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Old Feb 16, 2007, 09:01 PM
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shaping epp/eps

ok i have some foam im geting ready to use for a build its 1.25" thick either epp or eps and my question is what is the best way to shape it for the wing surface?
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Old Feb 27, 2007, 12:10 PM
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so anyone have a recomendation on how to shape the foam? ive recently built a hot wire cutter so cutting it is no problem but shaping the airfoil is what concerns me.
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Old Feb 27, 2007, 12:13 PM
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Medium grit sandpaper on a sanding block. Be prepared for a mess!
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Old Feb 27, 2007, 12:26 PM
Time for another motto!
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What do you mean with 'shaping the wings'? I thought the main advantage of a hotwire bow was you could cut out precise airfoils. Or do you mean smoothing out the ridges after hotwiring? I think people use a sanding block for that, or just cover it with foil.
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Old Feb 27, 2007, 01:33 PM
Ajutor de băgător de seamă
San Carlos, CA
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Quote:
Originally Posted by ssjwizard
ok i have some foam im geting ready to use for a build its 1.25" thick either epp or eps and my question is what is the best way to shape it for the wing surface?
What I found to work very, very fast and with excellent surface finish is to use a wet sandpaper-covered sponge (I think they're made by 3M), grit 150 or more.

The resulting dust gets mixed with water into a milk-like fluid that both bites faster and polishes the surface. Plus, the sponge can be washed periodically.

Find a flat area right next to the kitchen sink and give it a try; you'll be amazed by the results.

Serban
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Old Feb 27, 2007, 01:53 PM
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the hotwire i built is similar to a band saw while it will let me cut flat shapes very accuratly it is not setup for cuting angles.
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Old Feb 27, 2007, 02:05 PM
Time for another motto!
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Oh ok, build yourself a long bow then too. You already have the electrics, less than an hour's work can result in a hotwire suitable for cutting wingcores. Or just bend your airfoils from fff or depron.
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Old Feb 27, 2007, 03:49 PM
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Quote:
Originally Posted by ssjwizard
the hotwire i built is similar to a band saw while it will let me cut flat shapes very accuratly it is not setup for cuting angles.
What JelleB said - construct a bow (not hard or expensive) and then cut your airfoil shape out of a suitable template material; personally, I have quite a bit of old panelling, which works just fine, with a scroll saw to cut the airfoil shape. These two templates screwed to each end of a straight, scrap 2x4 will make a fine cutting jig. Some folks also use that matt cardboard stuff you frame pictures with.

Actually, it's quite a bit of fun to do. I gave it a shot one evening before I even had a bow, just holding the ends of the wire by the battery charger clips I was using, and I cut out a dozen splendid wing cores in no time.
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Old Feb 28, 2007, 08:08 PM
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could you show me a picture or a link to a thread about your bow?
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Old Mar 02, 2007, 10:35 AM
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Hmmm - I was starting one some time ago when I was interrupted. I do have a picture of the bow; just not the template yet:

In the picture you see 1) the bow, a simple wooden frame, 2) stretched in the bow, a Wal-mart stainless steel fishing leader (the package from which it came is sitting there) and 3) the battery charger, 12v 0.5A. The clips clamp to the bow frame and form an ON/OFF switch! Speaker wire carries the electricity to each end of the wire.
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Old Mar 02, 2007, 10:49 AM
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Here's a conceptual picture of the template

It's this simple, though, really. Two pieces of panelling, cut at the same time on a scroll saw, and fastened to a length of 2x4 such that the whole device is not wider than the cutting area of the hotwire blade:
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Old Mar 02, 2007, 12:22 PM
Will work for foam
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ssjwizard - below are links to a two part article on everything you need to know to get started in hotwiring wing cores. they are newsletters from a local club so the articles begin on page 6 or 7. They contain instructions on how to build the power supply (you already have), a bow, templates and very helpful tips on how to do it sucessfully. its what got me started.

http://www.slnt.org/newsletters/2001_01.pdf
http://www.slnt.org/newsletters/2001_02.pdf
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