I thought it about time to test the theory and fit one myself. My 1990 Halmatic 30 has a now rare composite hatch from Canpa, made in England and apparently the Lowline model. I say apparently as try as I might I can find no reference to this on the net. The task; remove the Canpa and fit a Lids4Lend lifeboat lid, what could possibly go wrong...
Canpa Lowline hatch ~595 x 595mm of composite construction
Other than the fact 9/8/2020 was one of the hottest days of the year I also had no idea how the hatch was fixed to the coachroof moulding. I had identified previously that three of the sides were attached with 25mm SS self tapping screws and that what appeared to be a silicone based sealant had also been used. The forward side, with three hinges was guesswork as there were no screws on show.
Getting a blade under the frame from the outside proved impossible, so I moved to the inside. The Stanley blades were new but even so progress was slow and shallow. Dripping in sweat I plugged on until at least some progress (~10mm) had been made on the three now unscrewed sides. I had wondered whether the screws holding the support tracks in place may also have been into the deck but in practice this was not the case.
Next it was time for a wedge, the thinner (ie smallest angle) and wider the better. Sadly my ideal tool was still in the workshop, so careful use of screwdrivers was the order of the day. Even with only moderate pressure the frame lifted by a mm and allowed the blade in further. As this progressed one corner came free and then it was possible to work around the frame, using some acrylic wedges to hold the frame up.
With three sides now free I moved to the hinges. It was (unsurprisingly) clear that something was holding the frame down, so I picked away at the hinge tops and eventually released some sealed in plugs which when removed gave access to a single self tapping screw through each of the three hinges. With these out, more cutting and some gentle levering the based gave up and came away. Phew! Time for some water!
One of three hinges. The cap in the centre has to be removed to access to securing screw.
With base removed the residual sealant was ready to be removed with acrylic scrapers
The next phase involved cleaning the GRP hatch opening. For this I used some of our acrylic scrapers (cut from old window acrylic on our band saw; other methods are available). These worked a treat as they proved excellent to remove the silicone without scratching the GRP.
GRP cleaner helped show the last layers of sealant
With most of the silicone off, I used a GRP cleaner to clean the top surface. This has an unexpected benefit in that it showed up any remaining traces of silicone which could be removed with a scraper. Note that the scrapers do lose their edge so I had a box full, but if not I suggest you take along the means to resharpen.
We now had a clean hatch opening so it was time to mount the temporary lid. The lid I had was sized for a Lewmar 60 hatch so was a fraction small, but still worked.
Temporary (Lifeboat) lid fitted.
With the top in position it was down to the forecabin to attach the corner clamps. I found that tightening each gradually in turn worked best rather than one at a time. By this time, under a clear hatch with a burning sun, I was cooking nicely so keen to finish.
Corner pieces in position to hold the lid firmly in position
The great thing about these lids is that not only do they keep the water out, they also provide security (the bolts cannot be opened from outside) whilst having a clean underside so no danger of stripping you head on unprotected bolt threads.
Bolted from under with only the M8 head showing
The outer bolt has a flush finish so secures the hatch and safeguards the contents.
Will the Canpa go back? I think not as I've got my eye on an Ocean 60.