Need Help CONVERTING A PURE GLIDER TO ELECTRIC LAUNCH?
02-28-2014, 05:37 AM
#1
Need Help CONVERTING A PURE GLIDER TO ELECTRIC LAUNCH?
CONVERTING A PURE GLIDER TO ELECTRIC LAUNCH
Ed Anderson
I often see questions about converting a pure glider to electric launch. Often it is an older 2 to 3M woody that has been neglected because the pilot no longer wants to bother with a hi-start or a winch. So I thought I would draft something as a starting point for pilots looking for advice on such a conversion.
Have you done a conversion like this? We would love to hear your feedback and for you to add your set-up for other people. Please also add any tips or advice.
What glider did you convert?
What did you use?
What would you do differently if you did it over?
Here are some sample components that would work in many cases. These are certainly not your only options and these are not necessarily the best options for your individual glider, but they give you a feeling for what is needed and you can branch out from here. How much power you need will depend on the weight of the glider, after the conversion, and what kind of climb you want to achieve. My power to weight ratio recommendation would be to shoot for 75 watts/pound for about a 45 degree climb for sport flying. For electric contest flying, like ALES or F5J, I would suggest about 130 watts per pound to hit 200 meters in 30 seconds or less. More than that and you are building a helicopter, but some people feel that way too much power is just about right.
This particular combination of components was based on the conversion of a Spectra 2M to brushless power. The Spectra was built for electric power but used an old heavy brushed motor. This set-up will run about 250 to 300 watts and the estimated finished weight of that glider was about 3 pounds, 48 ounces. Depending on what prop was chosen this would provide a power to weight ratio of about 80 to 100 watts per pound.
I have limited experience with HK motors but many people like them so I have used one as an example here. If you prefer some other brand you can use the specs of these components to help you find the parts you want from another maker.
Most pure gliders have fairly thin noses with tight interior space, so I have selected a 2836 mm outrunner motor with the assumption you are going to put the motor inside. The outside of the motor itself is 28 mm and the length of the internal motor is 36 mm thought the overall motor is actually longer than that. You can see the actual dimensions on the page at the link for the motor. Remember that you need to leave space for the spinning can and have to safely route the wires.
You don’t have to put the motor inside fuselage. Some pilots just cut off the nose block and mount the motor on the outside, later adding a cowl over it. If you do that then you are less constrained in motor size, but again a 28 MM wide motor will work well in most situations. Also having the motor further forward can work well for balance in SOME gliders.
If you are converting an old electric glider, like a spectra, that was based on a brushed motor, be sure to take into account that the brushless motor may be lighter than the old motor. For example a Speed 700 motor is almost 8 ounces while the 2836 motor suggested below is about 5.5 ounces. That means that you will have to add lead to the nose or reposition components forward in order to get the glider to balance properly. Take that into account. An electric conversion can often be an opportunity to move things around to achieve the best weight distribution possible and avoid adding a lot of lead.
I am using a 2836 motor as the example. Max power is 330 watts. However the actual power level will be based on what prop you use. I would guestimate about 250 to 300 with one of the props I recommend. So this could be a good fit or a 30 ounce glider at 130 watts per pound for ALES contests or a 48 ounce glider at 75 watts per pound for casual sport soaring.
HobbyKing doesn't provide a prop recommendation for this 28X36 motor but, from the posts by users, a 10X6 or 10X7 should do. Maybe an 11X6. Be sure to test with a watt meter.
http://www.hobbyking.com/hobbyking/store/__18158__Turnigy_Aerodrive_SK3_2836_1040kv_Brushle ss_Outrunner_Motor.html
If you have a lighter glider you can consider a 2830 for lighter weight at a lower amp draw, about 180 watts. This would work for a 20 to 36 ounce glider depending on the power to weight ratio you want. Be sure to use a proper prop size, probably a 9X6, and a proper ESC, around 20 amps. Always look for a manufacturer’s recommendation and look at recommendations by users. Always check it with a watt meter.
