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Rebedding front Bomar hatch

 
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Chuckpacific



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PostPosted: Wed Aug 14, 2019 9:06 pm    Post subject: Rebedding front Bomar hatch Reply with quote

Greetings...

Just curious as to recommended sealant for rebedding front Bomar hatch.

Butyl tape, 3M Adhesive Sealant Fast Cure 4000 UV, Boat life silicone rubber?

Other suggestions?

Thanks,

Chuck

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tsturm



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PostPosted: Wed Aug 14, 2019 9:51 pm    Post subject: Re: Rebedding front Bomar hatch Reply with quote

Chuckpacific wrote:
Greetings...

Just curious as to recommended sealant for rebedding front Bomar hatch.

Butyl tape, 3M Adhesive Sealant Fast Cure 4000 UV, Boat life silicone rubber?

Other suggestions?

Thanks,

Chuck


I used 5200 on the 2 I have done! Thumbs Up
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thataway



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PostPosted: Wed Aug 14, 2019 10:33 pm    Post subject: Reply with quote

4000. Because you may have to remove it again some day. I am not a fan of butyl tape, if screws loosen, the water and dirt get under it. Silicone generally has little use on a boat as a sealant. Its adhesion properties are not the best. Once used, other compounds will not stick well...

Also many of the hatch cutouts were too large, If the hatch is out, you need to remove about 1/4 inch core around the outside (or any which is wet or rotten), and remove any core where the screw holes are. Fill these also with thickened epoxy. Then redial the holes.

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srbaum



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PostPosted: Thu Aug 15, 2019 9:55 am    Post subject: Reply with quote

I have bedded over 10 Bomars in the last year and just helped a friend re-bed over 500 fasteners on the deck of his (wood core) boat.

My path is the same as several of the high end yacht manufactures and I have yet to have a failure (no leaks).

As Dr. Bob states, it is very important to remove the hatch, remove all old caulk and prepare the boat for the hatch.

If the balsa core is exposed in the hatch opening, seal it with two part epoxy. If the core was not sealed before and the balsa is wet/damp, dig out the wet/damp balsa and fill it with two part epoxy, but mix a filler (I use wood flower, but you can purchase other fillers at the counter where you purchase the epoxy) with the epoxy to make a peanut butter paste. Work the paste into the dug out area, then cover the wet epoxy using duct tape (taping the fiberglass about and below the epoxy to keep it in place) until it hardens a bit. Remove the tape while the epoxy is slightly uncured (green) and you will be able to trim any edges that are not fare, without having to sand. The duct tape will not stick to the green epoxy and will come off very easy. Clean up all of the final residue with denatured alcohol.

For all of the holes that will be used to fasten down the hatch, drill the holes oversize and use the same epoxy filling procedure outlined above. Lay the hatch in the opening when done, place blue painters tape around the perimeter of the hatch for alignment and center punch the location of the fasteners. Remove the hatch and drill the holes to the correct size for the fasteners. Once the holes are drilled, using a chamfer bit, drill slightly into each hole to form a chamfer (the chamfer aids in prevention of surface cracking and also allows the bedding compound an area to rest in.

Last but no least butyl rubber tape the entire mounting surface. place a small bead of the rubber near the top underside of the fastener. Tightening the hatch in a uniform pattern is very important (use something like an x-pattern as is done to tighten lug bolt on a car wheel). Tighten a little at a time and, so that the bedding is taken down in a uniform pattern.

When done, remove excess butyl rubber around the perimeter using a plastic putty knife or an old credit card (I same these cards that I get in the mail that really are not credit cards, but are made from the same plastic).
I purchase my butyl rubber on eBay from a vendor that sell a LOT of it, so it is fresh. I purchase white, 1/8" x 3/4". It sticks to itself, so if you want it thicker, just lay it onto of itself, same thing for making it wider.
This is the vendor that I have used over the last severl years for BRT:https://www.ebay.com/itm/DEHCO-COLORIMETRICS-BUTYL-TAPE-PUTTY-TAPE-BLACK-GRAY-WHITE-MANY-SIZES/231095305882?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

You may ask when I would use other caulks/sealers and I do have them, but use them in very limited applications. Examples of 3M 5200 would be to glue a block of wood to the boat, where I want to mount something, without drilling into the boat. I would use 3M 4200 for the thruhull fitting such as the Wallas exhaust (Wallas provides a cork gasket for this, but the cork fails to expand and contract with the heat over a few years), or sink drains.

