Hatches Revisited

Earlier this spring I replaced all the gaskets on all the opening ports and hatches before taking off the cover, but found that 2 overhead hatches (the large fore hatch and the small hatch in the head) still leaked once I took the cover off and allowed rain to hit the boat for the first time in many years.  The problem wasn't with the gaskets, it was either where the hatch mounted to the deck (in the head) or the acrylic in the forehatch.

Unfortunately, that meant pulling both the hatches on the boat. In reality, both hatches came off pretty easily but it wasn't a job I really wanted to do.  The leak in the small hatch was just the seal on the deck, so the hatch just needed to be re-bedded.  Normally, I use butyl tape for deck fittings under compression, but Atkins and Hoyle recommended BoatLife Caulking.  I really like butyl tape for anything that can be clamped down with force and in theory, these hatches should have been good candidates but the design of the hatch flanges on the was odd.  

When you look at the hatches from above it appears that the flanges are nice and flat and wide.  Perfect for sealing with butyl tape.  Unfortunately, the underside is a different story.  When I pulled them up, they were sealed with some sort of butyl tape, but it was a bit on the runny side and was yellowish in color.  I spent some time cleaning that up and once most of it was removed, I found that the underside of the flange had been modified.  The original hatches had a 'cove' running along the flange, but a someone had filled the cove with some sort of pink Bondo to make the flange flat.  I suppose it could have been done when the boat was built, but when I spoke with Atkins and Hoyle, the person told me that they new of no manufacturers who had ever done something like this and recommended against using butyl tape.  

Bondo???

In any event, the Bondo was very cracked with some stuck to the deck and some still in the flange coves.  The only thing I could do was to clean up the coves. It was slow going for sure, but I had a set of cheap wood carving tools with similar profiles to the cove and finally got both of them cleaned up. 

The smaller hatch didn't need new acrylic so I used Atkins and Hyle recommendation to run a bead of Boat Life Life Seal along the outer edge of the flange.  I opted to run a bead along both the outside and inside edges of the flange for a little extra security (maybe false sense of security).  Boat Life was nice to work with and only took about 15 minutes from start to finish to get it re-installed.

The big hatch was a much bigger job because I had to replace the acrylic as well as rebedding it.  Once I had the flange cleaned up on the underside of the hatch, I set to work pulling the old acrylic.  I took a razor blade and cut along the perimeter between the acrylic and the frame and cut away the silicon adhesive.  It didn't take too long before I was able to remove the acrylic, but removing all the residual silicon took a lot of effort and several hours of scraping.  I tried GooGone Silicon remover, but that didn't really do much other than make a mess.  It pretty much sucked, but I did it over several sessions on my back deck with a few beers to make it more palatable. 

Next, I set the hatch aside and moved onto the acrylic.  The big hatch has 2 latches that can be opened from the outside or inside, so these latches penetrate the acrylic through a spring loaded rotary seal.  To remove them, you first have to remove a set screw on each of the aluminum top knobs to remove them.  This took a bit of PB Blaster and patience because I was told by Atkins and Hoyle that if you ruin those, the assemblies are about $150 a piece.  The stainless steel screw and the aluminum knobs do not play well, but I eventually freed them up.  One other note is that the latches are also stainless steel and connect into the center of the aluminum knob.  These are isolated by a teflon tube.  One of the tubes was destroyed when removing the assembly, so I printed another 'isolation' tube from PLA on my 3d printer. 

I ordered a new piece of 1/2" smoked cast acrylic (25.25"x25.25") with 2" radius on all 4 sides from Tap Plastics and 2-1" rotary shaft seals from McMaster Carr here. I also ordered a 10oz tube of GE SCS1200 adhesive silicon sealant (same as what Atkins and Hoyle use, but purchased for half the price on Amazon).  The total cost for new parts was ~$275 USD.

Once all the parts came in, I got right to work because I was working on borrowed time with the half-assed hatch cover I taped in place when I removed the hatch.  Using the old acrylic hatch as a template, I carefully marked out the location of the holes where the latch assemblies would penetrate the hatch.  I drilled a pilot hole first and then used a 1/2" forstner bit to drill the underside of the hatch (1/4" through the acrylic).  Then I turned it over and used a 1" Forstner bit to drill out where the rotary shaft seal would mount.  Based on the condition of the old hatch, I decided to epoxy in the rotary shaft seals because I know that the next time this hatch leaks I will probably replace it with a new Lewmar (or something like it).  

I decided it would be best to re-bed the both the hatch itself and the acrylic lense on the boat so it would not need to be moved and one of us could clean up the underside if needed, so my wife and I took everything over to the boat and got started.  First, we flipped the hatch frame over and put a bead of Boat Life on the inner and outer flange on the underside.  Then we carefully laid it onto the deck so that the screw holes lined up with the holes on the hatch frame.  

Once that was in place, I put a small blob of Boat Life into each screw hole and then screwed it all down.  We spent a few minutes cleaning up the squeeze out with our fingers (and soapy water) before turning to the acrylic lense.  

I pulled off all the paper from the acrylic and then we swapped out the boat life for the GE SCS1200 silicon adhesive/sealant.  I laid in a generous bead of the sealant onto the lense flange and then we lowered the acrylic lense into the frame and squished it down and centered it in the hatch frame.  Because the acrylic is about 3/8" smaller than the hatch opening, the next thing to do was to fill in the area between the hatch frame and the acrylic.  My understanding is that this is what really holds the acrylic in place (they do the same thing on buildings with big glass plates, there are no fasteners, just the adhesive).  Once completed, we cleaned up that bead and re-installed the hardware and called it a day.  

I'm happy to report that after several torrential rainstorms a few days later both hatches have not leaked a drop. So I guess we can call this job done, except I still have to clean up the old tape glue around the perimeter of the small hatch, but that shouldn't be too bad. The new acrylic looks really nice, if the other hatches were leaking I would have done the same to them, but for now I'll just add it to next years list because I want to get this boat launched next summer.