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Oct 20, 2006, 08:31 PM
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Build Log

Altec/Lion Models Sky Dancer .25


This thread is something that I have wanted to do for a long time.

I grew up flying hand-me-down RC models in the 70ís. Being just a young lad I had no ability or knowledge to build the complex sport planes I would see at the field with my Father. Kaos, Kougars, Kobras, Contenders Birdis, you name it!

As I got older I graduated to an old P-51 my Popís buddy gave up. The model was so glow soaked in the nose it needed a ton of weight to get it to balance. All the model did was make me crave a sleek looking Sport Flyer even more.

My Dad built his Last RC model for me. It was a pretty hot little Sig Kobra. At last I would have my sport model. As luck would have it before I could get to fly it the model was trashed. My Pops moved on to model trains and I to Hot Rods.

Well itís almost 30 years later but Popís I got my Sport Plane! My Dads gone but I bet he would hold up his nose to this one, as itís an AFR. Pops spent WWII in China and might find it funny thatís where most of my models come from now.

Sky Dancer .20

The instructions are marked Altech <MRC?> and the wing Sport Flyers. If anyone knows for sure the history of this kit feel free to chime in. I found it on The-Bay for under thirty dollars. The price tag on the kit is for over 100$.

Wing Span 49Ē
Length 36Ē
Wing Area 433Ēs
Weight 3.52lbs
Engine 28 <2c>


The weight of the components are as follows

Left Wing Pannel 6.5 ounces
Right Wing Pannel 6.5 ounces
Fuselage 8.0 ounces
Rudder .8 ounces
Elevator 2.1 ounces
Canopy .5 ounces
Wheels/Piano Wire 3.3 ounces
Hardware Bags 2 Ounces Kit Weight 29.7 ounces!

My overall impression is wow; this thing is built like a balsa outhouse! I could surely remove a lot of weight behind the wing on the fuse with some holes. That could play a roll in the event the model is tail heavy. I will have 10 ounces of battery in this plane though!

Itís perhaps the WORST covered ARF I have ever seen! Now granted the covering just might be 20 years old <and very saggy> but it appears more like plastic then traditional heat shrink film.

Ill have to remove the glow rails and a fellow RCGroups friend will help me out with some standoffs for the Outrunner.

My Gear Choices

Motor Chinese 2915-5D 6.1 ounces <with hardware>
ESC CC-45 1 Ounce
2 TP 2100 3s PL 10 Ounces
3 HS-81 MG Servos .7 each <2.1> ounces
Dx6 RX .2 ounces

Power train weight of 19.4 ounces

Power Train Plus model weight is 49.1 ounces. Just around 3lbs.

If the AUW ďcouldĒ be achieved 49.1 ounces that gives a wing loading of 16.3 ounces. Thatís pretty darn light in my book!

Iím always open to suggestions and hope some people will chime in as I assemble this model.

Ill shoot some photos of the model tonight as my back allows, seems I strained it at work Thursday.

Wish me luck!

Tommy D
Last edited by Tommy D; Aug 12, 2007 at 04:43 PM.
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Oct 20, 2006, 09:09 PM
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A few photos of the plane


Here is a shot of the model in the box. Yes it was still sealed in the plastic!
Oct 20, 2006, 09:11 PM
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A shot of the Sky Dancers fuse alongside my .25 Ultra Stick.

About the same size.
Oct 20, 2006, 09:14 PM
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A quick shot of the motor rails. They are very beefy. Ill have to make sure the firewall I'm going to mount to is strong as well.
Oct 20, 2006, 09:18 PM
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Last one for the night. The .25 Stick has a nice rate of roll <for me>. I suspect the roll rate to be slower on the Sky Dancer with the more narrow ailerons. Thats said I have seen similar sized ailerons on Super Sport's and they roll just fine.

Ill just hope for the best.

Tommy D
Oct 21, 2006, 11:40 AM
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Did a little more work on the Model today.

Itís difficult to do anything right now with the way my back feels. That said my already slow process of building will be even slower.

