Step 3: Adding the spars and dihedral.
Instead, I tape the spars down to the sail onto the cutting surface. The tape needs to be pressed down firmly, probably with the edge or back of your finger nail.
Once it is firmly fixed, I use the knife to trim around the edges of the sail, leaving some of the tape on the mat.
You will see that I also trimmed off the ends of the side-to-side spar at this stage, to make them exactly the same length as the width of the kite.
I did not, however, trim the longeron (the front-to-back spar). Instead, I matched it up to the front corner, and left the rest sticking out the back - I am going to fix the tail to it later.
I then gave the spar a slight bend at the centre-point. This bend is known as the dihedral angle, and adds stability to the kite. Generally, the more the dihedral is bent, the more stable the kite is, but the less lift it has. Finding a balance between the two is a trick that can only be learned by doing, but as a rule of thumb you should start at an angle around 135o and work from there - windier weather need a sharper dihedral, calmer weather needs less.