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Old Sep 15, 2014, 03:29 PM
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Question
Cutting .007" thick carbon strips? ( Simple Solution Found post #6)

Hey All,

I am building a bubble dancer sailplane and I ordered from CST some .007" pre-cured prepeg strips .250" wide for the tip spar cap. Trouble is the pieces that showed up are anywhere from .375 to .450" wide. Real quality control there, ... Hmmm?

Anyhow, I need to get them to be .250" wide, ... any hints on what to use to cut these? They are .007" thick so a cutoff wheel will just tear them up.

Regards
Bill
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Last edited by MicroRotors; Sep 15, 2014 at 04:55 PM.
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Old Sep 15, 2014, 03:54 PM
Duane
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Stick them down to a cutting board with double sided tape, lay a ruler (preferably foam or cork backed) on top covering .25" of the strip and tape it in place. Use a utility knife with a fresh blade, and make multiple light passes. Don't press hard or try to cut all the way through in one pass.
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Old Sep 15, 2014, 04:02 PM
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Quote:
Originally Posted by Wazmo View Post
Stick them down to a cutting board with double sided tape, lay a ruler (preferably foam or cork backed) on top covering .25" of the strip and tape it in place. Use a utility knife with a fresh blade, and make multiple light passes. Don't press hard or try to cut all the way through in one pass.
Hi Wazmo,

Thanks for the reply, ... I thought about that, but this stuff is pretty flimsy and I'm not sure I'll be able to get the double sided tape off without fracturing the carbon. i guess a small test cut wouldn't hurt. I have about 3" to practice with as the rest needs to be used.

Regards
bill
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Old Sep 15, 2014, 04:08 PM
Duane
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How about using a balsa strip cutter? Might be tricky to keep the blade from wandering though.

If you use the double-sided tape, I'd use tape wider than the carbon. After the carbon is cut, carefully peel the tape off the cutting board, taking the carbon with it. Flip the carbon over so the tape is on top and peel the tape back on itself to remove from the carbon.
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Old Sep 15, 2014, 04:21 PM
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At .007" thick, ... it would be like trying to cut a sheet of notebook paper with a balsa stripper.

Ahhhh, ... maybe an extremely lite mist coat of 3M-77, ... has anyone ever tried that?

Regards
Bill
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Old Sep 15, 2014, 04:55 PM
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Simple Solution Found

Ok, ... That worked very well.

I lightly misted some 3M-77 on one side of the carbon, > Laid the carbon on a smooth surface, > Put double sided tape at both ends so the ruler would be held in place, > Made 2 lite cuts and that was it.

The pieces of carbon came up easily and the taped ruler was the hardest part to remove. The the way that ruler came up, ... the .007" thick carbon would NOT have survived the double sided tape.

Regards
Bill
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Old Sep 15, 2014, 06:24 PM
Little Red Plane
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Be sure to save the left over pieces. They make excellent cap strips for the ribs.
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Old Sep 16, 2014, 08:56 AM
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After reading your first post I was going to suggest 3M 77 but you got it. 3M 77 is very useful for building. I have an aluminum T-bar and hardwood blocks that I spray a light coat on and stick sandpaper to ithem. When it wears down I spray another light coat on the old sandpaper and stick another piece of paper on. After a few get used up I peel them all off and use mineral spirits to clean up the 3M that's left and start over. It's also good to get fiberglass and carbon cloth to stay put while you brush on epoxy and work with it. Just a very fine misting is all that's needed. Back in the day we used it to spray foam cores and either balsa or obechi for wing skins. Once the wood touches the foam, it's there......forever Put 3M on two pieces and it never lets go but it's great on one item to hold it firmly in place until you want to remove it.

Trey
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Old Sep 18, 2014, 03:00 PM
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To separate double-sided tape (or masking tape for that matter) from delicate material like .007" carbon, just flood the area with dope thinner. Pretty soon it just floats off. I use this when cutting light carbon cloth. Lay the masking tape along the line to be cut so there's some on each side; that stops the cloth fraying when you cut along the middle of the tape. Thinner will float the tape away from the piece of cloth you want.
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Old Sep 18, 2014, 03:13 PM
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Buster, ...

The problem with that is the dope thinner dissolves the 3M-77 glue and the cloth wicks it up and spreads it throughout the weave, ... more or less contaminates the cloth.
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