Skinning the Hatch

The hatch structural design calls for laminated ribs covered by a 3/8" "beadboard", topped by a layer of 1/8" birch plywood.  While the beadboard has been installed (see previous post), we have recently been determining how exactly to install the birch plywood layer.

The issue is that we have a 57+ inch wide piece of plywood bent to the contour of the hatch, layered on top of the beadboard.  We need to assure a good fit and tight bonding, since we can only provide firm attachments at the ribs, and must rely upon glue for the balance of the bond.

Shown below is our solution:  13 band clamps, anchored to the table at both ends, with the hatch itself in the original construction jig.  This arrangement prevents the hatch from spreading under pressure, and allows us to apply adequate forces to the plywood to closely bond it to the rest of the structure.

Only one of the two pieces of 1/8" birch plywood is shown.  The joint will be made in a relatively flat portion of the curve.

The straps are anchored at the bottom end of the hatch by wrapping them under a 2x6, which positions them tight to the curve, and then around an anchoring block.  At the hinge end the straps flow down over the table end and through the ratchets, which are anchored to an angle iron clamped to the bottom of the table.

The strap assembly will be slackened and held off the hatch while glue is applied.  The straps will then be repositioned and tightened to uniformly clamp the plywood to the structure.  Staples will then be nailed along each rib to hold the plywood in place.  After the glue has cured for the main (large) sheet of plywood, the process will be repeated for the smaller piece.

Since our temperatures are near freezing at night, the entire assembly will be covered and warmed by an electric heater to promote proper curing of the glue.