[Ken Currell]

Originally Posted by benjhind

Thanks Gary! I'll keep it in mind. Any idea of how much the wire costs?

I'll try a couple more guitar strings to see how it goes. There's no point in owning a cutter that needs a new string every three cuts though!

Cheers,

Ben

If you need something longer than 3 feet, which is all that I can find on the net, let me know.

Ken

[bear57]

I would suspect your guitar string is going west because of excessive current through it.
For years I have used stainless steel down rigger line, available from sporting/fishing shops.
A roll will last several life times. I have had my roll for 15 years and I have barely dinted it.
Sorry, my memory does not allow me to provide diam and brand names. I can get this if there is any interest.

[Ken Currell]

I have made at least 200 or more cuts and still on the original wire.

Nichrome lasts a long time if it isn't abused. Part of that is probably due to the thickness of the wire I use.

[benjhind]

Hey Ken, thanks for the offer. I'll try a couple more guitar strings and see how it goes. I realize it likely isn't ideal, but it fit the budget. The whole bow only took about 10 minutes to assemble!

Cheers,
Ben

[Vulcan1]

If you have a friend that flies control line then you could ask him for an old line that he broke or kinked. I have been using a braided Sullivan .018" line for quite a few years. I purchased a set of lines a long time a go and have a lifetime supply.
John

[Guest]

Ben, nice variation on a working design.

I got my cutter from a design posted on a RC aerobatics website. The original design used a basic 12V Radio Shack ("the Source") doorbell transformer with a simple circuit providing a variable pulse to the cutting wire (the more frequent the pulses, the hotter the wire got.)

I never got the circuit to work and substituted a standard wall dimmer feeding into the transformer.

One thing that I did notice is that you do not have a fused link in your circuitry. My setup uses a 15 amp fuse on the DC side. Fusing does save your cojones in the event of a whoopsie and short-circuit.

My main problem in using the setup is getting enough tension on the wire (currently SIG nichrome wire).

I'm trying to chase down a source of 0.020 stainless steel wire used in the aviation industry as tie-downs. I've spotted steelwire at Home Desperate but need to pack along my digital calipers to make absolutely sure. Looks to be about a 25 guage is 0.020 inches if you're using the Brtish Imperial measurement.
http://www.artlex.com/ArtLex/wxyz/wiregauges.html

Nexst project that I need to undertake is a new bow for hands-free cutting and a band-saw setup for free-hand pieces.

[Gary Maker]

Ben wrote: "Any idea of how much the wire costs?"

Ben, don't worry about it, if you want to try it, I'll send you out a package. Its really not that much! (along with a certain muffler I've been meaning to get out to you) Consider it a gift for putting up with my procrastination! You may find it works a lot better than a guitar string as its meant to carry the current for a foam cutter.

Originally Posted by Vulcan1

If you have a friend that flies control line then you could ask him for an old line that he broke or kinked. I have been using a braided Sullivan .018" line for quite a few years. I purchased a set of lines a long time a go and have a lifetime supply.
John

I happen to have a roll of, I believe it's Sig, control line wire but didn't think you could use braided wire! It's not too thick?? The stuff I have comes on a red plastic spool and the wire is not shinny but a darkish colour - Does that sound similar to what you use??

[Ken Currell]

Ok Guys.

It's time we mentioned that ALL FOAM cutting should be done outside and you should also wear a good quality mask with a proper filter. I believe that a filter for organic vapours is the correct one to use.

THE VAPOURS from foam cutting are extremely bad for your health. If you can smell it you are too close. I have a 16 inch industrial fan that I use even outside as you still need to blow the vapours away from you.

On to a couple of tips.

Get yourself some lead shot and make up some bean bags to hold the foam in place while you are cutting it. They won't damage the foam.

I also use a couple of ajustable squares clamped to the table to make right angled cuts if I need them. This also helps to cut the dihedral into the center of the wing halves. Just block up the tips to get the angle right.

If you are not sheeting the wing you will likely need to make the templates larger than the finished size as the wire will melt the foam as it passes over it.

Place marks along the edges of the template at no further than an inch apart and number them the same on each template. You should use 2 people to do the job. Don't pull the bow too fast or the wire will start to sag and the curve or taper on the wing won't be correct.

When I do it each person calls off the number they are at as soon as the wire meets the mark. Usually the person who is going too fast slows down.

IMPORTANT

Make sure the surface you are working on is FLAT!
Also be certain that your block of foam is square before you start to work.
I save the cut offs to put under the wing for the second cut to stabilize the wing.

Good luck!

[benjhind]

Originally Posted by Gary Maker

Ben wrote: "Any idea of how much the wire costs?"

Ben, don't worry about it, if you want to try it, I'll send you out a package. Its really not that much! (along with a certain muffler I've been meaning to get out to you) Consider it a gift for putting up with my procrastination! You may find it works a lot better than a guitar string as its meant to carry the current for a foam cutter.

Hi Gary,

Thanks a heap for the offer! Guitar string #2 is still going strong. If I have any more issues, I'll be sure to take you up on your offer

Thanks,
Ben

[Spitball]

Benji - due to the way the dimmer works, the output from the transformer will be far from sinusoidal and volt-meters (DVMs) will be affected by the waveform and indicate incorrectly, so don't put too much faith in the readings you'll get. A very useful way is to get hold of a simple little AC current meter (5- or 10 amp) and then you'll get a good indication of how hot a wire is going to be, regardless of the length of bow. Surplus places or Princess Auto may have such a meter.
Another point is that NiChrome wire, stainless steel fishing wire, control-line wire (which I've used), SIG and other will all have different resistances for the same thickness so will need different voltages/currents for the same temperature. But for a given wire your current meter will always give you a useful reference point.
But as Ken says, do take care!