RC India

hi guys

this plane will be a simple 2 channel model good of beginners or people looking to start of into rc by scratch building

target weight of ready to fly will be under 300grams

Equipment :1. one 3.7 grams DYS servo
                2. futaba 4 ch AM 72mhz receiver
                3. 7.4v @ 400amh lipo Hyperion battery pack
                4. one brushed ESC (my own)
                5. one GWS EPS350C geared setup (6.60:1)
                6. one GWS EP orange DD prop 10x6 inch

                futaba attack 4 AM 4 channel transmitter.

the plane isl built using packaging foam (high density thermocol or EPS 22kg type) n 10mm fiber glass boom. plane

design will look like a stick type model in pusher configuration !

sahil

update

1st up will be the wing, i have decided to built the wing using low density EPS foam locally available at book store with 10mm fiber glass as reinforcement half way through.

wing dimensions

span 39 inch
chord root/tip 9.75 inch
chord thickness 1inch
spar at 1/3rd of chord-8.333inch
Aspect ratio A/R =1:4

to construct the wing one needs a 1 meter by .5 meter by .5 inch thermocol sheet, cut the sheet into 4 equal parts of .5 meter by .25meter, now cut a grove to fit the fiber glass tube at 1/3rd chord from leading edge of the wing to a lenght of .25 meters on all four thermocol pieces and glue two pieces to form a basic wing from which simplex airfoil will be cut

see pictures for info

 

Hey Sahil,

Only 2ch? Does it fly up and down?

And How you gonna connect the only servo to rudder or elevators or ailerons?

Am so anxious to see how?

MEROG

its a rudder only model, altitude can be controlled by motor !

Which glue do you recommend for sandwiching the thermocole sheets. Don't you think normal thermocole is too brittle ?

Rao

Hi can anybody tell,

how the up and down or altitude can be controlled thorugh throttle in 2ch? 'Coz I need this when I try to fly my indoor 2ch foamies!

Awaiting your reply...//MEROG

increasing throttle results in pitch up and decreasing the throttle results in pitch down.

I'm using FEVICOL SH, also to get a good joint the trick is to lightly sand (see 1st picture one can notice a difference in shininess) the themocole sides which are being joined so that it will bond better n stronger but the fiber glass tube was glued using 24hr standard Araldite (blue box one's)

the reason for doing this is (sandwiching the two sheets)

1. compare to one single piece it will have better strength in terms of breaking due to the fevicol holding the together n
   forming something like a three layer sheet similar to a car glass wind shield which prevent shattering of glass in an   
   accident etc.
2. secondly its very easy to install the fiber glass tube correctly and glue every thing nice and strong !
3. coming to your point of brittleness, i would rather take advantage of the bounciness of the material and by doing the
   steps one,two and also cover the finished wing half with single layer of packaging tape (brown stuff,one can also get   
   them in different colors) will give it an near unbreakable like features

note: one can still get dents n stuff and as a whole its hard to break the wing based on my experience (slow fliers) !

sahil

let me put it like this, the motor I'm using is connected to a electronic speed controller (ESC) then to a battery. The ESC will control the power being sent to the motor from the battery which i turn reduces the output power making the plane come down or vice verse make the plane go up hence altitude control or up down.

sahil

update, last night i cut the airfoils from sheet metal and nailed it to the side of the wing block will cut the wing when i find time.

Sahil,

Can you find any solution (cheap) for 5 min bonding for thermocol?

MEROG

well, Fevicol if applied in right quantity on thermocole will bond with in 10min and has good strength .

update, finished cutting the wing (it came out okay but needs light sanding)

the foam cutter i have used is a simple n light weight structure made from aluminum with self load spring design.

Spec.

1. 35 inch long bow
2. 17inch width
3. music wire as heating element
4. power supply is via regulated 12volts @ 2amps 

see pictures for more details.

sahil

never thought tat cutting a thermocole will be this simple using homemade stuff. {:)} can u tell some more info abt this music wire?

update, the wing is almost done just need to give it name n cover it with tape  :)

hi akash

music wire or guitar string is the primary part of the foam cutter where power is passed through it, the string heats up (high resistance) which is held tough by a bow kind of system, the hot wire is passed through foam via template which gives the desired shape to the foam (thermocole)

for more details try Google search (word foam cutter)

sahil

wing before covering, and named the model GARUDA (wiki for meaning)

sahil

Dear Sahil,

I have tried a lot to make a handy foam cutter with guitar string (3rd Steel) and a DC adopter of 12v across it! But it didnt catch that much heat enough to cut thermacol!

