Originally Posted by Stuart annat

B&Qfoam?

lovely stuff to work with !

This fascinating. Your method is quick.

Your method is so much different than mine (all learned from Phil Barnes's DVD). You have simplified the worst part about foam core cutting, making the templates. Those templates must be somewhat stiff. You say that they are zinc plate but here in the US the litho plates ARE aluminum and very thin. Our litho plates would be too thin to be workable....or maybe I should just try it.

I like your weights. Do you have an overhead crane to move them about?

Kent

Hi Kent, the litho plate is pretty thin stuff but it works for me.

There are many different ways to skin a cat and the two template method has several advantages over my system, but like I say I'm just plain lazy!

No crane yet, might need one in my old age though.

There is a fine line between lazy and smart. I do wonder how you'll manage the start and stop process when cutting. The video is an early attempt (all of mine were) at a hands off cutting method. From the looks of your bow, I'm thinking that my wire should be tighter.

Kent

Hot Wire Foam Cutting - Bottom Cut (0 min 54 sec)

Here's me cutting a wing a year or so ago. I usually just rest the wire on the trailing edge of the template and switch on, sometimes it needs a nudge to get it going. If I get one side lagging behind I just slow the other side a bit with my finger. The wire pops out the end and onto the board, I wipe off the residue and switch off, flip the core and do the other side.

foam wing cut (0 min 49 sec)

...anyway cores are cut, and with a little light sanding they'd be good enough for bagging with glass straight onto the foam, but I don't want to turn up to the slope with another pink wing so the obechi is on order

4 1/2 hrs to get to this stage

So just to put things together....with the single template you must cut on top of the template, so you flip the foam block over to cut the other side.

Also, you start cutting at the TE which has the template flush with the foam block, so you hold the wire on the template the hit the juice.

Is that about right?

Kent

Paul,

You're making fast work of the new wing.....It looks good. It's funny we take totally different aproaches to cutting wings, but that's what makes this a great hobby. I am looking forward to the first flights. Keep up the good work!

Vern

Yes that's right Kent. All you need is a mm or so of trailing edge template to sit the wire on before switching on the power. I have used a few pins in the past if I can't get the wire to sit. Just stick the pins in the foam at an angle, sit the wire on and hit the power.

As you mention you must cut on top of the template.

From your video the temperature of your bow looks spot on judging by the angel hair, I would only tighten it if you're getting wire lag in the middle.

Paul

Although this is a swept wing, I see from your drawing in post #5, that the cores are cut with square ends. This should simplify cutting quite a bit. So are the root and tip ends cut square too then trimmed later?

If the template is placed square to the sweep, then you must be modifying the airfoil for the template so that you get the properly airfoil at the sweep angle. Is this correct?

Kent

Originally Posted by Vernon Hunt

Paul,

You're making fast work of the new wing.....It looks good. It's funny we take totally different aproaches to cutting wings, but that's what makes this a great hobby. I am looking forward to the first flights. Keep up the good work!

Vern

Thanks Vern, I find it really interesting to see how other people work too. I spent too many long hours in the dark back in the days before the internet, but since things have opened up I've come across many tips and ideas to speed up the building process.

I'm planning to make the first flights off the slope. I'm making a small pod in the first instance, and then a larger one to house the lipo and motor if I'm happy with light lift the performance.

Originally Posted by Knoll53

Although this is a swept wing, I see from your drawing in post #5, that the cores are cut with square ends. This should simplify cutting quite a bit. So are the root and tip ends cut square too then trimmed later?

If the template is placed square to the sweep, then you must be modifying the airfoil for the template so that you get the properly airfoil at the sweep angle. Is this correct?

Kent

Well spotted Kent, yes I squash the aerofoil along it's length in AutoCad before printing so that when I trim the root and tip, I get the true 'foil.

I think there is some contention as to whether or not this is the correct approach, and on any swept wing you get some spanwise migration of the airflow anyway.....but I'll leave the theory to others and get on flying my models

Originally Posted by miniphase

I squash the aerofoil along it's length in AutoCad

I'm always looking for good examples for using Rhino 3D and this maybe one of them.

In Rhino, you can create a wing surface with the airfoil pointing into the air flow then cut sections square to the sweep to get a perfect template. Not all NURBS modelers will produce an accurate surface, but Rhino does.

Scaling the airfoil, in the X axis, in a 2D CAD package should work as well, but to be honest, I'd have to think about it a bit more to be sure. Upon first inspection, it appears to be a linear relationship. The wing twist may make this a bit more interesting and maybe too academic too.

Just thinking out loud.

Kent

I have a sneaking suspicion my method may be too simplistic, to be honest I've never checked the aerofoil once I've trimmed the root and tip

Originally Posted by miniphase

Well spotted Kent, yes I squash the aerofoil along it's length in AutoCad before printing so that when I trim the root and tip, I get the true 'foil.

That's not really necessary. On a high aspect ratio airflow sees the pressure distribution perpendicular to the leading edge. There quite a few threads about sweep effect in the modeling science forum