Kadet Mark II conversion
02-12-2024, 11:25 AM
#1
Kadet Mark II conversion
Just purchased a Sig Kadet Mark II from eBay. I would like to convert this plane from gas to electric. Looking for any advice on what motor,esc, battery and charger to use and any other helpful information on the conversion installation. I'm sure it is not that difficult.
Regards,
clc58
Regards,
clc58
02-12-2024, 02:18 PM
#2
Join Date: Sep 2002
Location: Nijmegen / Nederland
Posts: 628
Likes: 0
Received 22 Likes
on
17 Posts
For now: forget glow/gas↔e-motor equivalencies, those can set you off on the wrong track and will restrict your choices. E-motors are way more versatile.
A selection method by scirocco
How to design a custom electric power system
User scirocco a.o. is also active in the Electric Power Systems subforum on RCG, should you need help/advice/feedback/checks.
Vriendelijke groeten
Ron
• Without a watt-meter you're in the dark ... until something starts to glow •
• E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •
A selection method by scirocco
How to design a custom electric power system
User scirocco a.o. is also active in the Electric Power Systems subforum on RCG, should you need help/advice/feedback/checks.
Vriendelijke groeten
Ron• Without a watt-meter you're in the dark ... until something starts to glow •
• E-flight calculators • watt-meters • diy motor tips&tricks • Cumulus MFC •
Last edited by ron_van_sommeren; 02-12-2024 at 02:54 PM.
03-03-2024, 11:21 PM
#5
I’ve done more than several like this now. My mkii however is still sup Tigre 40. I have all kinds. Either way, trainer 5-7 lbs. stick with me. Do this from small .049 size through 1/4 scale…not limits but goes to show a range.
1hp is 746watts.
brush motor is 50% efficient (you know that this won’t work)…partly why.
brushless is 80% efficient. Let’s try this one.
that .40 os max is 1hp (746 watts)
we need that 10x6 to spin at the same glow rpm to get the SAME power (plus 20% from electric loss right?)
so 746w plus 20% of 746 is 895watts.
shop for 895watts for a power setup. ..can’t have “too much power” right? Okay, round up then.
Now I just became a fan of innov8tivedesigns dot com for publishing PROP AND CURRENT DATA for all their motors! I don’t think that anyone else does this. Maybe hacker. Now, I will tell you a shortcut… I’ve used milehighrc dot com for years. I’m trying flex because data sheets are paramount and I need them. I’m also squeezing out the most time and power that I can because physics lets us get away with nothing (Phoenix Giles that I rebuilt too heavy years ago needs some compensation).
I took a tower trainer 40, put a g46 motor I think it is on it, 5s battery, and it takes off, and can immediately go into a vertical climb to a loop of 60’ diameter or as nice as you please for a nice ROUND loop. 7lb fly weight. Heavier than glow with that brick of a battery. Also Can’t do that on a glow 40/46. You won’t notice the wing loading. I rounded up! I sent them the video for feedback but Mike, the guy there never posted it. Too bad. I view these trainers the benchmark by which to judge all else just as you can say “if the tower trainer does it, my mkii can do it and so can the big stick 40”…AND this plane flies for 45min on one charge. That I didn’t see coming. The plane flies on 4s as well. That math, you can do to check…
42-50-500 is a motor size that I just made up. WIDTH - LENGTH - “rpm per volt”
focus on the last part. 5s lipo at 4.2v per cell works out to 10,500rpm. It may not be the 13.5k rpm of the osmax but the prop is fatter and the loop maneuver … well can’t do that with glow so rounding up works. Yes there is voltage sag. Redo it. 3.7v a cell x 5 cells draws it down to 9,250rpm. It’s enough to notice on the plane you fly all the time. Now 4s… just going to use the sag voltage because it’s bed time and I’m keeping this SHORT. lol. It’s my passion in this hobby. I like this part. 7,400rpm. Quite a bit lower. It’s like 5/8 throttle of the 40 or 5s glow power. LIGHTER by the battery weight difference I’d say to the tone of weight at takeoff with a 8oz tank vs at empty. It’s worth a chunk of elev trim clicks but nothing crazy. But it feels like a 32-35 on the plane. Not a McCoy, but perhaps another osmax.
now this is my last post before bed so it may be a bit choppy.
we see lots of internet ideas feedback. “Watts per weight” or something. We can get into the weeds, so support your math with the extras that you find and be driven to get that prop at your glow engines rpm. Electric props will be fatter and often don’t rev as high. There are slight differences. I like this power method. Yes the charts at flex will make you cross eyed at first. Take little bites. You’ll get there.
okay one more!
049 is 80w.
6x4 prop and i can’t remember the rpm. Find it.
80% efficiency on a brushless motor setup, so strive for 100w motor
get that 6x4, 6x3 etc prop the same rpm
one more thing. I was once behind a guy at Oshkosh and heard a conversation… a kit builder finished his plane and using a gearbox conducted a take off. The tail wheel came up but BARELY. that’s all it wrote. Math oops. He figured power but failed to translate it to PITCH SPEED and thrust. He obviously just focused on thrust. Can you imagine!?
