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Oct 21, 2018, 08:03 AM
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Build Log

Time To Electrify My Oly III


I spent a lot of time building my Skybench Oly III. It has yet to get a real flight after it's initial short maiden 8 yrs ago! It's sad I know and a bit embarrassing. We lost our field and life got in the way. I flew other planes (mostly the Radian) and it's just been ignored. I always thought that I should have just done this from the git go. At the time we winched everything except the Radian and there was no reason to build an electric.

Now life's changed and calmed down quite a bit for the most part. I've found a new club to fly at. The winch & retriever sit due to the effort it takes to drag them out with my health issues. A good share of my fleet has been switched over or at least have "E" fuses as well as non-"E" fuses. I'm back and enjoying the hobby again. So I decided it was time to finally give the Oly the attention it deserves.

What I started with. Skybench Oly III stretched to 140", 2-S-3003 servos and balanced for 2-2700 nimh batteries. I was planning on using it for XC tasks in the SSP and didn't want to worry about battery power. It came in at 66.4 oz RTF.

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Mentally, the hardest part was chopping off the nose.

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Then I ran a band saw down the sides of the fuse all the way back to the former at the rear of the canopy. The piece of scrap former is to spread it out to make it easier to see what I did. The blue canopy is under it to highlight the cuts.

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Most of the taper from side to side will be eliminated to allow for the motor. The bottom plate will be curved up a bit and the canopy redone to make a smoother transition to the new nose shape. Now that I know what size spinner I need, the spinner is ordered and work will continue shortly when it arrives.

I received the motor a few days ago. It's getting a Turnigy L3010B 1300 kv 420 watt dropped in it. I will be running it on 3S 1300 lipo with a 60 amp Plush ESC. I'm not going for a rocket ship just a winch in the nose.

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The goal will be to keep weight gain to a minimum. To do this I will be using smaller servos, lighter RX and not planning for a huge battery. I just bought a Taranis so I have telemetry so I'll always know what I have left for power. No longer need to plan in overkill to make sure I have enough power. I will be trading out the Fut RX for a smaller FrSky one but will be adding a lipo sensor and vario. The nose will be a bit shorter as well to allow for the motor's weight. Until I get all of parts in I won't know what is possible. I'll mock it all up and go from there.

Part of the gear change. Top to bottom: old RX, new RX, lipo sensor. Sorry, I don't have a vario handy to add to the pic.

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Current gear:

S-3003 (x2) 74.2 g
2700 nimh (x2) 252 g
Fut R617FS 9.92 g
chopped off nose 46 g
total 382.12

New gear:

HS-85 MG (x2) 43.8 g
3S 1300 45-90 C 119 g
Rx6r rx 2.92 g
mini lipo sensor 3.1 g
high precision vario 3.1 g
motor 108 g
ESC 60 g
total 339.92

So I'm close. Of course I have to put in new formers, servo rails and a prop. However, rough calculations put me in the ball park.

Stay tuned for more.
Last edited by Steve Boone; Jan 02, 2019 at 10:44 AM.
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Oct 21, 2018, 06:38 PM
Registered User
I put a 2836 930 kv motor in my Oly II and it’s amazing. Again don’t need a rocket either and 200’ is plenty for this with the light 1300 mah lipo for mine.
Oct 22, 2018, 06:32 AM
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At 4.15 lbs (weight before mod) it gives me 101.2 watts/lb. More than enough for what I want. I'm trying to keep it between 90 - 100 watts/lb. At the same time, I'm trying to not gain any weight making it electric.
Oct 28, 2018, 05:45 AM
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My spinner came in yesterday. Now I can get back to this project. More to come.
Oct 29, 2018, 12:22 PM
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Cut the bottom out as it will need to be wider.
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Motor, mount & new former.
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Initial mock up of motor, mount & bulk head. There will be hardwood blocks in the corners to add strength and support to this. 5 degrees of down and 3 of right.
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The front of the fuse will be re-shaped to blend in with the spinner. This will include bringing the top and bottom towards the center line.
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Next will be a full mock up to see if the balance is close. This will tell me if I need it to be shorter or longer before I go on. If it's close, the next step will be to decide on the new shape and do some more cutting. Slow and easy is the plan.
Oct 30, 2018, 08:12 AM
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I found a couple Airtronics 94761Z servos in my standard Ava fuse. For a small 1.1 g per servo weight penalty, I can gain 13.4 oz-in torque. Well worth the trade off for a higher quality servo. So they were pulled and added to the build pile.

