Bomar Hatch Lens Replacement

[NSboatman]

Hi Folks-


I have 3, 1990's vintage, Bomar cast aluminum deck hatches, with roughly 24" square lenses. just removed them from the boat to replace the lenses, which after 30 years of continuous exposure are showing significant signs of imminent failure (cracks, crazing, seal separation, etc.). strangely enough, none of them leak... and I love these hatches because of how positively they can be dogged down. So, seeing as how the boat is out and covered, I thought it might be time to do a little refresh on the lenses...


Now that they are on the bench and I'm looking at them, I'm wondering about the best way to remove the old lenses (they are still stuck in place extremely well); and indeed how to re-bond new ones in place.



I'm sure more than one member of this forum has done this before... anyone care to share their experience and advice?


I'd also like to consider going up an additional 1/8" - 1/4" in thickness when replacing these lenses... because even though nothing has broken to date on them, they seem to be no more than 1/4" thick acrylic... which is easy enough to deflect with a thumb or finger, and does not inspire confidence. i realize this will require chamfering the edge of the acrylic that is exposed above the frame, but that's not a big deal with a good router.



Any words of advice or wisdom to impart before I tear into this job? I'm sure this is one of those sorts of jobs where a little bit of experience would go a long way...


I've also contemplated sending them to Hatchmasters and outsourcing the whole job... anyone else done this?


thanks in advance -


bg

[Smooth Move]

My Bomar Hatch was leaking on my 1987 Catalina 30 . I priced out time and materials , finding a new latch dog of similar vintage and ended up just replacing entire hatch for about $700. New Bomar has been in place for about 2 years without issues. Some other cabin windows with crazing have not replaced as not leaking yet — though one replaced with leakage and re replacement . As it goes “ if it ain’t broke don’t fix it” my motto.

[pcmm]

Originally Posted by Smooth Move

My Bomar Hatch was leaking on my 1987 Catalina 30 . I priced out time and materials , finding a new latch dog of similar vintage and ended up just replacing entire hatch for about $700. New Bomar has been in place for about 2 years without issues. Some other cabin windows with crazing have not replaced as not leaking yet — though one replaced with leakage and re replacement . As it goes “ if it ain’t broke don’t fix it” my motto.

There is no way you can replace that hatch for $700 the one in the picture is a $2200 hatch! well worth the cost of a refurbishment. They are bulletproof hatches that you can safely stand on!

[Orion Jim]

Lexan is the lens material and Dow-Corning 795 is the sealant.

[Scott Fuller]

I re-lensed all of our Lewmar overhead hatches last year. The Lewmars had silicone sealant around the perimeter of the lens and the lens was bedded in butyl tape. I cut the silicone with a razor blade all the way around and was able to get the lens out by pushing with both thumbs in a corner until it began to separate from the butyl. The hardest part was getting all of the old silicone off of the hatch frame.

I purchased tinted cast acrylic pieces from a local plastics supply house - they had drops from full sheets that were cheaper than buying a whole sheet, I paid about $35 - 40 a piece for material for my hatches.

After I cleaned the silicone off the edges of the old lens, I used it as a pattern to trace the shape on a new piece of acrylic. I then rough cut it with a jigsaw with plastic cutting blade. Once I had it close, I clamped the two together and used a pattern bit in my router to cut the new lens to the correct size.

Each of my hatches had holes for the hinge bolts and holes for the hatch dogs. I purchased high speed drill bits in the proper sizes and ground a sharp relief on them then with the lenses still clamped together, I drilled the holes in the drill press.

I purchased a roll of new black butyl tape from a local glass company (shower doors, storefronts windows, etc). It comes in a few different thicknesses. I bedded the new lenses in the butyl as before. I removed the protective paper and used painters tape around the edge of the lens and the frame before caulking. I used Dow 795 in bronze for the seal and tooled it with a popsicle stick before removing the tape.

While I had them apart, I replaced the rubber seals with new seal material from HatchMasters.

I am very pleased with how my hatches came out - a huge improvement over the old crazed acrylic.

[Scott Fuller]

Originally Posted by Orion Jim

Lexan is the lens material and Dow-Corning 795 is the sealant.

I believe cast acrylic is most typically used for hatches - it has greater UV resistance and is less susceptible to scratching than Lexan.

[Pizzazz]

I also have the cast aluminum Bomar hatch on my Hunter 31 that needs a lens replacement. I was advised to keep the hatch and just replace the lens in place. I believe Lexan is the way to go for these hatches. Replacing the entire hatch is a possibility but cheaper hatches may leak in serious seas because they are more flexible and the deck may twist a cheaper, less sturdier hatch. You would not know until you get into a serious situation and that could become a problem.

My approach would be to remove the lens using a screw driver around the edges. You may chip it but Lexan would be unlikely to fracture. Then take the lens to a shop where they can cut one for you. You want to make sure that it is flush with the top I think, so I would not increase the thickness.

