SV Pilgrim - 1979 Morgan 382 - Homeport: Beaufort, NC

Saturday, September 20, 2014

Aluminum Angle Brackets In Salon

On the Morgan 382, 383, & 384 design,  the chainplates for the aft lower stays are anchored to cabinetry in the salon.  To port an installation of cabinets and storage bins that also serves as a seat back provides the anchor point for the chainplate.   
Starboard salon cabinets with new aluminum angle brackets installed.  Note: Lower, aft chainplate is angled metal tang in center.
To starboard the aft lower chainplate is attached to the seat back / pilot berth fiddle.
Starboard salon seat back / pilot berth fiddle with original angle bracket installed.
To structurally tie these longitudinal anchor points into the vessel Morgan Yachts utilized angle aluminum brackets at the fore and aft ends.  The 1/8” thick by approx. 18” long brackets are fastened to both the bulkhead and the longitudinal member with ¼” wood screws on 2” centers .   My initial assessment of this system was less than awe inspiring.   In preparation for painting the bulkheads, I removed forward brackets on both port and starboard.  Unfortunately removing the brackets revealed corrosion along the backside. 
Corrosion on the backside of the port, forward aluminum bracket.
More disconcerting was my discovery that the wood screws installed by Morgan Yachts, were only ¾” long.  The aluminum angle is 1/8” thick + the ¼” teak veneer on the bulkhead = 3/8”.  This means that at best only 3/8” of the fastener was in contact with the structural portion of the forward bulkhead.
Corrosion on the backside of the starboard, aft bracket.
I removed all four of the aluminum brackets, and discovered varying degrees of corrosion.  Unfortunately the ¾” wood screws were used throughout.  The ¼” veneer is on the starboard seat back and both forward bulkheads.  The aft, partial bulkheads and the port side cabinetry are finish grade ¾” plywood so the ¾” screws were more appropriate in these locations.

After removing the bracket from each corner, I used a scraper followed by 80 grit sandpaper to clean the surface.
Starboard, aft corner after scraping and sanding away the corrosion residue.
I then drilled out the screw holes to a full ¼” diameter.  Using a syringe, I filled the existing holes with thickened epoxy.

The old brackets went to the scrap pile to be recycled.  I purchased new sections of 1/8” thick aluminum with  longer sides,  1-1/2”. 
New aluminum angle for port, aft on left and original on right.
The original brackets were cut to remain hidden by the seat back cushions.  The new ones will run the full length of the cabinetry.  The old fasteners were installed at 2” intervals.  I chose to go with 3” intervals on the new brackets.  Since the new brackets are longer they all contain more fasteners than the originals.  I chose to remain with ¼” fasteners, but were possible use machine screws to thru-bolt.
The nuts and fender washers from starboard, forward bracket are visible in the locker forward of the bulkhead.
Where access eliminated my ability to thru-bolt, I used wood screws that took full advantage of the thickness of the bulkhead / cabinetry.  These modifications dramatically increase my confidence in strength of the aft, lower chainplates.

Here are some before and after images.
Starboard, aft bracket- Before.
Starboard, aft bracket - After.
Port, Aft bracket - Before
Port, Aft bracket - After.
Looking forward from companionway at freshly painted bulkhead and new angle brackets.

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