Let’s introduce the fact that 746watts (1hp=.40 engine) differs between a helicopter and a small dia prop racing plane to use the two extremes. the heli has thrust and the racer has pitch speed. It’s a slide scale. Matching the glow counterpart is a great place to start but just like using a 10x6 on the mkii and 40 osmax, you can use a 9x7 or an 11x5 as well! All I complicate this for with this now is that motors are more specific than glow engines on data and youll Be number crunching the “kv” of a motor (rpm if given one volt) of 500 in my example above to lower (more torque=thrust) or to more speed (less tq, higher kv number).
have fun!
andy
mkii since 1992. Crashed 6 times. 2-3 wot v dives into gnd! Lost visual site more than 2nm once!
3 full restorations to like new
currently restoration 3yrs ago and remains like new (with a symmetrical airfoil and 0 dihedral now)
learned how to fly on this one!
1hp is 746watts.
brush motor is 50% efficient (you know that this won’t work)…partly why.
brushless is 80% efficient. Let’s try this one.
that .40 os max is 1hp (746 watts)
we need that 10x6 to spin at the same glow rpm to get the SAME power (plus 20% from electric loss right?)
so 746w plus 20% of 746 is 895watts.
shop for 895watts for a power setup. ..can’t have “too much power” right? Okay, round up then.
Now I just became a fan of innov8tivedesigns dot com for publishing PROP AND CURRENT DATA for all their motors! I don’t think that anyone else does this. Maybe hacker. Now, I will tell you a shortcut… I’ve used milehighrc dot com for years. I’m trying flex because data sheets are paramount and I need them. I’m also squeezing out the most time and power that I can because physics lets us get away with nothing (Phoenix Giles that I rebuilt too heavy years ago needs some compensation).
I took a tower trainer 40, put a g46 motor I think it is on it, 5s battery, and it takes off, and can immediately go into a vertical climb to a loop of 60’ diameter or as nice as you please for a nice ROUND loop. 7lb fly weight. Heavier than glow with that brick of a battery. Also Can’t do that on a glow 40/46. You won’t notice the wing loading. I rounded up! I sent them the video for feedback but Mike, the guy there never posted it. Too bad. I view these trainers the benchmark by which to judge all else just as you can say “if the tower trainer does it, my mkii can do it and so can the big stick 40”…AND this plane flies for 45min on one charge. That I didn’t see coming. The plane flies on 4s as well. That math, you can do to check…
42-50-500 is a motor size that I just made up. WIDTH - LENGTH - “rpm per volt”
focus on the last part. 5s lipo at 4.2v per cell works out to 10,500rpm. It may not be the 13.5k rpm of the osmax but the prop is fatter and the loop maneuver … well can’t do that with glow so rounding up works. Yes there is voltage sag. Redo it. 3.7v a cell x 5 cells draws it down to 9,250rpm. It’s enough to notice on the plane you fly all the time. Now 4s… just going to use the sag voltage because it’s bed time and I’m keeping this SHORT. lol. It’s my passion in this hobby. I like this part. 7,400rpm. Quite a bit lower. It’s like 5/8 throttle of the 40 or 5s glow power. LIGHTER by the battery weight difference I’d say to the tone of weight at takeoff with a 8oz tank vs at empty. It’s worth a chunk of elev trim clicks but nothing crazy. But it feels like a 32-35 on the plane. Not a McCoy, but perhaps another osmax.
now this is my last post before bed so it may be a bit choppy.
we see lots of internet ideas feedback. “Watts per weight” or something. We can get into the weeds, so support your math with the extras that you find and be driven to get that prop at your glow engines rpm. Electric props will be fatter and often don’t rev as high. There are slight differences. I like this power method. Yes the charts at flex will make you cross eyed at first. Take little bites. You’ll get there.
okay one more!
049 is 80w.
6x4 prop and i can’t remember the rpm. Find it.
80% efficiency on a brushless motor setup, so strive for 100w motor
get that 6x4, 6x3 etc prop the same rpm
one more thing. I was once behind a guy at Oshkosh and heard a conversation… a kit builder finished his plane and using a gearbox conducted a take off. The tail wheel came up but BARELY. that’s all it wrote. Math oops. He figured power but failed to translate it to PITCH SPEED and thrust. He obviously just focused on thrust. Can you imagine!?
Let’s introduce the fact that 746watts (1hp=.40 engine) differs between a helicopter and a small dia prop racing plane to use the two extremes. the heli has thrust and the racer has pitch speed. It’s a slide scale. Matching the glow counterpart is a great place to start but just like using a 10x6 on the mkii and 40 osmax, you can use a 9x7 or an 11x5 as well! All I complicate this for with this now is that motors are more specific than glow engines on data and youll Be number crunching the “kv” of a motor (rpm if given one volt) of 500 in my example above to lower (more torque=thrust) or to more speed (less tq, higher kv number).
have fun!
andy
mkii since 1992. Crashed 6 times. 2-3 wot v dives into gnd! Lost visual site more than 2nm once!
3 full restorations to like new
currently restoration 3yrs ago and remains like new (with a symmetrical airfoil and 0 dihedral now)
learned how to fly on this one!
Last edited by amckevitz; 03-03-2024 at 11:44 PM. Reason: I keep mistaking watts as 776. It’s 746