I have also toyed with the idea of using tempered glass but I am a little hesitant. If you drop a tool while working on the mast, the tool will fracture the tempered glass but not Lexan. On the other hand, tempered glass will give you beautiful views of the night sky. A difficult question.

SV Pizzazz

[Smooth Move]

My bad $ 669 Catalina Direct plus installation— about 4-6 hours I recall

[Exile]

I have the exact same hatches as the OP on my 1986 Bristol. Afaik they are all original. None of them have ever leaked, and I have thus far only replaced the lenses in two of the smaller ones, but only as a preventative. It turned out to be a simple, inexpensive job. I sourced the exact same size & thickness from a local plastics shop, cut the old ones out with a razor knife, cleaned everything up well, and used BoatLife's Lifeseal to reinstall. I used the clear stuff since I knew I'd wind up with some slop. I did opt to replace with Lexan since they get stepped on occasionally, but I'll use acrylic when it's time to replace porthole lenses. This was probably about 4 years ago and no leakage or other problems since. I'll likely replace the other lenses in due time, but no rush. I think at some point I may also have replaced the inside seal, but that's easily sourced, comes with its own adhesive backing, and is no big deal (use the oem stuff).

Fwiw, Bomar (now Pompanette) told me that both my hatch & portlight frames were made from extruded aluminum. Might help anyone trying to identify what they have.

[NSboatman]

excellent info folks - thank you! keep it coming.



i was wondering if they were acrylic or lexan originally. given the relatively thin section of plastic, I'm leaning towards lexan. is there a conclusive, non-destructive test that can differentiate between the two?


pizzazz - why do you think it needs to be flush with the top of the aluminum? if there's a generous chamfer on the edge of the plastic it should be very resilient to chipping, and wouldn't catch a line or anything sliding over it... just wondering.

and yeah - I love these hatches - they are tough as nails and can be properly dogged down. At $2200 each, glad I don't have to buy new ones!!

bg

[DougR]

When I replaced the lens in my 24 inch Bomar, the lens that came out was about 1/8" lexan, and very scratched. I replaced it with either 3/16 or 1/4" acrylic, and that's plenty thick as the three aluminum cross bars provide support. If you use 1/4" or thicker a slight bevel on the edge works fine.

As mentioned, Dow Corning 795 is the stuff to use to seal the new lens. My installation is about 10 years old and still no leaks.

DougR

[Exile]

Originally Posted by NSboatman

i was wondering if they were acrylic or lexan originally.

I was told by Bomar/Pompanette that my hatches were Lexan and my port lights acrylic. I assumed the rationale was that Lexan is stronger (for standing on hatches or to resist a boarding wave), but acrylic doesn't scratch as easily and port lights have smaller surface areas. So I just replaced with same.

Originally Posted by DougR

As mentioned, Dow Corning 795 is the stuff to use to seal the new lens. My installation is about 10 years old and still no leaks.

While I've had no trouble with Lifeseal, I (vaguely) recall Bomar recommending Dow Corning 795 as well, with the final prep a wipe down with rubbing alcohol I believe. I'll probably go that route next time. Could be a different sealant recommendation if bonding to stainless steel or bronze.

[Singularity]

FWIW a video of Christian Williams replacing the acrylic in his Lewmar hatches:

https://youtu.be/eD3Hp8W07yY

[svmatilda]

Lexan is the lens material and Dow-Corning Windows sealant silicone #791 is the sealant. Don’t use acrylic, my hatches have been done 6 years and still look new. I believe Dow-Corning #795 sealant is also ok.
I did all my hatches (8) on Matilda, Lexan i didnt change the thickness of the material I went with the smoked color again as it filters the light. I cleaned the old sealant from frame. Cut the replacement polycarbonate Lexan to the same size, leave the protection tape on one side. Make sure this is the side exposed to the sun and is the side with the UV coating. However you should get Lexen with UV protection on both sides as the underside will get sun when open.

There is then 2 ways to go now. First uses thick VHB (very high bond) double sided tape. Cut the tape to fit into the frame, seat in the new lens carefully, leave the protection film on. Apply masking tape to the top of the frame then seal around the edge gap with sealant. Smooth it off with wet detergent coated finger and then after an hour or two when the sealant is tacky remove the tape.

Second method is to squeeze a bead of sealant approx 1/4 in diameter around the flat recess of the frame. Bed the lens, squash the bead until the lens is level with the top of the frame. You need the bead to finish at about 1/8 - 3/16" thick this allows for expansion of the frame and lens. Let it set overnight then in the morning mask up the frame and seal around the gap. Smooth it off with wet detergent coated finger and then after an hour or two when the sealant is tacky remove the tape.

[pcmm]

Originally Posted by Smooth Move

My bad $ 669 Catalina Direct plus installation— about 4-6 hours I recall

the hatch we're talking about is not available from Catalina Direct. the one you refer to for $669 is a much inferior hatch. Here is the hatch we're discussing

https://www.marineoutfitters.ca/inde...e=759739353443