Mini Popwings RevA

a Slow One and

a Reasonably Fast One

(Rev A Material at the end)

 

There seems to be an upsurge in these little 24” EPP wings at the flying fields, at least I see many these days, so I had to have one or two, maybe three.   We fly them at my work out back in San Jose.  They are distributed by www.nitroplanes.com  and made by Tech One Hobby. 

They are a lot of fun, fly very slow, so slow you can do combat with little to no damage.  There are a lot of videos of people catching them on landing as well as other tricks.  All weigh less than half a pound AUW. 

Nitroplanes sells the bare wing for $25 or an ARF version for about $60 that includes the motor, esc, servos.  For the ARF, just add batts and rx and you’re ready to go pretty quick. 

I’ve been using the little orange Hobby King receivers for $10 and remove the case to make it fit better, see pics. 

The slow version

Here is a pic of mine, several graphic designs are available and they seem to add new ones consistently.  5x3 GWS prop, ~5-8A ESC. 

mini pop top.JPG

Mini Pop Wing, Top View

 

The ARF version link is listed below. 

http://www.nitroplanes.com/02a-020-minipopwing-epp-aa-arf.html

mp bottom.JPG

Mini Pop Wing, Bottom View

The center foam cavity has the HK RX on the left and the ESC on the right.  Battery is up front and you can see the carbon I added for reinforcing the battery cavity which tends to be a weak spot. 

 

This one flies on 2S500 batts although you can go up to 800 if you like.  With the 500 batts you need about 10 grams of weight in the nose, but with the 800s you can get by without additional nose weight.

I use the 500maHr batts myself, and made up the needed nose weight with some carbon reinforcement and some finishing nails in the leading edge for added combat durability. 

mp bottom closeup.JPG

Caseless HK radio on left, ESC on the right

 

mp nose 1.JPG

Front view of Nose

with Finish Nail Weights Visible

There is a nice foam block on the front to act as a skid and the battery mounts just behind this. 

 

The T 1306 motors provided in the ARF are discontinued so, after the motor mount broke, I bought this one as a replacement after my motor mount broke. 3200kv, HK1612

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=17599

 

The fast version

We had been flying the slow ones for a while, then someone spotted this guy, JohnnyMega on rcgroups under the heading of “insanely fast mini pop wing”.  Seemed very fast on the vid and noone was disappointed. 

http://www.rcgroups.com/forums/showthread.php?t=1800040&highlight=insan+fast+pop+wing

JohnnyMega was strengthening them with some nylon tape on the nose, beefed up the motor, esc and servos and sold them for ~$100.  So, several of us bought them.  3S850 batts and 5x4.3 GWS prop. 

Mine measured 22A, on 3S, so about 440w and it weighs 8oz.  400w/lb!  WOW!  So, we call this the Mega mini pop wing, of just the Mega Poppy for short.  The name has nothing to do with the size and everything to do with the power system. 

Below are both of them in the same pic. 

 

mini and mega.JPG

Mini and Mega together.

 

I had some trouble with the ESC as it caused erratic motor operation, seemed to lose timing setting.  The ESC that JohnnyMeg used didn’t have the ability to change timing setting, so I substituted a more upscale one where I could set timing.  Worked well.  The motor RPM tached at about 24000 RPM on 3S850. 

 

He was secretive on the parts he was using.  So, of course, I took it as a personal challenge to figure out what he was installing.  Below is the part list of what I’m using along with HK links.

ESC  25A Basic(seems like a Plush, US warehouse).

http://www.hobbyking.com/hobbyking/store/__2163__TURNIGY_Plush_25amp_Speed_Controller.html

 

Motor, 24 gr Hextronic, 3000kv

http://www.hobbyking.com/hobbyking/store/__5453__hexTronik_24gram_Brushless_Outrunner_3000kv.html?strSearch=24gr%20hex

 

Prop, GWS 5x4.3 – see RevA material for apc

 

Battery, 3S850 NanoTech

http://www.hobbyking.com/hobbyking/store/__11899__Turnigy_nano_tech_850mah_3S_25_40C_Lipo_Pack.html

 

Servos HXT500

http://www.hobbyking.com/hobbyking/store/__23593__HXT500_5g_8kg_10sec_Micro_Servo_USA_Warehouse_.html

mega.JPG

Mega mini Poppy

 

More upscale ESC

mega motor.JPG

View from behind Motor

It doesn’t seem very critical to me if the battery is mounted on the top or bottom.  If on bottom, the Velcro strap and foam block prevent grinding it into the pavement on landing. 

