"Arena Rat" Ultra light indoor RC airplane.

[TooJung2Die]

This stuff is super cool! Is there such a thing as an indoor plane slow enough to fly in a living room? I'm imagining something that flies like the Vapor. I.e., permanently in high alpha.

This airplane will fly indoors in a large room. It might be flying in a constant circle and that could get boring.

 

[BrickPlane]

This airplane will fly indoors in a large room. It might be flying in a constant circle and that could get boring.

Looks like you're right. Sure would be a treat to find something slow and agile enough to not have to fly circuits. I might just need to stick to my tiny whoops

 

[Inq]

1. Yes, it uses a standard 3.7V 1S lipo.
2. Yes, it has a brushed ESC built in. It uses the 2-pin connector. Reverse the wires if the motor runs backwards.
3. The 3-pin connector is for a third servo, like ailerons.
4. Binding is no hassle. Plug in receiver battery. Hold down bind button and turn on transmitter. Turn transmitter off/on. It's ready to fly. You have to repeat the procedure every time you change batteries in the airplane but after you've done it a couple of times it becomes natural.
5. The FlySky FS-i6 transmitter has to be changed in setup to use AFHDS for the model in memory. Default is AFHDS-2a and won't work.

I attached the PDF document listing covering weight and thickness.

Hope this helps,
Jon

Outstanding... I'll give the binding a try. It's certainly will be no better off than I am now if it doesn't work.

I'll be satisfied with just the rudder/elevator/dihedral for at least a model or two. I've never seen servos this small before this 949 board. How large a servo do you think this board can drive safely?

I didn't have any balsa handy, this evening, so I thought I'd give the 3D printer a try.

Here's the first attempt.
Span: 9.5"
Chord: 4"
Foil: NACA 4416
Weight: 5.0 grams
It's a little too flimsy at the moment after the gluing. I'll try it in the morning. Otherwise, I'll try plan B!

 

[TooJung2Die]

That looks amazing! You can buy ultra-micro servos that plug into the F949 brick. There are several on eBay. I don't remember exactly what JST connector size it uses but I think it's 1mm pitch. I'd never use ailerons on an airplane light enough to be powered by those tiny coreless motors. It's overkill and useless weight. Even the elevator is rarely useful. Use the throttle for climbing and glide to come down. All I use is the rudder for direction. Super slow flight is the goal.

I'd only cover the top surface of the airfoil to reduce weight and get maximum lift. A super light covering material that is easy to get is those flimsy plastic bags in the produce section of the grocery store.

 

[Inq]

That looks amazing! You can buy ultra-micro servos that plug into the F949 brick. There are several on eBay. I don't remember exactly what JST connector size it uses but I think it's 1mm pitch. I'd never use ailerons on an airplane light enough to be powered by those tiny coreless motors. It's overkill and useless weight. Even the elevator is rarely useful. Use the throttle for climbing and glide to come down. All I use is the rudder for direction. Super slow flight is the goal.

I'd only cover the top surface of the airfoil to reduce weight and get maximum lift. A super light covering material that is easy to get is those flimsy plastic bags in the produce section of the grocery store.

1. Produce plastic bags - That's what I mean... I would have never found that one. I'm just not tuned to this level of flying. How did you take the measurements for your areal weight density... such low weights? Got to go scrounge at the Walmart with a different mindset.
2. 3rd servo - Sounds good not needing it. Just getting started, I definitely need to use the KISS principle.
3. Wasn't sure about your photos (or H.R. plans) if the covering was both top and bottom or not.
4. The plans don't have any scale. I'm guessing if I scale the wing section shown to be half of the given 19" span, I'll be close enough.
5. The plans also sound like this is a rigidly defined Class of planes. Is that your all's goal at "the Rink" or is it just free form and you're trying out anything goes? 3D, maneuverability, slowest/fastest, spot landing skill... that sort of thing. Do you all do combat too?
6. My wing did stiffen up overnight. I think it's strong enough without any spar or leading edge addition, but since I don't need the bottom for covering, I'll explore just doing upper camber and making it lighter.
7. I noted that the CG is WAY back from the aerodynamic center... what's up with that? Any other plane would be un-flyable.
8. How big a battery did/do you use to get that 55 grams all-up weight. I see lots of different sizes in these tiny batteries... 200 mAh to say... 850 mAh. How long is it good for? It looks like I have the same geared motor / prop as you have.

