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The "Arena Rat" ultra light indoor RC airplane

TooJung2Die

Well-known member
#1
There's winter weather outside which means it's building and indoor flying season! My last two airplane were foamies so it's time for a balsa airplane. Our RC club has access one day a week to the Hershey Bears hockey arena. We get to fly off the ice. Watch out and don't crash into the overhead scoreboard or protective nets!

Here's the Hanger Rat, a simple rubber powered airplane with a long and distinguished history. 2019 is the 40th anniversary of it's original design and publishing in "Model Builder Magazine". Read the article: A Rat's Tale

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If you read towards the bottom of the articles you'll see there have been many micro electric RC conversions of the Hanger Rat.
Here are the plans for the rubber powered Rat:

hangar_rat_starick_A4@30dpi.jpg

I've done some hand cut from printed balsa builds but I think this may be my first true scratch build from plans. Start simple. I'm going to do an RC conversion and put my spin on the design. Maybe I'll call it the "Arena Rat".

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Jon
 
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SquirrelTail

Well-known member
#2
There's winter weather outside which means it's building and indoor flying season! Our RC club has access one day a week to the Hershey Bears hockey arena. We get to fly off the ice. Watch out and don't crash into the overhead scoreboard or protective nets!

Here's the Hanger Rat, a simple rubber powered airplane with a long and distinguished history. 2019 is the 40th anniversary of it's original design and publishing in "Model Builder Magazine". Read the article: A Rat's Tale

View attachment 148638

If you read towards the bottom you'll see there many micro electric RC conversions of the Hanger Rat. I'm going to do my own RC conversion and put my spin on the plans:

View attachment 148639

I've done some hand cut from printed balsa builds but I think this may be my first true scratch build from plans. Start simple. Maybe I'll call it the "Arena Rat".

Jon
Looks awesome! May be a 1 day build for me at some point
 

TooJung2Die

Well-known member
#4
May be a 1 day build for me at some point
That's probably the average time needed to build a rubber band Hanger Rat. I'll be putting in an hour or two when convenient but want to have it done before next weeks flying session at the arena. The ribs are cut and the wing is going together.
Flying in a hockey arena every week! Very cool!
It's like a dream come true. :love: Anyone that's seen my airplanes knows I like to build small and light. There were some rubber powered free flights last Monday. I took out "One Nite 28" and said, "Watch how long this rubber band flies!" :LOL:
Jon
 
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TooJung2Die

Well-known member
#5
Moving right along... The first change is enlarging the plans 134%. The 19" wingspan rubber job gets blown up to 25.5" for the increase in weight and power.

Glued the rib template to 1/8" Masonite and cut it out on the bandsaw.

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Cut out the ribs. Stacked for sanding.

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Those thin ribs are very fragile at the front where the grain goes across the curve. I put a bead of thin CA along the inside edge to strengthen the balsa. A better way to make these thin ribs is to make a form and bend the balsa. Maybe for the next one...

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Left side wing pinned down, ribs cut to fit. There are two full size ribs where the plans call for thin ribs 'cause I have an idea.

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How do you make the right side wing when the plan only shows the left side? I measured the rib spacing and they are not evenly spaced on the drawing even though the plan claims they are. I swapped the leading and trailing edges on the plan so the uneven rib spacing will match exactly.

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Here's another modification. The Hanger Rat's radical dihedral doesn't fit my idea of TLAR. The Arena Rat will have polyhedral.

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There, that looks better. Gussets glued at all the joints for strength. It needs it, this wing is fragile. I think it may need a spar.

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The wing is ready to cover. What should I use to cover it? It will have to have little or no shrinkage. Slack pre-shrunk tissue is the traditional way to cover something this fragile.

Jon
 
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Joker 53150

Mmmmmmm, balsa.
Mentor
#6
To make the other wing in the mirror image you could flip the plan page over and rub on some vegetable oil to make the page translucent. It's a little messy and not good if you want to keep the plan page after the build, but it works.

Those thin rib pieces would be pretty easy to make with thin balsa sticks, as you mentioned. Soak them in Windex, bend them over a mold or form and let them dry for a day or so. Having the form a TINY bit smaller often helps since the parts want to spring back a little after drying.
 

TooJung2Die

Well-known member
#8
Having the form a TINY bit smaller often helps since the parts want to spring back a little after drying.
That and the thickness of the balsa adds to the size of the outside of the curve so it has to be compensated for when making the form. I've made some really tight curves by laminating glass cleaner soaked strips of 1/32" balsa. That stuff bends real easy when wet. This time I decided to keep it simple and follow the idea in the plan for making the thin ribs. Live'n'learn.
Here in Arizona, winter IS flying weather! Just had 3 days of rain and can't wait to get some stick time!
3 days of rain in AZ? What did you get, a quarter of an inch total? :LOL: I miss the mild Las Vegas winters. Why did I move to Pennsylvania?!? :cry:
Jon
 
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TooJung2Die

Well-known member
#9
I was given a few feet of some 1 mil clear film. The guys in our RC club iron it on their store bought foam airplanes. It is low temp heat sensitive and this film will shrink without melting foam. The story I was told is it's used to seal the opening of yogurt containers. o_O It looks and feels just like document laminating film but thinner. I made the horizontal stab to see how the yogurt film will do as a covering before trying it on the wing.

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It works great. I can tack down and seal the edges without causing the film to shrink. Since the framework is very fragile and only one side of everything gets covered you don't want shrinkage. Shrinking will turn it into a potato chip shape.

