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Jun 12, 2012, 02:26 AM
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mtesa's Avatar
OffTopic:


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Jun 22, 2012, 09:16 AM
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Packing tape will heat shrink! I discovered this by accident. I was trying to toughen up a foamie, so I covered the thing in packing tape, completely wrapping the wing. Then I spray painted it, and was trying to speed up the drying between coats with a heat gun, overheated it, and it shrunk the inevitable tape wrinkles out! It doesn't stick to foam so well though, so you've gotta wrap the wing such that there's a tape on tape joint or it'll pull off what you've stuck it to. Or CA the edges down, or something.

As a plus, heat shrinking it has significantly increased rigidity in that thin wing.
Jun 22, 2012, 09:19 AM
Registered User
Take a guitar string, string it across a 2' wide 8' long piece of melamine covered particle board at about 2mm higher than the thickness you want, and heat it up with your favorite foam bow cutting power supply. You can now slice insulation foam to whatever thickness you want. I use the blue 2x8 sheets in 1.5" thickness. The pink stuff is stiffer but heavier. The green stuff, if you can find it, is lighter, but flexier and needs a little reinforcement. 10 foamies for $20!

I find it works best if you stick one end up on the workbench and the other end on the ground, weigh down the foam with about 10 lbs of weights across it's length, and let gravity do the feeding.
Jun 22, 2012, 10:30 AM
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rcav8r2's Avatar
Since you mentioned heat and tape.... On foamies I use Scotch Brand tape (not the cheap imitations) and use my covering iron on low to set the tape in the foam when making hinges and such. Test on scrap, you want it hot enough to "set" the glue, but not too hot to melt the foam/tape. Also burnish it down with the iron.
Once set like this it will take a little bit of foam with it when removing so it is really on there. If you do need to remove it, just apply heat, and it will come off very easily.

Quote:
Originally Posted by digiex_chris
I find it works best if you stick one end up on the workbench and the other end on the ground, weigh down the foam with about 10 lbs of weights across it's length, and let gravity do the feeding.
HUmmm I always wanted to do this. With an 8' piece of foam, I'm guessing you have really high ceilings, and set the board at a 45? You would need 16' of space, right? Or does the shaved piece just curl along the floor?

I do use gravity to square up cuts in foam when cutting core blanks. Guaranteed a 90 degree cut every time
Jun 22, 2012, 12:41 PM
Registered User
with one end on my bench (3 feet high or so) and the other end a foot or so off the ground, and the wire in the middle of the sheet, it seems to work ok. half of the sheet is on the board before it even starts cutting. It's not 45 degrees, it's closer to 25 or 30. I also tend to cut half sheets, not full 8' sheets, that way it doesn't hang up on the section of the sheet that's hanging off the top edge and I don't need to hand hold the top half. Still gives you a 2x4' piece, which is plenty for a wing half for a 90" plane. But at that angle I can get an 8' sheet 4' onto the rig and 4' hanging off with room to spare in a 7' garage. Don't need 45 degrees, just weight. A dimmer on the heat control is good, lets you dial in the speed. Low as you can stand (time wise) seems to give the best finish. I cut a 4' sheet one pass in about 5 minutes.

The material is critical. Slippery! If it sticks anywhere, it won't cut well or you'll end up with a line across your nice finish from the wire stopping there. You'd probably need less weight or less critical of a surface with more angle, but then you run into the problem of the weights not staying put and leaving the foam behind and ending up in a pile on the ground.

