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Old Jul 27, 2015, 02:41 PM
mike912e is offline
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Help!
Spirit Elite electric conversion .

Having a hard time justifying the expense of a $1500 plus electric sailplane ( mostly because I'm on a fixed income ! ) . I have an unbuilt Great Planes Spirit Elite kit and wanted to know if anyone has converted one to electric power . If so, what mods have to be done to the nose section to install the motor, what motor would be recommended ? I have over fifty years of building and flying so there's no challenge too big . Any and all help would be appreciated .
Mike
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Old Jul 27, 2015, 03:33 PM
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Hi, Mike.

I'm on a fixed income myself and have always been cheap so I can say "HobbyKing is your friend". I can't help you on specific mods to a Spirit Elite but can make some educated guesses about electronics.

Motor: KDA 22-20L. I have three of these 28mm, 85gram, motors and love them to death. They are currently on sale for less than $10.00 a piece. HK has a typo in their performance chart and I having been pushing over 25 amps and 250 watts, with an 11X6 folding prop, for 3 and a half years. I would recommend them for any glider up to around 40 ounces. 48 ounces if you don't need above average climbing performance.

http://www.hobbyking.com/hobbyking/s...er_1000KV.html

ESC: I have been using HK Blue Series 30 amp speed controllers without complaint. dang! They are currently out of stock at the international warehouse but are available from the U.S.

http://www.hobbyking.com/hobbyking/s...arehouse_.html

Servos: For a plastic gear, 9 gram, servo it's very hard to beat the HXT900 at $3.00 a piece. If you want a faster servo with metal gears? The TGY 50090 is the only micro I have found with all metal gears.

http://www.hobbyking.com/hobbyking/s...log_Servo.html

I have had good luck with Rhino batteries and less good luck with some of the other brands at HK. I also like their covering material. At $8.00 to $10.00 for a 15 foot roll it works very well indeed. I would say that it falls somewhere in between Monokote and Solarfilm or Econokote on the "stick vs. shrink" scale. One needs a fair amount of overlap to hold but it shrinks really well.

One thing I no longer buy from HK is plastic props. I had a 11X6 plastic prop break at full throttle, on the very first flight, and discovered that there were bubbles and voids in the plastic that did not show on the surface. I chucked all my plastic props after that experience. I have a 11X6 CF prop that seems to be of good quality but for new props I stick with Aeronaut blades from Esprit Models. I have also had good luck with spinners from HK but it can be a challenge to figure out which one will work with a given set of blades and shaft diameter.

The best thing, IMO, about HK is that they do leave some bad reviews on the site. I feel pretty safe ordering something that has a number of good reviews and avoid stuff with bad reviews or no reviews at all.

The Spirit Elite shoould be a very good general purpose electric sailplane but, if you decide you want something better suited for a particular niche? There are some very good kits still available. The DJ Aerotech Chrysalis E springs to mind. Skybench and Mountain Models also have some great kits. It's rather difficult to save a whole bunch of money building a kit compared to some of the wood/glass composite ARFs available but one can save big in certain niches and one has the added security of knowing that the parts are actually well fastened rather than just having some CA squirted in their general direction!

Cheers!
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Old Jul 27, 2015, 04:01 PM
mike912e is offline
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Quote:
Originally Posted by peterlngh View Post
Hi, Mike.

I'm on a fixed income myself and have always been cheap so I can say "HobbyKing is your friend". I can't help you on specific mods to a Spirit Elite but can make some educated guesses about electronics.

Motor: KDA 22-20L. I have three of these 28mm, 85gram, motors and love them to death. They are currently on sale for less than $10.00 a piece. HK has a typo in their performance chart and I having been pushing over 25 amps and 250 watts, with an 11X6 folding prop, for 3 and a half years. I would recommend them for any glider up to around 40 ounces. 48 ounces if you don't need above average climbing performance.

http://www.hobbyking.com/hobbyking/s...er_1000KV.html

ESC: I have been using HK Blue Series 30 amp speed controllers without complaint. dang! They are currently out of stock at the international warehouse but are available from the U.S.

http://www.hobbyking.com/hobbyking/s...arehouse_.html

Servos: For a plastic gear, 9 gram, servo it's very hard to beat the HXT900 at $3.00 a piece. If you want a faster servo with metal gears? The TGY 50090 is the only micro I have found with all metal gears.

http://www.hobbyking.com/hobbyking/s...log_Servo.html

I have had good luck with Rhino batteries and less good luck with some of the other brands at HK. I also like their covering material. At $8.00 to $10.00 for a 15 foot roll it works very well indeed. I would say that it falls somewhere in between Monokote and Solarfilm or Econokote on the "stick vs. shrink" scale. One needs a fair amount of overlap to hold but it shrinks really well.

One thing I no longer buy from HK is plastic props. I had a 11X6 plastic prop break at full throttle, on the very first flight, and discovered that there were bubbles and voids in the plastic that did not show on the surface. I chucked all my plastic props after that experience. I have a 11X6 CF prop that seems to be of good quality but for new props I stick with Aeronaut blades from Esprit Models. I have also had good luck with spinners from HK but it can be a challenge to figure out which one will work with a given set of blades and shaft diameter.

