Quarterberth "Floating Bulkhead"

When removing the plywood battery tray to reconfigure for my 2 X lithium Group 31 house bank, I was surprised to notice - for the first time - a poor though fairly inconsequential repair job from Windstar's distant past.

   

As constructed - The  bulkhead in this area was trimmed shy of the hull and the 1" or so gap was covered by fiberglass tabbing that was less than 1/8" thick.  Disappointing really, especially as this is in the area where the aft cradle pad supports the boat when on the hard.   This is not unique to Windstar, and fellow 33-2 owner Bruno L had coined this a "floating bulkhead".  this port-side expanse of hull is not supported structurally, as compared to the starboard side, where the galley bulkhead serves this purpose.  My suspicion is the designer did not intend this bulkhead to float.

The thin web of glass is easily crushed if the cradle pad bears any of the boat's weight.  (as it does)  You can see the hull deflection where the pad rests.   

Repair was complicated by the fact that I do not have locating blocks on the cradle so the yard has some latitude as to where the boat sits.   This season the boat is too far aft, so the pad could not be retracted far enough to clear the hull.  As a result I had to raise and support the stern to allow the hull to return to its natural shape.   The correct positioning will be indicated with blocks for next haul out.   

Plan was:

• Remove crushed broken tabbing, (original and repair) clean and prep area 
• Cut hole for access to back (forward side of bulkhead)
• Laminated oak rib to be sprung and wedged in place
• Fill any gaps with glass-loaded putty
• Create epoxy fillet along length of joint
• Laminate heavy tabbing in place  

Prepping the patient.    You can see the gap between the bulkhead and hull. I cut the damaged glass back to the hull and to the bulkhead edge, ground the surfaces then cleaned with acetone.

 How best to fill the  gap between hull and bulkhead?     I decided go old school and to rip some red oak into strips, coat with epoxy and tape into a beam.  While it was still wet I coated the hull below the bulkhead with epoxy putty then I flexed  the laminations   into place, wedging them  it so that the stack pressed against the hull, bedding itself in the putty, and forming a laminated rib.  

Here are the oak strips ready to laminate 

 

 

Each oak strip was coated with unfilled epoxy, then the strips were assembled into a stack and taped with masking tape at each end to hold the bundle together.  The slippery stack was flexed and slid onto the gap, and further wedged with another few shorter strips,  so then new rib pressed against the hull    Any gaps were filled with the thick glass-filled putty, and smoothed along the edges,  and finally the joint was faired with a big fillet of putty over its length to make a fair radius upon which to laminate the tabbing.

With that still wet, I laid up 5 patches of biaxial stitch mat, (cut in advance), each around  12x9”, double in thickness along The middle, and laid them over the joint, tabbing the bulkhead to the hull.  There is a great deal of overlap, with a minimum of  4 thicknesses of material forming the new tabbing.    Strong stuff! For the heck of it I laid in several lengths of high modus carbon fibre tape I happen to have kicking around (as one does...) 

 Because all the work was done solo, and wet on wet, it was too busy and messy there to stop and photograph each stage, but here's the completed repair, prepped for the battery tray then paint.   

            It ain’t gonna crush now.