http://www.hobbyking.com/hobbyking/store/__32004__Turnigy_Aerodrive_SK3_2830_1130kv_Brushle ss_Outrunner_Motor_USA_Warehouse_.html
ESC – For the 2836 motor this needs to be at least 30 amps. Whatever ESC you use, confirm it has a brake before you buy or the prop will keep spinning and KILL the glide. Most ESC don’t need any kind of special programming card but some do offer them and they can make set-up simpler. I have my gliders set to brake on. If I have an option I set for a soft start and a soft brake to reduce the load on the motor. For gliders those settings are usually fine.
http://www.hobbyking.com/hobbyking/store/__2164__TURNIGY_Plush_30amp_Speed_Controller.html
Not sure if this spinner will be wide enough for the folded blades to clear the fuse of your glider with an internal motor mount. This is just a sample that would work with the 2836 motor. If you are mounting the motor externally than it is less of an issue as you will design the cowl to match to the spinner.
http://www.hobbyking.com/hobbyking/store/__17890__35mm_Carbon_Fiber_Spinners_for_Folding_Pr opeller_3_17mm_Shaft_.html
These blades are where I would start with for the 2836 Motor. I would get a 10X6, 10X7 and maybe an 11X6 to test. They are cheap enough. Here is where a wattmeter comes in very handy to insure you know what power draw you are creating with each prop so you don't under or over load the motor.
http://www.hobbyking.com/hobbyking/s...op_Blades.htmlhttp://www.hobbyking.com/hobbyking/store/__18068__Carbon_Fibre_10x6_Folding_Prop_Blades.htm l
I would recommend a 3S lipo for the 2836 motor in the 1800 to 2200 mah 20C+ range for fit and weight. Figure 20 to 40 second climbs at about 25 amps. Expect about 3-4 minutes full throttle run time from the 1800. That should give you about 4-6 good climbs with some reserve.
Something like this will probably work. Measure the space for the battery. And be prepared to solder connectors to match the battery and the ESC.
http://www.hobbyking.com/hobbyking/store/__9274__Turnigy_1800mAh_3S_20C_Lipo_Pack.html
Feel free to ask questions. If this all seems confusing because you don't understand electric power systems you might find this book useful. Read the above, then look at the chapters of the book, then read the above again and it will start to make sense.
EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
http://www.wattflyer.com/forums/showthread.php?t=31071
http://www.rcuniverse.com/forum/m_7100376/tm.htm
Ed Anderson
I often see questions about converting a pure glider to electric launch. Often it is an older 2 to 3M woody that has been neglected because the pilot no longer wants to bother with a hi-start or a winch. So I thought I would draft something as a starting point for pilots looking for advice on such a conversion.
Have you done a conversion like this? We would love to hear your feedback and for you to add your set-up for other people. Please also add any tips or advice.
What glider did you convert?
What did you use?
What would you do differently if you did it over?
Here are some sample components that would work in many cases. These are certainly not your only options and these are not necessarily the best options for your individual glider, but they give you a feeling for what is needed and you can branch out from here. How much power you need will depend on the weight of the glider, after the conversion, and what kind of climb you want to achieve. My power to weight ratio recommendation would be to shoot for 75 watts/pound for about a 45 degree climb for sport flying. For electric contest flying, like ALES or F5J, I would suggest about 130 watts per pound to hit 200 meters in 30 seconds or less. More than that and you are building a helicopter, but some people feel that way too much power is just about right.
This particular combination of components was based on the conversion of a Spectra 2M to brushless power. The Spectra was built for electric power but used an old heavy brushed motor. This set-up will run about 250 to 300 watts and the estimated finished weight of that glider was about 3 pounds, 48 ounces. Depending on what prop was chosen this would provide a power to weight ratio of about 80 to 100 watts per pound.
I have limited experience with HK motors but many people like them so I have used one as an example here. If you prefer some other brand you can use the specs of these components to help you find the parts you want from another maker.
