Installing Sea Dog Hatchplates

By Ole Helgerson - Carson, WA - USA

- What Worked for Me

Last fall, I acquired a 30-year-old, glass reinforced plastic (GRP) 4.5 meter sailboat. I observed that the EPS foam-chip-filled flotation bags in the side tanks were starting to fail. I decided to remove them and fill the side tanks with 2-part, 2 lb/cubic foot foam expanding polyurethane foam per U.S. Coast Guard specifications. After some thought, I realized that obtaining a good foam pour would require cutting holes in on the upper surface of the side tanks, that hardened foam could be excavated out from under the holes for storage and that the holes could be covered with hatchplates. I also observed that the two original forward 6 inch diameter hatchplates were failing and needed to be replaced.

I located the six hatchplates (three per side) for adding foam at the ends of the thwarts and near the stern to facilitate installation and be somewhat out of the way. The holes were centered between the thwart and gunnels. Rather than wrestle with a jig saw or router in a confined area, I purchased a 4.5 inch hole saw to ensure accurate hole cutting. I chose 4 inch plates (4.5 inch holes) instead of larger plates to minimize any reduction in strength of the surrounding GRP. Larger hatchplates, however, would have been handier for storage.

After hole cutting, I inserted a hatch plate and outlined its perimeter with a pencil to guide GRP cleaning and masking tape application. I reinserted the flange, carefully scored the tape around its perimeter with a shop knife, and removed the tape under the flange (Figure 1).

Figure 1. A hatch plate opening, cleaned, masked and ready for the silicon sealer and hatch plate.

I applied small tabs of masking tape to cover the screw holes on the hatch plate bottoms (facilitated cleanliness and drilling holes), applied silicon adhesive (per Chuck’s recommendation) to the flanges and pressed each, with its plate, into place. Each was rotated slightly back and forth to ensure good adhesive contact with the GRP. I used clear “hardware store” silicon sealer. I considered stronger adhesives, but concluded that the lower cost silicon was adequate and would remove more easily if the hatchplate needed replacing.

Figure 2. A completed hatchplate and cavity. I carved the foam cavities before installing the hatchplates. The foam carved easily, especially with a serrated knife. In retrospect, it would have been better to have excavated larger cavities before setting the hatchplates. I attached the plates to the flanges using light line connecting 12 gauge copper electrical wire loops glued to the plate underside and into the foam with 5-minute epoxy.

To complete the installation (Figure 2), I scored the hardened silicon around the hatchplate’s perimeter with the shop knife and peeled off the squeeze-out and underlying masking tape. The hatchplate holes guided the drilling for ¾ inch #8 stainless flathead screws. Using a bit the size of the hatchplate hole, I dimpled the GRP for centering the subsequent 1/8 inch bit. The screw threads were coated with silicon sealer before installation.

For the forward hatchplates, each hole needed to be slightly enlarged. I used a router guided by a template secured to the GRP with two countersunk flathead screws. These two holes matched opposing holes in the hatchplate to ensure their concealment after installation. A trial fitting showed that the underlying GRP had as much as 5 mm unevenness from the hatchplate flange. I emailed Chuck at Duckworks for advice. He regarded this as too great for silicon sealer. Per his suggestion, I bedded the hatch plate flanges in epoxy putty (System Three Silvertip Quickfair ), prepping and masking the GRP as with the silicon sealer. I prepared 3 to 4 oz. of combined resin and hardener for each hatchplate. The components were carefully measured by weight, thoroughly mixed (see Duckworks article) and applied to the hatchplate flanges. The hatchplates then were carefully pressed into place as with the silicon sealer. I discovered that is better to be a bit copious (mask the surrounding GRP well) in applying the epoxy to ensure complete squeeze out rather than not having enough around the flange. The latter required a bit of tooling for gap filling. The Quickfair did not droop or run on the nearly vertical surface.

When the epoxy was at the “soft-to-medium taffy” stage, the squeeze-out and masking tape were removed as with the silicon sealer (Figure 3).

Figure 3. The two forward hatchplates before and after trimming epoxy squeeze-out. The newly enlarged holes for the new hatchplates were a bit oversize. Before applying epoxy, I added more masking to the GRP, masked the hatchplate flanges to protect them and taped short pieces of wood to the side tanks to more accurately position the flanges.

I had applied release agents to the hatchplate flanges, intending to remove and re-seat them in silicon sealer against the epoxy. For release agents, I used extra strong hair spray followed by soapy shaving gel, then wiped clean. However, the hatch plate flanges were stuck in place. I am guessing that the shaving gel removed the hair spray allowing the epoxy to bond with the flange. In the overall process, I discovered two useful tips. First, gelled alcohol hand sanitizer works almost as well as acetone in removing unset resin and hardener. It is also safer and a lot easier to use. Next, the warning about keeping acetone from the Sea Dog™ hatchplates is apt. I cleaned a small amount of epoxy from a hatch plate with a shop towel only slightly damp with acetone. The towel was immediately smudged.



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