TWO (OR THREE) PART BOAT , page 2 |
Bulkheads & Bolt Holes
The bulkheads should be as thick as you would normally use for the transom of the boat. Well-braced 1/2-inch hardwood ply sheathed in epoxy is probably sufficient for smaller boats, but it's reassuring to use thicker bulkheads if weight is not critical. Two pieces of 3/8-inch hardwood ply glued together would make a much better 3/4-inch bulkhead, and 1 1/2 inches is still not too much for a larger boat of 16 feet or so. For hard service, sheathe the bulkheads on both sides with 4 or 6-ounce fiberglass cloth imbedded in epoxy and seal any exposed edges.
The hull sections are held together with stainless steel or bronze bolts and washers spaced around the perimeter of the joining bulkheads (Fig. 3). Hex head bolts, used with large washers on either end, can be tightened with a wrench of
appropriate size kept handy in the boat, perhaps on a lanyard. The bolts may also be equipped with thumb screws with the head epoxied into large rectangular ply, wood washers, allowing removal and tightening without a wrench (Fig 4). Another option is to epoxy glue the bolts and plywood washers permanently' in place on one of the bulkheads so they're always handy for re-attachment.
Drill the bolt holes after the bulkheads are in place and before the final cut is made to separate the hull. They should be drilled at exactly 90 degrees to the face of the bulkheads to ensure correct alignment. All holes in the bulkheads should be sealed with a liberal application of epoxy, then re,drilled to the correct size for the bolts. This is important to prevent rot.
After the bulkheads are permanently in place, be sure that all the attachment bolt holes are drilled, then slide a sharp, fine toothed handsaw between the two bulk, heads and make a clean cut around the hull. Clean up the cut edge with a block plane and seal it with at least three coats of epoxy resin. If it's a fiberglass hull, you might want to use a hacksaw blade in a pair of vise grips or an old handsaw you don't mind getting dull. Because an exposed fiberglass laminate will soak up water and turn mushy, it's just as important to do a good job of sealing fiberglass as sealing plywood and grain. Epoxy is the sealer of choice for this job and sticks tenaciously to clean, dry polyester resin.
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Expandable Boats The bulkheads are so easy to install that you will probably consider dividing the hull into three parts that may be used with or without the center section. Bolt in the middle piece for additional passengers, heavy loads, or extra speed. Whether the separate pieces are usable as boats themselves will depend on the hull size and shape and details like thwarts and oarlocks. If it can be arranged, you can have a lot of fun with the mini, boats, not to mention the added convenience of having a boat that takes up half the storage space. |
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