Most pure gliders have fairly thin noses with tight interior space, so I have selected a 2836 mm outrunner motor with the assumption you are going to put the motor inside. The outside of the motor itself is 28 mm and the length of the internal motor is 36 mm thought the overall motor is actually longer than that. You can see the actual dimensions on the page at the link for the motor. Remember that you need to leave space for the spinning can and have to safely route the wires.
You don’t have to put the motor inside fuselage. Some pilots just cut off the nose block and mount the motor on the outside, later adding a cowl over it. If you do that then you are less constrained in motor size, but again a 28 MM wide motor will work well in most situations. Also having the motor further forward can work well for balance in SOME gliders.
If you are converting an old electric glider, like a spectra, that was based on a brushed motor, be sure to take into account that the brushless motor may be lighter than the old motor. For example a Speed 700 motor is almost 8 ounces while the 2836 motor suggested below is about 5.5 ounces. That means that you will have to add lead to the nose or reposition components forward in order to get the glider to balance properly. Take that into account. An electric conversion can often be an opportunity to move things around to achieve the best weight distribution possible and avoid adding a lot of lead.
I am using a 2836 motor as the example. Max power is 330 watts. However the actual power level will be based on what prop you use. I would guestimate about 250 to 300 with one of the props I recommend. So this could be a good fit or a 30 ounce glider at 130 watts per pound for ALES contests or a 48 ounce glider at 75 watts per pound for casual sport soaring.
HobbyKing doesn't provide a prop recommendation for this 28X36 motor but, from the posts by users, a 10X6 or 10X7 should do. Maybe an 11X6. Be sure to test with a watt meter.
http://www.hobbyking.com/hobbyking/store/__18158__Turnigy_Aerodrive_SK3_2836_1040kv_Brushle ss_Outrunner_Motor.html
If you have a lighter glider you can consider a 2830 for lighter weight at a lower amp draw, about 180 watts. This would work for a 20 to 36 ounce glider depending on the power to weight ratio you want. Be sure to use a proper prop size, probably a 9X6, and a proper ESC, around 20 amps. Always look for a manufacturer’s recommendation and look at recommendations by users. Always check it with a watt meter.
http://www.hobbyking.com/hobbyking/store/__32004__Turnigy_Aerodrive_SK3_2830_1130kv_Brushle ss_Outrunner_Motor_USA_Warehouse_.html
ESC – For the 2836 motor this needs to be at least 30 amps. Whatever ESC you use, confirm it has a brake before you buy or the prop will keep spinning and KILL the glide. Most ESC don’t need any kind of special programming card but some do offer them and they can make set-up simpler. I have my gliders set to brake on. If I have an option I set for a soft start and a soft brake to reduce the load on the motor. For gliders those settings are usually fine.
http://www.hobbyking.com/hobbyking/store/__2164__TURNIGY_Plush_30amp_Speed_Controller.html
Not sure if this spinner will be wide enough for the folded blades to clear the fuse of your glider with an internal motor mount. This is just a sample that would work with the 2836 motor. If you are mounting the motor externally than it is less of an issue as you will design the cowl to match to the spinner.
http://www.hobbyking.com/hobbyking/store/__17890__35mm_Carbon_Fiber_Spinners_for_Folding_Pr opeller_3_17mm_Shaft_.html
These blades are where I would start with for the 2836 Motor. I would get a 10X6, 10X7 and maybe an 11X6 to test. They are cheap enough. Here is where a wattmeter comes in very handy to insure you know what power draw you are creating with each prop so you don't under or over load the motor.
http://www.hobbyking.com/hobbyking/s...op_Blades.htmlhttp://www.hobbyking.com/hobbyking/store/__18068__Carbon_Fibre_10x6_Folding_Prop_Blades.htm l
I would recommend a 3S lipo for the 2836 motor in the 1800 to 2200 mah 20C+ range for fit and weight. Figure 20 to 40 second climbs at about 25 amps. Expect about 3-4 minutes full throttle run time from the 1800. That should give you about 4-6 good climbs with some reserve.
