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Nov 30, 2019, 03:23 AM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by GeoffS
My EzFly Trainer didn't seem to fly very well. It felt sluggish and wouldn't climb much at all.

My hypothesis is that the blunt wing leading-edge isn't contributing to good airflow over the wing.
To help I decided to try applying an air-foil leading-edge to see if that would help things.
I remember seeing some posts about people cutting and sanding the foam into a better leading-edge shape.

I decided to try 3D printing the forward portion of the NACA 2414 section and glue them onto the wing.
I choose the NACA 2414 since it is a good airfoil for model planes (and I happened to already have the coordinates for another project...).

I installed the new leading-edge today and went out for a quick test-fly just before dark.
The plane seems to fly noticeably better. It will climb nicely on about 3/4 throttle where before it would struggle at nearly full-throttle.
I need to get some of my flying buddies to try the plane and see if they notice any improvement before I make any definite conclusions.

All the files are at: https://www.thingiverse.com/thing:4010523
Rounded leading edges can certainly be helpful on an EzFly .

Other common causes for poor climbing and sluggishness are :
1) prop is on backwards .
2) under powered due to wrong motor , prop , and/or battery .
3) overweight .
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Nov 30, 2019, 01:11 PM
Registered User
Lawn Dart Flyer's Avatar
EZ Fly uses a KFm wing, you are supposed to bevel the leading edge. I built a 55 inch wing version of this and use a Hextronic 1200 blue wonder for it and i have no such issues
Nov 30, 2019, 06:08 PM
Registered User
GeoffS's Avatar
Quote:
Originally Posted by balsa or carbon
Rounded leading edges can certainly be helpful on an EzFly .
Quote:
Originally Posted by Lawn Dart Flyer
EZ Fly uses a KFm wing, you are supposed to bevel the leading edge. ...
I had beveled the leading-edge to start.
The KF wing is the main reason I'm concentrating on the LE and haven't done anything with the downstream step and the trailing edge.

One of the most critical parts of an airfoil is its leading-edge radius.
A sharp/narrow-radius (like you get with simple tapering cuts) will exhibit a very sudden stall.
http://article.sciencepublishinggrou...040501.19.html
Here is a graph from the above paper.
The purple AFR1 line is from the airfoil with the smallest LE radius:
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Description:
Since my primary use for the plane is as one I can loan to friends to try out RC flying, I wanted to try and get very docile behavior.
I thought about trying to cut/sand a more rounded LE into the foam, but in the end I decided that having pre-formed LE segments seemed like the best bet to get the same stall behavior on both wings, along with a proven LE profile.

Quote:
Originally Posted by balsa or carbon
1) prop is on backwards .
I assume you mean having the motor rotating backwards so the designed trailing edge of the prop. is being used as the leading-edge (?).
Most of my planes are pushers, so I'm pretty familiar with them.
I just looked my EzFly's prop and the actual LE looks like the correct one from an airfoil perspective, and the numbers are facing forward...

Quote:
Originally Posted by balsa or carbon
2) under powered due to wrong motor , prop , and/or battery .
The 1500kv motor and 7x6 prop both came from Fancy Foam; I have to admit I didn't check through this thread to see if there were more recent recommendations.
My 500mAh 3S battery weighs 50g (just a bit heavier than the 450mAh from Fancy Foam).

Quote:
Originally Posted by balsa or carbon
3) overweight .
Weight may be part of the problem. I think I got carried away with the glue laminating the fuselage and wing double-layer sections.
The airframe ended up at 253g originally, with the LE cuffs it's up to 271g (9.6 oz), a bit over the 6-8 oz mentioned in the instructions.
My battery is 50g, so the fly-away weight is now 321g.
Nov 30, 2019, 07:17 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by GeoffS
Weight may be part of the problem. I think I got carried away with the glue laminating the fuselage and wing double-layer sections.
The airframe ended up at 253g originally, with the LE cuffs it's up to 271g (9.6 oz), a bit over the 6-8 oz mentioned in the instructions.
My battery is 50g, so the fly-away weight is now 321g.
In my opinion , 321 grams is heavy for a standard size EzFly .... especially if you want docile ( slow ) flight for your friends . If you build another EzFly , I recommend increasing the wingspan and reducing the weight for low wing loading ( the main ingredient for slow flight ) .
The advantages of low wing loading are :
1) slower flight
2) less likely to crash than a faster heavier plane
3) less likely to sustain damage if it does hit the ground due to : slower speed , less mass , less inertia .


