hybrid silicone/polyurethane
Life Seal by Boat Life. A bit confusing. Life Calk is the p.sulfide. That's Life.
The hybrid mix has the attributes of both but without silicone's nasty oily gelcoat contaminating quality. The gelcoat contamination of silicone means that nothing, no caulk, will ever stick in that place again - not even silicone. I have had to remove the gelcoat in places on 338.
It does not appear that silicone contaminates, in this way, when combined with polyurethane.
While we were out to lunch, hybrid caulks have progressed somewhat. We now have specific choices coming from Bostik. My understanding is that while we've had the one Boat Life product, Bostik has expanded the hybrid line in construction, industry, and marine for more than a decade in Japan and Europe. Successfully. We no longer have to depend on the restricted uses of polysulfide caulk or polyurethane caulk - BOTH OF WHICH HAVE REALLY LIMITED USE ON A BOAT. Neither can be depended on to stay elastic or flexible on deck for long (5 to 7 years springs to mind) - which is what the newer hybrids promise to fix - at least twice the life on deck of p.sulfide & p.urethane. With silicone caulk having NO USE ON A BOAT.*
I have not yet used these Bostik products (There are four listed at the address below - but there are more Bostik SMP, silyl-modified-polymer, products - some of which have revolutionized wood (and cork) deck applications.
Bostik 70-08A is a low slump, high green strength bedding for windows, windscreens, glass, p.acrylate, p.carbonate, hatches, portholes, cleats, fittings. Directed toward glazing situations. More of a paste, less compressible.
It is permanent, elastic, UV resistant, sandable, paintable. Can be tooled with soapywater or alcohol. User friendly, that's what they say.
Bostik Marine 940A (the slow version with 30/45 min open time)
will give us permanent elastic bonds, the same UV resistance, and it sticks all metals, fiberglass, epdm rubber, pvc. No primer needed. Both caulks produce No outgassing, No isocynates, No organic solvents. B.M. 960SR will not 'pull gelcoat'. It may be comparable with 3M4200 in that regard - except it is a silyl-polymer hybrid. BM940A may be compared with 3M5200. This is my take.
While these second two caulks seem to be the solution for nearly EVERY caulking situation on a boat, the data sheet says it is not for glazing.
google Bostik - Marine Sealants and Adhesives
www.bostik-us.com/products/index.asp?fa=categories&divisionld=11&categoryld=4 7
[if you get main site: curser 'Marine' on menu. Then curser SMP. Data sheets here.]
Use the primer (MSR Primer M) for high stress wet conditions. While the data sheet states no primer is necessary, it does say the primer will enhance adhesion and bond.
Imco, along with a chainplate upgrade, it ought to be included. Could possibly help where damn silicone caulk has gone before.
By the way, Bostik has been in the US since 1892. You can get the stuff through JamestownDist.
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This comment here is a later addition:
Jamestown Dist Online lists only the usual array of caulks.
THEY ARE NOT LISTING ANY BOSTIK PRODUCTS.
Finding an internet catalog site for Bostik (also Samson) marine products is totally frustrating. There is no direct source for Silyl Modified Polymer that I am able to find. Torresen is a source but consistently have the highest prices for anything, so I do not visit their site anymore. Other sources are equally useless. For instance, using Bostik's own distributor index for marine caulk brings up local construction contractors. They do not have any marine sealants, And they do not retail to the lumpen sailor.
Haven't a clue why their marine rubbers are not able to be sold in our marine catalog venues. THEIR LOSS.
It means their, what looks like great products, will not enter the mainstream.
Recommendations from the gallery forums would do a lot to spread the word. OUR LOSS as well. I will not pursue this any further.
IT MAY INDICATE BOSTIK PRODUCTS ARE TOO DIFFICULT TO USE.
AND IT MAY ALSO BE AN INDICATION THAT THE PRODUCTS ARE TOO OVERPRICED TO SURVIVE THE COMPETITIVE MARKETPLACE.
VIZ; TO PROTECT THEIR DISTRIBUTORS THEIR CAULKS WILL NOT BE DISCOUNTED IN CATALOGS AND STORES.