VBR
Inq => Inquisitor - Coined by a college professor who said I made his class feel like the Grand Inquisition with him on the receiving end.

 

[TooJung2Die]

The plans also sound like this is a rigidly defined Class of planes. Is that your all's goal at "the Rink" or is it just free form and you're trying out anything goes? 3D, maneuverability, slowest/fastest, spot landing skill... that sort of thing. Do you all do combat too?

Ha! We have no class (literally). It's no rules free form "that looks about right" design. We're just a bunch of guys that were lucky to have a big indoor venue to fly in during the winter. That all ended due to the pandemic. Most of us buy retail airplanes. I'm one of very few that actually build airplanes.

I noted that the CG is WAY back from the aerodynamic center... what's up with that? Any other plane would be un-flyable.

Weird CG huh? You find the CG way back on many rubber powered airplanes. The CG of the Guillow's Lancer is at the trailing edge of the wing! Put an electric motor up front and the CG is the same. I can't explain it, it just works that way.

How big a battery did/do you use to get that 55 grams all-up weight. I see lots of different sizes in these tiny batteries... 200 mAh to say... 850 mAh. How long is it good for? It looks like I have the same geared motor / prop as you have.

The batteries I use are from 250 mAh to 350 mAh. I get about 5-10 minutes flying time. I used the 820 coreless motor. (8mm x 20mm)

 

[Inq]

I'm sitting here in the office CAD'ing up a kind-of Arena Rat, kind-of Hangar Rat. It turns out my motor isn't as strong as yours... I think I just have a 716 geared motor/propeller unit.

Anyway... I'm on-board with the wings having the skin on only the top surface. I imagine the stabilizer is also only one the top surface... but what do you do with the Fin / Rudder. Since it sounds like the primary control, do you cover both sides of it or is it only one sided also?

Thanks for all your help. This is fun... I'm looking forward to flying my own plane inside a warm toasty room. Got it all picked out... can fly as much as I have batteries for!

BTW - Do you or anyone else in your group... or even does your local public library have a 3D Printer?

 

[TooJung2Die]

All the surfaces are covered on one side only. The goal is to shave off every fraction of a gram you can. At this slow flying speed drag isn't a problem. The covering is slack because shrinking it would warp the airplane.

The Hanger Rat was designed by someone with lots of time on his hands in an airplane hanger. He and a friend had a contest to see who could make a rubber powered airplane fly the longest in the hanger. The result was the winning Hanger Rat. You start with a design idea and keep improving it, keeping it simple and easy to build.

Put the battery mount right on the CG so you can use different size batteries and the CG won't move.

I don't know anyone with a 3D printer.

 

[Inq]

The Hanger Rat was designed by someone with lots of time on his hands in an airplane hanger.

I can just imagine some kid back in the '70s volunteering to sweep-up just to be allowed to hang around with the mechanics at the hanger... loves airplanes... and just wings the original Hangar Rat. Could have been me! Not having any feel for this, I was wondering if weight or symmetry of the fin/rudder trumps since yaw seems to be the most important thing.

I don't know if I'll be light enough using the plastic, but driving 100 miles to get 22 grams worth of balsa seems a little sycotic The plastic is denser and not as stiff as balsa... I couldn't make 1/16" strips usable. I'm using 100's of milli-grams experimenting, but I like the challenge.

The biggest problem I'm having is not having these connectors for the receiver. I replaced the wired power connector with something I can see and connect a battery to. I was able to setup a plane on my Flysky for the AFHDS, power up the receiver and bind! I think your AFHDS clue was the main thing. Without any documentation, I didn't even know if it was compatible with my transmitter, much less that this AFHDS even existed. Thanks! Now, I have a whole slew of motors and project planes ahead.

Now, my last "electrical" hurdle - Any magic bullets for connecting the motor to the receiver's ESC? I can't solder to something this tiny and even if I could buy connectors, I doubt I could assemble them either. I have enough trouble with these large ones. All thumbs.

The only battery I have light enough is this messed-up 150 mAhr LiPo. It still takes a charge and works... not sure how long though. Hopefully it'll be enough to give me a working taste of flying this plane before I order some decent sized ones.

I'm really looking forward to sitting in warmth and flying!