Here is a video of a standard size EzFly with the wingspan increased to 36" ( I've gone as high as 40" ) and the lightest possible electronics that will provide enough thrust for a mild climb . I've built standard size EzFlys as light as 144 grams AUW .



Copy of EzFly with under-cambered wing (1 min 57 sec)
Nov 30, 2019, 10:22 PM
Registered User
GeoffS's Avatar
Quote:
Originally Posted by balsa or carbon
In my opinion , 321 grams is heavy for a standard size EzFly .... especially if you want docile ( slow ) flight for your friends . If you build another EzFly , I recommend increasing the wingspan and reducing the weight for low wing loading ( the main ingredient for slow flight ) .
... and the lightest possible electronics that will provide enough thrust for a mild climb .
... I've built standard size EzFlys as light as 144 grams AUW .
Well, I doubt I'll build another EzFly.
I've got a decent one, and at ca. $100 for the kit foam and all the parts there are other planes I'm more interested in right now...

I wish I'd weighed the kit contents before I started to know how much weight I added during construction.
The 8mm EPP in the Fancy Foam kit is pretty heavy just by itself.
I used metal-gear servos for durability; they probably added a bit more than all-plastic servos.
The radio and ESC are pretty light; I might have shaved a couple of grams there, but not easily.
I used a FlySky X6B rx (about 4.5g) with an extra 3g for a cover.
The 10A ESC is for a small quad, and is also pretty much on the low-end of the weight range.

Having said all that, I do have a sheet of stupid low-density Divinycell sitting around from an ice-boat project...
With some strands of uni-carbon, very light covering, and something for abrasion resistance on the bottom...
Nov 30, 2019, 11:16 PM
IMO ( In My Opinion ) →
balsa or carbon's Avatar
Quote:
Originally Posted by GeoffS
Having said all that, I do have a sheet of stupid low-density Divinycell sitting around from an ice-boat project...
With some strands of uni-carbon, very light covering, and something for abrasion resistance on the bottom...
I have never used Divinycell , I just use cheap foam from the dollar store ..... an airframe typically costs me $1 - $3 .

But for beginners learning to fly , I'm a firm believer in slow and stable . Here's another cheap dollar store foam plane built with very low wing loading , you can see how it would be easy for a new RC flyer to manage :


Lightweight 40" wingspan FT Old Fogey-ish (2 min 58 sec)
Dec 01, 2019, 12:44 AM
Registered User
GeoffS's Avatar
Quote:
Originally Posted by balsa or carbon
I have never used Divinycell ...
After I wrote that I realized that Divinycell would probably be more appropriate for a 3m plane than a sub-1m plane...
It's really intended to be the core of a composite structure and is mostly optimized for shear-strength.

Quote:
Originally Posted by balsa or carbon
... I just use cheap foam from the dollar store ..... an airframe typically costs me $1 - $3 .
But for beginners learning to fly , I'm a firm believer in slow and stable . Here's another cheap dollar store foam plane built with very low wing loading...
Some foam-board planes are in the plans soon.
Right now I'm concentrating more on the small end of the spectrum (think HZ Champ).
My next project will probably be something on the order of a scaled-down Slo-Stick; a half-size EzFly built from 1/8" pink foam is something else I'm thinking about.
I need to get a lightweight 2S motor and ESC first...

I love flying my Bixler 2, but hauling it around is a real PIA. The EzFly trainer is even a bit on the large size to keep in the car.
These days my favorite is the ZOHD Dart (not exactly a beginner plane...). It's small, light, and can fly in winds reaching the mid-high teens (mph). A pretty universal flyer.
To be honest, the EzFlyer is kind of replacing the Champ as my "go to" simple fun plane. The extra weight is an advantage when the wind is up.