Something like this will probably work. Measure the space for the battery. And be prepared to solder connectors to match the battery and the ESC.
http://www.hobbyking.com/hobbyking/store/__9274__Turnigy_1800mAh_3S_20C_Lipo_Pack.html
Feel free to ask questions. If this all seems confusing because you don't understand electric power systems you might find this book useful. Read the above, then look at the chapters of the book, then read the above again and it will start to make sense.
EVERYTHING YOU WANTED TO KNOW ABOUT ELECTRIC POWERED FLIGHT
http://www.wattflyer.com/forums/showthread.php?t=31071
http://www.rcuniverse.com/forum/m_7100376/tm.htm
Last edited by aeajr; 02-28-2014 at 09:57 AM.
03-24-2014, 11:19 AM
#3
My Feedback: (5)
About a year ago I took a Spirit Elite kit and built it as an electric. Having done this, I don’t think I would do it again. One problem is that the fuselage had to be redesigned from the wing forward. The fuselage for most pure sailplanes is too narrow for a motor and the nose moment is too long. I’ve been building models for more than fifty years, so modifying the plane wasn’t that much of a hassle for me but it would be for a person without the experience.
The other problem is that the Elite’s specified CG and trim were off. Paul Naton speaks of this in his videos. Unfortunately, I didn’t review the video until after the plane was built. Initially the Elite was the worst flying sailplane I ever had. After moving the CG back and reducing wing’s angle of attack, it flew decently. But reducing the angle of attack effectively made the motor have up-thrust. I wasn’t about to redo the nose. I used a program mix on my transmitter of throttle to elevator.
I wouldn’t say that converting a pure sailplane to electric is inevitably an easy task. Unless a person likes building and trimming and having the risk of the first flights being a disaster, they should stick to a model that was designed for a motor.
Allan
The other problem is that the Elite’s specified CG and trim were off. Paul Naton speaks of this in his videos. Unfortunately, I didn’t review the video until after the plane was built. Initially the Elite was the worst flying sailplane I ever had. After moving the CG back and reducing wing’s angle of attack, it flew decently. But reducing the angle of attack effectively made the motor have up-thrust. I wasn’t about to redo the nose. I used a program mix on my transmitter of throttle to elevator.
I wouldn’t say that converting a pure sailplane to electric is inevitably an easy task. Unless a person likes building and trimming and having the risk of the first flights being a disaster, they should stick to a model that was designed for a motor.
Allan
03-25-2014, 12:05 AM
#5
My Feedback: (5)
Ed,
I used a Himax HC3522-0990 that I had left over from an NSP Sunset. My first electric sailplane was a 2-meter electric Chrysalis. It uses the MP Jet AC 28/20-7 combination that Don Stackhouse recommended for the plane. I was very satisfied with its performance so I tried to duplicate it with the Sunset. As the MP Jet was no longer being sold, I bought the Himax motor that was similar to it. My Sunset like others was short-lived. The wing exploded while doing a dive test. I salvaged the motor and put it in the Elite.
Installing the motor wasn’t any more difficult than the LiPo battery, receiver and servos’ installation. The receiver and servos were placed under the wing where the fuselage really narrows down. Had I known then the CG had to be moved behind the recommended range, I would have placed the battery under the wing instead of behind the motor. But these are unknowns one encounters when modifying a plane.
Your first post is informative and I’m not saying one shouldn’t try converting their sailplane to electric. But they should do it expecting problems. It is not always a slam dunk proposition. In this age of ARFs and pre-builts, I wonder how many are willing to take on the task.
Allan
I used a Himax HC3522-0990 that I had left over from an NSP Sunset. My first electric sailplane was a 2-meter electric Chrysalis. It uses the MP Jet AC 28/20-7 combination that Don Stackhouse recommended for the plane. I was very satisfied with its performance so I tried to duplicate it with the Sunset. As the MP Jet was no longer being sold, I bought the Himax motor that was similar to it. My Sunset like others was short-lived. The wing exploded while doing a dive test. I salvaged the motor and put it in the Elite.