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The wing is finished.

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I may have the Arena Rat finished this evening. For sure it'll be ready to fly for the next indoor session.
Jon
 
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TooJung2Die

Well-known member
#10
Busy day but I found time to build the Rat. The original idea was to use 1/4" carbon tube for the fuselage. I weighed the same length of 1/4" bamboo dowel and was surprised to discover it is lighter and stiff enough.

Gluing and clamping the cabanes. Rudder and elevator are hinged with the covering film.

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Close up of the bamboo cabanes and carbon fiber struts.

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Assembled airframe.

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Experimenting with different positions for the electronics to achieve CG without ballast. The CG in the plan is 55% of the wing chord back from the leading edge. Landing gear wire and tail skid installed.

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Gotta finish it today. Tomorrow is our day in the Hershey Arena. We get more people showing up at the indoor sessions than on a nice Saturday during the summer. I liked the idea of using tissue to cover it but the arena can be damp and the raw tissue wouldn't do well.
Jon
 
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Rclements

Junior Member
#11
Is the Hershey arena in Hershey PA? I live near Gettysburg and have heard about indoor flying there, but I figured it had died off awhile ago. The Hangar rat is looking good, I definitely need to build one eventually.

Ross
 

TooJung2Die

Well-known member
#13
Is the Hershey arena in Hershey PA? I live near Gettysburg and have heard about indoor flying there, but I figured it had died off awhile ago. The Hangar rat is looking good, I definitely need to build one eventually.
Yes, that's the place. Some people drive pretty far; farther than Gettysburg. Tomorrow 10AM to 2PM. We break for lunch when the hockey team practices at noon.
Jon
 
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TooJung2Die

Well-known member
#15
It's a "Rat" but it's no longer a "Hanger Rat". Plans are only one person's idea of how an airplane should be built. It's been scaled up 135%. The shape of the wing was changed. The shape of the tail feathers are different. The fuselage, cabanes and struts are different. Instead of rubber band power it has an electric motor and 3 channel RC. I've been calling it the "Arena Rat" because of the flying venue but I'd like a better name. (No, not the "Chopstick Flyer") :LOL:

Here's how you make really light weight wheels. Laminate two pieces of balsa with the grain set 90 degrees apart. Glue in a dowel and sand to shape in a drill.

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Total weight for two wheels: 3 grams.

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Made a foam cradle for the receiver/esc/servo brick.

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Glued the brick to a piece of balsa with foam-safe CA and glued it to the fuselage. CF push rods with adjustable ends. When the length has been fine tuned a tiny drop of CA on ends of the heat shrink tube locks it in place.

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Homemade gift card control horns.

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Motor mount with a bit of down thrust. It's solid.

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Gift card and Velcro battery tray. It's extra long so I can play with the CG. The correct CG was achieved without the battery so the starting point for a slightly nose heavy maiden will be with the battery towards the front of the tray. I'll move it back a bit each flight until it's correct.

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The "ONE NITE" won't be making it to the arena today. The tissue on the horizontal stab got torn last week on a failed first attempt at ROI take off. (Rise Off Ice) :) Too much up elevator and it stalled. It's in the airplane hospital getting new tissue on the horizontal stab.

IMG_1578.JPG

Jon
 

SquirrelTail

Well-known member
#18
It's a "Rat" but it's no longer a "Hanger Rat". Plans are only one person's idea of how an airplane should be built. It's been scaled up 135%. The shape of the wing was changed. The shape of the tail feathers are different. The fuselage, cabanes and struts are different. Instead of rubber band power it has an electric motor and 3 channel RC. I've been calling it the "Arena Rat" because of the flying venue but I'd like a better name. (No, not the "Chopstick Flyer") :LOL:

Here's how you make really light weight wheels. Laminate two pieces of balsa with the grain set 90 degrees apart. Glue in a dowel and sand to shape in a drill.

View attachment 149055

Total weight for two wheels: 3 grams.

View attachment 149056

Made a foam cradle for the receiver/esc/servo brick.

View attachment 149057

Glued the brick to a piece of balsa with foam-safe CA and glued it to the fuselage. CF push rods with adjustable ends. When the length has been fine tuned a tiny drop of CA on ends of the heat shrink tube locks it in place.

View attachment 149058

Homemade gift card control horns.

View attachment 149059

Motor mount with a bit of down thrust. It's solid.

View attachment 149060

Gift card and Velcro battery tray. It's extra long so I can play with the CG. The correct CG was achieved without the battery so the starting point for a slightly nose heavy maiden will be with the battery towards the front of the tray. I'll move it back a bit each flight until it's correct.

View attachment 149061

The "ONE NITE" won't be making it to the arena today. The tissue on the horizontal stab got torn last week on a failed first attempt at ROI take off. (Rise Off Ice) :) Too much up elevator and it stalled. It's in the airplane hospital getting new tissue on the horizontal stab.

View attachment 149062

Jon
Sewer rat!!!
 

TooJung2Die

Well-known member
#20
I really wanted to play hooky from work yesterday but work happened. This working for a living is overrated. :p It was dark when I finally got home so I couldn't even test it in the backyard. Since there's no video to share yet here are a couple of photos of the ready to fly "Arena Rat".

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I hope she floats like one of the Parkzone Vapors some of the guys bring to the indoor fly. Those are incredibly slow.

Vapor.jpg

Jon
 
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