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Damaged area cut out. Gel coat removed around perimeter to allow glass tabbing.

Wood form installed and covered with plastic to support top skin and allow release.

Foam-Sandwiched Fiberglass Repair: Swim Platform


everal boat manufacturers are now integrating molding swim platforms into their hull designs. These are a great addition to comfort and make boarding your dinghy and climbing aboard a much safer evolution. In addition, they also add waterline length to your hull, which can improve performance. Most sailboats out there do not have platforms, but that doesn’t mean you cannot add a platform to your existing hull. By far, the easiest way to do this is to use the concept from the powerboat industry, which is to make a platform and then use bracket supports to mount to your transom. Swim platforms can be made from a variety of materials, such as teak, mahogany and fiberglass designs. While not suited for blue water boats, a swim platform comes in quite handy in the coastal, recreational class of sailboats, which won’t experience large waves from astern. I’ve seen some very nice teak platforms that really added a nice touch to a sailboat and had mounting points that allowed for the platform to be folded up or removed when docking stern-to in a slip. Unfortunately, one of my customers had an accident while backing into a slip, and the swim platform took a direct hit to a dock piling. Fortunately, the hull was not damaged, but the platform did not fare as well. This platform was off a large motor yacht and was the bolt-on type, so we removed it and started repairs at my shop. The project required using a wide range of fiberglass, body work and paint techniques that can be used in all sorts of boat repairs. This can serve as a good primer on repairing foamsandwiched fiberglass repairs. The first step was to cut away the damaged section. I penciled in some lines making sure that I was at least an inch wider than the fractured area. Taking a jigsaw, I then cut out the damaged area. This left a symmetrical area where the repair could be made. This platform was foamsandwiched between glass and resin. It also had vent slots incorporated, which required integrating them into the repair, increasing the complexity of the project. After cutting away the damaged area, I took a grinder and removed the gel coat approximately two inches around the repair area. This was done to allow room for tabbing in glass during the


November 2010


repair process. The next step was to fashion a template out of wood and mount it into the repair area. This served to provide a support for the resin and glass while glassing in the top skin of the platform. I covered the wood form with plastic sheeting to prevent the resin from bonding to the wood and set the wood down below the original glass to allow for the resin and glasswork to be poured and leveled with the rest of the platform. Once the support was in place, I poured a bed of resin onto the form and worked fiberglass mesh for strength, fibers for binding and then cloth to tie the structure into the platform. Try to do this while the resin is still working; otherwise, you will have to sand in between pours. Once the top skin cured, I flipped the platform and then removed the wood form and scuff-sanded the inner surface of the top skin. I then mixed up a 2-part marine foam and poured it on the top skin. The foam expands and it doesn’t take much. Another option is to use rigid foam and tabbing it into place. The foam keeps the weight down and provides the support for the bottom skin. The foam cured in minutes, and then, taking a flat saw, I reduced and leveled the foam. Using a sander and some 80 grit, I then smoothed and reduced the foam to the same level as the existing foam on the platform. Now it’s a matter of repeating what you did to make the top skin, except the foam will now support your glass and resin. Make sure you use the same method as the top; fiberglass roving, then fibers and then tie in with cloth. With the structural portion completed, I then fashioned a template for the slots from the section next to the repair area. Using a pencil and paper, I traced the slots and then transferred the template to the repair area. I then drilled a hole on each side of the slat and used a jigsaw to cut out the slots. This exposed the foam core again, and the slots will need to be glassed in. Again, using a grinder, I prepared an area around the slots to accept the glass and resin tabbing. I wet the foam with resin and applied several layers of wetted cloth to the slots pressing out any air pockets. This now completes the glasswork. At this point, you will need to sand the entire repair area. Using a guide coat will allow you to identify high and