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Apollo EP-5 ARF 72" Sailplane

TooJung2Die

Well-known member
#1
I picked it up at a flea market last summer. I normally wouldn't look twice at an ARF but it is all balsa and ply and too cheap to pass up. It has a 72" wingspan and a hefty AUW of about 3 pounds. I can't find anything about this Taiwan made airplane on the web. At all. I've looked and looked. It's an old electric judging by the motor that comes with the kit. I was able to identify the motor because they're still available. Suggested use is an electric drill motor. Hmm, that's an odd choice.

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Kit contents:
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DC brushed motor:
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Seems to be a heckuvalotta of motor for the 7" folding prop it came with. Motor weighs almost 1/2 a pound! At least it gives you a clue to what size brushless motor to use.
jon.
 
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TooJung2Die

Well-known member
#2
Let's get started.
First thing to do is fix the covering film. It sagged and some edges peeled up over the years as it sat in the box. It has an unusual PVC covering film. The manual warns in big bold letters, "Do not use a covering film iron for any reason on PVC covering film!" It says only use a heat gun. They're right about the heat gun when shrinking the open film areas. First the film sags and then it slowly tightens up. It gives off a smell I remember but can't quite place. I got one wing tightened up without burning the film.

Wing before:
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Wing after:
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The heat gun was no use where the film edges were peeling up or bubbled over sheeting. I had no other choice but to try the iron with a hot sock. With the iron set to medium heat I was able to stick down the loose edges. It worked to flatten out some bubbles on the wing sheeting and the fuselage. No damage done with the iron but it takes a while for the film to shrink after it goes through the sagging stage.

jon
 
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Joker 53150

Mmmmmmm, balsa.
Mentor
#3
AUW of 3 pounds? Sounds like it's made of lead! :) I wonder if you'll end up needing tail weight after replacing that big lump of motor. Maybe shifting the battery forward will compensate for the lighter weight components available today.
 

TooJung2Die

Well-known member
#4
The manual says AUW is 1350-1450 grams. Weight of the airplane parts without the motor, battery, electronics, etc: 2 lbs. I haven't even started looking at motors for it yet. Since it's a sailplane do you think I can use less than the 100 watt per pound rule of thumb? I'm baffled by the 7" propeller in the kit. It looks a lot like the one on my Sunbird and that weighs under 1 pound. Is that really enough prop?!

I'd like to use a motor that mounts behind the firewall like the chunky drill motor it came with. Suggestions and sources are welcome and encouraged. (y)
 

TooJung2Die

Well-known member
#5
So many motors to choose from! After searching a while my head is spinning. I never had an airplane this big and heavy so I have no experience. Most of my airplanes are well under a pound. I like the "Heads Up RC" site because they group motors by watts, airplane size or motor size designation. I'm almost ready to place an order for this motor. Leopard 2835/6T 1350KV Outrunner Brushless Motor

Leopard 2835-1350kv.jpg

Comments?
jon
 

rockyboy

Skill Collector
Mentor
#7
So many motors to choose from! After searching a while my head is spinning. I never had an airplane this big and heavy so I have no experience. Most of my airplanes are well under a pound. I like the "Heads Up RC" site because they group motors by watts, airplane size or motor size designation. I'm almost ready to place an order for this motor. Leopard 2835/6T 1350KV Outrunner Brushless Motor

View attachment 123790

Comments?
jon
I've got a Leopard motor from them on my Easy Stick 40 and love it - great motor without killing your wallet.

Looks like the size you've got there will be plenty for a 2 pound plane.
 

TooJung2Die

Well-known member
#8
Looks like the size you've got there will be plenty for a 2 pound plane.
I think you're right. That's the motor. I don't expect to achieve unlimited vertical flight. A healthy climb is the goal. The only parts I have on hand that can be used are the receiver and servos. Too bad Heads Up RC doesn't sell folding props. All my props fit 3mm motor shafts and the Leopard motor is 4mm. I won't know what size battery to buy until it is known much ballast is needed to make up for replacing the heavy motor and NiCd battery.
 
#11
I am fortunate to have this vendor in my town I order online skip the shipping by picking up on the way home. If I had not checked on the location of RMRC, I would not have know that they we available for local pick up. Fly On~!
 

TooJung2Die

Well-known member
#13
I have the Leopard motor and after thinking about different solutions I've come to the conclusion it is not a suitable motor for mounting behind a firewall. The shaft is too short. Instead of buying another motor I'm going to see if I can buy a longer 4mm motor shaft. There seems to be a selection of shafts for other motors that are long enough. I'm hoping that all 4mm shafts are the same diameter. Fingers crossed. :unsure:
 

Joker 53150

Mmmmmmm, balsa.
Mentor
#14
I've had a few different motors over the years which had reversible shafts. I could press the shaft out, flip it 180*, and press it back in. That allowed me to mount it in front or behind the firewall as needed. No idea if your motor would work that way...
 

TooJung2Die

Well-known member
#15
The motor comes set up for mounting behind the firewall or in front. (see photo post #5) The shaft is just long enough to mount a collet type prop mount. Subtract the thickness of the firewall and motor mount and you run out of shaft for the prop to hold on to. The shaft can be reversed but that won't make it longer.
 

rockyboy

Skill Collector
Mentor
#16
Another option (probably not a better one, but just spit-balling here) would be to replace the existing firewall with a thinner one.
 

TooJung2Die

Well-known member
#17
I was going to replace the existing 5mm thick firewall with 3mm ply. Even then, there's only about 5mm of shaft protruding. That doesn't look like enough to securely hold a 45mm spinner with 9" blades. I'm going to replace the 45mm motor shaft with a 60mm shaft. That will be enough length.
 

TooJung2Die

Well-known member
#18
The longer motor shaft is perfect. Longer than needed. No need to cut it, just loosen the setscrew and slide it in to the correct length.

Original motor shaft.

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New shaft fully extended. The length will be adjusted with the spinner in place.

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Motor with new shaft.

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The 40A ESC arrived so that should be everything to finish this. I'm finding it hard to get excited about assembling this airplane. Probably because I didn't build it. There's plenty of winter left and it'll be ready for spring.

jon
 
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TooJung2Die

Well-known member
#19
It's been hard to get real motivated to complete the Apollo. Some antique clocks and vintage air rifles came in the workshop and helped to distract. Now the weather is better and flying season is here again. Time to dust it off and "getter dun".

Modified a 'X' motor mount to support the motor. The screw holes were too close to the existing motor shaft hole to secure the screw heads in the firewall.

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Backside view of the motor.

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Front view with the prop spinner.

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Ailerons installed and wing halves glued together. It has been a very long time since I had an airplane wing this long.

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jon
 

TooJung2Die

Well-known member
#20
This is the photo from the Apollo manual showing the suggested aileron servo. Is this size servo still in common use? It looks big. I made a new servo tray to fit two metal geared servos of the size I often use. With two servos you can mix in spoilers and some camber.

apollo servo.JPG

I didn't use the servo tray from the kit. I wanted to just cut a hole in the bottom of the wing and attach the servos but there wasn't enough depth in the wing center so a tray had to be made.

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There is barely enough room for the servo arms to fit inside the fuselage. I may trim the tips of the arms.

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jon