Once winter kicks in around here big time, I'll probably mostly fly my Eachine Trashcan micro-quad around the office after hours.
I'm thinking of getting a BNF E-Flite Vapor for that kind of flying too.
Dec 06, 2019, 08:12 AM
Registered User
motorhead's Avatar
Thread OP
Good job on the 3dprinted LE.
Weight is going to be the biggest issue on poor climb performance and stall behavior. At the slow speeds that we fly at I have found that the square leading edge has better stall performance.
The rounded leading edge will help glide performance the most. We all know that with power off the EzFly decends like a brick. This can be good to prevent a fly away. After someone gets the hang of flying I think beveling the leading edge is a good thing.
I have experimented with a nice airfoil shaped leading edge and a bevel on the LE of the doubler and there is so little difference it is not worth the effort.
In the end I love experimenting and encourage others to do so.
Just have fun flying.
Mike
Fancyfoam
Dec 06, 2019, 08:15 AM
Registered User
motorhead's Avatar
Thread OP
I now have an in shop printer and am printing the EzFly. For now I still have the same basic paint scheme but will soon be working on something that looks allot better. I would love to get some input and ideas for a graphic design. I was thinking of keeping something like a transport or waterbomber theme but am open to other ideas. I can do panel lines, weathering, ect... Lets make this plane look cool!
Thanks.
Mike
Fancyfoam
Dec 06, 2019, 08:26 PM
Quads & Planes, cant beat them
sleb's Avatar
Like the water bomber theme, the yellow and red would look great.
Dec 06, 2019, 10:09 PM
Registered User
GeoffS's Avatar
Quote:
Originally Posted by motorhead
Good job on the 3dprinted LE.
Weight is going to be the biggest issue on poor climb performance and stall behavior. At the slow speeds that we fly at I have found that the square leading edge has better stall performance.
Curious observation about the stall behavior with a square-edge wing.
There are lots of counter-intuitive things that can happen at low Re (esp. in the 10,000 and under range).
It wouldn't surprise me that there is something odd happening at the leading edge with such low-energy flow.

Quote:
Originally Posted by motorhead
... We all know that with power off the EzFly decends like a brick. ...
I see no reason to insult the flying qualities of innocent bricks!

In my experience the poor glide performance makes landing pretty easy.
Basically fly down near the ground and when you get to the landing point just cut the throttle.

It's kind of like a 3D model, pull back all the way on the elevator, bleed off speed, use the throttle to control altitude, and set it down where you want.
Dec 06, 2019, 10:11 PM
Registered User
GeoffS's Avatar
Quote:
Originally Posted by motorhead
... Weight is going to be the biggest issue on poor climb performance and stall behavior. ...
I forgot to ask: do you happen to know what the pre-assembly weight of the parts are?

I'd like to try and figure out how I ended up with such a heavy plane.
Dec 07, 2019, 12:41 PM
Registered User
motorhead's Avatar
Thread OP
This painted airframe with servos and stick mount is 4.2oz. My other one, ready to fly with landing gear is 8.2oz and it will climb strait up. Maybe you have a power issue. Might need to calibrate your esc. Is the battery old and weak? Motors usually work or don’t.
The second pic is how I do my leading edge. I bevel the doubler 45 deg. I just eye ball it.
Mike
Fancyfoam
Last edited by motorhead; Dec 07, 2019 at 02:30 PM.
Dec 09, 2019, 02:44 PM
Registered User
GeoffS's Avatar
My plane is flying pretty nicely now.

I did a full-power climb and a few stall tests yesterday while I was testing some LEDs I added for night flying (more weight, but they look cool and with the short daylight this time of year they will probably get some use).

It wouldn't quite climb vertically, but it did get some good altitude before stopping.
Power-on stalls were a non-issue. The nose just dropped a bit at the stall. There was no problem keeping the wings level.

Just flying around, the plane responded nicely too.

Quote:
Originally Posted by motorhead
This painted airframe with servos and stick mount is 4.2oz. My other one, ready to fly with landing gear is 8.2oz and it will climb strait up. Maybe you have a power issue. Might need to calibrate your esc. Is the battery old and weak? ...
I'll check the ESC. I tried to calibrate it last night. I forgot the BLheli calibration sequence, but next time I will get that done.

Battery should be good. It has only a few cycles on it; I don't remember seeing an unusual voltage drop at full-throttle, but I'll check that too.

Quote:
Originally Posted by motorhead
... The second pic is how I do my leading edge. I bevel the doubler 45 deg. I just eye ball it.
I tried that too - mine didn't come out looking anywhere near as nicely...
The LE cuffs cover my butchering nicely.
Dec 09, 2019, 03:27 PM
Registered User
GeoffS's Avatar

Wall hanger for EzFly Trainer


I've been 3D printing hangers for my planes, and I just finished one for the EzFly Trainer.
It is designed to hang on a 3M Command™ Medium Utility Hook (17001ES).

I don't have a photo of the EzFly hanging, but I included one of a Bixler-2 to give an idea how the it works.
Name: EzFly Trainer Medium Utility Hook 17001ES.png
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Description: Name: featured_preview_IMG_9509_1500.jpg
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