|SJ23 Tech Tip B27, (Created 2011-05-24) Taz Coffee|
Title New Forward Hatch for Shangri'-La
I bought a new acrylic hatch from Gene Adams in Seattle. The nice thing about getting stuff from him is that he knows what size everything is. I got the handles from Go2Marine, an online parts supplier. I was able to reuse the old hinges but I did make new spacers for them. I have a stainless steel hatch riser arm from the old hatch that I may not install. The hatch stays open when it leans back against the mast. For now, I'm going sailing; I can always install the riser arm later.
INSTALLATION - I built a prototype hatch out of 3/8" plywood, using the new acrylic as a template. For this hatch, I attached the hinges first to help hold it in place while working out the location for the handles. For the actual hatch, I got some VERY good advice from Bob to position the striker plates BEFORE attaching the handles.
I had new striker plates made from stainless that are longer than the original plates. I highly recommend a minimum striker plate length of 2", unless you can get a flush mount and use bevel head screws. I used pan head screws and the extra length is just enough to mount the screws far enough apart so as not to impede the rotation of the handle. I positioned the handles far enough apart on the hatch so they can rotate inward without hitting each other. If you turn them the wrong way they hit the side of the opening and still hold the hatch closed. This is an added bonus. I put the striker plates on prior to the final hatch installation, in part because the prototype gave me an excellent guide for positioning them and it worked out fine. In retrospect, I would probably get the final hatch installed and then put the plates on.
The trickiest part of this whole operation was positioning the handles on the actual hatch. The plywood prototype was on the boat for a week, during which time it baked in the sun and was drenched with two days of rain, so it was a little deformed when it came off. It definitely helped to have done it once on the plywood hatch. I measured everything about six different times but ultimately there was a little bit of guesswork involved in determining where to drill the pilot holes. I drilled a 3/32" pilot hole using a standard bit (the specialized acrylic bits are ridiculously overpriced) with the drill press set to the lowest speed possible. I then used a 5/8" hole saw to cut the final hole. To be sure this would not damage the acrylic, I did test holes in the old hatch. I used a router bit attachment to my Dremel tool to chamfer all the holes.
Much to my relief, all my measuring and practice paid off. The handles lined up perfectly. The spacers were the correct length and all that remained was to install the hinges. When I removed the old hatch, I drilled out the old holes with a 1/4" bit and then filled them with epoxy. When I reinstalled the hinges, I drilled slightly oversized holes for 10-24 stainless bolts. I attached the hinges to the cabin top first. I put a layer of Sikaflex between the spacer and the gelcoat and made sure some went in each hole. I did the same for the part of the hinge that attached to the acrylic. Gene Adams suggested using two bolts thru the acrylic, omitting the bolt closest to the edge of the hatch. This kept the bolt from impinging on the weather strip. I replaced that as well. Very easy to do. I had some 1/8" aluminum backing plates cut for the hinges on the acrylic, instead of washers. I stuck a some rubber gasket material on the backing plate between it and the acrylic. I let the whole thing dry overnight and woke up to a fully functioning hatch in the morning.
Overall this job went very well. A lot of thanks to
Bob and to Gene for their
suggestions. I think I took more time than I needed to. I certainly
over-engineered it. I tested the water integrity today by scrubbing
Shangri'-La's decks. Not a drop below. I'll be in touch. Taz Coffey