I was able to shrink the covering to some degree. Unlike most covering I have used this stuff seemed to implode more then shrink! It has wrinkles in some odd places as it stuck to itself while shrinking. In all honesty its still covered better then I could do in my current working conditions. What I would give for a talented neighbor who loved to cover planes!

The color still has not grown on me. Perhaps if I were to be wearing a plaid leisure suit while building it might help.

I removed and replaced the factory aileron hinges. They were so stiff there was no way in hell a mini servo would have worked. The new DuBro pinned ones allow them to move like butter. I think a Hitec MG-81 ďmightĒ work but as a measure of safety the HS 2255BB will most likely be used. Thatís another .3 ounces added!

The motor choice is up in the air now. Guess Iím getting cold feet on this Chinese Out Runner. As Iím lazy it also looks like it would be easier to use a Mega 22 20 4 I have here with a clamshell style mount. Easier meaning less trimming of the factory mount. Ill include photos of the motors/rails/mounts ect.

Thatís it for now. Time for a hot soak in the tub.

Tommy D
Last edited by Tommy D; Oct 21, 2006 at 11:52 AM.
Oct 21, 2006, 12:04 PM
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BalsaPr predicts the 2915-D to make 460W for a cost of 40A. I do not know if the motor was tested with a power supply and experienced no voltage drop.

The Great Motor Test predicts the Mega 22 20 4

9 x 7.5E on 10 Cells costs 43A 437W
Oct 21, 2006, 12:24 PM
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These last photos will show how much room I have for a pair of 2100 3S Pro Lite packs.

The wing will be held on by rubber bands <boing!> so I'm not so sure about cutting a hatch. I do know a spoon scoop will be added to help get some air in.

An appropriate sized hole will also be added as an exit.

There is something to be said for larger models!

Tommy D
Oct 23, 2006, 09:59 PM
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Some Old School Help is in order


Ok so with 100 or so views someone is reading this besides me. I need some help here guys.

I mocked up the Mega Motor tonight. Taking the lazy way out I removed enough material in-between the motor rails to let the Mega fit. Then using a simple clamshell mount I mounted directly to these glow mount rails.

A few questions for the experts. You can use the supplied photos to help answer some of my questions.

Does the centerline of the motor shaft look like itís in about the right spot? On a glow .25 for example where is the shaft vs. the mounting rails on the motor?

I followed the rails and have what looks like an excessive right thrust. I have tried to calculate it as follows.

Measuring from the tail to the left 8Ē propeller tip I have 35 Ĺ inches. Rotating the prop 180 degrees and measuring it on the right side shows 35 ľĒs. Ok so just how much side thrust is that? Ideas anyone?

You will notice the motor is mounted about as far forward as I dare. This is all in an effort to get the model to balance without lightening the tail.

Ok guys what do you think?

Thanks!!

Tommy D
Last edited by Tommy D; Oct 23, 2006 at 10:05 PM.
Oct 23, 2006, 11:56 PM
Speed Demon
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The Mega installation looks just right. I'd stick with the stock side thrust as they frequently need it. Your thrust line center is probably within 1/4" of where the stock glow engine would be so that should work as well.

I ran up your Mega combo on M'Calc and it says you should have a great combo here. I believe the higher weight of the Mega will also help you put the CG where it needs to be as a .28 glow engine would be more than that. All indications are that'll be successful. All you have to do now is finish putting it all together, fly, and have fun! Hope that this helps.
Oct 24, 2006, 08:08 AM
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Yes Greg, it helps a lot!

I know you have done this before so having an experts advice means a lot to me.

Thinking of useing the Dewalt power cells on this one. A 4S pack looks like it would weigh about 1 ounce more then the twin 2100 PL packs. I'm to understand those cells would be happy delivering the 45A or so I think this model is going to draw. While it would be a weight gain, its a gain in the right spot!

I don't know about some, but I wish someone made a lazer cut model that looked like this in this size. Guess I'm stuck on these old school trikes!