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Micahbigsur@msn.com



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PostPosted: Thu Aug 15, 2019 10:09 am    Post subject: Reply with quote

If the hatch is plastic you have to check to see if it is compatible with the polyurathane sealants like 4200. A lot of plastics will be degraded over time by them and are not recommended. Silicones are good for these plastics, there are many grades, the best (marine, $) adhere ok and since the hatch is mechanically fastened down it should not be an issue but do not tighten so much that all the sealant is squeezed out. Silicone is not good for applied caulk, 5200 is used as a glue on sealant, never to be removed but aren't recommended on a fuel tank where another sealant should be used, sealants unfortunately are very specific and different in their applications. I Google each and research if I am unsure.
If the hatch mounting surface is metal any one of the 3 4200's or butyl will work fine, of the 4200's one less affected by the sun, one fast cure and one slow cure (days).
If the laminate is balsa cored the screw holes must be protected with epoxy plugs to prevent rot.

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ssobol



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PostPosted: Thu Aug 15, 2019 11:20 am    Post subject: Reply with quote

I've found that 5200 is not all that hard to remove from fiberglass. A heat gun, DeBond, straight edge razor blades, and some patience and it'll come off. Done it a few times.

Biggest problem is that the DeBond will dissolve it, but when the DeBond evaporates the 5200 will set up again on whatever the little bits of it have landed on. Have to be careful wiping up the adhesive as you remove it.
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Marco Flamingo



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PostPosted: Thu Aug 15, 2019 12:01 pm    Post subject: Reply with quote

If you have the luxury of a helper, once you have hogged out the balsa from the perimeter of the hatch opening, using a homemade grout bag (aka frosting piping bag) makes things go fast. The helper follows the fill around applying the duct tape. More photos in my album under Balsa Core Issues.

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thataway



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PostPosted: Thu Aug 15, 2019 1:37 pm    Post subject: Reply with quote

I'll start this by saying that some years the manufacturer "sealed" the Edge of cutouts using their preferred sealant (A Bostik product, which seemed to be used for everything, including the water pipe connections where threads were mis-matched!) They even sent me 3 tubes of it, when I discovered that had not sealed the joint between the cabin top and aft bulkhead on the Tom Cat 255.

Second, no matter what product you use, the surfaces must be really clean. Any prior sealant should be removed. (If silicone has been used, it seems to get into the "pores" of the fiberglass, and keep other materials from sticking in the future, even though it often is not a good adhesive.).

Lots of good information in the thread. But we all may have different experiences and backgrounds.

Generally the ONLY silicone type product which I believe should be used on the exterior a boat is Boat Life Life Seal--it is a hybrid urethane/silicone product, and is OK for plastics. (There is an exception of a specific polymer of silicone used for bedding Polycarbonate; aka Lexan) However, the Bomar hatches are aluminum framed, so the 4000 which is UV resistant, is satisfactory.

My objection to butyl tape is that I have removed hundreds of fastenings which were bedded with it, and invariably there has been both water and dirt intrusion under the butyl tape. Basically the butyl tape is being used as a gasket, which depends on fasteners remaining very tight. As butyl tape ages, it looses some adhesive property. Manufactures used it because it is faster and cheaper than other sealants. But these same manufactures don't seal the core properly--!!
Even better is to use solid glass laminates or specific blocks of embedded water resistant materials, in areas of fasteners or high shear loads.

Yes, 5200 can be removed, use Marine Debond, which is both expensive and very time consuming. I removed some pieces of teak which were used as stops for a small propane stove in the galley last year. The use of wooden or plastic wedges will help give "lift", also score the 5200 seal with a razor knife (like "Xacto" ) to create an entry point into the core of the 5200 bead. Harder on horizontal surfaces. Even on the Debond web site, they admit professionals take 30 minutes to remove 12" of Debond.