 

A cautionary tale

I was flying the mega at the field, doing horizontal figure 8s and all of a sudden the motor/prop noise just stopped.  It was going sorta fast, so I had plenty of momentum, allowing a glide back to the runway.  As it got closer I could see something hanging down from the back of the wing.  The motor mount had come unglued from the wing and collapsed, but all the pieces were there, so luckily the CG didn’t change and I retained control.  So, if you build one, make sure to reglue the motor mount.  Below is a pic of the prop damage.  I lost the prop and O ring, but nothing was broken and all the parts were there.  So, I just re glued the interlocking motor mount together and to the wing using foam tack. 

Wing Damage from Motor Mount Issue

I did buy a bare wing and will put together another Mega with some digital servos.  The HXT500s don’t seem to center very well, I have to retrim almost every flight. 

 

http://www.hobbypartz.com/exi-servo-s0820.html

 

 

So, if you’re looking for something a little different with a bit of punch, you might give a Mega Poppy a try. 

 

RevA Material, 1/2015

I’ve been flying these for a while, pretty much the mega only, sort of an old standard.  I was using a GWS 5x3 prop on the mega which was pulling 22A at about 22,000 rpm.  I finally broke all that I had and bought another batch.  It seemed that all of the new batch would cavitate, sort of a howl about half throttle, and not make it to the former rpm or speed.  One online guy commented that he just uses GWS props as stir sticks and, at this point, I have to concur.  So, I decided to tweak in an apc type which turned out to be a very solid performer.  

 

A bumpy ride.  The process was a bit more of a bumpy ride than I had anticipated.  I got some testing in and was pretty underwhelmed by performance as I could not attain previous speeds at target amps and RPM no matter what I did using apc.  I always ended up around 25A or more, which was the ESC rating.  I expected the improved efficiency of the apc should help here, but  for whatever reason, couldn’t seem to get there.  So, I started tweaking on the timing as well, but this also didn’t help and the motor started to smell like it was cooking, so I changed the motor as I had one in the box($12 from HK).  Much improved, and aligned with expectation, but had to start over. 

During this process, I had also bought a new wing from NitroPlanes and ended up with a significant aileron trim, you could see how the cores were cut assymetrically, increasing drag.  I could trim it out at slow speed, but not a lot a fun at speed because it would not lock into the groove.  After some pics and tech support talk, NitroPlanes sent me an RMA number and I sent it back for replacement. 

 

The plan.  I planned to start with some apc e props around the same diameter and pitch, and explored a bit beyond that, in amps and rpm.  Unfortunately, even though apc shows 3” pitch props in e versions, I couldn’t find them on the shelf at Aero Micro or at Sheldon’s.  I did find a 3” pitch non e, and picked up a couple of them to use as reference.  I next went to tweak in 4.5 and a 4” pitch props.  First I trimmed the diameter and balanced, then ran each to measure amps and rpm. 

The D2P number is a measure of the prop loading on the motor.   It says that the loading varies as the square of the diameter and linearly with pitch (D2P = D * D * P).  It is a nice figure of merit to compare different props which takes into account differing diameter and pitch.  D2P helps as sometimes on the smaller props, it’s not obvious if the next incremental increase in loading needs to change pitch or diameter. 

 

Mega pop Prop Test Table

 

At this point I’m favoring the 4.7x4.2e, although I’ll continue to do more testing with the cut down 5.5x3 (from 6x3).  With this small battery, 3S800, there is some variability due to the battery temp and state of charge.  If you’re interested in a mega poppy, let me know and I’ll update you.

Overall, I learned some things by going through the process, even on some cheap foamie.   So, you don’t have to spend a lot of $ to learn stuff in RC. 

Happy Flying

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