Tabbed bulkheads are bulkheads that are attached to the interior of the boat's hull and deck via fiberglass tabbing. This can range from a few sections of fiberglass tape
(a poorly done job usually) to the entire edge of the bulkhead being glassed in all around.
If you're going to be tabbing in bulkheads, remember to leave a slight gap between the edge of the bulkhead, usually filled with foam, and the hull or deck. This gap is necessary to prevent a hard spot or edge from occurring along the bulkhead's position, and would probably weaken or stress the fiberglass laminate, acting as a
hinge point for any forces acting on the hull or deck at that point.
If you do a google search for "fiberglass tab bulkhead sailboat" you'll get a lot of info on what it is and how it is done.
Here's a good
page with some photos showing what it is. Here's a photo from that page.

__________________
Sailingdog
Telstar 28
New England
You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
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