If it really works for you, can you please tell me how much voltage you have given and how you have connected the string?

Awaiting your reply...//MEROG

Merog

Why dont you just use a 12v battery (7000mah... usually used in 500va ups systems) and connect it across the music wire (thin guitar strings also serve admirably). I have used this method a few times to cut foam. But the daunting part is the bow and how the bow is suspended from the sealing.

Have fun

Saju

Thanx for the suggestion,

Actually I tried, without creting tension at all in the string. Thats why I think the heat was not produced. Somewhere someone has used 25v, with tension in the string. I knew now that tension is must either way of use of voltage!

And am planning to make a frame with variable tension (I mean, in such a way that we can modify the tension to increase or decrase the heat, other than with voltage).

Am on my way to be succeeded in it,
Thanks for the suggestion...//MEROG

Using a Battery as fixed voltage source is not advisable .The temperature of the cutting wire is regulated by varying the applied voltage to the bow.
 
Rao

tension has nothing to do with the wire heat. Tension is to prevent the wire from sagging.

Rao

Yes, I too agree with Mr. Rao,

The temp. can be regulated by using the DIMER SWITCH, which is connected to the adapter, which can supply a regulated voltage! It's safe too!

Mr. Rao, tension is nothing to do with the temp? Then can you tell any possible reason why I failed when I connected 12V adapter to a guitar steel string, which is bent in U-shape (to fecilitate handy cutting)?

Awaiting reply...//MEROG
MEROG

try using a voltage transformer which has amp adjustment and keep increasing the amps until you get the right amount of heat. increase amps slowly :)

Here is a simple Hot Wire Foam Cutter

Ok.. just to make it clear,... You cannot increase just the amps without decreasing the resistance of the wire (or) increasing the voltage. (I=V/R)... A wise man named Ohm discovered that long time ago!... ;). So, I would say you better increase the voltage until you get the right amt of heat. And make sure your transformer output current is rated high enough (~5A) for this kind of job..

i used a 12v 2amp transformer and no rectifier(diodes and capacitor) and the bought "e" string for guitar (which is the least dia string- so higher resistance hence heating takes place here). i had a 1.5" dia pvc pipe, fixed a 0.5 feet plastic rulers perpendicular to the ends of the pipe and fixed it firmly using tapes. then tied the string between these rulers as ends. result- i now cut thermocole as a cake :)

For a good variable heat foam cutter, here is a best link for scratch building...

http://www.instructables.com/id/Hot-wire-foam-cutter/

MEROG

Can you post some pictures of the cutter, don't the wires also cut into the plastic rulers?

good question... the simple trick is to solder the wire with the string between the rulers(inside) and not outside. so the heating occurs between the soldered points. dont confuse with the 2 wires which i soldered, they are just parallel. i made this arrangement to allow more current to pass (as i dont have a bigger dia wire).

update,I have finished building the wing n covered it with cello tape plus added small pieces of fiberglass that i had at the wing center near leading n trailing edges to give it a better strength, i decided to use a readily available fuse that i built for a 1.5 HLG glider long time back.Change of plans the power setup will be a pull type with slight difference.

see pictures

guys, from now on the build will get slower sorry i want to finish the long pending rc project that i have taken up .

sahil

okay guys stay tuned i will be finishing the model today

sahil

update, i have decided not to use balsa fuse instead a EPP fuse  ;D motor mount is fixed,servo press fit n receiver guard, antenna wire cover all done. Hopefully i will be finishing the entire model today and will be left with only the ESC part.

some pictures,

update, added rubber band mount

Hi, please confirm.......this is an actual EPP fuse of some plane or is some EPP packaging of DVD Player or something  ;D

It looks like EPS  packaging of something to me. Clever use  {:)} {:)} {:)}

Rao

its EPP from packaging of a blue ray player  ;D

sahil

Although you have changed your design, but if you were to use the balsa fuse you were better putting a block of wood to anchor the motor post as the pull from motor coupled with the leverage due to height would sure at some point of time yank the post off the base.
Also just wanted to warn you that you should consider appropriate up thrust on the motor at that height from the fuse, if the motor was mounted zero zero you would find that the craft will pitch down severely when you open up the throttle.   

Could you pls explain the up/down thrust that should be used when mounting these motors. A bit of down thrust is what is recommended when mounting the motor on the nose, here we seem to need up thrust instead.

