KADET LT40 Electric + MODS (bolt-on wing, dual servo ailerons, floats, covered nose) - RC Groups
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Nov 21, 2011, 10:33 AM
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KADET LT40 Electric + MODS (bolt-on wing, dual servo ailerons, floats, covered nose)

For some time know I have been waiting to build a trainer with floats with an electric motor (the lakes were we can fly do not allow the noise of combustion engines).

I picked up a SIG KADET LT40 for this project along with several modifications I had in mind:
  • Electric motor conversion
  • Bolt-on wing
  • Dual servo ailerons
  • More robust main and front landing gear
  • Floats
  • Covered nose
  • Magnetic lock hatch
It took me some time and some experimentation to collect all the information needed and though that migth help some of you guys.

Right now I am in the process of covering the plane.
Last edited by tonysantos; Nov 22, 2011 at 10:46 AM. Reason: Title correction
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Nov 21, 2011, 10:40 AM
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doc993's Avatar
Sounds like a nice plane ,please show us pictures.
Nov 21, 2011, 11:11 AM
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Bolt-on wing

Regarding the bold-on wing system I found a very good approach on this article from Sport Aviator.

I did follow it and with very good results. Here are some pictures of the Sport Aviator build and some of my final results.
Nov 21, 2011, 11:38 AM
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Dual Servo Ailerons

For this modification I also followed the approach I found on the Sport Aviator article.

Because of the electric conversion, I knew I was going to end up with a plane very much tail heavy. For this reason (and also to maximize its flying characteristics) I tried, as much as possible, to keep its weight down. One of the things I did was to use some miniature servos instead on the Futaba 3004. They are really very small and lightweight and have the necessary force to control all the surfaces. I don't have the servos reference with me, but will get this information and picture posted asap.

I configured the radio so that the ailerons could also be used as flaperons. I have never tried to fly with flaperons and I have read that the result is not very exciting. Either way its there if I want to give it a try.
Last edited by tonysantos; Nov 22, 2011 at 08:17 AM. Reason: Add image
Nov 22, 2011, 08:23 AM
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I just got some pictures of the servos I used. I used a Futaba 3004 servo for comparison.

These are digital servos Graupner DES 587 which were easy for me to get, but I am sure any other brand with the same specs will do as well.
Nov 22, 2011, 10:40 AM
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Power Setup

First of all let me just say that I am not looking for a high speed, highly maneuverable plane. The LT40 is a trainer and I want him to perform as such.

With that in mind, with the help of a friend of mine on the necessary calculations and trying to reuse some equipment I have, here is the setup we came up with:
  • Motor AXI 2826/12
  • FlightTeh 60A Brushless ESC
  • Overlander Battery 3900 14.8V 4S 25C
  • APC prop 11x8 / 12x8
With this setup I am expecting to be in the 60W/lb with flight times in the order of 10+ minutes. As I will show, I made the battery compartment to be able to accommodate larger battery packs, in case I want to increase the flight time.

The prop, with the land landing gear, will be the 11x8. With the floats I think it will be better to use the 12x8 since it will give more thrust as long as I don't go full throttle for very long (calculations show 2A over the recommended max).

I will test and measure this setup and post the results that I get.

Will post the info/pictures of the motor mount and battery tray that I made to fit this plane.

Any suggestions and opinions are very welcome.
Nov 22, 2011, 02:08 PM
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doc993's Avatar
Tony that's going to be awesome ,your craftsmanship is very good.My brother and I are building the Sig cadet in this forum.Tom built a Sig kadet Jr in the 80's,I converted it to electric, and it is my go to airplane.You will love the way it fly's and with that power set up you'll find that most of the time the throttle will be way under half.On floats So much fun!I put a go pro camera in the belly and get great videos .I've really had it up high ,spec high!It has a glide ratio that is truly impressive.
Nov 23, 2011, 05:50 AM
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Thanks doc993 for your very kind words.

I built a Kadet Senior last year with a Saito 62 and I love that plane. It teached me to fly and so far with no crashes. I have some pictures somewhere and I will post them here.

Regarding my current project I hope it comes up to my expectations. If time allows I hope to try it out in 4 or 5 weeks.
Nov 23, 2011, 07:18 AM
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Sig Kadet Senior

Here some photos of my Kadet Senior, starting with a box of wood, construction fase and ready to fly. You can also check out this video I made for my nephew when I was teaching him the first basic moves.

This plane is very nice to fly, very relaxing and forgiving. It is big so I can see it well and the sound of the Saito 62 is just perfect.

By the way, building it is also a lot of fun. The only mod I did was the main and front landing gear which I replaced the wire ones by some stronger stuff (and what a difference that makes!!!)
Nov 23, 2011, 11:40 AM
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doc993's Avatar
Wow Tony nice plane! It's true nothing fly's like a Sig.There neat to build too.I'm not building this one because I have to many planes on the bench.I got a good price on a new kit, and my brother was kinda itching to build again, so I gave it to him to build ,as he did such an awesome job on the Kadet Jr.He has exceeded all expectations.Keep up the good work this is a good thread.
Nov 24, 2011, 07:42 AM
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Battery Compartment

Back to the LT40. There is plenty of space in the fuel tank area to accommodate the batteries.

I had in mind a system that would allow me to exchange batteries quickly at the field, and at the same time allow for some bigger packs if necessary.

The battery tray I made is screwed to a support so that in the future, if I want to use a more powerful battery, I just have to make another tray. I saved some of the weight that will be necessary to balance the plane to be applied bellow the battery tray. This way if I use some heavier batteries I can easily compensate.

On the bottom of the compartment I drilled some holes to serve as ventilation (out). More detail on that later.

With the magnetic lock on the hatch, it is very easy and quick to change the battery; pull up the hatch, open the velcro and replace the battery.
Nov 24, 2011, 08:16 AM
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Hatch with a magnetic lock

To avoid using the screw driver everytime I wanted to exchange the batteries, I exchange this screw with two magnets, one glued on the hatch and the other on the back of the firewall.

It works great and is very strong. I am sure it will hold the hatch event if the battery pack gets loose from the tray.

I got this magnets from here. They are very small and with a magnetic force of 1.7 Kg. I sure I could have used less force and still have a secure lock, but did not want to take the risk of loosing the hatch during the flight.
Nov 24, 2011, 10:55 AM
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Motor mount

The motor is way to short to clear the nose of the plane. I made a very simple but effective mount with 4 threaded rods (M4) and 4 cylinders made out of hardwood. The length was calculated for the spinner backplate to just clear the nose.

I used blind nuts on the firewall to screw in the threaded rods and lock nuts on both ends of the rods.

I did a test run of the motor on this mount and it looked very good with no signs of vibration or things coming loose.

This setup can be easily adjusted to other motors.
Nov 25, 2011, 10:39 AM
Visitor from Reality
Bit late now, unless you fancy a re-do, but those servos hanging out the wing bottoms are in about the second wettest place on a floatplane after the floats.

A full cover over each servo with minimal opening at the rear for the pushrod would be an easy fix solution. If you have an urge for a rework, one good idea is to mount the servos on a ply plate screwed and then tape or film sealed into the wing bottom and pass the pushrods out through the wing's topsides - much drier all round. That's off the Clancy Aviation Speedy Bee, which sits real low over the water on its floats.

Hope that helps, and enjoy your floatplaning

Nov 25, 2011, 11:24 AM
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Thanks Dereck. Better late than never. Thanks a lot for your input.

I did not think that water would reach that high since I have an height of 5,5 inches from the top of the floats to the bottom of the fuselage.

I will try to figure out the easiest way to get a workaround to this problem. Will post the solution.

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