Discussion A 1M Zone Wing

[Alex Hoekstra]

Berrie,

Your cuttingtemplates are made of steel I think this wil cool down your cuttingwire and thats why it might stick. I always learned not to use any metal for cuttingtemplates

[Buddy Roos]

Deleted.....

[Berrie]

@Alex, I know some people give the advice not use metal templates.

I have made templates out of 1mm carbonsteel, 1mm aluminium, 1mm wood and from the 1mm stuff used for covering desks etc. All these templates NEVER showed a "problem" I have now.

A few minutes ago I tested the 0.45mm thick stainless steel and a 0.5mm wire. Guess what? No problem!! i have a lovely piece of foamcore.

If I look closer to the samples I have cutted with the 0.45mm stainless steel templates I noticed the following:

1) 0.3mm wire: surface of the core is indeed better than cutting with 0.5mm. The 0.5mm surface is a bit rougher and has "melting holes".

2) The theoretical thickness of the core should be 6.4mm. (Zone 36, 123mm)
Both cores are 6.1mm thick before sanding of the surface.

3) The theoretical thickness of the core should be 3.9mm. (Zone 25, 76mm)
Both cores are 3.8mm thick before sanding of the surface.

4) So 2) and 3) 'proves' that there is no difference in thickness of the core when you use a 0.3mm or 0.5mm cuttingwire. (At least, according to what I did now. Someone else might have other experience)

**We will make new templates with a minimum thickness of 1mm. The ramps for the cuttingthread for the uppersurface of the foil needs to be a bit less steep.**

Below a picture, diffucult to show the differences between the surface quality. The above foamcore is cutted with the 0.5mm wire. Other one cut with 0.3mm wire.

p.s. Almost forgotten; The thin trailing edge of the core cutted with the 0.5mm wire was melted down on the lower foambed wile cutting the uppersurface. I needed to use a knife to free the core. But thats not a problem, just a remark.

[Berrie]

Alex is right. Metal template do cool the foam, or wire, during cutting. Let me explain a few things. I got a PM with the remark that it is possible to cut cores with a much better surface quality. That's interesting, because I've build a several planes cutting the cores the same way. I use to cut with a sort of "light my wire" style. I use to cut with a real hot hotwire cutter. The key for better surface quality should be in cutting with as less heat as possible. A cuttingspeed of 5mm each second should be the mark.

I couldn't resist and did a few tests. I collected some pieces foam, took a dive in the cabinet for 1mm aluminium templates and start testing. The thinnest availeble wire for me is still the 0.3mm one. So all the cuts are made with this wire. Normally I set my adjustable powersupply ready with a setting, press the button and the wire starts to cut. Not this time. I turned the potentiometer to zero and switched the powersupply on. Now I "opened" the powersupply slowly till the wire starts to cut with the desired speed.

As you can see on the picture below, it didn't work:



Altough the 1mm alumium templates are very slippery, the cutting was very ribbed. In my opinion the following happened:

You need heat to cut. Let's call that: Heatinput. Heatinput is nothing else than electic energy (V*I*time(s)) distributed over some distance

Cutting the rooth cord and tip cord happens in the same time. But the rooth is bigger than the tip, so the roothcord takes the less heatinput.

In fact, the heatinput at the root is so critical low, that the aluminium template absorbed to much heat. A small edge of foam doesn't melt. It is more or less teared apart. The terings make the ribbing. See also the close up. You see some pieces of foam.



The tipcord get's a bit higher heatinput. Just enough to cut the way you want. But again, it's critical. You can see some "glassy" edge.



If the above is more or less true, an expirement with formica templates is worth trying. As you can see, cutting with low speed/cold as possible wire, gives no problem! The formica don't absorbe the heat of the wire.



I will make formica templates for one mini Zone panel. Time consuming, hoping it makes sense.......

[Trey4U]

When we were learning how to cut foam cores 20 years ago we found that templates made from either 1/8" or 1/4" phenolic stock (available at some electrical supply houses) was a good choice because it wouldn't cool down the wire. I don't remember where we got it but there is a teflon tape that we stuck to the surface of the template that gave the wire a VERY smooth surface to run on. (It's thin enough not to affect the airfoil) Phenolic isn't as hard as steel but it's a hard material which makes it very hard to get an accurate airfoil. I found someone that could laser cut plywood templates, (more accurate than trying to make the phenolic ones by hand) then added the teflon tape which seemed to work pretty well. If there is a source now for laser cut plywood templates I would try that and get the teflon tape.

just my .02

[Pook]

Thanks for those photos Berrie...most informative!

I'm hopeing to be cutting some wings in the next few weeks so every bit of info I can get now the better