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Feb 21, 2011, 03:00 PM
beginner scratch builder
tayarati's Avatar
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Build Log

LLG: Light Lazy Glider… for 7$


I ‘m sharing some scratch build experience. I hope you enjoy it.
Your comments, questions and suggestions are welcome. Don't forget, I am a beginner, in the hobby just 5 months ago.

I ‘m sorry about the photos quality (iPhone screen is covered with hot glue) and correct me if I do some language faults (English is my third language)

I started drawing an easy to build glider.
As you see in the blue ink pen non-scaled sketch, it’s something near the springer’s OSG, with less work needed, but less efficiency too. The OSG is lighter with a better build. This is not a comparison, it‘s just another way.

WeoCalc helps by suggesting the propeller size.
It indicates that the perfect propeller should be the 9x4.7, but I will try with the 8x4: it gives less thrust, but it’s enough. My only worry is about the direct drive, 8x4 prop needs some 0.84 gear ratio. Let’s go for it, life is a test.

Technical specifications
All up weight : 12oz
Wingspan: 60” (Main wing: 30” / Dihedral tips: 2x15”)
Wing area: 255 sq in
Wing chord is 4.5”
Wing tips chord go from 4.5 to 3.5” on 15” long (that’s why area is 255” and not 270”) [different from the sketch]
Airfoil: Kfm2 (flat bottom)
Fuselage 27” long

4 Ch (throttle, ailerons, rudder, elevator)
Brushless motor: Small 1300kv outrunner
20A ESC
(GWS 8x4 gives 13 to 16 oz of thrust and 8~9A of current)
Lipo: 2S 1000mAh 30C

-------------------------------------------------------
Total Co$t: ARF, without Tx/Rx, without lipo: 29$
-------------------------------------------------------
Frame building cost: 7$
Foam: 1$
Carbon fiber: 1$
Rods and clevis: 2$
Tape, glue, wood: 1$ (less than)
Balsa wood: 2$
-------------------------------------------------
Electronics cost (w/o lipo, rx): 22$
Servos: 3x2.5= 7.5$
Motor: 4.7$ (+1.5$ shipping)= 6.2$
EBay ESC, 20A: 6.8$
Bullet and dean connectors: 1$
GWS 8x4 Propeller: 0.5$
-------------------------------------------------

Total work (design and build) took me something like 8~10 hours.
Last edited by tayarati; Feb 21, 2011 at 07:36 PM.
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Feb 21, 2011, 03:01 PM
beginner scratch builder
tayarati's Avatar
Thread OP

the fuselage


As I said, I was working without plan, but following the pattern (sketch). A good scratch build should be based on a good well done plan.
It ‘s just a good point for laziness.

I cut the foam structure. Notice that the one dollar foam was peeled.
The fuselage basement (black, reinforced with one 3mm carbon rod) is cut from a crashed plan. Laziness is reuse friendly.

The pink foam is extruded: this relatively heavy material should support the fuselage shape and the wing fixation.

Fuselage compartments:
First quarter: Lipo and ESC
Second quarter: Rx (remote Rx is outside), aileron’s servo installed on the bottom of the wing
Third quarter: rudder and elevator servos and rods (installed on light white foam).
Feb 21, 2011, 03:02 PM
beginner scratch builder
tayarati's Avatar
Thread OP

Wing and tail


Rudder and elevator are installer.
The remote Rx is installed outside: it’s the only visible component.

The wing is the master piece. It’s a tip dihedral form.
To make tips more strong, I used 2 binded 2mm rods (2” each) to have some structure. The wood reinforcement of the tip is glued on the central part, to the balsa spar.

Central wing is reinforced with 1/2 “ balsa spar, it makes heavier but it is really strong.
The balsa spar is supporting the Kfm2 aifoil.

This laziness: airfoil is made using transparent tape only, I will test if it works really. I reinforced it with some strapping tape on the wing edge.

Tips angle is about 35° or a little less. Too much? May be.

