My favorite technique for making new gapless hinges is to use Monokote as a hinge material. The hinges are very light, are gapless, and are flexible (which is important; especially if you use micro-servos). Furthermore, they're fairly easy and stress-less to install, with absolutely no CA. They work well on small models, up to about ``40'' size. Stronger covering material and stitching of the seams may allow the same technique to be used on arbitrarily large models. Have a look:
Figure 1: Cut out small strips of Monokote, up to 2'' square as model
dictates. Lay them in pairs next to each other, with adhesive sides
facing each other, as shown.
Figure 2: With plenty of overlap, iron strips of Monokote together to
make a hinge, ready to apply.
Figure 3: Apply the hinge to the model as shown. Each adjacent hinge
should ``criss-cross'' as depicted above. Each hinge puts tension on
adjacent hinges, allowing for a tight, clean fit.