Re-bedding bomar hatch

Hello all,
Sorry if this is a repeat but I found nothing in search.
My Bomar hatch is leaking but otherwise in good shape.
I figure I'd try re-bedding it.
Perhaps the collective wisdom of the group could weigh in with advice.
My thoughts, subject to change, are to remove all screws pull hatch up from above, then scrape existing sealant and clean thoroughly with acetone.
Then re-bed with 100% silicone and re-install. Simple right? Probably not!
I await your replies...
Thank you in advance.
Steve

Ahhhhhh.....Sorry, anything BUT silicone. This may be a good application for butyl tape.

I did the exact same thing but not silicone-I used 4200.

Hi RTF,
Never worked with butyl tape before. Sounds less messy than silicone. Is it literally "tape" on a roll? How would you suggest applying it around hatch opening? Both sides of screw holes or just outside? Is it readily available? I don't know how the hatch is bedded now but I have no strong desire to reinvent the wheel. However, if there's a better way, I'm game.
Thank you.

I did mine with Butyl tape several years ago it worked out well. If you go to a hardware store they may not know it as "Butyl rubber tape" if not ask for "Metal building panel seam tape"
Below is information on using it, this fellow sells the tape also, ordering information in the article below

https://marinehowto.com/bed-it-tape/

Be careful removing the old sealant! I wasn't, mine was caulked with something very hard, knife slipped and I wound up with 5 stitches across the knuckle of my left "bird finger"!

Good luck

Greetinggs,
Mr. S. Thank you so much for providing that link. I was wracking my memory trying to remember the tutorial and I came up blank...
Whilst the link provides an excellent source to purchase the tape, I bought mine at a travel trailer store where they use it to bed windows etc...

RTF is right, don't use silicone. It will make it impossible to get paint to stick in the future should you want to paint and it's not a very long lasting sealant anyway.

I'd use 3M 4200 or my new favorite, Sudbury Sealant. I like the Sudbury because it seems cleaner to handle than 4200 and 5200 and it drys quickly.

I've never used the butyl tape but I understand it continues to ooze out for several days after installation. Probably not a big issue but something to be aware of.

Has anybody noticed that 5200 can jump several feet through the air to get on your cloths? If I walk within three feet of fresh 5200, it gets on me.

HopCar said:

Has anybody noticed that 5200 can jump several feet through the air to get on your cloths? If I walk within three feet of fresh 5200, it gets on me.

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Sure, but that's why disposable hazmat suits were invented as far as I'm concerned.

Wow! Thank you everyone for the replies.
Butyl tape, 4200, Sudbury sealant. I have some research to do.
I appreciate the thoughts and cautions.
Steve

Butyl tape. Perfect application for it.

No muss. No fuss. Low cost. No waste.

There are (is?) a number of other brands of polyurethane sealant/adhesive like 3M and Sikaflex. Are they equivalent? Time will tell. I used an Aussie brand "Parfix" to attach solar panel brackets, still stuck after 5 years even though the deck around them has been heavily sanded and redone in nonslip.

There are a variety of butyl tapes available as well. I keep both a soft gooey tape and a firmer, more dry tape on hand depending on how much pressure will be applied on whatever I am bedding.

I get them both from a motorhome supply place. Cost is almost nothing. $20 buys enough to re-bed everything on the boat.

I've seen a tutotial on how to rebed hatches. Don't recall ig it was one of Compass Marine How To or West Marine.
A Goigle search should turn up several. Worth a look if you have neverdone one.
Yricky part is frequently getting the old one off...don't want to pry and break it

Before you pull and re bed the whole deal, you need to be 100% sure it is leaking around the frame. I just finished fixing up our Bomar hatch last weekend. I replaced the gasket (Bomar says do it every 8-10 yrs I think) it didn't completely stop it, so I found a local glass guy to re bed the lens for $100. He actually cut a new lens and did the messy job of caulking it up. It is all good now.

I was scared to start pulling the frame until I was sure it was the problem. That, to me, is opening a big Pandora's box. There should be a serial number on the hatch. Call Bomar and talk to them.

