Building A Fiberglass Hatch

Although we have put many dollars and hours of effort into the old Mercedes, Sarah and I have decided that we need better worldwide parts support and modern compact performance that the Old Mercedes diesel engine can't offer.  Enter our newly rebuilt, 0 hours, Japanese-built Yanmar diesel.  Half the weight, half the size, less a cylinder, and still 80% the power of the old beast.  Parts are cheap and readily available around the world.

Since a leaking flush-mount hatch led to the damage on the Mercedes, I decided to make a new raised-lip style one from scratch.  The lip will be glued into the hole remaining from the old flush hatch, and the new hatch will fit properly over.

Here is the initial fiberglass cloth trimming.  The mold is simply 1/2" MDF covered in packing tape, then taped to glass, and then the whole assembly is waxed with mold release.  Corners are filled with modeling clay and rounded with a popsicle stick to provide a smooth surface with rounded corners after the wax has been polished.

Tools of the trade: Polyester Resin, MEKP catalyst, respirator, rollers and a Bondo squeegee to remove bubbles, cheap natural bristle paint brushes and plastic pails for mixing not shown.  Acetone for clean up.

Learning the hard way: Lay up of the hatch lip (version 2.0).  The first one was done as a reverse lay up for ease of bending the glass mat, but and the sealing surface was unacceptable, so I reversed the mold and made this one.  Better dimensions and surfaces, but it was difficult to keep it in the tight inner corner as it cured...  difficult, but not impossible.

Here is the hatch the next day, fresh from the mold.  Notice modeling clay around the corners, unfinished edges, and the 1/2" core material in the middle.

Smooth as glass (face) ...  and packing tape (edges) ...  and modeling clay (corners)

Fiberglass cuts with good plywood circular saw or table saw blades, but I used a small lightweight tile circular saw to cut the edge to the mold line.  Then a bit of cleanup with a small air grinder and some hand sanding.  There are some half bb or smaller pits in the surface that will be faired and filled with Bondo before final sanding and white polyurethane topsides yacht paint from Interlux, and then re-laying the teak from our old hatch on top using just Lifecaulk or 3m 200 (no screws).  The core is a plastic honeycomb backed with flocks so the resin binds with the outside surface, but the core remains air-tight, hollow and resin free.

I stopped by Sarah's work to show off the finished hatch.

The hatch will be plenty large for our new engine to come in from the top instead of through the engine doors into the cabin and then up through the companionway...  even though the hatch is the exact same size as the old one...

Soon the shop will be unavailable and Sarah will be quitting her job in 30 days.  The plan is to have the motor in and be headed to a haul out right about the same time.  These next 30 days will be full of wiring, solar panel installation, engine room painting, and general rebuild on the aft end of the boat!  At haul out we will be able to pressure wash and paint the bilge, hull, and decks, seal the stanchions and windows, and ready the boat for the new rig.  We'll tell you about it soon!  - AJ