
No wonder my box of servos is empty....
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Old 12-17-2015, 09:25 PM   #15
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Re: LX SU47 twin 70mm build

Yeah, I laid out the wires and servos and was disheartened by the number of wires required. I'm thinking of mechanically joining the canards somehow and the TV will only be elevator and rudder. Just trying to eliminate as much weight as possible and to keep things as simple as possible.
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Old 12-17-2015, 09:46 PM   #16
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Re: LX SU47 twin 70mm build

The Lander brake/wheels are pretty heavy too. I can't be much heavier than our A10 so I'm confident it will fly, but certainly not having 1:1 thrust either.
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Old 12-18-2015, 12:20 PM   #17
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Re: LX SU47 twin 70mm build

Just had a evil thought, I wonder if the airframe could be converted to a single 90 mm, or even a single 80 mm. With the reduction in weight and with only one system feeding off the battery, the run times would be longer and less strain on the battery. I'm going to do some measuring. 😏
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Old 12-18-2015, 05:20 PM   #18
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Re: LX SU47 twin 70mm build

One more servo added today for the "drag chute" release making the total 15!
Took a couple hours figuring how the stock release was supposed to work but we managed to get it working with a solid pull linkage made from one of the stock TV linkages. There is a spring hair trigger which allows a coiled large spring to push the capsule holding the chute to fall off and unpack itself. We added another pin to hold the capsule on should we wish to prevent it opening when using the same channel for the electric brakes. The Lander electric brakes provided a nice surprise when I figured out that the braking force can be modulated by limiting travel on that channel. I will have to look into the A10 and T33 to see if they have the same controllers as less braking would be better.
I also eliminated the separate TV mixer and decided to mix the ailerons with the elevator and canard controls to provide additional roll control as the scale ailerons will be quite small once the flaps are cut out. The TV servos will be linked to the elevator and canard channels which gives the desired results for 360 movement (along with the rudder input).
Fun and games, but the real fun will be seeing it all work together in the air!
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Old 12-19-2015, 09:52 AM   #19
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Re: LX SU47 twin 70mm build

Would you believe a 90 will fit, and the thrust tube section is simply reshaping the foam to act as a bifurcate section. Of course, I will have to get creative adding foam blocks to fill in the sides so the airflow smooths out to and after the EDF unit.
Plus, the twin setup with ESC weighs 18.9 oz. and the 90 single with ESC IS 13 oz.
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Old 12-20-2015, 08:37 PM   #20
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Re: LX SU47 twin 70mm build

Check my supplies I brought and discovered I forgot my Castle ESC for the 90 mm I have here, so installed the twin 70's like yours. I recessed the foam and epoxied in 1/8" plywood mounts and mounted the fans with cap screws. I see by the way you displayed the fans that you too didn't like just sticking them into those foam slots. Here's what my setup looks like at the moment.
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