Coring the Aft Deck

December 24, 2018

There are several locations across the deck of the Allied 24 that require new core and either top skin, bottom skin (or both) repairs:  the location of the aft cleats on the poop (aft) deck, a significant portion of the coach roof, and the foredeck in its near entirety.  I am at a stage in the restoration where I need to begin repairing these areas.  Of course, I have yet to sand the deck and topsides, but that will soon come.  I wanted to get the deck "sealed" up as more a matter of peace of mind (aka need for a nice milestone), so to that end I got to work.

I had removed the damaged core in a previous work session, and then followed that up with grinding roughly a 3" taper in the deck around the area where the core was removed.  Essentially, I had the work area prepped; I did need to remove any fine contaminates, so I thoroughly wiped all surfaces to be worked with acetone.  This process primes the glass, and other surfaces, to receive new laminations.  The next step would be to create templates for the new material: balsa core, and two layers of 1708 biaxial fiberglass.  I began with the port side of the aft deck.  I laid out a piece of plastic, and then traced for the inner balsa core, an initial layer of 1708 biaxial, as well as a secondary layer of 1708 that would cover the entire work area.   

I then repeated the templating process on the starboard side of the aft deck.

With my templates in hand, I returned to the shop and unfurled a rather large piece of 1708 biaxial cloth.  In cutting the 1708 biaxial for the new top skin, I began, naturally, with the larger of the templates, and worked my way to the smaller.  I cut out the larger template (the secondary piece) from the plastic templating sheet, and then laid it out onto the fresh fiberglass.  I traced the outer edge of the template as my cut line, and then removed the secondary layer of 1708 biaxial with a pair of very sharp scissors.  I cut out the template for the first layer of 1708 biaxial from the templating sheet, laid it onto the fiberglass, traced it for a cut line, and then removed the first layer of 1708 biaxial from the fresh fiberglass.  I now had both layers of 1708 biaxial ready.  Next, I cut out the balsa core template from the templating plastic sheet, laid the template out onto the 1/2" balsa core material, and then removed the new core.  I applied this process to both the port and then the starboard side, preparing all new material for installation. 

With the new materials cut and set to the side, I focused my attention on the work surfaces.  As I mentioned previously, I wiped the surfaces down with acetone to remove any remaining contaminates - shown below.

Next, I mixed a small pot of "neat" epoxy - West System epoxy resin without any thickening agents - and "painted" out the work surfaces, including the exposed edges of the original balsa core material.  This process of painting out the surfaces is to ensure there are no resin-starved surfaces/materials that could contribute to future issues in the lamination.   After the surfaces were wet out with the neat epoxy, I then mixed another batch of resin.  This time, I thickened the epoxy with 406 colloidal silica and 407 low-density filler.  This combination creates an exceptionally strong gap filling material.  I applied this thickened material to the small voids in the perimeter of the areas to be cored and across the top surface of the bottom skin, creating a "bed" of thickened epoxy for the new core in nestle into.

With the deck voids further prepped and ready for the new balsa core, I pressed the port side core into place.  I firmly worked the new core patch into place while making sure that I saw ample squeeze out of the thickened epoxy.  With a small squeegee, I worked the thickened squeeze out epoxy into the voids to ensure no gaps existed between the new and original core material.  

I repeated this process with the starboard side of the aft deck.  

I failed to capture step-by-step pictures for the following work sequence, so you'll have to use your imagination along with my Pulitzer-worthy prose...

I applied the first layer of 1708 biaxial cloth over the new balsa core material.  I wanted to ensure that I had a fair surface for the secondary layer of 1708 biaxial cloth, so I mixed and applied another layer of thickened epoxy, using the same 406 and 407 thickeners, to the top of the first layer of 1708.

With the surfaces of the port and starboard work ready for their next layer of 1708 biaxial, I wet out the sheets and applied them.  With the secondary layers of 1708 biaxial applied and covering the entire work surfaces, I work them in with a squeegee to ensure no air bubbles were caught and that I achieved a good bond.  My final application would be a layer of release fabric.  This release fabric would reduce the need to sand the cured epoxy, itself creating a textured mechanical bonding surface.  Whenever I can avoid sanding fiberglass...I'm all over it!

Total Time Today: 2.25 hrs