Another Eg. of "Best out of waste".........really appreciate   {:)} {:)} {:)}.
I will try to search some more for me

yes capt. i had a similar issue with my air boat,can you explain the science behind it please and this whole process of changing design was to prevent damage to the prop/motor shaft but i have given up due to CG problems so i have changed it to ordinary front motor mount with prop saver n rest is in gods hand  8-)

sahil

Hey Sahil...

Come on hurry up man, I wish you should fly first than I could, with my Scratchy 'Indian Trainer'!

Dying to see you fly.....//MEROG

well i had this lying around in my room, all of a sudden i see a potential pod n rest you know  :)

sahil

its raining like hell in hyderabad since last night n still raining........hoping tomorrow will be sunny,clear sky,clam no wind.....so that i can maiden the model.

sahil

update, had some problems with the ESC but got it working need to fine tune the LVC values and capt. can you please explain the motor angle thing  ???

The "motor angle thing"  :D 

When you look from the back of the plane to the front, point the motor 2 or 3 degrees down AND to the right.

 ;D anwar i was referring to this post by capt.


yeah the motor angle thing  ;D ;)

Sahil and Capt

I don't know whether it is right of me to interfere at this stage... Capt has to have his say about what he meant.

Sahil, I believe now you are not going with the post mounted motor concept right ? If you are not, then the motor thrust should be directed a few (2 to 3) degrees  down and to the starboard side (i.e. to your right as looking from the cockpit forward). This is to counter the reaction torque of the motor trying to pitch the plane to the port side ( opposite of starboard) and up

I could add the following in explanation of what I think Capt meant:

With the post mounted motor, the thrust line is above the wing. Since the wing is what is holding the whole plane, its cg point tries to act as a fulcrum and the moment (thrust x moment arm) tends to pitch the nose down. To negate this tendency, perhaps, Capt said that the thrust line should be modified to reduce the moment arm, by giving a certain amount of upthrust. (moment arm is the perpendicular distance between the line of force and the fulcrum point)

Saju

OK Guys,
How does one get to measure the 2 or 3 degree shift while mounting the motor? Its all good when its on a drawing board, but in applying the principle, what is one supposed to do?

Pankaj

Simple Pankaj , just put an additional washer or two under the left hand top screw this will achieve what is recommended I do it all the time  :D ;D

thanks for the clarification saju  :)

update,hoping to maiden it tomorrow  8-)

hopefully my final update on this built log



 

specifications

power setup

1. 7.4v @ 400amh lipo Hyperion battery pack
2. one brushed ESC (my own)
circuit/code link
3.one GWS EPS350C geared setup (6.60:1)
4.one GWS EP orange DD prop 10x6 inch

plane dimensions

wing dimensions

span = 39 inch
chord root/tip = 9.75 inch
chord thickness = 1inch
spar at 1/3rd of chord = 8.333inch
Aspect ratio A/R =1:4

horizontal stabilizer

span = 15.5 inch
chord root/tip = 5.5 inch
Aspect ratio = 1:3

vertical stabilizer = 1/3 area of horizontal stab.

Electronics

1. E-sky 8gram servo
2. Futaba Attack 4ch receiver/AM
3. Futaba Attack 4ch transmitter 72mhz AM

material

wing = 10mm fiberglass tube + normal stationary store EPS foam + clear/brown tape for covering + fiber glass inserts at
          tips for wing placement/protection

horizontal stab = 1/2 inch thick EPS foam + tape covering

vertical stab = 1/4 inch thick EPS foam + 2mm spad for rudder + tape covering

Fuse = junk packing foam pod (fevi kwik safe) + 10mm fiber glass tube boom + misc.

others

1.GWS prop saver
2.10mm fiber glass tube motor mount
3.broom stick with heat shrink as wing placement/ rubber band supports
4.6mm plastic straw for antenna/control rod routing
5.GWS control horn
6.Diwali sparkling with broom stick form connecting rod

first flight report

the model flies okay but had problems with ESC  8-) it was cutting off way early and i just checked the weight of the model its a whooping 367 grams vs my target weight of 290 grams no wounder the plane needs full power to climb but the good part is the ESC Fet are cold as ice  ;D

time to do some reprogramming of the ESC n some more testing,measuring then fly it again  :)

sahil

Congrats on the maiden..  {:)}
Add some MOPOWA and enjoy!

thanks Ismail,will try to get a video b/w what is MOPOWA ??

sahil

More power!   ;D

wooow...was a nice attempt.... :salute: