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Old 07-10-2010, 16:56   #1
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Bostic Marine 920 for Bedding Deck Hardware ?

I am considering using Bostik Marine 920 urethane adhesive/sealant to re-bed my genoa tracks. As it it a big job involving removal of the headliner, I want a lasting job done right the first time. Comments? Suggestions? TIA
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Old 07-10-2010, 17:54   #2
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Don't do it! I just got finished rebedding my salon windows that were bedded with that product by the boat manufacturer. The windows leaked after 6 years and badly after 8. When I took the frames out absolutely none of the adhesive had stuck to the metal. I did some research and there are only 3 products that actually adhere to both fiberglass and metal. I used 3M 4000 UV to rebed them. The windows were only the latest thing to leak. Over the years I've had to rebed all of my hatch frames and hand rails and all were bedded with Bostik 920. I've used the 3M 4000 for all of them and so far have not had another leak, but the longest I've had it on anything is 4 years.
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Old 07-10-2010, 20:04   #3
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I would use 4200, 5200, 101 or LifeCaulk. These are all proven sealants that have been around a long time.

What will probably make the job last forever, however, is routing out the core material with a dremel bit like this Dremel 3/8'' Disk Bit Hss | Western Tool Supply. Then fillng the puka with thickened expoxy. That will give a water tight seal of the core if there should be a leak and an incompressable structure whilch will keep the fasteners from crushing the core and creating a potential leak. Also do a light counter sink of the fastener pukas so there is a sealant donut around the fasteners where they go into the deck. If you do the above, you will have a truly permanent installation that won't leak.
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Old 08-10-2010, 08:33   #4
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Quote:
Originally Posted by roverhi View Post
I would use 4200, 5200, 101 or LifeCaulk. These are all proven sealants that have been around a long time.
The life caulk product was one that was OK for use with metals. The other three products are 3M products and if you read their literature, 101 is listed as obsolete, and 4200 and 5200 are only recommended for metals if you use a special primer. The 4000 UV product is recommended for metals without a primer and is rated better than 101. I've had several people tell me that they had used 4200 and 5200 and that they did not bond to metal, but they did not use a primer.
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Old 09-10-2010, 06:54   #5
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Hi Arclight, I re-bedded my tracks this year and learned a lot. You don't say why you are doing yours so I may include info not relevant to your situation. I did mine because they leaked ... to put it mildly. My decks are balsa, and the combo of the leaking jib sheet track bolts and leaking screws in the teak deck made mush out of the balsa. Since it would be a year or two until I have time re-core the deck under the jib sheet tracks I did what roverhi said. If you are not clear on his concept, it was explained by DRSandbo and svHyLite in this thread: Backing Plates.

First I drilled a 3/4" hole down to the inside GRP skin. This pic also shows the penetration of a screw for the teak deck into the core, and you can see how wet the core is.

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This is the same hole after removing the wet core around the hole - wet balsa comes out very easily.

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Even if you have foam core, remove it a little bit from under the outer skin like roverhi described so the epoxy plug extends under the outer skin. If you do fill the holes with epoxy, I have found that epoxy makes tape come unstuck, and cleaning around the bolt hole on the underside of the deck with acetone and using Gorilla Tape to cover the hole works best. This is the countersink that roverhi also mentioned.

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As soon as you have a hole in your deck it will start raining. I used corks to plug the holes (got these from McMaster-Carr).

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5200 should be forbidden on any boat! Everything on a boat is a maintenance item, and 5200 is a PIA to remove. Suppose you made a mistake mounting your tracks and had to remove them to fix it ... you would be Hating 5200. BoatLife Life Caulk is polysulfide, which is great for bedding deck hardware. For this application though I recommend BoatLife Life Seal, which is for joints subject to structural movement. It adheres to fiberglass, metal including aluminum, wood, nylon, plastics...

VERY important that all surfaces are clean clean clean. I ream out all bolt holes with a round metal brush of the same diameter and suck the dust out with a shop vac. The metal brush also roughens the bolt hole a bit giving a better surface for the sealant to stick. These metal brushes are also great for cleaning the old sealant out of the bolt holes in your deck hardware.

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All surfaces are wiped with acetone until clean, and I wash the bolts with a toothbrush and Simple Green to remove the dirt and oils from manufacturing, and rinse them with acetone after they are dry. Insulate the SS bolts from the aluminum track using Tef-Gel or plastic sleeves. When you re-mount the tracks, have someone outside to hold the bolts still with a screwdriver while you tighten the nuts inside. Also, you might want to leave the headliner off for a while until you are sure there are no leaks.
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Old 09-10-2010, 08:31   #6
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I used other products of Bostik and they all did fine for the application they were designed.

b.
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Old 09-10-2010, 17:27   #7
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Thank you all! Roverhi and ShipShape, thank you for your especially detailed responses. I plan to use your technique. Most likely with Boat Life Seal (I was however advised to use the Bostik Marine 920 by a well respected boat yard) and the Tef-Gel. Which epoxy do you recommend and do you use a thickener?
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Old 09-10-2010, 19:10   #8
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I've been using LIfeCaulk for 40 years, 4 boats, and on my house. I find it very easy to work with, cleans up easily with paint thinner, and never had a leak with it. Another plus is it seems to not setup in an opened tube nearly as fast as the 3M products do. Seems I never throw away an old tube of LifeCaulk, polysulfide, but have to do it regularly with the 3M polyurethanes. It doesn't harden and sticks to almost everything. Pulled off my solar water panels after more than 30 years on the roof here in Hawaii. The LifeCaulk was still flexible and firmly attached to the metal roof and the wood support frame. I'm very happy with it and I've used cases of it commisioning two boats, bulding another from a bare hull and rebuilding my current boat.