Good stuff. Thank you all.
I will first try to determine exactly where the leak is coming from. I was thinking it was the hatch to deck seal as the water is coming through and dripping into the cabin through a hole in the trim ring. There's also a bit of rust on the attaching screw on the deck just above that spot. Of course, water can migrate before dripping so no assurances.
I will use extra care if I must remove the hatch from the deck. I will check with Bomar first and try to find some online tutorials great idea!
Thanks again,
Steve

I second the gasket idea. I used a stip of paper closed into the hatch to see if the seal was tight.

Rebedding our Lewmar forehatch (almost) as I write. I don't think it was ever removed or rebedded since 1984, but it has leaked a few drips for a great long time. The PO(s) tried resealing around the hinges with at least two different ineffective goops. The original Taiwanese bear **** used for sealant on the hatch and on the windows elsewhere is a black goo that cured soft, stretchy but sticky; where it remained stuck, it was utterly tenacious and only moderately dissolved with lacquer thinner and/or paint remover. It would eventually come off with great effort and lacquer thinner.

Derived from Lewmar's instructions: the hinges and therefore the cover are fastened to the boat independently from the hatch's aluminum coaming; they say through-bolt. Their hatches have hinges which hold the hatch at various opening positions without the use of struts; means the hinges are constantly flexed and the bedding stressed if the bolts aren't tight enough, as you operate the hatch. Our cover was fastened with 4" long 1/4-20 bolts but I don't think there were any nuts; this would have been a PO trick that I've found elsewhere on the boat.

So, my first problem, after cleaning the boat's Teak coaming, is to figure out how/if the thing was ever bolted and how to access the nuts for proper bolting. I may have to disassemble the overhead in the forepeak to do so, but I have no enthusiasm for messing with an otherwise perfect and undisturbed interior finish.

I don't yet have any idea of what the constructions is around the hatch opening; it's certainly possible that there's plenty of wood and that the hinges had been mounted with wood screws that subsequently were stripped and replaced with the gooed-in bolts. I could then drill out the gooey holes, epoxy in dowels and use screws. It's also possible that the hatch trim is relatively thin and the bolts were installed through adjacent construction before the overhead went in. If the holes I drilled out had bottoms (rather than open into the space above the fabric overhead), I could still epoxy and screw the hinges.

I've been researching sealants for the fixed windows and this hatch. Clearly, silicone is absolutely the wrong thing due to the subsequent repair issue. Previous experience with 3M 5200 and discussion with their rep says that that's the wrong stuff for the fixed windows; their website says that their 3M Scotch Weld bonding adhesive 5400 FC is the stuff to use. Their website says that their 3M 4200FC or 4400 BC is excellent for the hatch bedding.

HopCar said:

I've never used the butyl tape but I understand it continues to ooze out for several days after installation. Probably not a big issue but something to be aware of.

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I bought some butyl tape after reading rave reviews of the stuff from the various sailboat sites. Where I have used it on my sailboat, no more leaks

What I don't recall reading about was that it will continue to ooze and wiggle as it sets. I would need to draw up my fittings several times over a summer as things oozed and clamping pressure was applied and it finally would "set". Even after cleaning up, there is always a thin line around the fitting with a hairline of butyl that catches dirt and turns grimy. And it doesn't clean up 100% if your gelcoat is chalky, so you end up with a larger grime line.

Finally, only thru-bolt your fittings with butyl. If you try and run a screw thru it, the turning of the screw will draw the butyl up like taffy on a machine and you will end up with a lump you cant draw all the way tight.

Personally, when I start rebedding the hatches on my Bayliner, I'll be using a tube of goop :lol:

In regards to Silly-cone. . .I think some plastic hatch manufactures say to bed in silicone only. . .my Beckson deck plates I believe called for silicone.

Tom.B said:

Before you pull and re bed the whole deal, you need to be 100% sure it is leaking around the frame. I just finished fixing up our Bomar hatch last weekend. I replaced the gasket (Bomar says do it every 8-10 yrs I think) it didn't completely stop it, so I found a local glass guy to re bed the lens for $100. He actually cut a new lens and did the messy job of caulking it up. It is all good now.

I was scared to start pulling the frame until I was sure it was the problem. That, to me, is opening a big Pandora's box. There should be a serial number on the hatch. Call Bomar and talk to them.

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Good deal, good info! I have an older Bomar that leaks under the seal when the wind is howling and I am taking heavy spray. I didn't know the seal had a life span, mine is original and almost 18 years old now...

Last fall I re-did two leaky hatches on my new-to-me 2002 Nordic Tug. I'm no pro, but here's how I did it - not super quick, but better technique and results than the first 1-2 times I did this on other boats.

Remove hatch top, arm(s) which hold it open, and all screws which hold the metal hatch frame to fiberglass. Careful use of a sharp putty knife, assisted by a hammer, patiently taking a good part of an hour to loosen frame from FG. Another good part of an hour thoroughly cleaning every bit of old sealant and corrosion off FG, screws, and frame, with help from acetone.

Apply 4200 to each screw hole in the FG, then carefully and evenly to the sealing surface on the underside of the frame. Set frame precisely in place. 4200 on each screw before inserting it.

Tighten screws gently, a little at a time, criss-crossing round the frame multiple times to be sure tightening is even. Some 4200 should be squeezing out everywhere around the frame. (Don't super-tighten - could squeeze out too much of the 4200). Clean up excess with putty knife, smooth with finger, and finish wipe with mineral spirits or acetone.

Make sure mating surfaces on hatch and frame are clean. Silicone spray (not the sealant) on the rubber part is good.

Voila! no more leaks.

I wish the rest of the story had gone as well - the PO(s) had apparently allowed leaking to persist for a long time, so there was a fair bit of ugly black rotted plywood in the ceiling around the worst hatch. Freaked out when I saw it - looked like a disaster! Took a lot of digging out, then drying out all winter and replacing lost wood with new this spring, but now all is well.

I would add my support to the idea of first checking the hatch seals. Then if you do need to rebed, I would suggest the butyl tape. Just avoid silicone at all costs.

Dolphinite is my favorite as it is easy to clean off when the time comes.

The tape sealants work best with hatch for window flanges designed for its use .

5200 never, and any goop that hardens in the tube after its open is not for my use.

This year I plan to try using Phenoseal in lieu of 5200. 5200 can be a BPITA because once you open a caulking tube, plan to use it all....soon! The small tubes with a cap seem to survive without problems though.

My Bomar hatches were also leaking. However, my leaks were between the lens and metal frame. After removing the old sealant from the gap between the lens and metal frame the lens came out with very little pressure. Cleaned everything and re-bed with Dow Corning 795. Leaks are gone.

Well almost. Now getting a new very slight leak between the hatch and deck.

In the past I've used a bedding compound like 4200 but didn't completely tighten the item to the deck. I would just tighten the screw or through bolt enough to secure the item. Wait a few days until the bedding compound was completely cured and then completely tighten the item to the deck. Now instead of the bedding compound oozing out it compresses to make a tighter seal, more like a gasket.

However, with what I have read here I may use butyl tape for this project.

foggysail said:

This year I plan to try using Phenoseal in lieu of 5200. 5200 can be a BPITA because once you open a caulking tube, plan to use it all....soon! The small tubes with a cap seem to survive without problems though.

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I don't use 5200 for anything anymore. Not even for underwater projects. And I would never say to use it on something like a hatch. That stuff just makes any future removal a huge pain. Sik-a-Flex is superior in so many ways.

Tom.B said:

I don't use 5200 for anything anymore. Not even for underwater projects. And I would never say to use it on something like a hatch. That stuff just makes any future removal a huge pain. Sik-a-Flex is superior in so many ways.

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Tom (and all), which Sikaflex do you use for bedding fittings . . . and which for seams that are exposed to UV? How does the latter hold up to sun exposure? Thnx.

angus99 said:

Tom (and all), which Sikaflex do you use for bedding fittings . . . and which for seams that are exposed to UV? How does the latter hold up to sun exposure? Thnx.

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295 above the waterline, 291 below it.

I very much appreciate all the thorough input. I am a bit nervous about wood rot now (Thanks RCook?) but will get a good look at all the parts to come off before I do anything. First, as suggested by Tom.B, I'll check other possible leaks sources.
Hopefully I won't have to remove the head liner in the cabin below the hatch to complete the job correctly.

" I am a bit nervous about wood rot now"

Wet wood does not rot, Dry wood does not rot.

Wood rots when going from wet to dry or dry to wet.