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Great Planes Spectra questions

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Great Planes Spectra questions

Old 04-21-2009, 10:27 AM
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Default Great Planes Spectra questions

I recently acquired a Great Planes Spectra RTF, and I have a couple of questions. I would like to eliminate the 12oz NiCd brick and go with a 2s LiPo. This will shave about 8oz from the AUW(50 oz) of the plane. I plan on using the stock T600 brushed motor, and I will go brushless when it dies.

Will the plane still perform well in 10 to 15 mph winds at this reduced (42 oz) weight? I don't want to limit my flying conditions to little or no wind days.

Will the stock ESC work with the 2s LiPo battery? The speed controller did not come with any instructions or specs as to the type of batteries it supports.
Old 04-21-2009, 10:52 AM
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Default RE: Great Planes Spectra questions

I've also got a Spectra but it's one of the older ones that just used a servo controlled switch for the motor. The place you need to be asking your question is on the electric sailplane forum on R/C groups. The guys there can help you out and most of them know their stuff.

For what it's worth, I'd be worried about the ESC if it's not rated for a brushed motor and or Lipos. You stand a good chance of frying it if it's not. If there are any markings as to the maker of the ESC on the controller, go to their website and see what you can find out for information on it.

As to your weight question, you can always add a little ballast if the wind is blowing and the plane is hard to control. So lighten it up but make sure you can add ballast weight back into it securely on the CG and you'll be fine in that respect.
Old 04-21-2009, 11:10 AM
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Default RE: Great Planes Spectra questions

Your only issue with using the original brushed controller will be low voltage cut off for the lipo. keeping track of the amount of time you run the motor will help, though not easy to do unless your radio allows a timer to be controlled by the throttle stick.
The lipo weight loss should not be a problem in those wind levels
Good luck, the Spectra is a very fine handling plane, the ARF as you have is a bit improved over the BIY kit, the length of the nose is about 1 inch greater on the ARF/RTF. One caution on the Spectra ARF, the inboard wing spars are balsa, not basswood as on the kit, so watch out for over stressing the wing, getting rid of the Nicads is a good thing
Pete
Old 04-21-2009, 12:08 PM
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Default RE: Great Planes Spectra questions


ORIGINAL: scaflock

I've also got a Spectra but it's one of the older ones that just used a servo controlled switch for the motor. The place you need to be asking your question is on the electric sailplane forum on R/C groups. The guys there can help you out and most of them know their stuff.

For what it's worth, I'd be worried about the ESC if it's not rated for a brushed motor and or Lipos. You stand a good chance of frying it if it's not. If there are any markings as to the maker of the ESC on the controller, go to their website and see what you can find out for information on it.
Thanks Scaflock. I will check out the other forum. The ESC is for the stock brushed T600 motor. It does not have any markings on it. Maybe Great Planes will have some info.

ORIGINAL: pilotpete2

One caution on the Spectra ARF, the inboard wing spars are balsa, not basswood as on the kit, so watch out for over stressing the wing, getting rid of the Nicads is a good thing
Thanks Pete for the info about the spars. I don't know if it will help with the strength but I did epoxy the wing halves to together.
Old 04-21-2009, 03:28 PM
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Default RE: Great Planes Spectra questions

I have made the change out to brusless and lipo battery in my plane, it works just fine. Just so you don't have problems get a esc that is for lipo batterys. The best buy for the stuff to do the change over is Value Hobby or Hobby city in China. Be sure and get a speed control that has a brake that can be set Best of flying to you Old Sky Sailer
Old 04-22-2009, 11:04 AM
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Default RE: Great Planes Spectra questions


ORIGINAL: Old Sky Sailer

I have made the change out to brusless and lipo battery in my plane, it works just fine. Just so you don't have problems get a esc that is for lipo batterys. The best buy for the stuff to do the change over is Value Hobby or Hobby city in China. Be sure and get a speed control that has a brake that can be set Best of flying to you Old Sky Sailer
What motor did you use? Are you using a 2s or 3s LiPo?
Old 04-24-2009, 04:03 PM
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Default RE: Great Planes Spectra questions

I just purchased a brushless motor for the Spectra. I'm guessing it should have a pretty good climb rate. The motor is rated at 350w 1100kV and it will be spinning an 11X8 folder. Battery is a 3s 2100mAh LiPo and a 40 amp ESC. I also got rd of the AM radio and will be using Spektrum 2.4ghz. I'm guessing this should shave close to 16 oz off the AUW of the plane. Hopefully I can maiden it Sunday if the weather cooperates.
Old 04-25-2009, 01:53 AM
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Default RE: Great Planes Spectra questions

never got mine in the air and still have the red nicad , can you tell me what motor and speed controler lipo , can i use the old folding prop?? to get at hobby city thanks frank
Old 04-26-2009, 10:16 PM
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Default RE: Great Planes Spectra questions


ORIGINAL: frank99

never got mine in the air and still have the red nicad , can you tell me what motor and speed controler lipo , can i use the old folding prop?? to get at hobby city thanks frank
Frank,

The motor I am using is an A2814-8 1100 kV, 350 watt. I don't know who makes it as it was packaged by my LHS. I imagine it is on of the china made motors because it was about half the cost of a name brand motor. I am using an Acer 40amp ESC that came from an electric heli that I moth-balled two years ago. The battery is a DN 3s 2150 mAh 25C LiPo. I used the stock prop hub and spinner on my setup but went with the Cam 11X8 folding prop.

I maidened the plane today and it was awesome. The wind was blowing around 15 with gusts to 20. I was a little concerned because of the drastic weight reduction that the plane might not handle the breezy conditions but it did great. The brushless motor will pull this plane to a spec in less than a minute at full throttle. Very impressive! I was able to fly for well over 30 minutes and the battery still had plenty of juice to go longer.
Old 04-27-2009, 08:15 AM
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Default RE: Great Planes Spectra questions

i have a top flight glider like the spectra and 60 sec run time and down to earth . never got any thermals, gave up on the spectra and gliders for a while, high start was so so too. going to get something like your specs and get it in the air, should i add a small nicad for the servos and stay in the air longer if i get lucky and find a thermal thanks frank
Old 04-27-2009, 02:10 PM
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Default RE: Great Planes Spectra questions


ORIGINAL: frank99

i have a top flight glider like the spectra and 60 sec run time and down to earth . never got any thermals, gave up on the spectra and gliders for a while, high start was so so too. going to get something like your specs and get it in the air, should i add a small nicad for the servos and stay in the air longer if i get lucky and find a thermal thanks frank
Frank,

You could probably set up the sailplane with a dedicated battery for the receiver and servos, but I believe most people(myself included) are using the LiPo as a single power source for both radio equipment and motor. If you go with a brushless motor, most brushless ESCs have a BEC (battery elimination circuit) which eliminates the need for a separate power source for the receiver and servos. This setup also eliminates the additional weight of the receiver battery.

I'm not familiar with the Top Flight glider, but the Spectra requires some modification of the firewall to get the brushless motor installed. The main thing to keep in mind is the brushless outrunner diameter will need to be small enough to fit in the fuse and still spin freely.
Old 04-28-2009, 01:15 AM
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Default RE: Great Planes Spectra questions

got it, pics to come today . will show the new motor old frame equipment servos hope it will work thanks frank

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