Specifications:
Modulation: Digital
Torque: 4.8V: 55.00 oz-in (3.96 kg-cm)
6.0V: 66.00 oz-in (4.75 kg-cm)
Speed: 4.8V: 0.15 sec/60
6.0V: 0.12 sec/60
Weight: 0.81 oz (23.0 g)
Dimensions: Length:1.06 in (26.9 mm)
Width:0.47 in (11.9 mm)
Height:1.18 in (30.0 mm)
Motor Type: 3-pole
Gear Type: Metal
Rotation/Support: Dual Bearings
Oct 31, 2018, 05:38 AM
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First mock up showed that I'm tail heavy. My CG is about 1" back from where it should be. I'll be mocking it up again today with the motor mount all the way to the front of the fuse cut off. I'll just build a new nose around the motor. This will also allow me to bring the battery further forward. It will also get me closer to the original length of the fuse.
Oct 31, 2018, 11:27 AM
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The second mock up went a lot better. The original lines on the side view are now close to the original. The top view is almost straight instead of tapered until the last bit by the motor but I'm good with that. It now balances about 1/2" behind the CG. That should be good as I still have to ad back some wood. If it's off hopefully it will be nose heavy. That way I can simply move the battery back to get the CG right. I don't want to add lead to the nose as that will add to the overall weight.

I just tacked the motor mount former in place with CA to be able to mount the motor temporarily. It will need to be raised.

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The new gear layout is so close I might actually be able to mount the servos in the same place as they were originally. The Taranis RX is so tiny that finding a place for it or it's weight isn't even an issue.

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First I traced the fuse on the bench using tape at the front so if I needed to start over it would be easy to peel off and try again. Then I raised the motor position to the top of the old fuse line. Next I placed a couple of servo screws in the bench to hold a wire push rod in the starting position. This allowed me to bend it up to the bottom of the spinner to get a nice curved line for the new shape of the fuse.

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Oct 31, 2018, 02:44 PM
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Using the tape from the bench, I transferred the new shape to the fuse.

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I put the temporary motor mount former in as a spacer for sanding.
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Then it was time for a trip to the disc sander for some shaping. Here's the new profile. Not too bad.
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An end view shows the new width compared to the old.
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This shows where I'll be adding some balsa to the canopy and then re-shaping it to fit the new contour.
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So far so good. Now it's time to start putting it all back together. Starting with the bottom plate.
Nov 07, 2018, 05:21 PM
AMA 179-CD
Nice work on E-powering the Oly 3, I've enjoyed mine and have done well in the "woody" classes.
Nov 07, 2018, 06:17 PM
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Thanks. I need to get back on it and finish it up. I've had to take a short break. I'm hoping to get the bottom on tomorrow.
Nov 08, 2018, 01:56 PM
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We were having a bit of decent weather. That means leaves this time of year for us. The good weather left us again. So time to get back to building.

I epoxied the floor back in today. Not much I can do until it cures. I left my temp motor mount in to keep things in place. Then clamped it. You can never have too many clamps.

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Nov 09, 2018, 06:27 AM
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Last night after the epoxy dried I rough sanded the fuse bottom to shape.
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The temp motor mount was then laminated to a 1/4" piece of ply. I wanted a robust motor mount. It will get shaped out today.
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Nov 09, 2018, 07:24 AM
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Following with interest Steve. A friend gave me an old OlyII that I plan to electrify one day, so this will be my inspiration. I just finished electrifying a 132 Yardbird with about 350 watts, and it climbs very nicely.


FWIW, I never put right or down thrust in my e-gliders. I want the thing to stand on end and go straight up under power. If anything, I might program down elevator during full power, but most of the time I just fly it up to the intended launch height.

If you plan to fly it around like a regular plane then the down/right makes a world of difference obviously.
Last edited by dion9146; Nov 09, 2018 at 07:53 AM.
Nov 09, 2018, 02:56 PM
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The motors in my gliders are simply a winch in the nose.


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