Yes .....................
......... it can be done very nicely and some day when I'm too old to remember where I left my boat, I'll collect a series of photos to show how it's done.
I've done one Lewmar and two Bomar hatches on our H-310 and they still look brand new after three years in service. The 13" X 13" Bomar hatches were about $15.00 each and the 21"X 21" Lewmar was about $40.00. After perfecting the installation technique, I've actually decided against the idea of installing Sunbrella UV protection covers for the new hatches. It's easier to just install new lenses every eight or nine years.
On later model Lewmar hatches, I understand the lenses can be replaced by simply sliding out the old one and installing a new one. As your needs replacing, I would suspect it's not a newer model and therefore you have some work in front of you.
Basically, if you have a home woodworking shop, you have everything you need for a professional job which is identical to the original Lewmar hatch ............. a table saw with carbide blade, router, drill press, and assorted Forstner bits.
There's no great skill required in doing this but it's a rather slow, long drawn out affair. Very briefly and without going into too much detail:
- Remove the hatch cover by pulling out the hinge pin. The replacement work has to be done in the comfort of your shop.
- Seal the open hatch.
- As you take the old lens out of the frame, notice how it is assembled. This will make this explanation a little easier to understand.
- Use an Exacto knife to carefully cut (on the top) the sealant between the aluminum frame and the acrylic lens. The gap is about 3/16". Make numerous cuts until you can force out the lens. Do not damage the lens as you will need it later as a pattern.
- Use a plastic scouring pad to remove every trace of the old sealant from the aluminum housing. Do not scratch the anodizing on the aluminum frame or you're looking at future corrosion.
- Use an Exacto knife to quickly and carefully remove the sealant from the old lens.
- Purchase the tinted acrylic material of your choice from a dealer. Don't waste money getting it cut to size.
- Use a felt pen to roughly mark out the size of the new lens you"re cutting.
- Cut out the rough size of the new lens on the table saw, leaving about 1/8" waste for trimming. Remember when cutting acrylic, use high speed and very light pressure.
- Take the old CLEANED lens and attach it to the new, rough cut acrylic sheet using spongy double sided tape.
- Use a template bit in your hand held router to to trim off the waste material on the new acrylic sheet. You now have an exact copy of the outside of the old lens +/- 0.001".
- Drill out the large handle hole using the Forstner bit and the hinge holes using a twist drill. Your drills must be sharp. I know there are reams of material on how the "professionals" cut acrylic but in my experience, the cuts have been flawless using sharp tools, high speed and very light pressure.
- Apply a strip of 1/16" thick X 1/4" wide single sided adhesive backed foam rubber around the bottom of the inside of the aluminum frame. The new lens cannot be adhesed directly to the aluminum frame due to their differences in thermal expansion. The foam rubber allows for a "floating motion".
- Mask the top of the new lens with 1/4" wide elastic automotive masking tape and then cover this tape back a bit with cheap painter's masking tape.
- Apply the same masking procedure to the aluminum frame.
- Remove the bottom protective paper from the lens.
- Drop the lens into the frame and temporarily centre the lens with whatever is at hand.
- Drill a 1/16" hole in the tip of a tube of Dow Corning #795 to get the smallest extrusion hole possible.
- Warm the #795. It extrudes much better.
- Practice forcing the silicone into the bottom of the 3/16" gap between the lens and aluminum frame. This take a bit of practice to avoid air bubbles so be prepared to clean up the lens and frame and try it a few times before you perfect the technique.
- When finished , IMMEDIATELY pull off all layers of masking tape before the silicone has a chance to set and start tearing.
- Allow to set for a couple of weeks due to the depth of the bead.
- Install the hatch lid back on the frame.
- Tear the protective paper from the top of the lens and you're done.
So much for a the brief description
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