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Building Tips and technical articles. => Building techniques => Topic started by: Rob Killick on May 08, 2009, 06:56:14 PM
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Hi ,
I was wondering what gauge of nichrome wire would be adequate for cutting foam wing cores ?
Thanks ,
Rob Killick
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I bought a DIY foam-cutting kit, and the wire (not absolutely certain it's nichrome) is about .008 dia. About 24-gauge???
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Hi Ralph ,
Thanks for the info . I checked a few do-it-yourself foam cutting sites and most of them use a 20 gauge wire ,
I checked and .008" wire is 32 gauge
Thanks again ,
Rob Killick
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I've never used nichrome wire. For over 15 years I have used .012 stainless flying line. It holds up very well to many cuts and the ends were easy to make up using the same techniques as making flying lines. If you want to see how well it works look on youtube at:
http://www.youtube.com/watch?v=jb39MgI8jY0
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Hi Guys,
If someone has a "Feathercut" wing cutter system then you must only use their wire, which is .018 T-370 inconel wire. They warn that using nicrome or other wire could harm their power source, so I only use their wire with my Feathercut. you can get the wire from "Aerospace Composites", "CST" composites store and of course directly from Feathercut.
I also have a rheostat power source which can use other wires. I don't like nicrome wire because I have had it heat deform and ruin cores even with lots of tension, plus it broke on me much more than any other wire I have used.
I have used .012 and .008 braided control lines and it holds up well and gives consistent heat. I am thinking about trying .008 solid control lines next. I looked online and I found references to others using control line or guitar strings and etc because they did not like nichrome. I am sure some folks have had perfectly good results with nichrome but I and others have not, and control line is a much cheaper and easier to find alternative.
The Feathercut guy reccommends using sandpaper to thin the wire on the side that cuts the shorter wing chord when cutting a tapered wing. the wire has to move slower across the shorter tip chord than the wider root chord and this can cause an excessive burn out and produce inaccuracy in the cut. Sanding the wire reduces the burn out at the tip and yeilds a better core. I went ahead an thinned the wire but I didn't do side by side comparisons with an unthinned wire to compare results so I can't personally swear thinning is better but I figured it couldn't hurt.
This may be more information than you were looking for but I thought I would pass it along.
PS. I just saw Bob Furr's post about using control line for your bow. See I told other guys were doing it
Happy Foam Cutting,
Pat Robinson
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I use single-strand stainless steel fishing leader wire, about .016", as I remember, tensioned with a guitar tuning head. Nichrome is good to higher temperatures, but I think stainless is stronger at the temperatures we use to cut foam. I spent several days trying to taper wire, but gave up. I hold down blocks of foam to the cutting table using a shop vac sucking on holes in the table. I just put more holes near the LE and the wing tip to pass air through the foam to cool the wire where it's moving slowly.
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Pat,
I think you may be happier with the larger solid wire Howard suggested as the resistance in .008 solid would be quite high and I am guessing you could make a nice flash bulb out of it... resistance seems to be related to the surface area of a wire (this is one reason that extension cords are made up of many very fine wires) and the .008 solids have much less surface area than the stranded wires.
Bob
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Hi Bob,
Thanks for the suggestion. In the past I have use .015" braided control line and .014" solids and they worked fine but then I moved to .012" braided lines. They required less bow tension and less power and seemed to help reduce burnout issues at the tip but again without rigorous comparative testing to verify it I can't swear that it was better. Anyway, .012 is what I have used most. I only use .008" braided lines once and it worked okay. Maybe I need to go back to .012" braided lines.
As an aside, I always ran straight test cuts on scraps foam to check if the temperature setting cut the foam cleanly before I even considered cutting the wing and I reccomend everyone run tests as well.
Bob, I think I am going to buy your foam wing cutting video because even though I have already cut foam wings I am always interested in learning new tidbits of info on how to do things better. I would reccommend anyone new to foam cutting to get Bob's video and study online sources and then practice cutting. Even then you will mess up some cores but that is the price of learning. My problem is I only cut foam every few years so I get rusty and have to resharpen my technique.
Once again thanks Bob,
Pat Robinson
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In the video I use a dowel rod for the bow. I think my next bow will be a wooden yard stick from Ace hardware. It is almost as light (which I have found to be really helpful in making accurate cuts) and is more durable than a dowel rod (and less expensive). I am not sure why I so love finding frugal ways to have fun in this hobby but I do....
Bob