I have been wanting to hotwire my own air foils from foam. I hate to spend the time building up balsa wings.
I saw a video by David Windestål on hot wiring.
He is using but one template and a fulcrum, instead of the usual two templates and C shaped machine. His machine makes an aero surface all in one cut. You hold the hot wire by a T handle. The nature of the technique is that it gives you tapered wings that vary depending on how long the wire fulcrum is from the template. I have mine set at about 39.37"
I think I may have improved on David W's technique by screwing the template on a plywood mount then clamping it to the table. I used a piece of Formica laminate for my template. I glued on a paper diagram and cut out the shape on the formica accurately. I also didn't split the template but run the wire through the template before starting. The Foam is sandwiched between the plywood mount and another board which I place lead weights over to hold things steady.
I had some solid core .023" steel MIG wire and used my 2 amp battery charger for a power supply.
I made several right wings then removed the template and turned it around and made left wings. I used scrap pieces of foam that were in my attic.
My first few cuts were not as good as I did after a bit of practice. My template is smaller than I would like. Am going to build another larger template.
My wife made a foam body and we glued the wings on. (They have a chord to span ratio of about 5:1) Balanced the plane with a penny. Had several decent flights. Something that made for a nice Christmas afternoon.