I don't trust the Life Seal/4000 products 'cause they seem to have some sillycone in them. May be wrong in this but why switch from something that's been so reliable for so long.

I use West Systems because their pump measuring system is so easy to get the proper ratios. I've also used a 'Silver' something epoxy with good results West used to have a problem with Amine Blush affecting subsequent layup bonding. Believe they've changed their formula so it's no longer a problem. Still, wiping down with acetone or alcohol between layups is a good idea with any resin.

Colloidal Silica is a non compressible filler. West has 6 or more different fillers depending on the use. Read there literature and pick the one one that is labelled as high strength.
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Old 10-10-2010, 08:33   #9
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Thanks again roverhi...Life Caulk it will be. I used it on my last boat with excellent results, but 30 years on the roof in Hawaii seals the deal for me.

Fair winds,

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Old 10-10-2010, 16:27   #10
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Quote:
Originally Posted by Captain Bill View Post
I used 3M 4000 UV to rebed them.
I used the 3M 4000 UV to rebed some windows two years ago. Inside the boat it is still flexible, but outside has gotten hard and chalky where the sun hits it - so much for the UV feature.


Quote:
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I've been using LIfeCaulk for 40 years, 4 boats, and on my house.
I don't trust the Life Seal/4000 products 'cause they seem to have some sillycone in them. .
That is funny the Life Caulk works so well for you - it doesn't like me or my boat! The Life Seal is a silicone and polyurethane mix - the silicone is what makes it so flexible, and the polyurethane gives it its good adhesive properties. So far I have had perfect results with the Life Seal, but maybe that is because I am so fastidious about clean surfaces. Many years ago someone told me that silicone and aluminum do not get along - something about silicone being acidic. I never looked into this, but the Life Seal tube says use it on aluminum. The jib sheet tracks is the first time I used it on aluminum, I'll find out more when I remove the tracks next year to recore the deck.
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Old 10-10-2010, 16:30   #11
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Which epoxy do you recommend and do you use a thickener?
For epoxy I most highly recommend West System - I have never seen a company do so much to make it easy and convenient to use their products. In addition to their detailed and easy-to-understand user manual, they have several excellent publications - be sure to get #002-550, Fiberglass Boat Repair and Maintenance; I got mine free at a West Marine.

They also have a phone number for tech support - you call and a human answers, and I have never waited more than two minutes for a tech. If you are in the US, some West Marines have lunch-time video seminars on using West Epoxy. BTW, the thickener you want to use is 404, but get the User Manual and #002-550 and you will have no doubts about how to proceed.

Glad to be of help, feel free to PM me if you have questions or want to see more pictures, but I think once you get the West System literature you will be good to go.

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Old 10-10-2010, 17:05   #12
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For epoxy I most highly recommend West System ...
... be sure to get #002-550, Fiberglass Boat Repair and Maintenance ...
... I think once you get the West System literature you will be good to go.
www.westsystem.com
866-937-8797 (USA)
West System Use Guides and more ➥ WEST SYSTEM | Use Guides

002-550 ➥ http://www.westsystem.com/ss/assets/...aintenance.pdf
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Old 10-10-2010, 18:29   #13
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House hold grade, the stuff you buy at Lowe's, sillycone has acetic acid as a catalyst or something. You can smell it if you are into sniffing sillycone. Marine sillycones and industrial stuff doesn't use the acid from what I understand.
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Old 11-10-2010, 21:52   #14
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House hold grade, the stuff you buy at Lowe's, sillycone has acetic acid as a catalyst or something. You can smell it if you are into sniffing sillycone. Marine sillycones and industrial stuff doesn't use the acid from what I understand.
Thank you for taking the time to let me know this - it has been in the back of my mind for many years. Funny what your mind chooses to hang on to over the years. Wish it could be so good to remember where the car keys are from day to day.
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Old 12-10-2010, 16:03   #15
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I'm adding some cheek (or turning) blocks and fair leads to the balsa cored deck and am wondering how to do it. For adding winches or mooring bitts I hollow out the balsa and fill with epoxy to through bolt, but I didn't want to through bolt the fair leads and cheek blocks. Too much work to get access underneath and doesn't need to be that strong. So I was considering these alternatives:

1) Lazy way -- drill deck for screw, squirt in 5200 and sheet metal screw the fixture to deck

2) Better way -- drill larger hole than screw, chip out balsa, fill with epoxy, let dry then sheet metal screw into epoxy.

3) Same as 2), except tap threads into epoxy plug and use metal screws.

What do you do? Any other suggestions?
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