Rear pushrods are installed, as clean as I can.
Feb 21, 2011, 03:04 PM
beginner scratch builder
tayarati's Avatar
Thread OP

Setup, check and test


Time to check the gravity center. I was lucky because I worked without plan, and there is no place to correct a tail heavy scenario.
Fortunately, my building was nose heavy when lipo is installed to the bottom. I used the oblique position the get a CG to the 1/3 of wing chord from the leading edge. (I let it a little bit nose heavy).

Tx channel is bind and configured.

The test was done Sunday at 22h pm (last night), in front of the house. I was just testing gliding abilities, without too much thrust nor control. Sorry for the bad photo quality.

To do list:
Install and check real pushrods for ailerons servo
Cover to top of the fuselage (transparent tape)
Make a real testing
Change incidence angle from zero and retest
Trim if required
Crash it

Videos and pictures should follow, just wait for the nice weather (currently, it’s 35km/h wind).
Can’t wait !

Thanks for reading.
Last edited by tayarati; Feb 23, 2011 at 10:39 AM.
Feb 23, 2011, 11:00 AM
beginner scratch builder
tayarati's Avatar
Thread OP

Maiden flight: test, trim and repair


Weather conditions:
Wind 11km/h – 6 mph
Temperature -17°C / 2° F
Sunny day

I was skating rather than walking, a lot of ice in this period of the year.
My keychain camera betrayed me . It was frozen and didn’t work (unless inside my warm pocket).

I hand launched the glider, it gets up, but turned right sharply. First hard landing.
The wing rubber was not tight enough, I ‘ve made a reinforcement.
I also trimmed the rudder.

Second try, ailerons were not responding well.
Anyway, I think it was a bad idea. Rudder-elevator is enough to control such a plane.

The motor betrayed me too get out of the mount, and I got another hard landing.
Peeled one dollar foam has no strength, at all.

Here is my to do list:
- Reinforce the nose (2 popsicles) instead of peeled foam.
- Some easy repair
- Remove ailerons
- Mount the motor (tightly)
- Check the CG

My daily lessons are:
Never ever rely on one servo to control 2 ailerons.
On a long wing with dihedral tips, ailerons are not efficient as on an small wing.


To be continued…
Feb 23, 2011, 03:39 PM
flyin' fool
goldguy's Avatar
Your design should fly fine with just rudder and elevator. The ailerons don't work with a lot of dihedral anyway.
Feb 23, 2011, 03:48 PM
beginner scratch builder
tayarati's Avatar
Thread OP
Quote:
Originally Posted by goldguy
The ailerons don't work with a lot of dihedral anyway.
That was my lesson today
That 's what happen with beginner's design

I will glue and/or tape ailerons, and remove servo.
Also, I m' moving rudder control to the right hand.

(It's messy for me to have rudder with throttle, I usually turn but change throttle in same time)

The glider floated well this morning, but there was a lack of control (I used ailerons)

Thanks.
Feb 23, 2011, 09:38 PM
beginner scratch builder
tayarati's Avatar
Thread OP
Just to say that the used motor is for one use only, GWS propellers last more.
The prop is not broken (without prop saver) and the motor is out :-(
Mar 18, 2011, 10:19 AM
beginner scratch builder
tayarati's Avatar
Thread OP

Airfoil V2.0 What cans can do


I 'm back with an upgrade for my tape cheap airfoil.
The new airfoil is also cheap :-) not perfect but should be better.

And never forget: green to the right, red to the left!

Wing total weight: 4.5oz
Wing span: 60"
Wing chord: 4.5"
Mar 24, 2011, 12:15 PM
beginner scratch builder
tayarati's Avatar
Thread OP

It glides!


Just to say: it's working!
See the worst quality screenshots
Mar 24, 2011, 04:22 PM
In Rc for a LONG TIME FFAA#1
laserman's Avatar
nice build and it flys nicely, where abouts in the now melting great white north are you i am in ottawa if you are close we could hook up for some flying some time

jim
laserman
Mar 24, 2011, 08:39 PM
beginner scratch builder
tayarati's Avatar
Thread OP
Thanks Jim!
I 'm in Quebec
Glad to have your invitation.

May be one day.
Apr 02, 2011, 09:46 PM
beginner scratch builder
tayarati's Avatar
Thread OP
Finally, here is the video :-)
Glider building and flight (3 min 23 sec)


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