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Glider Conversion to "E"

Old 05-09-2010, 09:56 PM
  #1  
Terry.0132
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Default Glider Conversion to "E"

I got a second hand slighly abused motor glider at a good price. No name 3m two piece wing, FG fuze, RET control. Have done some basic repairs to the wings. Removed the pylon mounted engine and fuel tank and wanting to convert to electric. I did not want to remove the servo trays and create more work, but that would be the only way to get a battery in. I removed about 11oz of lead shot from the nose, thinking that I would be able to get the battery in there but not enough space, also just not enough space for the battery to fit under the servos at the moment. The all up weight with the fuel engine previously was 48oz.
I was wondering if I mounted a 450gm thrust edf ontop of the fuze instead of a motor and folding prop on a pylon whether I would be going in the right direction. Less weight than pylon, motor and prop, (can't be folding because of the pylon), less wind resistance and also only used to get up to thermal hunting height.
Any ideas on whether a edf setup would be advantageous in comparison to an e motor on a pylon.
Thanks
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Old 05-10-2010, 12:15 AM
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MaxAdventure
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I would guess that an EDF is going to create a lot more drag than a folded motor pod. Just look at that frontal area, and the fan stopped or freewheeling would probably not let air by like a regular prop, so that's all drag. Maybe you could mount the motor in front of the firewall, rather than behind to leave enough room for batteries? It's not as pretty on the ground, but at thermal height it looks fine. I have a BoT conversion this way because I couldn't fit my motor inside.
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Old 05-10-2010, 12:44 AM
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Sky Sharkster
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Default Powered By EDF?

Hi Terry,
I don't believe the pylon-mounted EDF will work. One reason is the drag, as Max mentioned.
Another is weight distribution. Ideally, the motor and battery just replace the ballast. But a wing-mounted pylon won't be far forward enough to do this. It may be slightly ahead of the C.G., not nearly as far forward as the ballast (or a nose-mounted motor) would be. While the battery is the greatest part of the weight, the motor, shroud and pod will be a substantial part, too.
Next we have thrust; 450 grams is 16 ounces, while the glider did (and likely will) weigh 48 ounces. One pound of thrust in a 3 pound glider won't get you where you want to go.
I've converted several thermal duration gliders to E-Power, and most required the servo placement be changed. It's not too difficult, usually I just moved them back by shortening the pushrods and moving the tray.
Then I had a larger space for the battery and the motor replaced the ballast.
In two cases the nose was too narrow to fit an outrunner. I used a geared inrunner for those models, with planetary gears.
Perhaps if you could post photos of the nose we can provide more help.
Ron
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Old 05-10-2010, 02:31 PM
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riverrat
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Default E-Conversion!

Subscribed!!

Can you post some pics??

Regards
Jimmy

Last edited by riverrat; 05-10-2010 at 02:34 PM. Reason: spelling
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Old 05-10-2010, 09:29 PM
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Terry.0132
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I meant to have pics ready but things got too busy today, I did not manage to get to the garage to put the glider together for a pic. I was not thinking of mounting the edf on the pylon but rather directly on the fuse where the pylon came out, but looking at Skysharkster's figures the edf I had in mind might not have enough power.
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Old 05-10-2010, 11:17 PM
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riverrat
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Default E-Conversion!

Originally Posted by Terry.0132 View Post
I meant to have pics ready but things got too busy today, I did not manage to get to the garage to put the glider together for a pic. I was not thinking of mounting the edf on the pylon but rather directly on the fuse where the pylon came out, but looking at Skysharkster's figures the edf I had in mind might not have enough power.
Mr. Terry

Ron sure has helped me alot, & I consider him a Master Builder!!! I am interested in your conversion, & I jump at any chance to learn something new!

There are some very good 28MM Dia. inrunners out there, anychance you could fit one of them in the fuse??

Regards
Jimmy
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Old 05-11-2010, 12:48 AM
  #7  
groundrushesup
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Originally Posted by Terry.0132 View Post
I meant to have pics ready but things got too busy today, I did not manage to get to the garage to put the glider together for a pic. I was not thinking of mounting the edf on the pylon but rather directly on the fuse where the pylon came out, but looking at Skysharkster's figures the edf I had in mind might not have enough power.

Not only would the thrust not be there, the EDF package itself would be VERY draggy - think about the blade configuration - there is no real space between the blades, so as it windmills with power off, it will effectively meet the wind like a flat plate.

Have you considered a folding pusher on a pylon setup? Works the same as the tractor - blades fold back in the airstream...

Something to think about.

GRU
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Old 05-11-2010, 09:42 PM
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Terry.0132
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I have got some pics ready, now let me see if I can bring them in.
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Old 05-11-2010, 09:55 PM
  #9  
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I was thinking on how to convert one of my 11" folding tractor props to a pusher, I've tried with a smaller prop on an electric wing but did not have much joy. Whilst I had the glider built up in the garage I weighed it again, with most of the ballast removed it actually weighs 53oz, so in reality AUW will be close to 4lbs needing about 240 to 280w to get a good climb rate. This is a longish term conversion, I have admired the skill and abilities of those who have converted BoT to electric but I do not have the fg skills and would be very afraid of cutting the nose to put in a firewall. But having had a close look I will have to see about repositioning the servos so that I can find a way of securing the battery under them, I will also closely measure the wings to work out the area to see what I have as basis for wing loading. Will still be working on this.
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Old 05-12-2010, 02:07 AM
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Sky Sharkster
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Default Nice Glider!

Hi Terry,
That's a good looking glider, hope you get it flying, whether powered or not!
The servos look like an easy fix. Just pull them out with all hardware, then chop out the tray. You might want to use a "Moto" tool (Dremel) to grind out any residue from the old tray, so as to not leave any sharp edges that might puncture the LiPo.
Then measure the space under the wing, I'd suggest all the way back in the opening. Make a new tray that's a snug fit there, cut out openings in the tray for the servos.
Epoxy 2 side rails (say, 1/8" square or 3/16" square balsa) along the fuselage insides, that the tray will sit on.
Shorten the pushrods, hook up the servos, mount the tray. Done!
I'm like you, no real F/G skills. But that glider should be easy. Figure out a typical spinner size for the intended motor. Let's say it's 40mm diameter.
Measure back on the nose until you get to the point where it's 40mm. The spinner is going to replace the nose.
Measure back from there the distance you need for the motor. Mark this location on the inside.
Make a firewall that fits into the marked location. Don't glue it in yet, but you can mount the motor to the firewall.
Ready? Take a sharp saw and a deep breath. Cut the nose off at the 40mm mark. I cut it a little "long" and hold the fuselage straight up to sand it flat, both vertically and horizontally. Slide the motor and mount into place. With a prop mounted it will be easy to see any thrust offsets. When all is straight, epoxy the mount in place. Mount spinner.
It sounds harder than it really is!
Ron
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Old 05-12-2010, 09:43 PM
  #11  
Terry.0132
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Thanks Ron,
I'll start by looking into possibilities of moving the servos back, one prob being the wing holding rods another being the distance back is limited by the size of my hands to get to the servo horns and adjustment.
I was originally going to go for bungee launch, but just in time a couple of the club members said the wing strengths between motor power and bungee launch are different and I might end up launching the fuse without wings.
Luckily winter has struck with a vengeance, so I can look carefully at my decisions, maybe even using slightly smaller servos mounted a bit higher so I can get the lipo underneath. To tell the truth I will be scared to cut for a front motor mount because I will be needing to get the motor out from time to time to replace the shaft.
Thanks again, will keep you posted,
Terry
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