A lot of work and effort has been put into getting the rabbet beveled properly with the angle of the frames. This will allow the bottom planks to lay flush along the rabbet and the frames, forming a strong and well sealed bottom that will keep water out, keeping us dry as the dinghy floats.
The chine lays opposite to the keel, and needs to be beveled in the same angle as the rabbet and frames. This is because the bottom planks will lay over the topside planks and extend outward. Once the bottom is planked, these overhanging ends will be cut to size and sanded flush with the curvature of the hull. The bevel also increases the width of the bedding compound which will promote further sealing. The added width gives yet another advantage: space for fasteners. The chine is a mere half inch wide, and the planks are a mere 1/4 inch wide. This all adds up to form a 1 inch width to fasten the bottom planks. Adding a bevel greatly increases this width, especially in the forward part of the boat where the angle is quite severe, creating what looks more like a scarf instead of a beveled junction.
A wooden batten is very convenient to verify the trueness of the bottom. The batten starts on the keel in the rabbet, and then passes flush over the frame and over the chine. The batten should lay flush and flat along the entire journey. If there are any gaps, then you will need to bevel the chine a bit further since the rabbet was beveled to perfection before the topsides were planked.
Beveling this much wood may seem like a tricky task. If the hull were carvel planked, we could use a block plane to bevel the chine since grain would all be oriented in the same direction. Since we did double diagonal planking on the topsides, the chine experiences three different grain directions and attempting to use a plane would result in a chipped up mess! Instead, abrasives are needed to smooth everything up.
A sander works for this task, but it is rather slow and time consuming. A much faster method is to use an angle grinder fitted with a paddle sander wheel. This attachment is practically a book of sandpaper that spins around as it blows the wood away in record speed. The angle grinder also has a long handle that allows you to better visualize the angle you are grinding the chine into.
Using the angle grinder and double checking your work over and over will ensure that the chine is beveled flat and flush with the bottom planking. This will create a very strong and fair bottom that will glide through the water with ease.