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Aug 19, 2019, 02:30 PM
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Build Log

Sig LT-25. First build & Conversion


6 hours into the build, and this is about as far as I've gone. Learning to read the instructions 3x, before proceeding forward. Learning lots, as I plod along.

Planned Power Setup.

Scorpion SII 3026-710
ESC - Hobbywing 80A V5 FlyFun
Battery 4S. 3000 25C
Prop - APC 11x7

or 3S. (13x8x3)


But after doing more research

Hacker A40-12L 13x10. 6S 2200 - (which will save me a few dollars. )
Last edited by Snailmale7; Aug 19, 2019 at 04:52 PM. Reason: Its going to be a build log.
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Aug 19, 2019, 05:49 PM
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I ran my LT-25 on the A40-12L and 6S 2200. It was a sweet setup with heaps of power, good low power efficiency and it also balanced easily. IIRC I was flying about 8 minutes of mixed aerobatics and touch and goes.

There is no intrinsic efficiency benefit in using 6S vs 3 or 4S,but you can get away with a 40A ESC and still have around 700W available
Aug 19, 2019, 07:50 PM
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That is good to know -). I am using the 80a ESC that I had reserved for the TF P-47, and gaining building experience.

Iím learning that everything is a trade off , there is no free lunch with eConversions and airplanes.


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Aug 20, 2019, 10:25 AM
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Quote:
Originally Posted by Snailmale7
………….

Learning to read the instructions 3x, before proceeding forward. Learning lots, as I plod along.

…………..
And the learning is incremental, sometimes exponential, in improving our building skills and developing our individual building preferences.

In additional to really understanding the building instructions, thinking ahead several major building and finishing steps ahead can help accommodate your preferences in later stages (eg. how you want to hinge the control surfaces) and possible problems (eg. with center of gravity, access to parts that might need servicing). Mostly I have learnt this after completing models with mistakes and do better on successive models.

Construction preferences...….. after a while, ok, after a long while, we likely develop construction preferences and try to build these into new models, which sometimes means building from plans rather than kits so as to not "waste" kit materials designed for construction methods we no longer like.

For example, with balsa wings I don't like a couple of features of this LT-25 kit: the inlaid center section sheeting, the lack of cap stripping over the ribs and I like a different rib/leading edge/leading edge sheeting design to provide more gluing area. Please do fill in the open gap between the center leading sheeting and leading edge - I think this whole area derives part of its strength from a continuous "monocoupe" outer skin. Stuffing the small open gap with slivers of balsa, gluing in with a sandable adhesive and then sanding down this area to a continuous smooth joint should strengthen this area of the wing.

just my learnings, others will have different suggestions

Michael in Ontario, Canada
Last edited by 2michaely; Aug 20, 2019 at 10:30 AM.
Aug 26, 2019, 07:33 PM
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Sig LT-25. First build & Conversion


Let me just go ahead and buy the recommended package .
Last edited by Snailmale7; Aug 26, 2019 at 08:55 PM. Reason: Question answered in the previous thread
Aug 26, 2019, 09:05 PM
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And I already typed a nice reply when you were editing . Here it is anyway

Within reason, a higher voltage and lower voltage system using the same power with the same prop can weigh the same, and should have similar efficiency.

The A40-8l @ 610 rpm/v on 4S and the A40-12L @ 410 rpm/V on 6S is a good example. They will both turn the same prop at about the same rpm, using similar power, just 1.5 times the current at 2/3 the voltage for the 4S setup. And a 4S 3300 pack has the same total energy and weight as a 6S 2200 pack. Note that they will also be loaded at the same C rate at the same power.

Where the 6S has a potential advantage is that depending on ESC chosen, you might be able to use a smaller ESC on a 6S setup, eg 40A on 6S vs 60A on 4S, with a small cost, weight and space saving. This does not work when you go above 6S as most ESCs above 6S are classed as 'high voltage' and take a big step up in price, and will also require use of an external BEC.
Aug 26, 2019, 09:06 PM
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What is the recommended system?
Aug 26, 2019, 11:54 PM
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Sig LT-25. First build & Conversion


Scirocco,

Thanks you for taking the time to reply to my questions. I sincerely appreciate your feedback.

After spending a day tinkering with eCal, Iíve come to the conclusion that I will start with a A40-12L-V4. 6S 2200 system, with the Hobby Wing 80A ESC I already have on hand.

Iíve looked at AXI 2826 motors, Scorpion motors, but after all my calculations, and what I think I understand about eMotors, I keep coming back to the A40-12L-v4.


