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Feb 15, 2017, 12:02 PM
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parajared's Avatar
Quote:
Originally Posted by Granted
I use 1/16" piano wire as pins + some adhesive-transfer tape to secure the templates. Cut one profile, slide off template, slide on next profile, cut.
Spar slots/grooves are cut using custom tools.
That's a really cool idea using xt60 connectors as a detachable head for different spars.
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Feb 15, 2017, 12:11 PM
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psychedvike's Avatar
Here's a link to my wing core cutter. I posted a thread on it not long ago but since the topic has come back around I thought some might want to check it out.
Hot wire wing core cutter. (13 min 27 sec)
Feb 15, 2017, 05:21 PM
Registered User
flypaper 2's Avatar
Here's another bow I use for light stuff. It'll cut 24 in. panels so you can make a 48 in. double tapered wing.
I'm cheap, so I made it out of a piece of plastic hot water pipe. It does work well and light to handle. .020 piano wire for cutting.
I keep it unhooked so the pipe won't get a permanent bend in it.
Gord
Feb 16, 2017, 12:03 AM
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Mooney_Driver's Avatar
Quote:
Originally Posted by flypaper 2
I tried using aluminum templates on the ends of a block to cut wing panels. About the last 1in. or 1 1/2 in. would leave a rough, ripply finish , where the aluminum was absorbing some of the heat from the wire where it sits on the template.
The foam cutter at this link uses ,020" thick litho aluminum:
http://www.charlesriverrc.org/articl...gmancutter.htm
and
http://www.charlesriverrc.org/articl...ancutter_8.gif
shows the template layout.
The reason he used the thin aluminum was so the metal did not act as a heat sink and cool the wire appreciably.
Feb 16, 2017, 07:04 AM
Registered User
flypaper 2's Avatar
Another thing that might work, is to put a balsa or foam spacer, a 1/4 or 1/2 in., between the aluminum and block being cut, glued to the aluminum.

Gord.
Mar 29, 2019, 02:32 PM
Registered User
Hey everyone,

Back to this thread, hoping its not dead and I can get some help. Im wanting to make wing for making my own delta wing and would like to make them out of foam while I learn to fly them.

I have the following

Hampton bay wired 16v transformer
Input 120vac
Output 16vac-10va

Rotary dimmer -Leviton

How do I wire this to make my own hot wire cutter. Id like to get my wiring done before I do the wiring to my bow.

Below are the pictures
Mar 29, 2019, 04:20 PM
Registered User
Mooney_Driver's Avatar
Quote:
Originally Posted by Shaheed40

I have the following

Hampton bay wired 16v transformer
Input 120vac
Output 16vac-10va

Rotary dimmer -Leviton

How do I wire this to make my own hot wire cutter. Id like to get my wiring done before I do the wiring to my bow.
I posted a couple links a couple messages back. Take a look at that web page and page 9 of that web page will show you a suggested wiring diagram:
http://www.charlesriverrc.org/articl...ancutter_9.gif
Apr 01, 2019, 10:28 PM
Registered User
I've spent many years hot wire cutting foam for making both models and full scale experimental aircraft. The best hot wire cutter is very simple and it's cheap and easy to make, except perhaps for the power supply.

As noted in the drawing, take a piece of lumber suited to the task at hand. A 1m or 1 yard cutter can use a piece of 1x2" ordinary lumber a few inches longer than the desire cut.

Make two support arms out of springy piano wire about 1/8" in diameter.

Drill two holes through the EDGE of the wooden bar near the ends at about a 15 degree angle. You can eyeball this.

Cut your 1/8" springy piano wire to length, depending on the thickness of your foam. Chuck the piece in a drill and use the corner of a sharp file to cut a groove as close to the end as you can. This will retain the cutting wire

Insert the heavy wire arms into the holes you just drilled in the wooden spine with the ends splaying out and the other end protruding from the other edge of the wooden spine far enough to attach your power supply.

I use light weight stainless steel safety wire. It's strong, cheap, and comes in various diameters. You'll want a wire as thin as possible, but one thick enough not to break. A broken wire halfway through a cut ruins the job. I think a diameter of .018" or so is a good starting point.

Wrap the cutting wire around the groove and then around itself to secure one end. Then attach the other end in such a way that the springy piano wire arms are bent inward more or less perpendicular to the wooden support spine. This will give you good tension without any springs getting in the way. Good tension is required for a good cut. Naturally, too much tension will lead to broken wires and ruined parts.

Attach your power supply to the upper part of the piano wire arms.

Adjust the power so that the wire produces a little bit of a sizzling or frying noise. As it exits the cut, you should have "angle hair" stringing out all along the cutting wire. The cut should be smooth. If it's rough, chances are your wire is too hot.

Do everything you can to avoid reversals when you cut. When making airfoils, I prefer to use two templates on each end which extend well beyond the leading and trailing edge. One is a template of the lower surface of the airfoil. The bottom edge of this template is flat and rests on the table. The upper edge of the first template is concave, representing the lower surface of the wing. I make mine out of 1/16" birch plywood and I locate it by pinning it to the end of the foam blank using small nails. Of course, a similar template is attached to the other end and is adjusted in size and position to give the desired taper, sweep, and twist.

After I make the first sweeping cut of the lower surface, I replace that template with one for the upper surface. It too has a flat bottom which rests on the table and index holes matching the ones in the lower surface template so that the locating nails go into the same holes in the foam. Naturally, the top of this second template is convex, representing the upper surface of the airfoil. The flat bottom helps insure that the templates don't shift while you're cutting, even under considerable downward pressure.

You'll have to do a bit of clean up and rounding on the leading edge and most likely you'll have to trim the trailing edge straight.

If you want to cut spar notches or other modifications, you will use a third or fourth set of templates. NO PEEKING until you're done.

A "U" shaped template can be used to cut a spar notch nearly, but not quite, the full depth of the thickest part of the wing. You can open the airfoil pieces like a book, insert some adhesive along with a 1/16" plywood spar and have yourself a neat and tidy wing core and spar unit with surprising stiffness, especially when you cover it with balsa.
Apr 01, 2019, 10:48 PM
Registered User
Here is a drawing of what a typical pair of airfoil templates looks like. Note the flat bottoms which match and which rest on the table as well as the matching alignment holes into which you insert small nails when cutting. Be sure to size the holes accurately to the size of your nails. Good alignment is one key to making good airfoils.
Jan 11, 2020, 02:03 PM
Registered User
AviatorFPV's Avatar

Melted foam Residue on the Wing


Hi, I am using Owens Corning pink foam board insulation with my CNC hotwire foam cutter but there is lots of melted foam residue left on the wing after cut that I need to sand off from the wing. Should I increase the speed or I should reduce the temperature? How can I fix this issue?
Jan 11, 2020, 04:23 PM
Registered User
psychedvike's Avatar
You may find you need to increase the heat. I'd try both hotter or cooler. it will always have some hairs on the surface but they should easily whip off with fine sand paper. What are you using for wire?
Jan 11, 2020, 09:16 PM
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AviatorFPV's Avatar
Quote:
Originally Posted by psychedvike
You may find you need to increase the heat. I'd try both hotter or cooler. it will always have some hairs on the surface but they should easily whip off with fine sand paper. What are you using for wire?
I am using 0.5mm wire I bought from Ebay along time ago. What's the best wire to use?


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