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I have to re-bed the Lexan in Silverheels’ original Bomar hatches. Is
anyone familiar with Sikaflex? I’ve never used that particular brand.
Does it come in black? Is it strongly adhesive, like 4200? Is it better
than Boat Life for this application? Is it UV resistant? Any experienced
opinions are appreciated.Thanks,
Tor
Silverheels, P-424 #17
http://www.silverheels.us <http://www.silverheels.us/>
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Tor,
I know it’s available in black. Check the label, since it’s a brand. I’m not sure whether it’s an acrylic, a silicone or a urethane, but the label will tell you.
5200 is tough to beat if you need good moisture resistance and durability.
Acrylics have good UV resistance but not longevity. Silicones are allround good but adhesion is not strong. We use silicones for hatches and portlights because there is not much shear forces on the caulked surfaces.
5200 is a bugger to remove, should you need to.
I’ve not used Sikaflex brand.
Joe,________________________________
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Thanks, Joe. I only use 5200 when the fix is “forever.” Anyway, these
Lexan panels are screwed down so I don’t need adhesion from the sealant.
I tend to avoid silicone because it’s so difficult to remove the next
time. In this application, after sealing water out it seems to me the
most useful sealant characteristic would be its UV resistance. If that
means “acrylics,” maybe that’s the direction to look. Do you know what
brand sealants are acrylic?Anybody know what Bomar or other hatch manufacturers recommend?
Tor
Silverheels, P-424 #17
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Bomar recommends P-100-75 if you want black glazing sealant, or P-100-76 if you want white. They don’t say if these are acrylics and I could not find a spec sheet. You would have to look at the label..$32.95 from Bomar catalogue.
Joe,________________________________
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My best guess is that P100-75 is a private label for Bomar, but it is really a GE silicone SSG4000.
That is what I use and recommend it for its’ resistance to UV, long lasting strength and wide temperature range application.
Joe,________________________________
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Yes, I saw that. Big price for a tube of sealant.
I’ve found a couple of blogs with various thoughts on the subject, one
of which says that megayacht crews use GE SilPruf SCS2002 Silicone
Sealant ($11+ on Amazon), which 2 sailboaters also confirmed worked well
for them. From what I’ve now read on this stuff, it’ll do the job (even
if it is silicone). I’m going to Home Depot to poke around their
shelves.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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GE silicone SSG4000 seems to be a more adhesive version of GE SilPruf
SCS2002, but the latter’s specs mention UV resistance. I guess that’s
the way to go.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Don Casey in Sail Magazine March 2009 recommended
GE Silpruf SCS2000 or Dow 795 Silicone Building SealantRick
EclipseOn Tue, Dec 18, 2012 at 12:34 PM, Silverheels wrote:
Quote:GE silicone SSG4000 seems to be a more adhesive version of GE SilPruf
SCS2002, but the latter’s specs mention UV resistance. I guess that’s
the way to go.Tor
Silverheels, P-424 #17
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Tor,
Years ago a plastics fabricator recommended Silpruf to me as having the
best coefficient of expansion for bedding plexiglass. I assume it would
be equally good for Lexan. I used in on a previous boat to bed Plexiglass
sheets over very large portlights on the cabin trunk sides. The ports
never leaked for the next 15 years of my ownership.
However, why not go with the rope caulk solution you recommended several
years. I used it on several deck fittings and they have held up fine.
Don’t know how well it works with acrylics.Regards,
John Stevenson
http://www.svsarah.comOn Tue, Dec 18, 2012 at 12:42 PM, Rick Dugger wrote:
Quote:Don Casey in Sail Magazine March 2009 recommended
GE Silpruf SCS2000 or Dow 795 Silicone Building SealantRick
EclipseOn Tue, Dec 18, 2012 at 12:34 PM, Silverheels
wrote:Quote:GE silicone SSG4000 seems to be a more adhesive version of GE SilPruf
SCS2002, but the latter’s specs mention UV resistance. I guess that’s
the way to go.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Yes, SCS 2000 might be less expensive…a little softer, but fine for sealing a hatch. I used SCS 4000, probaby overkill.
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That’s encouraging. Thanks, Rick.
Tor
Silverheels, P-424 #17
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I’m sure you did the right thing. I don’t care if a tube costs a few
dollars more or less, but the SCS 2000 specs promised UV resistance,
something I didn’t see in the 4000 specs. Possible I just missed it,
though.Thanks for your in put, Joe.
Tor
Silverheels, P-424 #17
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Hey John,
To tell the truth, I don’t know if the tinted plastic in these old Bomar
hatches is Lexan or plexiglass or acrylic or something else. Good to
hear yet another vote of confidence for the GE Silpruf SCS2003, though
(the last “3” signifying the black version).I thought of using Rope Caulk for this, but I’ve found its surface turns
brittle with prolonged exposure to the sun & weather. For bedding down
deck fittings it’s great, but I feared it would be too exposed in this
application.OK, I’m off to Home Depot.
Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Plexiglass is a brand name for an acrylic sheet. I hope you have polycarbonate ( GE trade name Lexan).
Joe,________________________________
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Hi Tor,
Sikaflex makes a sealant for acrylics (lexan, poly carbonate, etc.) You
have to look at the product to get the right one and the sikaflex site will
have information as well.If you’re rebedding hatch plastic, I use a product Dow Corning 794. It’s
used in glazing buildings and will adhere to plastics. You can apply it
from -20 deg to 140 deg F. It will last as long as you own the boat, for
sure. The down side is the length of time it takes to completely cure
which is 7-21 days depending on temperature, humidity, and bead thickness.West Marine also markets a sealant for plastic, I think a
silicone-urethane. If one’s nearby, just have a look at the tube.If it doesn’t mention acrylics specifically, don’t use it on them. The
results will be mixed, but usually not in a good way.About silicone as a sealant: Silicone is a compressive sealant. That
means you make the seal and after a day or so you tighten the thing you’re
sealing. If you don’t do it that way, you will guarantee leakage within a
year, probably less, due to capillary action. There is no place for
silicone sealant on a boat except, perhaps, to keep rigging cotter pins in
place and protect sails from the sharp points. There are too many good
sealants, adhesives and bedding compounds that it isn’t worth the
aggravation of using silicone.For all of you who have spread silicone around portlight glass expecting
grand, if messy results, you’ll be sorry.Silicone. Feh!
Bob
On Tue, Dec 18, 2012 at 11:42 AM, Silverheels wrote:
Quote:Thanks, Joe. I only use 5200 when the fix is “forever.” Anyway, these
Lexan panels are screwed down so I don’t need adhesion from the sealant.
I tend to avoid silicone because it’s so difficult to remove the next
time. In this application, after sealing water out it seems to me the
most useful sealant characteristic would be its UV resistance. If that
means “acrylics,” maybe that’s the direction to look. Do you know what
brand sealants are acrylic?Anybody know what Bomar or other hatch manufacturers recommend?
Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Tor,
You must have missed it..both have UV resistance. The 4000 is higher molecular weight and forms a harder polymer when fully cured. Both will work in your application.
I was surprised to read Bob Fine’s remarks about silicones. They are used so often in glazing….oh well.
I would be careful with acrylic for a hatch since we tend to stand on them so often. Eventually they will get brittle and crack. But if you do use acrylic make sure the sealant does not have a solvent that attacks it.
Joe,________________________________
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Hey, Joe,
Silicone can be a terrific sealant if used properly. Just smooshed on and
clamped will ensure you have water everywhere you don’t want it. The
silicone/urethane or silicone/polysulfide mixtures are ok, as long as they
won’t attack plastic. The purpose of mixing them, I suspect, is to make up
for the weaknesses of each alone. As you or someone mentioned, silicone is
not a great adhesive which is what causes the capillary action. The
urethane/polysulfide are both pretty aggressive adhesives.So rather than recommending it, I recommend against it for just that
reason. The long and the short of it is, though, read the instructions.Bob
On Tue, Dec 18, 2012 at 2:43 PM, Joseph Steiner wrote:
Quote:Tor,You must have missed it..both have UV resistance. The 4000 is higher
molecular weight and forms a harder polymer when fully cured. Both will
work in your application.
I was surprised to read Bob Fine’s remarks about silicones. They are used
so often in glazing….oh well.
I would be careful with acrylic for a hatch since we tend to stand on them
so often. Eventually they will get brittle and crack. But if you do use
acrylic make sure the sealant does not have a solvent that attacks it.Joe,
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Thanks again, Joe. “I” am not using acrylic. I am using whatever Bomar
put in their hatches in 1978. Any guesses what it is? Anyone?Tor
Silverheels, P-424 #17
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You can buy the stuff from Bomar or you can use Dow Corning 794 or you can
use a black polysulfide (if it says it’s for plastic, which I think it is).
5200 and 4000 are specifically not for plastics.Bob
On Tue, Dec 18, 2012 at 6:53 PM, Silverheels wrote:
Quote:Thanks again, Joe. “I” am not using acrylic. I am using whatever Bomar
put in their hatches in 1978. Any guesses what it is? Anyone?Tor
Silverheels, P-424 #17
http://www.silverheels.us
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Thank you, Bob. This is all much harder than I ever thought it would be.
Perhaps I’ll just learn to live with the leaks.🙂
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Tor: I used black Sikaflex when I had to rebed a skylight on my Hunter 33.5. The stuff I used was black and was easy to work with. I rebedded the skylight around 7-8 years ago and never had problems with leaks again (I sold the boat last summer so I could direct all my attentions and pocketbook to our 424). I would not hesitate to recommend the stuff.
Dan Kalinowski
Jolly Lama #135
Ko Olina, O’ahu -
Thanks, Dan. Now I’ve truly come full circle. Seems like almost anything
will work for this.