One addition I want to make is melamine sides to guide it, it'll tend to fall off one side or another.
Last edited by digiex_chris; Jun 22, 2012 at 12:52 PM.
Jun 22, 2012, 12:52 PM
Registered User
I only tried an 8' sheet once, I just raised the rig enough keeping the angle the same for it to clear on the ground. I just ran it through the CAD, for a full 8' sheet, at 25 degrees, you need 15' of floor space and 7.2' of ceiling height.
Jun 28, 2012, 10:02 PM
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Xanadu's Avatar
Hot wire foam cutter (1 min 16 sec)





Quote:
Originally Posted by digiex_chris
Take a guitar string, string it across a 2' wide 8' long piece of melamine covered particle board at about 2mm higher than the thickness you want, and heat it up with your favorite foam bow cutting power supply. You can now slice insulation foam to whatever thickness you want. I use the blue 2x8 sheets in 1.5" thickness. The pink stuff is stiffer but heavier. The green stuff, if you can find it, is lighter, but flexier and needs a little reinforcement. 10 foamies for $20!

I find it works best if you stick one end up on the workbench and the other end on the ground, weigh down the foam with about 10 lbs of weights across it's length, and let gravity do the feeding.
Jun 29, 2012, 06:34 AM
Bleriot's R Us
xairflyer's Avatar
Excellent what are you using as a power supply?

Also the wire seemed to be slack at the end
Jun 29, 2012, 06:55 PM
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Xanadu's Avatar
Quote:
Originally Posted by xairflyer
Excellent what are you using as a power supply?

Also the wire seemed to be slack at the end
Uses a home made power supple with a transformer gong from 120v to 12v, and a dimmer switch to alter the power in.

I know the wire stretches a bit but it never seems to effect the cut thickness so far. Hard to get the right power setting for cutting versus not having the wire stretch while its hot. Maybe puting a tension spring would help, but I have broken a few wires as well with greater tension.

Works great for what I need. I also made a hotwire "band saw". Go to youtube and search for Xan2k. There you will find the other videos.
Jun 29, 2012, 08:08 PM
Registered User
Quote:
Originally Posted by Xanadu
Uses a home made power supple with a transformer gong from 120v to 12v, and a dimmer switch to alter the power in.

I know the wire stretches a bit but it never seems to effect the cut thickness so far. Hard to get the right power setting for cutting versus not having the wire stretch while its hot. Maybe puting a tension spring would help, but I have broken a few wires as well with greater tension.

Works great for what I need. I also made a hotwire "band saw". Go to youtube and search for Xan2k. There you will find the other videos.
Any specifications on the transformer label? Other than 120 to 12 volts..Amperage for example or anything else. I want to build a foam cutter and am not sure of the amount of current delivery required without burning out the transformer.
Jun 29, 2012, 11:07 PM
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Xanadu's Avatar
Actually it cuts it down to 6.0 - 6.3 volts and 6amps. I just looked at the transformer. Bought it at Radio shack 4 years ago for $10.

Quote:
Originally Posted by barry wilson
Any specifications on the transformer label? Other than 120 to 12 volts..Amperage for example or anything else. I want to build a foam cutter and am not sure of the amount of current delivery required without burning out the transformer.
Jun 30, 2012, 06:53 AM
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RknRusty's Avatar
If the stretch was causing a problem, you could try different types of wire. Tungsten might do it. Or different thicknesses. The necessary current would vary with those differences.
Jun 30, 2012, 09:58 AM
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Xanadu's Avatar
Quote:
Originally Posted by RknRusty
If the stretch was causing a problem, you could try different types of wire. Tungsten might do it. Or different thicknesses. The necessary current would vary with those differences.
Been thought that, just using what I currently have. Works good enough for me.
Jun 30, 2012, 06:40 PM
Registered User
I found was to use a cheap stanley knife with those break off blades. Because you really only use the tip of your knife(thats why xacto knives have a short blade and not a 3 foot samuri blade) you just snap off that section with a pair of pliers and PUT IT IN THE BIN!!!! Not on the bench. And you have a practically brand new blade.
Jul 02, 2012, 08:08 AM
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rcav8r2's Avatar
@Xanadu... Thanks for the video... that was a lot less complicated than what I was thinking about making. I see your not using a whole sheet which simplifys things. I'll have to make one of these... BTW, I have the same basic dimmer/Xformer setup, but include an amp meter. This way I can set the current no matter how large or small my bow is. I find about 2.1 amps to be idea for cutting.


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