How to Halve the Spar Sections of a Flexi Super 10 (if You're Foolish Enough to Try)

Or - "how to cut-down a Flexi Super 10 spar from a 3 piece X 1mtr into a 6 piece X 500mm - ish". This is in order to make it small enough to fit into typical luggage.

This kite marked the beginning of power kiting in the 1970's. This is a seriously fantastic wing which in a big wind is hugely fast and powerful and capable of ripping your arms out their sockets and if that fails it will find another way to ruin your life.

The only downside to this kite is the 10ft spar incorporated into the leading edge. It comprises a center piece of carbon fiber and two outer, tapered ones made from glass fiber. The three sections are joined, prior to flying, with two brass ferrules. It is my intention to cut each section in half and follow the original concept in re-joining them with three additional ferrules.

Fortunately, this kite is still in production and so too are replacement spars - this fact made cutting the sections in half a tad less stressful.

Step 1: Spar Ferrules.

I bought the ferrules before cutting the pieces in half - unusual for me to be patient but I needed to be certain of the theory, particularly in respect of the tapered parts.

The ferrules I bought are of a well engineered, high(?) quality brass alloy and of a similar (ish) spec to the existing original ones. I needed one 8mm X 80mm for the center, carbon fiber section and two 6mm X 60mm for the outer fiberglass ones.

As mentioned, the two outer sections of the spar are tapered linearly along their meter length. I expected this to be an issue as the ferrules are straight sockets. Retaining the mechanical integrity of the shaft whilst not restricting it's flexibility needed in flight, required a degree of calculation - the ferrule needs to push-fit onto the thin end of the thicker half of the tapered section, coming to rest with a snug fit at the halfway point of it's socketable length and for that to coincide with the measurements of the shaft when cut exactly in half. The ferrule is then permanently fixed to the other, thicker end of the thinner half of the shaft leaving half of it's socketable length vacant for the thinner end of the thicker half :-)

Step 2: Cutting the Pieces in Half.

The cut is quite straightforward, although, carbon and glass fiber materials can be a little iffy when cross-cut, as they often have a grain and are prone to fraying and splitting.
I used a micro-bore rotary pipe cutter to score a line on both sides of the cutting point and then used a vice lined with cloth for protection and a junior hacksaw for the cut. I then used a fine wet-and-dry paper to smooth the edges of any burs and finished off by wiping a little epoxy resin over the ends.

Step 3: Fitting the Ferrules.

After tidying the edges of the cuts I double checked that the 6mm ferrules actually fitted the thinner ends of the thicker halves, as planned, to a halfway point and coming to rest where the tapered spar section becomes wide enough - BINGO!
Next step was to wind enough insulation tape around the thicker ends of the thinner halves to form a wide seat for the ferrules to sit on at a measurement of 30mm from the end. I popped them vertically into a soft-lined vice, daubed them with epoxy resin and slid the (only slightly loose) ferrules over them, turning them on, as I would with a threaded nut, to evenly spread the adhesive. The shelf fashioned from insulation tape acts as a rest and helps to stop excessive leakage of epoxy. I then left them in the vice for twenty four hours.

The center 8mm ferrule, as with the two outer 6mm ones, doesn't have an internal "stop" at the midway point and will slide all the way onto the spar. For the sake of convenience, I decided to create a midway stopping point by inserting two 8mm drill bits to almost halfway from both ends to offer support from misshaping and gave the ferrule one good tap with a center punch. I decided not to permanently fix the center ferrule, but to do so semi-permanently with insulation tape.

I should mention at this point that it is normal practice to use insulation tape to hold this kite's spar parts together. Once this kite is in the air the spar is curved to an extent that makes it impossible for it's parts to separate - if it was to happen, it's likely that a hurricane is in effect, at which point, the kite will collapse and harmlessly float away like a discarded carrier bag - all you gotta do, is, let go :-)

Step 4: Before and After.

So here it is, a Super 10, modified to half of it's original packed-away length.

I hope to update this instructable when the mission is complete.

I'm goin' in...