Construction of the Dillon Pro Tunnel

Step one is the tunnel sides. But they are much more than that as they extend all the way up to the underside of the deck, becoming two girders running the length and depth of the hull.
Here, I've bent a batten through the curve of the deck -- from the transom to the sponson tip.

The bulkheads will interlock with the tunnel sides to form the basic shape of the boat.

The tunnel sides, notched to recieve the the bulkheads, stem and transom beam.

Next step is the bulkheads. The narrow slots at the corners of the tunnel will interlock with the slots cut into the tunnel sides.

A dry assembly of bulkheads and tunnel sides. Right-side-up for now, but will be up-side-down when this stage is final assembled.
Also note holes cut wherever possible. The total weight of the wood removed was less than three pounds, so the biggest benefit for this step is hull ventilation.

And now we're upside-down, the bulkheads, transom and stem glued to the tunnel sides. The small bulkheads at the sponson tips have yet to be installed.
The pine board across the bow is there to keep the sponson extensions square and properly spaced. It will probably have to stay in place until all the sponson's longitudinals are installed.

A dozen stringers for the top of the tunnel. Now the structure is lined up along its centerline and has stiffened up considerably.

Outlined by its sheer clamps, the Pro Tunnel is starting to look really wide. At about 6.5', I guess it is. The tunnel keels have also been installed along the bottom edges of the tunnel sides.
At this point I've also removed the pine board that spanned the sponson tips, holding them true. They're not going anywhere at now.

Well actually....
As I bent the chines into place the sponson extensions wanted to twist a bit, so the pine board went back on.
With the chines now installed, and additional battens along the sponson pad in place, I took the brace off once again. As I lookened the screw on one side, the distance between the sponson tips did increase, but by less than a sixteenth of an inch. I think the brace is off for good this time; the only think left to bend on, while the boat is still upside-down anyway, is the plywood.
Next step, plywood planking.

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