The best thing, IMO, about HK is that they do leave some bad reviews on the site. I feel pretty safe ordering something that has a number of good reviews and avoid stuff with bad reviews or no reviews at all.

The Spirit Elite shoould be a very good general purpose electric sailplane but, if you decide you want something better suited for a particular niche? There are some very good kits still available. The DJ Aerotech Chrysalis E springs to mind. Skybench and Mountain Models also have some great kits. It's rather difficult to save a whole bunch of money building a kit compared to some of the wood/glass composite ARFs available but one can save big in certain niches and one has the added security of knowing that the parts are actually well fastened rather than just having some CA squirted in their general direction!

Cheers!
Great info ! Thank you . I'm perusing the Sprit Model website and see that they offer some models without covering . I have found over the years that yellow is the best color for me to see when a model is in the air . Any feedback on their models ?
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Old Jul 27, 2015, 05:06 PM
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Originally Posted by mike912e View Post
Great info ! Thank you . I'm perusing the Sprit Model website and see that they offer some models without covering . I have found over the years that yellow is the best color for me to see when a model is in the air . Any feedback on their models ?
Their models, especially the ones built by TopModel cz., have sterling reputations. The Avia/Prelude has a large and enthusiastic following and the Pegasus sounds pretty hard to beat for a 2 meter pure floater. There are a couple other U.S. vendors with offerings from the same line, some as special orders only. Esprit seems to only offer the ARC options at erratic intervals.

I have been tempted to order a Astra V, ARC, direct from Topmodel but I keep having this nightmare of my precious new plane sitting at the bottom of a shipping container full of bowling balls! However, depending on the daily exchange rate, one could get a ARC at a price where the shipping cost would be offset and I really like the idea of being able to get at the wing structure and choose my own color scheme.

http://www.topmodelcz.cz/index.php?&...nu_eshop_id=12

I am a big fan of transparent wings, fluorescent accents, and asymmetrical color schemes. I vacillate between transparent yellow and red for maximum visibility under the widest set of conditions. I was able to combine the whole works on my Specter, which came with the yellow wings already covered, and it shows up as well as any sailplane I have owned.

Speaking of the Specter. It is on sale from HK for $52.00 through Thursday. There were some small building issues, sticky pushrods and a lack of room to mount servos in the installed tray, and a couple of guys received fuselages that needed to be untwisted with a heat gun, but it's one heck of a deal if you are looking for something that can be flying within a day or three of opening the box.

http://www.hobbyking.com/hobbyking/s...Search=specter

I began a very long thread about my Specter and many others have chimed in with their experiences. If you have any questions about it feel free to ask me on either thread.

http://www.rcgroups.com/forums/showthread.php?t=1688351

Cheers!
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Old Jul 29, 2015, 06:54 PM
Ricardo RW is offline
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Does your Spirit Elite have the wood fuse or the fiberglass fuse?

If is it a kit, try to build her light, replace some wood with Carbon Fiber, especially the spar.

Also I suggest you to redesign the fin-rudder, just make it with a high aspect ratio, it has less drag.
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Old Jul 29, 2015, 07:36 PM
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Originally Posted by Ricardo RW View Post
Does your Spirit Elite have the wood fuse or the fiberglass fuse?

If is it a kit, try to build her light, replace some wood with Carbon Fiber, especially the spar.

Also I suggest you to redesign the fin-rudder, just make it with a high aspect ratio, it has less drag.
Thank you Ricardo . At this point I'm still deciding to build the all wood kit or sell it to fund one that has all the necessary features built into it already .
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Old Jul 29, 2015, 11:26 PM
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Be careful about substituting carbon for wood. The carbon has a better strength to weight ratio, and yes, properly done it can be lighter than an equivalently strong and stiff balsa structure.

However, per cubic inch the carbon is much heavier than balsa. You can't just substitute a piece of 1/4" square carbon for a piece of 1/4" balsa! You have to go back through the stress analysis, including things like buckling failures when under compression loads, and figure out a new structure with the minimum amount of carbon needed to equal the strength and stiffness of balsa.

There's also the problem of carbon's extremely high stiffness. If you mix it with other materials (such as using a strip of carbon to reinforce a balsa structure), the carbon will try to carry all the load all by itself and make the rest of the structure just come along for the ride. It's like the grandstanding basketball player who hogs the ball to themself and won't share it with the other team members. Worse yet, that very high stiffness tends to cause stress concentrations that can actually weaken the structure instead of making it stronger.

There's a derogatory term in the Aerospace industry called "black aluminum". It means taking a conventional aluminum structure and just replacing all the metal parts with carbon ones the same size and shape. The result tends to be way overcost and overweight. The way carbon likes to carry loads is different than other materials, and to get the full advantage of it usually requires a "clean sheet of paper" design.
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Last edited by Don Stackhouse; Jul 29, 2015 at 11:31 PM.
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