Now for my next question, a weight saving question. Would you recommend I slide into a 40A ESC on this model, and keep the 80A for a bigger project? I PROMISE, I am making my purchase at the end of the week.







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Last edited by Snailmale7; Aug 27, 2019 at 12:08 AM.
Aug 27, 2019, 12:41 AM
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Happy to help. I really enjoyed building and flying my LT-25 and was sad when an overconfident buyer demolished it on his 3rd flight after I sold it.

I found the A40-12L @272g and a 6S 2200 balanced well with the batteries sitting on a shelf, angled a bit IIRC and inserted through the windshield. I made up a 1 piece combined windshield and forward hatch which made life super easy.

So for those physical reasons plus it is a nice efficient understressed setup that you will be able to reuse in a bigger higher performance model simply by running a bigger 6S battery and bigger prop, I think you'll be very happy with your choice.

Re ESC, for up to 13x10 (which will be great performance, guaranteed) , 40A would be ample, but if you're not using it elsewhere you might as well use the 80A you have than spending more - the weight penalty is negligible.

Just to throw out an option if you were wanting to save weight, 6S 1500 would be only loaded at 20C pulling 30A at full throttle and would still give over 6 minute flights. The slightly heavier motor than some you could use gives you flexibility to use lighter batteries and still balance without ballast.
Aug 27, 2019, 01:12 AM
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My good sir, thank you and thank you again. Now I can go to sleep with confidence, instead of trying to understand everything about electricity in a day. Iíll post pics of my build when i can get back to the bench. iíll order the motor by the end of the week.

Really sorry to hear about your LT 25. I am learning so much in assembling this kit, that I feel like i should buy another one , just to correct the mistakes iíve made starting with this build.

What are you flying these days ?


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Aug 27, 2019, 03:18 AM
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Quote:
Originally Posted by Snailmale7
My good sir, thank you and thank you again. Now I can go to sleep with confidence, instead of trying to understand everything about electricity in a day. Iíll post pics of my build when i can get back to the bench. iíll order the motor by the end of the week.

Really sorry to hear about your LT 25. I am learning so much in assembling this kit, that I feel like i should buy another one , just to correct the mistakes iíve made starting with this build.

What are you flying these days ?


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All sorts! Last weekend was a Beast 60E and a Multiplex Acromaster. A lot of F5J gliders. On the bench now is a 4.7m ASW-20 scale glider. Dozens of kits and ARFs in the pipeline. But I do not have a problem with rc.
Aug 27, 2019, 07:14 AM
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Just remember, this plane is a trainer not a flippy floppy 3Dbird.
In the scale of power needed, trainers can fly well on 50-75W/lb.
A full size Piper Cub flies on just under 50W/Lb using a Continental 65.
Sig's recommended flying weight is 4-4.5Lbs. so you don't need gobs of power. You can get into trouble with too much power as well.
Having built many Sig kits I have never had one that was a bad flier.
Aug 27, 2019, 08:49 AM
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Originally Posted by scirocco
All sorts! Last weekend was a Beast 60E and a Multiplex Acromaster. A lot of F5J gliders. On the bench now is a 4.7m ASW-20 scale glider. Dozens of kits and ARFs in the pipeline. But I do not have a problem with rc.


Oh I see no problem at all, I see you making a huge contribution to the world, by inspiring the next generation of pilots ! Yeah, thatís how I look at it.

I have 2 helicopters [ Align 450L and Align 470LM ] Iím building this baby, so I can maximize my flying time at the field. At my flying field, I must surrender the field to let the fixed wing pilots take to the sky. 1 flight, then wait 10 minutes, then another flight, then wait 10 minutes . But with my LT-25, I can fly the heli, land, and launch the airplane with my airplane buddies ..... #MaximumFlightTime.

@Jollyroger - and by keeping the Ďthrust gimble to a mimimum flying thrust. I can extend my flight time .


Thank you all soo much.





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Aug 27, 2019, 05:48 PM
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Okay last and final question about the Hacker. Does the A40-12L v4 come with a prop adapter (with the motor?). Thanks


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Aug 27, 2019, 06:41 PM
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Quote:
Originally Posted by Snailmale7
Okay last and final question about the Hacker. Does the A40-12L v4 come with a prop adapter (with the motor?). Thanks


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My V2 did, with a collet for front mounting and a bolt on driver and x mount for back mount, like in the images here https://www.hacker-motor-shop.com/Br...33726615&p=310


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