CO5 build - RC Groups
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Dec 21, 2015, 01:11 AM
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Hussle's Avatar
Build Log

CO5 build


Well, I have pretty much all the bits together and am ready to start my build.

So far, I've constructed my hot wire cutter and power supply and cut the airfoil templates. I've got plenty of foam to play with😀

Hussle
Last edited by Hussle; Dec 21, 2015 at 07:01 AM.
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Dec 21, 2015, 04:43 AM
Slow builder
_AL_'s Avatar
Do yourself a favor & download this.
http://www.rcsoaringdigest.com/pdfs/...SD-2008-11.pdf
Build the automatic cutting arm.
It'll result in a lot less wing cutting failures & a much better result than trying to do it by eye & hand.

Al
Dec 21, 2015, 06:28 AM
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Hussle's Avatar
Intriguing, but, correct me if I'm wrong, most of the advantages seem to be for cutting wings with a varying chord. Would such a system give any advantages for constant chord wings?
Dec 21, 2015, 12:03 PM
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EdSoars's Avatar
Yep, they cut at a nearly-constant speed! At least, more constant than I can manage!

I notice you've cut your templates already, so my advice on using a different airfoil is a bit late! Never mind. Now that you're infected, you'll soon have a drawer-full of templates.

ed
Dec 21, 2015, 04:05 PM
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Hussle's Avatar
Please, speak on! What airfoil would you use, and why?

Also, for a constant chord wing, would a simple weight on a pulley serve to achieve constant speed?

Hussle
Dec 21, 2015, 05:27 PM
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Knoll53's Avatar
Quote:
Originally Posted by Hussle
Also, for a constant chord wing, would a simple weight on a pulley serve to achieve constant speed?
Feel free to show us something new, but a drop arm can assure even movement on each line.

For the bow, I have found that wire sag is problem so my goal is as tight of a wire as possible, then cut with a low force to again reduce wire sag. I use a very stiff one piece bow then flex it as much as possible to create wire tension.
Dec 21, 2015, 06:47 PM
You know nothing....
Stuart A's Avatar
Check out pic 17 in the pdf files.The extended nose/tail makes starting the cut a lot easier.
Dec 21, 2015, 11:24 PM
Registered User
Hussle's Avatar
Ok, update:

Using 0.011" stainless steel fishing leader at 12 volts, my cuts are very slow.

The cores I need to cut are 700 mm in length and I'm in a bit of a catch 22: if I pull faster, the wire bends unacceptably; if I pull slower, the wing ends up horribly rippled.

So do I find thinner/better wire or buy a higher voltage power supply?

Cutting works fine on smaller lengths, do I simply cut the wing in 8 sections instead of 4?

Hussle
Dec 22, 2015, 04:37 AM
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Hussle's Avatar
Using 0.020" yields similar results, but cuts faster.

Ok, I really don't know what I'm doing wrong here, the pulley system seems to be pulling fairly evenly, should I try more/less weight to pull it, a cooler wire?

Hussle
Last edited by Hussle; Dec 22, 2015 at 04:57 AM.
Dec 22, 2015, 11:49 AM
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Knoll53's Avatar
Quote:
Originally Posted by Hussle
if I pull slower, the wing ends up horribly rippled.
I want pictures.........................
Is the wire moving smoothly over the template edge? I some times face the edge of the template with birch plywood to get a really smooth draw.
Dec 22, 2015, 03:43 PM
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EdSoars's Avatar
Quote:
Please, speak on! What airfoil would you use, and why?

Also, for a constant chord wing, would a simple weight on a pulley serve to achieve constant speed?
I described the HQS 15-09 airfoil in your Newbie thread, and why I like it.

The weighted drop-arm hotwire setup pulls the wire at a speed that is proportional to the chord. You can see how it works in the picture on my "BreakDancer 1.8m" thread on the third post.

The most important thing about smooth cuts with a drop-arm is to get the templates VERY smooth. Like MIRROR smooth. I sometimes put a 1/64 plywood cap over the templates, and I ALWAYS lubricate the surfaces with lots of pencil graphite.

ed
Dec 22, 2015, 04:29 PM
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Hussle's Avatar
Thanks for the tips guys!

I'll have another try today and report back.

Hussle
Dec 22, 2015, 06:34 PM
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Knoll53's Avatar
nice picture. It tells a lot. Those are some mighty ripples you have there. My theory is that your wire is not tight enough. You need a new bow that is very strong.

This bow is a big wood dowel with solid fiberglass rods at the ends and it is flexed to create a tight wire. Try some thing like that.
Dec 22, 2015, 11:11 PM
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EdSoars's Avatar
My bow is an aluminum channel, and the arms are 1/4" steel rods, about 14" long (it's a Feathercut bow). The wire is .010" diameter. I flex the arms about 2", so I don't have as much tension as Kent does. I can cut a 50" panel in either EPS or EPP with very little drag or distortion. I use 50v for EPP and 33v for EPS. It is not healthy to touch the wire, but I've been able to resist the temptation so far! BTW, the human body's internal resistance is enough to stop up to about 30 volts, so you would feel a very mild shock from if cutting EPS, and not a dangerous one when cutting EPP at 50v. On the other hand, the heat burn would be VERY uncomfortable. I speak from experience, and once was enough.

Getting a good panel is a matter of balancing the weight on the drop arm to the length and material of the panel. Experience is the Great Teacher. I'll post a few more photos of the drop arm setup within a day or two.

ed
Last edited by EdSoars; Dec 22, 2015 at 11:31 PM.
Dec 22, 2015, 11:40 PM
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awkward's Avatar
Great thread
Looking forward to the fotos of your set up Edsoar
What is the max width of foam that can realistically be cut?


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