Installing the motor wasn’t any more difficult than the LiPo battery, receiver and servos’ installation. The receiver and servos were placed under the wing where the fuselage really narrows down. Had I known then the CG had to be moved behind the recommended range, I would have placed the battery under the wing instead of behind the motor. But these are unknowns one encounters when modifying a plane.
Your first post is informative and I’m not saying one shouldn’t try converting their sailplane to electric. But they should do it expecting problems. It is not always a slam dunk proposition. In this age of ARFs and pre-builts, I wonder how many are willing to take on the task.
Allan
03-25-2014, 05:10 AM
#6
I did a bargain basement conversion on an old Kit built Bird of Time.. pretty cheap and straight forward..
A turnigy 35/36 1000 kv, this is the cheap gold and chrome motor...
Plush 40 speed control.
I have used different batteries but generally a 3 cell 2200 lipo goes in there.
the hub and folding prop was from HK as well. I can't tell you the prop size for certain ,However I think its an 11/6 ?
I don't compete with it, or claim its the best possible setup. However it works fine and has been a great setup for the money.
A turnigy 35/36 1000 kv, this is the cheap gold and chrome motor...
Plush 40 speed control.
I have used different batteries but generally a 3 cell 2200 lipo goes in there.
the hub and folding prop was from HK as well. I can't tell you the prop size for certain ,However I think its an 11/6 ?
I don't compete with it, or claim its the best possible setup. However it works fine and has been a great setup for the money.
03-25-2014, 05:43 AM
#7
Ed,
I used a Himax HC3522-0990 that I had left over from an NSP Sunset. My first electric sailplane was a 2-meter electric Chrysalis. It uses the MP Jet AC 28/20-7 combination that Don Stackhouse recommended for the plane. I was very satisfied with its performance so I tried to duplicate it with the Sunset. As the MP Jet was no longer being sold, I bought the Himax motor that was similar to it. My Sunset like others was short-lived. The wing exploded while doing a dive test. I salvaged the motor and put it in the Elite.
Installing the motor wasn’t any more difficult than the LiPo battery, receiver and servos’ installation. The receiver and servos were placed under the wing where the fuselage really narrows down. Had I known then the CG had to be moved behind the recommended range, I would have placed the battery under the wing instead of behind the motor. But these are unknowns one encounters when modifying a plane.
Your first post is informative and I’m not saying one shouldn’t try converting their sailplane to electric. But they should do it expecting problems. It is not always a slam dunk proposition. In this age of ARFs and pre-builts, I wonder how many are willing to take on the task.
Allan
I used a Himax HC3522-0990 that I had left over from an NSP Sunset. My first electric sailplane was a 2-meter electric Chrysalis. It uses the MP Jet AC 28/20-7 combination that Don Stackhouse recommended for the plane. I was very satisfied with its performance so I tried to duplicate it with the Sunset. As the MP Jet was no longer being sold, I bought the Himax motor that was similar to it. My Sunset like others was short-lived. The wing exploded while doing a dive test. I salvaged the motor and put it in the Elite.
Installing the motor wasn’t any more difficult than the LiPo battery, receiver and servos’ installation. The receiver and servos were placed under the wing where the fuselage really narrows down. Had I known then the CG had to be moved behind the recommended range, I would have placed the battery under the wing instead of behind the motor. But these are unknowns one encounters when modifying a plane.
Your first post is informative and I’m not saying one shouldn’t try converting their sailplane to electric. But they should do it expecting problems. It is not always a slam dunk proposition. In this age of ARFs and pre-builts, I wonder how many are willing to take on the task.
Allan
My greatest learning experiences have not been from my successes but from my "could have done that better" or "what was I thinking?"
