I built this plane following a plan (dont remember which) .. I knew nothing of rc when I started out on this build. So this plane has some classic rookie mistakes built-in The ones I can figure out that it is tail heavy and overweight and my control..
Specs are:

Construction:
2mm Coroplast
Wingspan 46"
Root chord 8"
AUW is more than 1.2 kg I think
Rudder and Elevator
kFm3 wing
Cycle spoke reinforcements
Hot Melt Glue (Heavy!! )

Power System:
D2826-6 2200kv Outrunner Motor: 205W
8x4SF or 6X5SF props
60A Red Brick ESC
2600mAh Turnigy NanoTech
2 x Turnigy 10gms servo

I will be posting my maiden flight video! Please share your thoughts on what went wrong

Thanks!
Trishit

Here is the Video. One of my friends hand launched the plane and another retrieved the crashed plane

Quote from: lastRites on July 02, 2012, 08:36:10 AM
So this plane has some classic rookie mistakes built-in

Many

to start with, wasn't tail heavy or something, power system was ok, not too under powered.

Flaws
1. Wing strength was less, wing flexure was too much, the first launch you saw it ? it was a classic Dutch Roll (see my Aerodynamics thread for what it is)

2. Thrust line was heavily skewed laterally and longitudinally, another cause for Dutch Roll

3. dihedral was different in both wings

4. Fuse is warped badly

5. Bad fixing of wing to fuse, should have been more rigid

6. To much of use of Rudder, reason for the last minute spiral

7. Chuck wasn't Javelin like, was more like a sling shot

Thank you!!
The wing is not attached to the fuse in the still pictures
The reasons by my estimations are:
1:       I do not have access to carbon rods or balsa wood.
2,3,4:  No prior experience with coro.
5:       I could not find an easy way to attach the wing. Used packing tape and rubber bands.
6:       The tail section is not in correct alignment with the wing due to the warped fuse.
7:       I do not understand this point
I am going to scrap this bird.. Am designing a new one taking inspiration from "tuffy".

The plane has no glide. As soon as I decreased the throttle it dropped like a stone..

#7. you Chuck Yeager needs some practice on chucking..

Quote from: lastRites on July 02, 2012, 08:36:10 AM
Power System:
D2826-6 2200kv Outrunner Motor: 205W
8x4SF or 6X5SF props
60A Red Brick ESC

with that powers system you sure to fry the motor in 30 secs.

2826 2200 KV is high speed motor props used are at max 6x4/7x3 with a 3cell lipo. ESC used it 40 Amps.

With 8x4SF/ 6x5SF it will draw more amps than the rated and by using an ESC of 60 Amps you allowing the draw and entire load will be on the motor there by frying it.

make something like this.

don't try too fancy fuse, just make a square tube, has enough strength and serves the purpose, this model weighs only 500 gms with electronics and doesnt need much power to fly. it also glides well, for having more lift you can also increase the chord.

once you have a simple plane flying then go for better looking design.

for connecting wings rubber band is enough but you have buy better one (rcforall has rubber band for wings) + 1.2 kg is much more weight for a beginner plane.

for reinforcements just put a cycle spoke just in the center not the entire wing as if you have the flutes of the coro parallel to the wing it has enough strength as long as plane is less than 500gms.

keep design as simple as possible for initial planes

also i noticed for initial flights you dont have enough space to fly, its always better if you can take off your plane from land.

Quote from: sundaram on July 02, 2012, 11:19:45 AM
with that powers system you sure to fry the motor in 30 secs.

The motor is only 1400kv! The preceding number is the model number
I don't think that it will fry on the plane as it has already endured prolonged use on  a football playing robot(conditions akin to a static bench test) on the same esc and battery.

Quote from: coderbanna on July 02, 2012, 12:25:49 PM
also i noticed for initial flights you dont have enough space to fly, its always better if you can take off your plane from land.

Thanks. That was the main reason for the second crash.. I had it going stable when I suddenly noticed the wall and cut the power
Will find a bigger field next time.

Quote from: lastRites on July 02, 2012, 02:13:13 PM
The motor is only 1400kv! The preceding number is the model number
I don't think that it will fry on the plane as it has already endured prolonged use on  a football playing robot(conditions akin to a static bench test) on the same esc and battery.

hi last rites

as i understand from the first post you own a motor similar to this

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=12919

i own a similar motor kindly note that that motor is primarily a pusher motor and is best suited for a 6x4 or 7x3 pusher prop. using an 8x4 as mentioned earlier can fry your motor. use a wattmeter to see the amps that motor is pulling.

and as i see it the application of this motor on the football playing robot was to spin a gearing mechanism right? for that use, the motor is  cannot be compared to a static motor bench test with an 8x4 prop or 6x4 for that matter unless the mechanism can put a high enough load on the motor.

would love to see some videos and pictures of this cool robot if possible kindly post a new thread  

kindly check amps the motor is consuming and if possible please avoid a 8x4 propeller

Subbu

 

2826/6 is a 2200 KV no doubt on that.

