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EZ Tunnel Race Boat Plans
Page Three
Hull Sides & Spray Rails

Add a second layer to the transom. This "outer transom" covers the inner transom, the aft edge of the tunnel plank and the aft edge of the transom beam. It is actually the first piece of the outer sheathing of the boat.

In the photo, a piece of scrap is clamped to the transom and the shape of the outer transom traced on.

Clamp or screw the outer transom into place.

In preperation for the hull sides, glue blocks need to be attached to the tunnel plank. Note that the glue blocks are glued to the upper surface of the tunnel plank -- which means the underside of the plywood, considering that your boat is upside down.

From bulkhead two to the transom the tunnel plank is straight, so a single long glue block can be attached here. You can also use two or more shorter pieces here, but I urge you to butt them together right at the bulkheads to make sure you are not introducing any weakness between the bulkheads in this critical part of the hull.

Forward of bulkhead two you will need to saw curved glue blocks, each about 12 inches long. Trace the curve directly from the tunnel plank.

Cut along that traced line, then cut again to make the finished piece about one inch wide.

Clamping on the glue blocks. Alternatively, they can be installed with screws.

The hull sides are made much like the tunnel sides, starting with making long enough pieces using butt blocks. Again, locate the joints so that they fall between bulkheads.

Start laying out the hull sides by drawing TWO centerlines. These two centerlines represent the upper surface and bottom surface of the tunnel plank, and the distance between the two centerlines is equal to the thickness of the tunnel plank.

The plans are drawn assuming a 1/4" thick tunnel plank, but you will space the centerlines according to the thickness of YOUR tunnel plank.

Layout the rest of the hull sides using the measurements from the plans. Measurements on the lower part of the hull sides are measured from the lower centerline; those for the upper part measured from the upper centerline.

Note again that the lower edge of the hull side is perfectly straight from bulkhead two to the transom, and take care to cut and/or trim this edge accurately for the best performance of your boat.

Install the hull sides with the double centerlines exactly aligned with the edge of the tunnel plank.

Attach with screws spaced about three inches apart.

Spray rails are added to the hull sides, attached with screws driven from inside the sponson.

I made my spray rails about 60 inches long. Longer ones are perfectly acceptable, but I wouldn't make them shorter.

The spray rails I installed on my tunnel sides are identical to hull spray rails.

BUT, I'm already a bit troubled by the way they tend to get hung up on the bunks on my trailer.

This is the more typical way to make spray rails for the tunnel sides, and the method the plans call for. (Pictures taken from the Pro Tunnel building notes.)

At the stern, the spray rails extend beyond the transom all the way to the "tails" of the tunnel sides.

Toward the bow, the rails curve into the tunnel plank.

Attach the rail to the tunnel side with screws driven from inside the sponson.

If you don't have a long enough piece of lumber to span the full length of the boat, make it with two pieces using a simple butt joint.

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