The bottom is flat, and not too wide in the forward sections. The tunnel is
an improvement over the regulation square box type. It is simply a
depression in the bottom of correct shape athwartships and fore and aft to
induce the water to flow uphill to the propeller and then sweep out through
the small orifice in the bottom of the stern. If built just like the plans
show it will work perfectly because I have tried it in other boats of
similar design. This form of bottom is a little more efficient than the
square tunnel type; but not as efficient as the box deadwood model having
negative deadrise aft as exemplified in my designs like Everhope, Heron,...
Islamorada [and Rescue Minor], to mention a few, which have appeared in back
numbers of MoToR BoatinG.

It will be seen that Twinkle can be run up on the shore without anything
striking, only the flat bottom or the heavy skeg. And it is very unlikely
that drift wood or snags will tangle with the propeller tucked up in the
depression in the bottom. A boat of this shape is an easy one to move on a
trailer or truck as it needs neither blocking or bilge poppets. Wherever she
is she will sit on an even keel.