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EZ Tunnel Race Boat Plans
Page Five
Deck Framing & Coaming

NOTE: I elected to finish the bottom of my boat before turning it over. Skip ahead to the finish section of these notes if want to do the same.

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Turn you boat right side up

The last time you turned your boat over, it was little more than a rough tunnel plank and some beams. I'm sure you noticed it was very flexible.

Though much stiffer at this point, your boat is still quite flexible and subject to twist. Take some time at this point to level the structure.

When the deck is installed it will become very stiff, and any twist present will become permanent.

The girders are very much like the tunnel sides, but with some additional features.

The girders must be notched to fit over the beams. Additionally, you will need to cut "limbers" forward of the beams. Limbers are holes or notches that allow water to flow outboard along the beam to the sponson, where it can then flow aft to the transom.

Besides the notches for the beams, you will also need to cut a long, shallow notch for the butt block between bulkheads one and two -- and limbers forward of those butt blocks.

Also, as drawn, the girder extends aft all the way to the transom beam, and you should draw and cut it out that way. BUT, afterward, shorten it at the aft end by about 1/2" to create yet another limber, again allowing water to flow to the sponson.

Cut-outs for the girders can be quite large, leaving 1.5 inches along the top and bottom edges and about three inches at the bulkheads.

Before going much further, I highly recommend that you skip ahead to the coaming, draw it and cut it out, then use the girder to trace on the deck line and lightening cut-outs. Glue blocks will be attached to the coaming at that traced deck line.

Long glue blocks, bent to the curve of the girder, can be attached from the transom forward to station two or so. For the sharper curve forward of that, glue blocks will have to be sawn to shape.

Deck bulkheads attach to the forward face of the beam at station one; to the aft face of the beams at the others.

Make certain the bulkheads are not blocking the limbers cut into the girder (and later, the coaming). If so, cut the limbers larger, or notch the corner of the offending bulkhead(s).

NOTE: The forward end of the coaming has not been cut to its final shape in this photo.

The coamings are laid out using the measurements on the plans. Consider cutting it out about 1/2-inch or so extra long at the aft end, to be trimmed later when the motorboard is installed.

Also note the notch cut into the coaming right where the forward sloping part meets the deck. This notch is 1/4 inch high on the plans, but should actually be made equal to the thickness of your deck plywood.

You will notice that the upper edge of the coaming on my EZ Tunnel is curved from the dashboard to the motorboard -- I like it that way. I drew it straight in the plans for the sake of simplicity, which is afterall the guiding principal behind this design. Make yours the way you like.

Use the girder to trace the entire deck line all the way to the bow beam.

Add a second layer of plywood to the coaming from a point just behind bulkhead four and then all the way aft. This strengthens the coaming to withstand the stress of the motor.

As seen in the photo, I doubled the thickness of my coaming all the way up to a point just forward of the dashboard. This adds just a bit of driver protection in case of a crash while racing.

The coamings are cut out same as the girder.

Glue blocks are added along the bottom edge, the upper edge at the bow, and along the line traced from the girder.

The part of the coaming that will be under the deck needs glue blocks on both sides, the inboard block extending a few inches into the cockpit.

Attach the the coamings to the tunnel plank using screws driven from underneath the boat, and into the bulkheads from inside the cockpit.

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