Hotwire issues

I was trying to devise the best way to cut the foam wing ribs for the KR.  There are 5 ribs in the outer wing.  The wing both tapers to a shorter chord at the tip, and changes airfoils completly!  I attempted to plot out the airfoil at each of the 5 locations but had less than perfect results.

After much time was spent working with a spreadsheet and CAD, I decided to see if I could do a hybrid of methods to acheive the wing ribs. 

On the origional KR, The foam was glued in place and a large strait edge sander was used over 2 templates to shape the foam.  This has a few downfalls:

1) Sanding is messy
2) The foam you would have to use is OPEN cell foam.  It requires a coat of micro to seal the cells
3) The foam is not available to me localy so I would have to drive 5 hours, or have some very large pieces of it shipped.

I decided on trying to use the standard Polystyreen foam and a long hotwire.  Unfortunatly, the hot wire would have to be so long that I was sure I did not have a way to power it.  I wondered if I could Segment the wire by making the electricity "Jump" across parts of the hotwire by adding a larger wire in some segments giving the electricty a path with a lot less resistance.

Here is our attempt using our long bow and a 14 gauge wire with aligator clips:



As you can see, It worked..  So, it was time to make a looong bow that could span all 5 wing ribs on the outer spars which as 90" long.

Here is the final product:



Now I just have to hurry and finish the foam spar extensions before it gets to cold to fiberglass!  I hope to have wing ribs in place and shaped by Halloween!