Hot Wiring With One Person

[spitzy]

I've completed the bulkheads and sides of the plane but don't have the space to assemble. So... I'm starting on the Canard.

 

Before I start cutting into the foam with two people, I'd like to know if anyone has used a device like the following description. The cutting arm would be suspended from a pully for easy movement along the airfoil. Separate strings would be attached to the arm on each end of the wire and pulled with equal, constant, and adjustable force over the correct distance.

 

A friend of mine did this with his model glider wings and said they come out much cleaner.

 

I've also been playing with differnt gauge wire for cutting. The wire specifid in the kit requires a stout supply of current and seems to be less acurate than smaller gauge wire.

 

Any thoughts or experience with this?

 

Love,

Mike

[Wayne Hicks]

(1) Make sure the edges on the hotwiring template are free from nicks and are as smooth as possible. The hotwire will tend to snag on any nick, gouge, or scratch on the template.

 

(2) Use 0.041 iconel wire (or something similar). You want to be able to tighten the wire alot to avoid wire lag as it's being dragged through the cores. A smaller diameter wire will lag alot more, resulted in scallops being cut into the core.

 

(3) I used hose clamps to secure the hotwire to the pipes. I wrapped the wire around the pipe, then held it in place with the hose clamps. I found that the wire breaks more often if threaded through a hole in the pipe like shown in the plans.

 

(4) Allow the wire to get hot before tightening it. To tighten the hot wire, drill a hole in the base of one of the pipes. Stick a screw driver in the hole and use it to turn the pipe to tighten the wire. I found that using vise grips would eventually crimp the pipe, causing it to buckle under load.

 

(5) When hotwiring, lean the saw into the direction of travel at about a 45 degree angle. In this way, the wire is being pulled along, not pushed. The wire will tend to ride over bumps and won't snag as often on imperfections on the hotwire templates.

 

(6) Always loosen the wire BEFORE turning off the power supply. A very hot wire tends to expand and yield. That's why we tighten the heck out of it before hotwiring a foam core. However, the wire will shrink up when it goes cold! Not loosening will fatigue the wire prematurely, causing it to break more often.

 

Addressing your questions, I never tried suspending the hotwire saw with pulleys. I actually like the weight of the saw helping to hold the wire on the template. I always used a buddy to help cut the wing and canard cores, but I did cut the lower winglets without help.

 

As for a power supply, spend the bucks and get a good power supply. You'll do a lot of hotwiring and it's worth it. Ebay is a good place to find cheap variacs and DC power supplies. Don't use thin wire for the sake of a power supply.

[Jerry Schneider]

Before I start cutting into the foam with two people, I'd like to know if anyone has used a device like the following description. The cutting arm would be suspended from a pully for easy movement along the airfoil. Separate strings would be attached to the arm on each end of the wire and pulled with equal, constant, and adjustable force over the correct distance.

It would probably work on the canard, where the cuts are all all the same from one end to the other.The set-up would be a real task.

But the wing cores are tapered from one end to the other, requiring less movement on one end.

Better to rent someone for a few hours!

[Kent Ashton]

Love,

Mike

 

That's sweet Mike. ;-) Seriously, though, no need for the special apparatus. A 2X4, couple of pipe, safety-wire, visegrips and you're building. My wife helps me cut cores. They come out fine. A bit of practice helps to know what you're doing. If you can find some 2" blue polystyrene foam to practice on--it is often used for building insulation, you'll be a pro after a one or two tries.

Love, Kent