Silverheels, P-424 #17
http://www.silverheels.us
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I find it interesting that Bob Fine is negative about the use of silicones as a sealant for Lexan polycarbonate in hatches, yet in the post below he specifically says he uses Dow 794. Well Dow 794 is a silicone sealant and it’s a direct match to GE SCS 2002.
The cure time is 24 hours, not 7+ days as he claims below.
Joe,
Half Moon________________________________
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794 and it’s replacement (I think 799) are specifically designed for
structural glazing where there can be large temperature changes. No
problem there. Too many times I’ve seen GE RTV or West Silicone Sealant in
a tube smeared around portlights, hatches, leaking teak, and so forth with
horrible results. The key is the right sealant for the right job applied
correctly. So, it’s only one silicone I abhor and it’s the general purpose
one that ends up causing more problems than it solves.Also: 794 and the GE equivalent can be removed cleanly where the general
purpose stuff resists cleaning forever.So, Tor, use whatever you like or is least expensive that is specifically
for plastics.Bob
On Wed, Dec 19, 2012 at 5:01 AM, Joseph Steiner wrote:
Quote:I find it interesting that Bob Fine is negative about the use of
silicones as a sealant for Lexan polycarbonate in hatches, yet in the post
below he specifically says he uses Dow 794. Well Dow 794 is a silicone
sealant and it’s a direct match to GE SCS 2002.
The cure time is 24 hours, not 7+ days as he claims below.Joe,
Half Moon________________________________
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Bob, I share your aversion for all-purpose silicone seal for the reasons
you listed. Won’t have it on my boat.It seems like either Sikaflex or GE SilPruf SCS2002 will do the job.
Home Depot didn’t have either. I’ll hit the marina office catalogs this
morning and have something delivered so I can get these hatches
re-sealed.Tor
Silverheels, P-424 #17
http://www.silverheels.us
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When I installed our new Bowmar hatch in the galley I used Sikaflex UV. We
also used this same product for installing the exterior ring for our New
Found Metal portlights. In addition to many other remounting of
hardware on the deck. It came highly recommended and it is very easy to
work with and stands up well in the UV of Mexico. 🙂
I also support the info about silicone. It really doesn’t belong on a boat
other then perhaps some interior projects. Our previous owners installed
the T track and hardware with it. Our teak was a damaged underneath the
track due to the hydrophilic nature of silicone pulling in water over the
many years. It is a total mess to clean up to ensure a proper seal for the
new hardware.
My 2 cents…
Dawn
s/v Deep PlayaOn Wed, Dec 19, 2012 at 4:01 AM, wrote:
Re: Sikaflex
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Thanks to all for your excellent and helpful feedback. FYI, I found GE
SilPruf SCS2003 (black) on Amazon for $9.25 ea. + $8.50 shipping for 2
tubes ordered simultaneously. Sikaflex 295 UV, at Jamestown
Distributors, was more than twice the price (plus even more shipping)
with no obvious doubling of value for my application. Check back with me
in 10 or 20 years and I’ll tell you how the SilPruf SCS2003 held up.Tor
Silverheels, P-424 #17
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Tor,
I have replaced the acrylic and rebedded the Bomar hatches on two boats, the P323 and the P424 (the first about 4 years ago) and I used BoatLife LifeSeal. It comes in black. Here is what Jamestown says about it:
BoatLIFE LifeSeal Polyurethane/Silicone Sealant is a one part, fast curing, low odor, high adhesion, non-sag compound. LifeSeal is excellent for sealing decks to hulls, underwater thru hull fittings, vinyl ports, windshield setting glaze and the bedding of marine hardware. It retains excellent adhesion and elasticity under all weather conditions.I called and talked to the president of Boatlife in Charleston SC and asked specifically which product she would use to seal acrylic to aluminum and that is what she emphatically recommended. It is a polysulfide compound called BoatSeal. The only mistake I made was that the first time I applied it, I went too skimpy, and it started to leak. I went back and put enough the second time to make it squeeze out all sides and never had another problem. If you put in new acrylic, blue tape the top before you apply the seal, and it cleans up much better.
I had a local plastics company cut out 1/4″ smoked acrylic from the original. It is a little thicker than the original, but it works great and I like the idea of having it a little stronger.
I personally think the rebuilt old Bomar cast aluminum with 1/4 acrylic is better/stronger than anything on the market today. -
Thanks for sharing your experience, CS. I ordered the GE SilPruf SCS2003
yesterday, so I’ll use it when it arrives. From what I’ve gathered,
it’ll do the job.I still don’t know what that plastic is in my original, 1978 vintage
Bowmar hatches.Tor
Silverheels, P-424 #17
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Good point. On the other hand, I did my refit based on a 10-year
expectation for keeping and using Silverheels. Now, after 6 years, I’m
not so sure it’ll end at 10. That’s fine, but re-doing that refit when
I’m 20 or 30 years older may be a challenge.Tor
Silverheels, P-424 #17
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