Tip for Blue and Pink foam

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RonL

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While doing some experiments with bonding foam, a simple solution to cutting and boring holes, came up.
Some may have already found this, but if you do not have a hot wire cutter, or the throat capacity of your cutter is not deep enough, the use of a 15/30 watt solder iron from radio shack (under $10 US) will melt thru quite well. After each hole or cut, the tip is easy to clean, using an old rag doubled or triple layer so as not to burn your hand, quickly wipe the tip clean.
Heat is so low, that very little fumes or smoke is generated. My tip is 3/16" round and 2" long.
For a deeper cut, i am thinking of buying a unit that has a 1/4" threaded shank, then bore a hole thru a short bolt, the hole should allow a 3" or 4" finish nail to pass thru and seat against the head of the nail. Then screw the bolt/nail head into the solder iron with the point sticking out, if heat transfer carries all the way to the end of the nail, then foam as thick as 3-1/2" can be cut.
Hope this is a help to someone, it is so simple.

RonL
 

Yellowhammer

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I was under the impression that blue foam insulation board was not to be cut with a hot wire.

Fumes and other problems may not be suitable for your health I was told.
 

Vigilant1

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Assuming the blue foam is extruded polystyrene (i.e Dow Styrofoam (tm)), it can be safely cut with a hot wire if normal precautions are used. There are other foams (polyisocyanurate, etc) that are not safe to cut with a hot wire unless you have a full positive-pressure mask, etc.
 

wsimpso1

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+1 on Vigilant1. Polystyrene foams are relatively safe to hotwire. Styrene is obnoxious smelling, but not terribly toxic in the air. All other plastic foams we know about either do not hotwire well or are very toxic and should absolutely NOT be hotwired nor burned...
 

Aerowerx

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You can also run it through your bandsaw backwards.

It may not be accurate enough for foam ribs, but is excellent for roughing out shapes. Of course it depends on how good your bandsaw skills are, I guess.
 

Yellowhammer

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Assuming the blue foam is extruded polystyrene (i.e Dow Styrofoam (tm)), it can be safely cut with a hot wire if normal precautions are used. There are other foams (polyisocyanurate, etc) that are not safe to cut with a hot wire unless you have a full positive-pressure mask, etc.

My Pulsar has a composite spar and Blue Dow ribs, I have to cut a few ribs that were ruined during a mistake in construction. Only the hot wire gives the clean cut finish I desire.
Thanks for the heads up!
 

Pops

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When building a lot of RC airplanes, I made a 2' plywood table top and an arm above the center ( like a table jigsaw table) and strung a hot wire vertical. Also had rip fence like a table saw. Was used a lot.
 

Vigilant1

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I've also thought that an electric hot knife (Here: Harbor Freight: $20) might be good when lopping off chunks of foam (for a male cowling mold, etc). It's limited to a depth of about 5 1/2", so it won't go as deep as a bread knife, but it might be a bit less messy (esp with EPS "beadboard") and maybe a bit more controllable.
 

Aerowerx

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Was just thinking about my post of running the foam backwards through a bandsaw.

If you had two plywood templates, one on top and one on the bottom, you could gang cut a stack of ribs rather quickly. Maybe a little bit of sanding needed.
 

Pops

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I hotwire shapes by using my soldering gun ( bought in 1954) and making a tip out of #10 copper house wiring with the insulation removed and shaped to any desired shape.
 

Pops

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Was just thinking about my post of running the foam backwards through a bandsaw.

If you had two plywood templates, one on top and one on the bottom, you could gang cut a stack of ribs rather quickly. Maybe a little bit of sanding needed.
Perfect job for the hot wire table with the rib fence.
 

8davebarker

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For straight clean cuts a table saw equipped with a thin friction cutting (metal grinding) blade makes a smooth cut without styrofoam dust.
 
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