Whether setting up a new glider, e-glider or other aircraft, one thing I have learned it so weight the components then either place them or small weight packs in the position I plan to mount them, tape them in place than try to balance the plane. Often I find that moving a component a few MM can make a major difference in how the aircraft balances. sometimes this helps me avoid nose weight or helps me take better advantage of space.
The small 1/4 oz stick on weights work well for this. Or you can use quarters which are about .22 ounces each.
It is not an exact system but a first approximation before I glue stuff in.
I had converted a Cox Dust Devil from a speed 550 brushed and NiCd and standard servos to a Rimfire brushless and Lipo with micro servos. The new motor was several ounces lighter but saved no weight as I would have to make it up in lead. If I had just mounted stuff where it had been before the conversion to brushed I would have been the same weight, less the difference in battery pack. By testing locations I was able to take out about 3 ounces of lead that I would have otherwise needed.
In retrospect I could have taken even more weigh out by moving the motor forward, outside the firewall and made a new fairing over the motor. I will know better next time.
Last edited by aeajr; 03-25-2014 at 05:54 AM.
03-25-2014, 05:55 AM
#8
I did a bargain basement conversion on an old Kit built Bird of Time.. pretty cheap and straight forward..
A turnigy 35/36 1000 kv, this is the cheap gold and chrome motor...
Plush 40 speed control.
I have used different batteries but generally a 3 cell 2200 lipo goes in there.
the hub and folding prop was from HK as well. I can't tell you the prop size for certain ,However I think its an 11/6 ?
I don't compete with it, or claim its the best possible setup. However it works fine and has been a great setup for the money.
A turnigy 35/36 1000 kv, this is the cheap gold and chrome motor...
Plush 40 speed control.
I have used different batteries but generally a 3 cell 2200 lipo goes in there.
the hub and folding prop was from HK as well. I can't tell you the prop size for certain ,However I think its an 11/6 ?
I don't compete with it, or claim its the best possible setup. However it works fine and has been a great setup for the money.
03-25-2014, 11:11 AM
#9
My Feedback: (14)
Join Date: Aug 2009
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Hello, Came across your Thread and I'm interested in the info etc.
Built a Goldberg Electra glider (72 in Span) many years ago (still have it) that used a "Can" type Mtr and 7 Cell Sub C Ni cad battery Pak. A little on the Hvy side
Am considering changing the Mtr to an Outrunner with a Li-Po Batt Pak
Plan to use a Cermark CEM-2820-1200 Outrunner Mtr & 30 amp ESC & 1500 mAH,11.1 V,30C Li Po Pak, 10-6 or 11-6 prop
Does that look "OK to Go"???
just getting started with the Elec Stuff and can't relate : What size Elec vs Glow ,ESC & Li Po Batt Size etc, etc
I'm an "Old Fashioned" Balsa and Monokote Builder/Flyer, Not into Foamy or Hotliner Type Gliders.
Your comments please,
Thanks rcroger
Built a Goldberg Electra glider (72 in Span) many years ago (still have it) that used a "Can" type Mtr and 7 Cell Sub C Ni cad battery Pak. A little on the Hvy side
Am considering changing the Mtr to an Outrunner with a Li-Po Batt Pak
Plan to use a Cermark CEM-2820-1200 Outrunner Mtr & 30 amp ESC & 1500 mAH,11.1 V,30C Li Po Pak, 10-6 or 11-6 prop
Does that look "OK to Go"???
just getting started with the Elec Stuff and can't relate : What size Elec vs Glow ,ESC & Li Po Batt Size etc, etc
I'm an "Old Fashioned" Balsa and Monokote Builder/Flyer, Not into Foamy or Hotliner Type Gliders.
Your comments please,
Thanks rcroger
03-25-2014, 11:20 AM
#10
links to the components you are using would help. As long as that prop is recommended for that motor with that battery pack you are OK.
I assume you have checked to be sure you have room to mount the motor, leaving space for the spinning can and can route the wires where they need to go.
