RC India

Hi all,

I'm making tapered wings for a plane for a project. Since it has a taper and then a sweepback, it is a pain to build using balsa.

I've tried using a hotwire cutter, but the nichrome wire "bends" inside the foam, so the wing in front view has a slight (very shallow) U shape. Is this avoidable in manual cutter?

Does anyone know of a CNC hot-wire cutting machine (which can cut tapered wings) in or around Mumbai?

Thanks
Pranav

To make that nichrome hot wire cutter. do we need transformer to reduce voltage or directly plug into 240v power supply?

Aniket, DO'NT ever plug a nicrome wire hot cutter directly into the mains, you'll be posing yourself to a serious risk of electrocution and burn injury...... Besides, the high temperature will evaporate the foam, step down the supply to something around 12 - 20V and then use it with the cutter

Thanks Bilal. I have 12V, 1amp battery eliminator, is that ok.

Firstly aniket your mains will just blow if you directly plug it in. Secondly fire!!!. And well as bilal bhaiya said electrocution.
I dont know of anyone that has a CNC hotwire cutter around mumbai. The foam i think is mostly directly expanded into preformed CNC moulds or compression cut. CNC hotwire will be with the BIG boys of foam cutting. Like sofa manufacturers. Or if you have a CNC you could make wing sections then make your full wing with the pieces.

Can u post what wing u plan to make ....... Picture of lookalike

Very well sai Neil, most of the commercial EPP planes are directly expanded into the mould rather than hot wired or die cut, commerciial CNC foam cutters are availaible in packaging sections of companies that export/ship goods, but then again not everyone has access to them

I have made a wing out of thermacol. I used sand paper and knife to trim it. it has uneven surface. that's why i asked about this hot cutter.
From thermacol I made this

This is for all the beginners interested to make a hotwire cutter

1. use guitar E string
2. make a bow - literally - like those used to shoot arrows about 2 feet.
3. connect the guitar string on each end using crocodile clips.
4. Get a brushed motor controller
5. get a Rc receiver
6. get a transmitter
7. get a lipoly pack.

Now connect the brushed esc to the receiver (channel 3 as usual)

the two ends of the bow should be connected to the motor connections in the esc - it
does not matter which wire goes where.

To operate:
put the wire on a piece of scrap foam
Switch on tx
Plug in lipo to esc and arm esc (just like operating a motor)
slowly advance throttle - you will find the wire getting hot
keep advancing until it gets hot enough to cut foam with only little pressure.

Will be happy to clarify any of the above

To make the surface smoother just go on sanding. Or take a knife and heat it and bring its flat surface close to the surface of the foam, only close enough so the heat radiating from the knife or any hot metal surface will shrink the foam to a smoother surface. If your application does not require Very strong wings then make simple wings like the Armin wing by experimental air. Some of his wings are even used by FliteTest :)
http://www.rcgroups.com/forums/showthread.php?t=1587275

which is guitar e string can u use no. like 1,2,3 etc..

the thinnest string

Instead of having tx around you could buy a servo tester and do the same will save some wear on the tx. :)

Yes - a servo tester is ideal - but i'm not sure that beginners would
be having access to one.

Anyone can tell me a link for buying one under 300

According to me the beginners should be the first ones to buy it. Very useful tool. Can not only test servos but also check motors, aides when testing power systems, can be used in hot wire foam cutters.

@saikat,
+1
Will it work with a brushless ESC?
Will await answer before burning an ESC on sunday.
Regards

KK sir used a brushed esc as hot wire cutting requires regulated DC output. Temp will be controlled by either a servo tester or tx. As more throttle higher amps more heat :)

Exactly the point.
Why should the hot wire care if its AC or DC or pulsed DC?
Remember room heaters and irons.
Guess i will have to try & see.

Well the hot wire wont care but figuring out the wiring will be a difficult task if you figure it out sir please share it with us sir :bow:
Also du to the fluctuating nature of AC i think keeping the temp constant will be difficult. Constant temp is required for smooth cutting.
Please correct if i am wrong.

Made one for myself as per saikat sir guidelines...
Only took 2 hour to make...electronic connection only 5min...already had turnigy 20a brushed esc so no difficulty part in electronics...

Great job yash

Mr Iyer - AC will work - but you would need a transformer , again beyond the scope
of beginners.
Brushless esc will also work - but will be terribly inefficient as you would be connecting
only two of the motor wires(remember the brushed motor discussion) - you would be placing
more load on the esc - not advisable

If there is interest I can post my setup for slicing foam and depron

Saikat, there is interest :D so please post

Anikethan : Out of topic though, but what airfoil were you trying to make, that looks way too thick.

For tapered wings, fix the hotwire to a screw at one end of the table and moving the other end over a airfoil template. Watch this : http://www.youtube.com/watch?v=R0ZCnR_g6ZU

Yes ! Saikat.....it would be interesting to see your setup. Please do post. Thanks

Wanted to ask,
If i use a servo tester with a turnigy 20A esc connected to a 3S batt will this work?
Also seeing i need 12V but ESC is 3S so will only get 11.1V is this enough? or i need to boost power to 12V for it to work smoothly?
The testers dial needs to be near low to keep amps low right or it could melt the foam fast right?

No need of exact 12v....11.1V is OK...

You are right about the tester dial....

Dial low -> Low amps -> less heat -> slow melting of foam

Thanks a lot santosh :), just wanted to clarify.

Hey guys  ;D
posting after a long time....
just improved my previous hot wire cutter making it more portable.. :giggle:

Items Used:
Guitar thinnest string
2 elbow
1m pvc pipe
some wires
Brushed ESC
1300 mah battery
and using it through tx/rx

Enjoy  :thumbsup:
Yash :hatsoff:

well... well.... well..... a CNC hot wire cutting maching.  For once we need to think about the cost involved and the product produced.... if you are mass producing... go and set up a cnc machine. OR ELSE.............
1.   Take a 4 feet bamboo pole and get it split into three pieces (length wise)
2.   Make a bow out of it... something used for shootin arrows. Fix the bow string made of E string of a guitar or the control line wire used for control line models.
3.   Take a 12 volt transformer.... house hold 12 volt adapter used for various appliance.... take two normal copper wires out of the output of the adapter.
4.   Fix aligator clamps to the ends of each wire.
5.   Fix the aligator clamps to the bow string (each ends of it) and wait for a couple of minutes for the wire to heat.
6.   Your hot wire bow is ready for use... use it by holding the bamboo bow to pull the hot wire across the foam. Use aerofoil templates fixed at the end of the wing planform of the foam to run the hot wire around them for getting the desired shape. DO NOT FORGET TO PUT WEIGHTS on the foam to keep it steady (for weights I use pieces of marble stone cut into 2 - 3 inch width and 6-8 inche length and about .5 - 1 inch thick.. (can but it from any construction material shop which sells marble or any other such stone.  They actually cost nothing).

The 12 Volt adapter gives 12 V DC (direct current).  For heaven's sake never mess with the commercial elecrtical home supply of 220 V and 5 - 15 amps.... it might blow the fuse or hurt you terribly requiring hospital admission for burns.

Using this setup you will not spoil your costly lippo or the esc.... use them for flying and use other low cost items which are readily avaiable for other jobs.

Happy cutting your foam..... Happy Flying