Sig LT-25 glow-to-electric conversion - AllMYRC.com-A Radio Control Helicopter, Airplane and Car Community

JustPlaneChris · 09-01-2009, 11:24 AM

The plane section is pretty sparse, so I thought I'd share the details of one of my planes.

Back in January 2006 I finished up a Sig LT-25 e-conversion. At the time, it was powered by an Astro Flight geared Cobalt 05 brushed motor and a 10 cell NiMH pack. Performance was "trainer-like" but it flew very well and showed you didn’t have to go high tech to fly a larger electric. The airframe was built mostly stock, with the exception of the "fuel tank hatch" area and nose, which was customized with a fiberglass cover and streamlined cowling. Other mods included a bolt-on wing, and ailerons that don't extend all the way to the wingtips.

After flying it for a while, naturally I got the itch to see how it would fly on brushless and lipo power. I purchased an inexpensive 1000kv outrunner and 60A controller from BPHobbies.com ($55 for both!) and paired it up with a 4S2P 4200 lipo pack. Performance was outstanding, since I lost nine ounces in the conversion and gained about 200 watts! I did have an issue with the motor mount included (it was thin and broke) and the motor seemed to vibrate at high rpm, which resonated in the airframe. Not show stoppers, but a bit annoying.

However, time marches on and since I'd been flying my Century Swift heli on 10S A123 cells for a while I couldn't help but wonder how well 5 A123 cells would work in the LT. I realized the weight would be almost the same as the 4S2P lipos and it fit perfectly in the LT. Power was up slightly, and flight times were still quite good (10+ minutes of sporty flying). And since the pack recharges in <15 minutes without requiring a cool-down, you can fly almost continuously with only two packs.

So that was fun, but the vibrating motor still annoyed me! I decided to experiment to see if I could improve on the power system by reducing rpm, hoping it wouldn't vibrate. I replaced the 5S A123 slab with a 4S2P A123 "stick/brick" configuration. This sits further back, making more room in the nose. The lower voltage (and rpm) let me bump up the prop size from an 11x7 to a 13x8, while keeping current draw similar (slightly more in fact, 59A / 700 watts). The beauty part is the prop has enough pitch you typically fly at half throttle or less.

How does it work? I took it out last Sunday and logged a twenty one minute flight! And that wasn't just cruising around either, the first 15 minutes were filled with loops, rolls, stall turns, cuban-8s and lots of touch and goes. Basically everything you can do with a plane like the LT-25 was thrown in the mix. After 15 minutes of that it still had enough power to loop from level flight at half throttle!

I think I've hit the magical combination here of power and duration. For flight training duty, I believe 30 minute flights would be possible. For messing around and doing aerobatics, 15 minutes doesn't push the pack at all (not that it's an issue to push A123). In short, I'd call it a success.

I'll get some pics of it in the latest config (showing the pack placement), and if any of you ARCA guys want a turn on the sticks some weekend just let me know and I'll bring it to the field!

Bobby Barr · 09-03-2009, 10:49 AM

That's awesome. I just finished converting my Hangar 9 Twist 40 to electric. I'll try to get some pictures and specs. Test flight went well. I'm using 6s 3000mah packs.

JustPlaneChris · 09-03-2009, 11:46 AM

Oooh, that sounds like a fun plane Bobby! I must admit, I came close to selling the LT-25 a while back because I wasn't flying it. But now I've got a resurging interest in planes so it's getting a new lease on life. In fact, it will be getting a different motor soon too.

Bobby Barr · 09-03-2009, 12:28 PM

That glider in your hand sure has my name on it

!

JustPlaneChris · 09-03-2009, 01:41 PM

Here are a couple of videos of the LT. I need to get some more footage!

The first one is the maiden flight with the new power system. You'll have to excuse all of Liz's crass comments.

http://www.youtube.com/watch?v=j1B6N21quJg

Here's one with some experimental "long leg" landing gear (since removed). In both videos you can hear that vibrating motor!

