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Pro Tunnel Race Boat Plans
Page Five
Chines and Sponson Battens


The intersection of the sponson pad and the lower side is the chine. The longitudinal at this location is called the chine log, or just chine.

As with the sponson keel, the chines are split down the middle from the sponson tip to the second bulkhead.

I found it easiest to fasten or clamp the chines to the sponson tips first, then bend them around to the transom. But the other way, starting at the transom, might work just as well.

A look at how the chine, sponson keel and sheer clamp relate to the sponson end -- before these pieces are beveled.

Sponson Battens

Here the sponson keel and chine have been beveled in preparation for installing the sponson battens. Beveling the sheer clamp can wait for the moment.

Please note that although I used only two battens per sponson on the original Pro Tunnel, the plans call for a third batten. This batten only extends from bulkhead #3 to the transom. The notches which you have already cut into the bulkheads reflect this change.

Use clamps or weights or fasteners to install the battens. I used a small scrap of wood to hold the forward ends in place.

Now is as good a time as any to install glue blocks along the bottom edges of the bulkheads where the sponson pads will be glued and fastened.

I installed such glue blocks on the transom and on bulkheads four and three only, reasoning that the stresses are greatest in this part of the boat.

You will want to cut limbers at each bulkhead, where each batten crosses and at the sponson keels. The limbers allow water to flow back toward the transom.

And these limbers, where the sponson battens meet the transom, allow water to flow to the lowest part of the sponsons where it can exit through the drain holes which you will be installing later.

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