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Mini GT Racing Tunnel Boat Plans
Page Twelve
sponson pads

Limber Holes

If you have not already cut limbers in the bulkheads, at the sponson keels, now is the time. See construction drawing for guidance.

Sponson Pads

The pads are installed much like the sides, but with one key difference. At the chine, the edge of the plywood is finised at right angles, as is shown on the construction drawing. You will want to trim this edge to its final shape before gluing it to the boat.

NOTE: Before installing the pads, this would be a good time to drill drain holes in the transom. I used 5/8" rubber stoppers and lined the hole with a copper coupling intended to join 1/2" copper plumbing pipe.

Another way is to drill a 7/8" hole, then completely fill it with epoxy thickened with silica. Then drill your 5/8" hole through the middle of the hardened epoxy, leaving an epoxy liner to protect the wood.

sponson pad left square at chine drain hole with plug

You will need to trim the inboard edge of the sponson pad to its final shape where it meets the tunnel plank at the stem.

Also, trim (or shim) the stem so that the pad plywood is just level with the tunnel plank plywood at the forward edge of the stem.

Also, make sure you leave enough extra plywood at the tunnel keel so that it can be trimmed off paralell with the tunnel side.

sponson pad at the stem

Lifting Strakes

The lifting strakes are also a type of spray rail. They serve to push the spray off of the sponson pad. Arguably, they may actually provide some lift as well, but not likely at Mini GT speeds.

The outboard lifting strake extends from the transom to approximately as far forward as the sponson-side spray rails. The inboard strake extends about 12" to 14" farther forward.

You can probably install with screws driven from inside the hull, as with the spray rails. I felt it would be simpler to screw in from the outside. Remove the screws when the glue dries, and fill the holes in the strakes. You can fill the holes on the inside of the sponson later, after the hull has been turned upright.

lifting strakes tapered at forward end

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