http://www.youtube.com/watch?v=lespajmRRSk

09-01-2009, 11:24 AM	#1 (permalink)
JustPlaneChris AllMYRC Member Join Date: Aug 2009 Posts: 423 Mood: Blog Entries: 5	Sig LT-25 glow-to-electric conversion The plane section is pretty sparse, so I thought I'd share the details of one of my planes. Back in January 2006 I finished up a Sig LT-25 e-conversion. At the time, it was powered by an Astro Flight geared Cobalt 05 brushed motor and a 10 cell NiMH pack. Performance was "trainer-like" but it flew very well and showed you didn’t have to go high tech to fly a larger electric. The airframe was built mostly stock, with the exception of the "fuel tank hatch" area and nose, which was customized with a fiberglass cover and streamlined cowling. Other mods included a bolt-on wing, and ailerons that don't extend all the way to the wingtips. After flying it for a while, naturally I got the itch to see how it would fly on brushless and lipo power. I purchased an inexpensive 1000kv outrunner and 60A controller from BPHobbies.com ($55 for both!) and paired it up with a 4S2P 4200 lipo pack. Performance was outstanding, since I lost nine ounces in the conversion and gained about 200 watts! I did have an issue with the motor mount included (it was thin and broke) and the motor seemed to vibrate at high rpm, which resonated in the airframe. Not show stoppers, but a bit annoying. However, time marches on and since I'd been flying my Century Swift heli on 10S A123 cells for a while I couldn't help but wonder how well 5 A123 cells would work in the LT. I realized the weight would be almost the same as the 4S2P lipos and it fit perfectly in the LT. Power was up slightly, and flight times were still quite good (10+ minutes of sporty flying). And since the pack recharges in <15 minutes without requiring a cool-down, you can fly almost continuously with only two packs. So that was fun, but the vibrating motor still annoyed me! I decided to experiment to see if I could improve on the power system by reducing rpm, hoping it wouldn't vibrate. I replaced the 5S A123 slab with a 4S2P A123 "stick/brick" configuration. This sits further back, making more room in the nose. The lower voltage (and rpm) let me bump up the prop size from an 11x7 to a 13x8, while keeping current draw similar (slightly more in fact, 59A / 700 watts). The beauty part is the prop has enough pitch you typically fly at half throttle or less. How does it work? I took it out last Sunday and logged a twenty one minute flight! And that wasn't just cruising around either, the first 15 minutes were filled with loops, rolls, stall turns, cuban-8s and lots of touch and goes. Basically everything you can do with a plane like the LT-25 was thrown in the mix. After 15 minutes of that it still had enough power to loop from level flight at half throttle! I think I've hit the magical combination here of power and duration. For flight training duty, I believe 30 minute flights would be possible. For messing around and doing aerobatics, 15 minutes doesn't push the pack at all (not that it's an issue to push A123). In short, I'd call it a success. I'll get some pics of it in the latest config (showing the pack placement), and if any of you ARCA guys want a turn on the sticks some weekend just let me know and I'll bring it to the field! Attached Thumbnails __________________ Chris www.InsideHeli.com PodCast Host

09-03-2009, 10:49 AM	#2 (permalink)
Bobby Barr Administrator Join Date: Sep 2009 Posts: 182 Mood:	That's awesome. I just finished converting my Hangar 9 Twist 40 to electric. I'll try to get some pictures and specs. Test flight went well. I'm using 6s 3000mah packs. __________________ Bobby Barr...Caldwell, TX

09-03-2009, 11:46 AM	#3 (permalink)
JustPlaneChris AllMYRC Member Join Date: Aug 2009 Posts: 423 Mood: Blog Entries: 5	Oooh, that sounds like a fun plane Bobby! I must admit, I came close to selling the LT-25 a while back because I wasn't flying it. But now I've got a resurging interest in planes so it's getting a new lease on life. In fact, it will be getting a different motor soon too. __________________ Chris www.InsideHeli.com PodCast Host

09-03-2009, 12:28 PM	#4 (permalink)
Bobby Barr Administrator Join Date: Sep 2009 Posts: 182 Mood:	That glider in your hand sure has my name on it ! __________________ Bobby Barr...Caldwell, TX

09-03-2009, 01:41 PM	#5 (permalink)
JustPlaneChris AllMYRC Member Join Date: Aug 2009 Posts: 423 Mood: Blog Entries: 5	Here are a couple of videos of the LT. I need to get some more footage! The first one is the maiden flight with the new power system. You'll have to excuse all of Liz's crass comments. http://www.youtube.com/watch?v=j1B6N21quJg Here's one with some experimental "long leg" landing gear (since removed). In both videos you can hear that vibrating motor! http://www.youtube.com/watch?v=lespajmRRSk __________________ Chris www.InsideHeli.com PodCast Host Last edited by JustPlaneChris; 09-03-2009 at 08:18 PM.

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