Tommy D
Oct 24, 2006, 03:48 PM
Marc Venis
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I too have a skydancer 0.20L.
I bought it at the Toledo show in 1995 for $83.
I never got around to building it, but last year I bought a AXI 2820/10 for it.
(I just copied what hobby lobby suggests for Bonnie, I didn't do any calculations).
I'll watch this thread as my winter project is to finish this plane for flying in the spring of 2007.
My ultimate goal is to add floats to it for lake flying.
Oct 24, 2006, 10:17 PM
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Welcome to RCGroups Marc


Hi Marc

When I started this thread I thought I might have a few ďI had one of those commentsĒ. I did not expect anyone to tell me they still have one NIB! Do you recall whom you bought the model from? I ask as Iím trying to research the models history.

Well if I plant this model on the maiden I know who to contact for a kit replacment!!

I do think Altech was aligned with MRC at one time.

The 2820 10 Axi motor is a nice one. I have it in a 2.7lb Nitro models Spitfire. With 2 Thunderpower 2100 3S Prop lites <In parallel> the motor makes 433W and propels the model at a nice clip. However it also draws 44A and is spinning an 11Ē propeller.

Considering a small glow engine originally powered this model the tricycle landing gear will not support a large 11Ē prop. If you drop down to a more reasonable 9Ē model in say a 7.5 pitch on a 10 cell pack The Great Motor Test quotes you 327W of power. One would think if the model builds to a flying weight of 3.5lbs 327W would be a bare minimum for spirited flight. Adding floats might seriously degrade the flight performance.

I had purchased that motor to originally convert the Ok Models Gaia. Itís very similar to the Sky Dancer slightly larger and lighter. The fact that I could not make the power I wanted with a small prop on the Axi put the kibosh on that conversion.

No work done on the model today, had a 14 hour day at my Job. I hope to get the tail feathers on and the motor run up for a power test by weeks end.

Take Care

Tommy D
Oct 25, 2006, 11:52 AM
Marc Venis
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Hi Tommy,

I bought it on the last day of the Toldeo show so I'd have something to bring back to Toronto, Canada with me. The receipt says:
RC House Inc
8142 Old W. Ridge
Elyria, Ohio 44035
(216) 323-8429

The seller, Moe, said that the enclosed wheels were too small for a grass field and mailed me a larger set.

As for the motor, thanks for your advice. So I'll either have to add some height to fit a larger prop, go with a 4S Lipoly pack (my Jeti 40A ESC is 3S max) or I'll have to buy a new motor.

Marc.
Oct 25, 2006, 09:59 PM
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Hi Marc

Either you have a spectacular memory, or keep very good records!!

I got a note from MRC today and they made indeed this plane under the Altech banner. However the person whom wrote the letter said no one seems to remember the model to give ant specific details on it! You have confirmed itís at 10+ years old, but I think the covering scheme lends itself to being even older then that.

A 4S pack I believe would be the better of two choices for your Axi. I am also going with bigger wheels < 2.75Ē mains 2.5Ē nose> but just barely. The Dubro models I chose are slightly lighter and thatís the real reason I chose them.

The Axi also weighs about Ĺ ounce less then the Mega 22/20 but your mount might account for another say ounce or more. Like Greg Stated earlier that could wind up being a good thing.

I have to do some work on my Axi powered Spitfire this weekend so if your really serious about using that motor I could run it up in my spit with a few different props to give you idea of how much power it will make on 4S. Although you said your ESC will not work on a 4S pack?

I mounted the Rudder and elevator tonight. If youíre into extreme maneuvers you might want to notch the bottom of rudder to give the elevator a little more throw. I used Elemers Poly glue mixed with a little water to get a nice bit of expansion. Also I had to shim the elevator a bit to get it 90 degrees to the fuse. The Rudder also required a little tape to hold it a few degrees to Port to get it on straight as well.

Last night I joined the wing joiner with the same glue. It took a fair amount of sanding to get it to insert into both wings. Its too wide, but not too tall. By looking at this joiner it appears the model will have some amount of dihedral. Thatís a surprise as the model box photos show otherwise.

My kit came with no pushrods so a trip to the LHS will be in order this weekend.

Ok thatís enough for now, time to wipe down any over expanded glue and relax a bit.

Take Care

Tommy D


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