Aft Hatch

We needed an alternate safety exit once our aft companionway was filled in.

Our aft companionway had provided the emergency exit for persons in the aft portion of the boat should there be a fire in the engine room. Once we had filled in the aft companionway (click here for details) we needed a replacement exit. We installed the new aft hatch as part of replacing all the hatches (click here for details).

As a safety issue we had to provide a replacement exit path and this implied a hatch similar in function to the hatch in the forepeak. We decided to fit a hatch in the aft cabin which was the same dimension as the forepeak. We were replacing the all hatches at the same time and so ordered 3 hatches of the same size (forepeak, main saloon, aft cabin).

  1. The first step was to trace the outline of the new hatch where we wanted to place it on the aft coach house – in our case we wanted it centred like the forward hatches. We cut through the upper GRP layer with a Fein ultrasonic saw – this saw eats through GRP and leaves a cut line about 1mm thick.
  2. Once the outer layer of GRP was cut through we lifted it off (it will be stuck to the foam underneath). Cut and scrape out the foam to bare the lower (inner) layer of GRP. By doing this before cutting the inner GRP layer a lot of dust is kept outside. Remember to cut out about 2 cm on each side where you will fill with epoxy later.
  3. Cut the hole in bottom layer, by taping a plastic sheet around the cut on the inside a lot of dust can be contained. You will now have a hole through the aft coach house and can try the hatch for fit. Sand any tight points but remember that you want a snug fit on this.
  4. Mix some thick epoxy with low density filler to peanut butter consistency and use this to seal the gap created at the edge of the cutout. Once this goes off it will both seal the coach house against moisture etc. as well as giving a solid mounting point for the screws or bolts the hatch will be mounted with. If this epoxy was not in place then mounting screws would have only the top GRP layer to grip to and mounting bolts would simply pull the two GRP layers together as they were tightened.
  5. We built a plinth from softwood (pine) to snugly match the mounting rim of the Lewmar hatch. Using a profile guide we then took off the corner radius of the forward hatches and using a bench sanding wheel shaped this radius onto the pine frame. We then used the profile guide to take the radius on the outer corner from the forward hatches and used a router to put this shape on the pine frame.
  6. We sanded margin around where the pine frame would sit, there was no reason for this other than making the new hatch look like the factory installed ones. We matched the width of the margin so appearances would be identical.
  7. In using the pine we were not worried about longevity as the pine was to be encased in multiple layers of epoxy – the pine was only there to give the underlying shape. We painted clear epoxy resin onto the pine once it was shaped. This epoxy was allowed to dry thoroughly before the next step.
  8. We bedded the frame onto the aft coach house using epoxy putty (i.e. epoxy with lots of filler to give it a peanut butter consistently). We had wrapped the mounting flange on the hatch frame in plastic film and it was fitted while the epoxy was fresh so we knew everything was aligned while the epoxy went off. A medical tongue depressor was used to make the radius between the side of the pine frame and the coach house roof.
  9. Once the epoxy set we removed the hatch, the plastic film had prevented the epoxy from gripping the hatch mounting flange. Numerous applications of epoxy resin with and without filler were then applied and sanded back until the appearance was matching the rest of the factory moldings. Once painted the new aft cabin hatch looks identical to those installed by the factory.

The hatch is facing aft (i.e. the hinge is on the front edge).

The aft cabin hatch has made the aft cabin much brighter and much better ventilated. As an emergency exit it works identically to the saloon or forepeak hatches. The aft cabin is much more private now as cockpit conversation etc. do not drift down through the aft companionway. Also when sleeping  the new hatch gives a great view of the stars at night.

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