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Bow Kite or Inflatable Kite bladder


hello. For the past moth i've been trying to make a inflatable bow kite, all fine till now, i printed out the plans, sewed the parts, but i've stumbled on the bladders, on the leading edge bladder to be more specific. How do i make the bladder when inflated to have the bow shape?i mean how to cut the material and seal it?(the material i use is celofane, cheap and resistent)
Thanks.