 

[Tench745]

Couple thoughts:
1) If you're interested in balsa, consider online suppliers. Balsa USA is one I can think of off the top of my head.
2) You can buy the correct motor connector attached to a pigtail for not too much money. Then you're only soldering a wire to a wire. I don't remember the exact plug type... Internet says it's a JST SH plug with 1mm pitch

 

[TooJung2Die]

Now, my last "electrical" hurdle - Any magic bullets for connecting the motor to the receiver's ESC? I can't solder to something this tiny and even if I could buy connectors, I doubt I could assemble them either. I have enough trouble with these large ones. All thumbs.

You got it to bind. Congratulations for clearing a big hurdle. For me a big frustration with these micro components is getting the connectors right. There are so many different kinds! It's been a couple of years since I built the Arena Rat but I did find and order some motor connectors that fit this receiver. Don't ask me now what type of connector you need. I remember looking up JST type connectors and finding the match. I think Tench745 is right, it's a 1mm pitch.

You are going to have to learn to do some fine soldering to connect to the motor. Some people pry off the plastic and solder directly to the board pins. I solder the motor wires to the connector wires and cover the solder joint with heat shrink like in this photo.



My eyes aren't what they used to be so I have a cheap jewelers magnifying headband so I can see to solder this tiny stuff. Something like this. I use a fine tip 25W soldering iron.

 

[Inq]

Some people pry off the plastic and solder directly to the board pins. I solder the motor wires to the connector wires and cover the solder joint with heat shrink like in this photo.

I had an order for the JST SH pins all ready and I realized the smallest cheapest order with 2 and 3 pin unit had 60 items and had 4 and 5's also. It didn't even have sockets, so I couldn't really use them anywhere else... for just the two connectors I actually needed. So, I took off the plastic and soldered to the pins.

Now, next problem... Does this sound familiar?

Got it all connected up, checked polarity. Good! Added inline connectors. Re-connect and tried it out. Servos and motor turns. then stopped as I advanced the throttle. Oh crap... I messed something up. Servos still working, motor at any setting doesn't. I took the motor off and checked the motor directly... It works. Checked the output out of the ESC... Nada. I disconnected the battery and checked for continuity between the two output wires. No, I didn't short them. Re-connected everything and it worked... until about 1/3 throttle. Stops and won't restart.

It's almost like the ESC has an over-current protection and won't reset until the receiver is de-powered. Does that sound right? Also, remember, I'm using only a 716 motor which should draw less than your 820 motor. I guess I could set a limit in the transmitter, but its doesn't seem to be anywhere near top speed of the motor when connected directly to the battery.

Edit: Couldn't set the transmitter low enough for the upper limit. So at anytime I'm flying and accidentally go over about 1/3 throttle... it'll be a dead-stick landing no matter what the situation.

 

[TooJung2Die]

I never had that problem with the ESC and I have four of these receiver bricks. I wonder if you can calibrate the ESC with the throttle? I don't see how because you have to bind the receiver to the transmitter every time you unplug the battery from the receiver. I'm baffled.

I don't think it can be an over-current issue because the WLToys Cessna F949 has three coreless motors wired in parallel to the ESC. You may have a defective receiver.

[edit] It could be the old battery. If the battery voltage drops too low the ESC cuts off the motor.

 

[Inq]

I never had that problem with the ESC and I have four of these receiver bricks. I wonder if you can calibrate the ESC with the throttle? I don't see how because you have to bind the receiver to the transmitter every time you unplug the battery from the receiver. I'm baffled.

False alarm, my fault (again) - Just for S&G, I hooked the receiver up to my bench power supply set at 3.7V. Everything works like a champ. I guess at the higher throttle, the current draw off my iffy battery was drawing down the voltage to the point the receiver was disabling the motor, leaving enough juice for the servos like my regular receivers do. Good to know it has this safety feature also. Guess I have to order some real batteries before trying it out.

BTW - What is the biggest motor you've put on this receiver's ESC? For instance, do you think it'll drive two of your 820's How about two of these motors? Just in case I wanted to do a P-38 model?

 

[TooJung2Die]

Since the original airplane has three coreless motors, two tiny motors should be no problem. Be sure to wire them in parallel like the three motors in the Cessna F949.

 

[checkerboardflyer]

This stuff is super cool! Is there such a thing as an indoor plane slow enough to fly in a living room? I'm imagining something that flies like the Vapor. I.e., permanently in high alpha.

Sure is. Watch this video.

It's called F3P. Visit my blog I have some more examples coming up soon. https://foamboardflyers.com

 

[Fred Pena]

Nice build!