Just use a distant pivot point and a hand-hold , with just a single template , on the near end . This works superbly well , at the cost of having to do a couple of back-of-fag-packet-sums . It was in Francis Reynolds ’ column and he describes it as “ pivot point cutting ” One end of the hot wire is attached to a fixed pivot point some distance away , and your hand at the other end provides the tension ( which can be varied at will ) and follows the one template .. It resembles a cheese-cutter , and does work very well , and is easy to set up .
The method can be used to cut wing and fuselage cores of any taper . Obviously it can ’ t cut rectangular wings , but that ’ s not too much of a problem . Tapered wings look better , can be built lighter and are a little more efficient .
Very low taper wings can be a problem as the fixed pivot might have to be in your neighbors back lawn . Fig 1 shows the quick bit of maths you have to do .
Key : R is root length , T is tip length , S is the span of the foam section to be cut , and PD is distance to the pivot from the tip .
So , in the case of the Mustang , the main wing has a root dimension of 225mm and the tip 150mm . The foam span is 422 mm . So the distance from the tip to the pivot point is 844 mm .
Picture 6 shows the setup and the result is in picture 7 .
Pivot Distance , PD = ( S ) divided by ( R / T – 1 )
This method also works well with a fuselage , calculate the taper and distances as above , place one template at the “ fat ” end and cut away .