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CONSTRUCTION ILLUSTRATIONS

FIG.1

CONSTRUCTION OF THE LOG PLATFORMS-THE "GRILLAGE"

First the swamp reeds and grasses were cut, then trampled and mixed into the surface mud. Next, large 18 x 28 foot canvas tarpaulins were placed over the treated areas. Large pine logs 40 to 55 feet long, 15 to 18 inches in diameter were laid side-by-side in rows directly on the tarp. The logs were then bolted together and sand was poured into the empty spaces between them. Where the logs overlapped, as illustrated, the upper row was bolted to the lower.

 

FIG. 2

CONSTRUCTION OF "GRILLAGE"

ARRANGEMENT OF LOG PLATFORMS ON THE TREATED GRASS AND MUD AREAS.

Canvas tarpaulins are first put down directly on the treated marsh surface. Two separate log platforms are then constructed on the canvas tarpaulins, leaving an open 20foot area between them.

 

FIG. 3

CONSTRUCTION OF "GRILLAGE"

 

ARRANGEMENT OF SECOND LOG SECTION

After the first two log platforms are constructed, a second set of platforms is constructed at right angles over the first. The second set was then bolted to the lower set, forming a square platform with an open square area between them. This smaller square area is where the gun platform will be located.

 

FIG. 4

LOG PLATFORM AND PILINGS

CONSTRUCTION OF GUN PLATFORM

After the outer platform, or "Grillage" was constructed, work on the inner open area, where the gun deck was to be located, was begun. This involved the driving of "sheet pilings" around the perimeter of the interior open square. These pilings, which extended down to the marsh substratum, anchored the outer floating platform, and prevented it from moving laterally.

 

FIG. 5

GUN DECK

After the pilings were driven and tops cut level, a gun deck was then constructed, which would bear the weight of the gun. This was constructed of three separate decks, with the top deck resting directly on the pilings.

 

FIG. 6

CROSS SECTION DETAIL OF GUN PLATFORM AND "GRILLAGE"

Gun deck detail, showing the mud, trampled reeds, tarp, 15 inches of sand, and three layers of 3 inch planking resting on the sand. The top layer of planking rests on the heads of the sheet piling, and the bottom row of planking rests directly on the sand and on a welting strip, which has been nailed around the interior of the box formed from the sheet pilings.

To the right of the sheet piling is the "grillage," or large outer platform, which rests on the tarp and mud, and is essentially floating on the marsh surface.

The sheet piling, which extends down to the floor of the swamp, anchors the "grillage" from moving laterally.

All illustrations by LAR using Accurender to render models created with AutoCad.

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