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The Hammerhead Shark is basically a large windsock, although it does generate some lift it is designed to be flown from the line of a lifter kite. Having built plenty of kites following written instructions, I know how easy it is to misunderstand them!
All pieces on the plan are inclusive of a 5mm hem/seam allowance. Nearly all pieces are in pairs which are a mirror image of each other, i.e. one for the right hand side and one for the left so pay attention to which side of the fabric is outermost. In the instructions, ‘good’ side refers to the outer side of the fabric, and ‘wrong’ side refers to the inside.