To be fair: If you have the hardcopy 1000 page Jamestown Dist Building and Marine Supplies catalog, you will find Bostik 940 and 960 listed for about $16/$17 a tube, Page 405 in their BIGBOOK. They do not seem to know that these two products are hybrid sealants. 1-800-423-0030. Good Luck.
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*Aside from the UV and heat exposure problems that p.sulfide and p.urethane both have, p.urethane cannot be used exposed to kerosene, diesel or gasoline - and many other solvents and cleaners. P.sulfide (OK with fuels) cannot be used with most plastics and exposed to potable water due to out-gassing. To be fair, NO mention on any Bostik data sheet iis given to SMP being OK with fuels. By inference in could be used with potable water as it has no solvents in it. Research needed here.
exterior chainplate install
I think that two years ago Ed's question about Ariel chainplates was answered.
Then there's ebb's way fat posts on what he thinks is related stuff!
Today, 6/5/10, littlegull's exterior bronze chainplates get installed.
There will eventually be a shot of them on the Gallery page.
For all the words on what goop to use I've decided to go with white butyl tape with some white tube butyl to juice the bolts with for insurance.
Butyl ALWAYS stays flexible, gummy and sticky. It is dirt cheap. The stuff you're bolting on can be removed without prayer in the future.
It is not an adhesive, so initially leaks are theoretically possible.
Cruisers who have used butyl for their port lights are universally happy with the stuff.
Some may have used it elsewhere on thirs boats that I have missed in research.
If I still had plates coming throu the deck, I would renovate their holes as described with epoxy, and use butyl instead of expensive rubbber.
I might leave a little door of opportunity open for the use of silyl modified polyurethane.
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EDIT: The rolls of narrow buty were deformed by inconsiderate packing from an internet RV source for the tape. The paper interleaf would unroll before the stickum leaving the butyl unsupported. The 'tape' will deform and stick to anything it touches. It is gummy so you cannot pull a piece off - it has to be cut with scissors - thins and narrows when pulled. What a PITA. So I ended up piling on deformed strips on the flat of the plate and slapping the plate onto the hull in this case) and depending on the clamping of the bolts to achieve an even 'bedding line'. The tube butyl I used under the heads of the bolts is much thinner and viscous and would not work imco alone to mount a fitting. You need somw thickness and resistance in the bedding. The tape is very sticky stuff.
But smears clean up easy with mineral spirits.
EDIT, Tremendous clamping loads by fat plates and oversize bolts will conceivably squash butyl tape to zero thickness. Did chamfer the bolt holes on the hull, so there is a small ring of waterproofing around the bolt. Better would have been using O-rings or plastic washers around the hole to help keep butyl from squeezing out all the way. They also contribute to waterproofing the holes by creating a barrier of their own.
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Later EDIT on BEDDING stainless:
316 stainless steel survives well exposed in the marine environment when chromium in the alloy is allowed to form c.oxide on its surface in the presense of air.
Bedding stainless is therefor frowned upon.
Seen countless boats with bleeding rust sprouting from underneath stainless steel fittings.
In My Considered Opinion when we bed stainless we must abrade the shiney surface of the polished fitting with a scotchbrite pad. [I'm not the only one!]
I'd bluetape off the exposed metal of a s.s. chainplate and scrub just the buried parts of the s.s. with at least a green nylon scotchbrite pad*.
We want to prep the buried parts of the fitting to stick VERY WELL to our choice of bedding compound. We want to create a surface on the polished s.s. that the compound wants to stick to.
NEVER grind or sand or use any abrasive! Don't even be tempted, you will be creating a cause for crevis corrosion.:eek:
Use only a nylon pad.
We can test for a well prepped surface by spraying a little water on it. If water "runs free" and does NOT REFORM INTO DROPS we have then the best surface we can expect for bedding and keeping salt water out of the joint. Any water out of the joint.
as always: imco.
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* I've frosted favorite glassware over time by cleaning with green nylon kitchen scrubbers. The stuff is sharp and abrasive in its own right.