Further 2826/10 is a 1400 KV

Subbu

Purely for my knowledge, what is the qualification for "primarily a pusher motor"? What is/are the effective change/s caused by just the change of direction of rotation, assuming the rest of the system remains unchanged?

Oh! I am so sorry! I posted the wrong model number, don't know how that happened It is a D2826/10.

@subbu: I did not gear down the motor! I simply used the motor with a prop on it and used it to defend my goal. Cant say the other teams were pleased As there was no rules regarding the use of "air", I won

Is your Battery loosely put inside Fuselage ? I Think so, that changes CG in Flight and caused more disbalance (Battery moves foward and right).
Fix it if yes, and everything that may change CG Even 60A ESC Too.

You can fix it by only Thermocol Packing or even GI wire/ Single strand electronics wire/PVC Protected GI wire that binds cords in Computer peripherials etc. binded with fuse.

And, where you find 2mm Coro ? I have found 3mm but not 2mm In Kolkata.

The battery is not loose! It is firmly fixed with velcro. Only the receiver is loose. I took down some "NIIT" adverts from gariahat more. They were made of 2mm coro..
I am thinking of making a coro pusher now. What will be a good Cheap pusher motor? I want to use 5 to 6 inch props with it. The target AUW is about 900gms max.

Dear Trishit,

You can try this one although I am yet to try out flying ........
http://www.rcindia.org/electric-planes/scratch-building-a-look-alike-of-axn-floater-or-fms-800-or-easystar/msg106000/#msg106000

Post #32

Regds
Saurabh

Quote from: sushil_anand on July 02, 2012, 09:09:25 PM
Subbu

Purely for my knowledge, what is the qualification for "primarily a pusher motor"? What is/are the effective change/s caused by just the change of direction of rotation, assuming the rest of the system remains unchanged?

hi sushil uncle

1. mostly a motor of a high Kv rating is what i consider as a good pusher motor since in pusher systems we use relatively smaller size props (compared to tractor systems) the higher kv makes them ideal to gain the thrust required by gaining a higher rpm with a lower diameter prop.
in the above mentioned motor i consider it as a pusher motor due to high Kv and since i have used it on a few of my pusher jets.

2. in the event of a change of direction (tractor system) i assume the motor should generate the same amount of thrust (though i have never tried doing this). even i am not sure as to what real effects it could have but i usually use lower kv motors in tractor configuration and higher ones in pusher configuration.

gusty bhaiya might be able to list the qualities of a good pusher motor and the effects of using it in tractor mode more clearly as i too am not an expert and just talking from my little experience with these motor systems

Subbu

I am thinking of sandwiching layers of normal low density thermocol(easily available) between two layers of 2mm coro on either size for the fuse. Is this a good idea? The wings are still an issue

Quote from: Pikle6 on July 03, 2012, 05:22:10 PM
in the event of a change of direction

1. There is no change in direction as viewed from front whether pusher or tractor it rotates CCW.
Read this
(http://www.rcindia.org/rc-general-topics/basic-aerodynamics-for-rc-flying/msg72935/#msg72935)

2. High KV High RPM motor swings a smaller prop, (a)suited for pusher because of ground clearance while landing (In case of fighters) (b) boom clearance in case of gliders, (c) thrust is affected by airflow mask due to the presence of fuse in front (d) straight line thrust suffices as the torque reation on the fuse is less

3. Low KV lower RPM motors swings larger prop therefore (a) torque reaction is high on the fuse (Technically Down and right thrust line skew required increases with increase in prop size) (b) gives more propwash, good for 3D (c) Typically less draw (Not always) more flight time

Small aeroplanes with less forward speed and chuck takeoff should not swing larger prop, forward speed initially wont be enough to counter the torque

Thanks so much for your inputs! This has helped me a lot!
The recommended props for the motor I have is 7" or 8". But I am afraid if I make the pylon that high, it wont be strong enough. So should I switch to a higher kV motor so that I can use a smaller prop (around 6") to get the same amount of thrust??
Since I am a complete newbie I want it to fly slow. Would a higher kv motor alow me to that?

yeah

What would be a good wing loading value I should aim for if I am making a parkfly trainer (around 30" wingspan)?

42-46g/dm2 is fine, most important thing to do is to keep the proportions right, good strength and lowest possible weight

Thanks!