For the thickening of Epoxy, I prefer a mixture Cabosil (Fumed Silica), and medium density filler, mixed to a "peanut butter" consistency. It is stiff enough to stay in place--but I recognize that the duct tape trick certainly has its place.
I feel one should coat the core (balsa) with "neat" or unthickened epoxy. I just mix the epoxy, brush on the coating to the core using a glue brush. Then add the thickening agent.

Obviously we have differences of opinion based on our own experiences. I'm not saying that my techniques are any better than any other--but have worked for me. I started working on fiberglass boats in 1952 when Glasspar donated a dozen 12 foot skiffs at Camp Fox, Catalina Island, where one of my duties was repairing the wooden skiffs which the campers used. They also left a gallon of poly ester resin some MEKperoxide catalyst and pieces of fiberglass mat and cloth. My experience with butyl tape is mostly from RV's which I have owned continuously since 1962.
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Micahbigsur@msn.com



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PostPosted: Fri Aug 16, 2019 2:36 am    Post subject: Reply with quote

I had to remove a s.s. shower pan flange off a teak floor that had been set in 5200 on my sailboat I used Debond, wedges, knives and swear words and was successful but I swore off 5200 for life.
Polyurethanes, Polysulfides, silicones, hybrids of all kinds each has a use that it is great for, (except anything containing latex) but matching them up can be confusing to say the least. Only by carefully researching the sealants characteristics with the materials to be sealed or bedded will you be happy over the long term.
We used a lot of Butylflex in the 60's but we have come a long way with better sealants since then.
I like adding some micro fibers to the epoxy mix when you don't need a smooth paintable surface, adds a lot of strenth.
I hope this thred is more helpful than confusing other than anchor choices, epoxy and sealants are always next up for spirited debate amongst boaters doing their own projects. I have seen a lot of mistakes made by pros I used to work with on the job, so getting someone else to do it is not the solution.
Are we having fun or what!
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tsturm



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PostPosted: Fri Aug 16, 2019 3:01 pm    Post subject: Reply with quote

[quote="Micahbigsur@msn.com"]I had to remove a s.s. shower pan flange off a teak floor that had been set in 5200 on my sailboat I used Debond, wedges, knives and swear words and was successful but I swore off 5200 for life.[/quote

A little bit of heat gun application works amazing with 5200
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thataway



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PostPosted: Fri Aug 16, 2019 6:58 pm    Post subject: Reply with quote

My first attempt at removing 5200 from plastic port rings, was a number or years ago--DeBond was avaiable and I used it liberally, cut into the 5200, use wedges and heat gun. Even then I pulled off some of the gelcoat and first layers of glass Fortunately it was under the trim ring of the new port (bedded with Boat Life, Life Seal).

Since then I have learned more finesse, works--but still one of the last favorite jobs...

There are plenty of resources on the internet--and some tend to confuse neophytes. But there are some good general rules also. Thank heavens we are not talking about bedding teak decks!...
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Micahbigsur@msn.com



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PostPosted: Sat Aug 17, 2019 1:14 am    Post subject: Reply with quote

Teak decks, remember Thiokol? I am one of the few people crazy enough to put a laid deck deck on a self built boat, my excuse is I was 24 and wanted to build a true "yacht" she did end up a beautiful Roberts 45 ketch that we sailed all over the Pacific but we paid the price for leaky laid decks plus all the extra hours and expence.

(A photograph in my photo album)
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Chuckpacific



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PostPosted: Sat Aug 24, 2019 10:21 pm    Post subject: Reply with quote

Thanks everyone for advice and perspective. Always appreciated.

I pulled the hatch, quite a bit more difficult than I expected, but finally got it off. There was no water damage to the core which was a combination of plywood and some kind of a plywood/rigid foam core product and for that I was quite relieved. I cleaned the old bedding off the opening with a flat headed screwdriver and acetone. This also took quite a while. Cleaning the underside of the hatch was easier since most of the bedding had been left on the gelcoat. I used the 4000 which was easy to work with. The project took 5 hours. A rain shower came through Wednesday evening and a quick check Thursday morning found everything inside and around the hatch dry.

Chuck
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