From a power point of view, I usually target between 75 and 150 watts per pound depending on what kind of climb I want. See the first post for more info.
See notes in previous posts about how to test balance to minimize adding lead to the nose.
I assume you have checked to be sure you have room to mount the motor, leaving space for the spinning can and can route the wires where they need to go.
From a power point of view, I usually target between 75 and 150 watts per pound depending on what kind of climb I want. See the first post for more info.
See notes in previous posts about how to test balance to minimize adding lead to the nose.
03-25-2014, 11:23 AM
#11
My Feedback: (5)
Paul Naton in one of his videos used the Spirit Elite, in its pure sailplane configuration, as an example how the manufacturer’s recommended CG and setup can be off the mark. I had a copy of the video but forgot about it when building the Elite. To get the CG to where the plans recommended, I added extra weight under the forward-positioned battery.
The really unexpected factor of the first flights was that while the plane was controllable with the motor on, it went wild with the motor off. Both of the wing hold-down dowels were broken during this initial phase. Following Naton’s trim recommendations as much as I could, the plane now flies decently. Being a full-house, two-meter aircraft, it is a little heavy. It doesn’t soar as well as my RES Chrysalis.
Allan
The really unexpected factor of the first flights was that while the plane was controllable with the motor on, it went wild with the motor off. Both of the wing hold-down dowels were broken during this initial phase. Following Naton’s trim recommendations as much as I could, the plane now flies decently. Being a full-house, two-meter aircraft, it is a little heavy. It doesn’t soar as well as my RES Chrysalis.
Allan
04-11-2014, 07:34 AM
#12
Some learning:
I have a Supra Pro, 3.4M composite sailplane.
http://www.kennedycomposites.com/suprapro.htm
One of my friends converted a Supra Pro glider fuse to electric but later decided to move to a different sailpalne. He sold all his Supra stuff and I got the fuse with motor and all.
It is very nose heavy. I have 2 ounces of weight on the tail. Would like to get rid of that.
He only cut away as much nose as necessary to get the motor and gearbox in. Looking at how the plane balances it might have been batter to cut it a bit further back. I will probably fly it this way this season but I am already thinking I might pull the motor, cut off more of the nose and remount it to shift the CG and try to get some weight off the tail.
So, if you are doing a conversion think about the after conversion balance and determine where your stuff should be placed. If you pull 4 ounces of lead from the nose of your glider and are going to put in a 3 ounce motor, how will you make up for the loss of the ounce? Move stuff forward?
In my case it was a glider that had the 5 cell battery in the nose at about 5 ounces. and no lead. The battery came out and a motor went in that caused it to be nose heavy. Mounting the motor further back might have been a better plane.
So test balance your glider with parts taped on and see where you will put things to avoid weight gain as much as possible.
I have a Supra Pro, 3.4M composite sailplane.
http://www.kennedycomposites.com/suprapro.htm
One of my friends converted a Supra Pro glider fuse to electric but later decided to move to a different sailpalne. He sold all his Supra stuff and I got the fuse with motor and all.
It is very nose heavy. I have 2 ounces of weight on the tail. Would like to get rid of that.
He only cut away as much nose as necessary to get the motor and gearbox in. Looking at how the plane balances it might have been batter to cut it a bit further back. I will probably fly it this way this season but I am already thinking I might pull the motor, cut off more of the nose and remount it to shift the CG and try to get some weight off the tail.
So, if you are doing a conversion think about the after conversion balance and determine where your stuff should be placed. If you pull 4 ounces of lead from the nose of your glider and are going to put in a 3 ounce motor, how will you make up for the loss of the ounce? Move stuff forward?
In my case it was a glider that had the 5 cell battery in the nose at about 5 ounces. and no lead. The battery came out and a motor went in that caused it to be nose heavy. Mounting the motor further back might have been a better plane.
So test balance your glider with parts taped on and see where you will put things to avoid weight gain as much as possible.
