Rubber caulking update

[Dan McCosh]

I posted a few times on the merits of using liquid neoprene roofing sealant as a seam compound. Just pulled the boat for the second season after I began using the stuff, and it still looks good. It stays flexible, and bonded to the seams, despite a mixure of old compound in the seams. As I mentioned earlier, it sets up quickly, and is relatively inexpensive. Two drawbacks have merged. One is that thick sections take relatively long to cure, which can be problematic with wide seams. (a few gaps prior to launching were about 3/8 ins.) The other is that a sharp chisel doesn't cut it easily, due to its flexibility. It does sand and can be trimmed easily with a Fein power scraping blade. I still find it odd that the stuff isn't used commonly as a seam compound, as most of its characteristics are superior to most others I've tried.

[sdowney717]

I think many caulkers are simply used to doing what has worked for them in the past. And the 5200 in the seams problem that others have had are not encouraging them to go for something viewed similarly.
The problem I have gathered is
1. hard rubber caulking in old greasy oily dirty wood seams is either spit out when the planks move and swell or wont stick allowing leaks.
2. the frames are old and likely weakened with rot and age, the screws have lost their holding power and therfore the frames either split open or screws pull causing even more leaks.
3. the stuff is difficult to remove where it does manage to adhere, damaging planks edges when someone eventually does decide to try to redo the caulking using conventional cotton methods.
4. since it has little give, plank edges are crushed when wood swells and then the cycle of drying and wetting when the boat is hauled and put back in means the planks never return to their original contour causing leaks when the rubber wont stick and falls out during the dry cycle.
5. Then when the stuff is successful and does adhere well and planks rot out and have to be replaced, it means more effort since planks have to be cut out of the boat.

These are just some of the problems. That being said, for I have simply removed my planks, renovated my frames, coated my planks inside and outside with sanitred permaflex, reinstalled with new #14 bronze screws and will fill any gaps with a polyurethane sealant. And since I no longer have a conventional cotton caulked hull I wont have these problems.
Also what I have learned is screw bungs do not keep water away from the screw, the vast amount of deteriorated wasted bronze screws prove this. Better to not bung the bottom IMO!
One of those its always been done that way type of thing for many. At least we can get better life thru chemistry for wood boats and dont have to do it the same way as the past.

[Dan McCosh]

I'm not sure what "hard" rubber is. The neoprene I'm using has an elongation factor of 300%, and is quite elastic and pliable. Thiokol sealants. (polysulfides) do set up relatively hard with old age, although they are medium when fresh. 5200 is quite elastic, although the high adhesive strength can be problematic. No sealant is intended to replace cotton caulking, which provides some degree of mechanical stiffness as well as an "edge" for planking to swell against. A few planking systems are intended to be dry-seamed, but that's a different story.

[TimothyB]

Liquid neoprene is a great idea for this! It should remain flexible for a VERY long time as well, considering what I know about the properties of Neoprene, so it should handle moisture changes and other issues with ease.

I would bet that you could use it for double planking compound with excellent results as well. And now you can get 5 gallon drums of it for $200 - $370 US retail (depending on grade). Not too shabby of a price for a seam and bedding compound.

--T

[Dan McCosh]

I've been paying about $3.50 a tube for the stuff. I use about eight tubes in the spring if the hull is dry.

[marsbar]

Do you think this sealant is appropriate for bedding outer bottom mahogany planks to inner bottom planking/plywood on a small Chris Craft runabout?

[mic]

Hey Dan , how do you think this liquid neoprene would work as a seam compound for a laid deck.

[Dan McCosh]

Re: bedding between planks. It would seem as if it would work well in this application. I actually stumbled across it about three years ago, among a shelf of basic roofing supplies. I researched it, and it turns out it is a pretty common product, used primarily on flat roofs as a replacement for asphalt-based tars and sealants. It cures to a stretchy rubber, and when troweled creates an elastic membrane.
I've been cautious in using it as a seam compound, but it seems to be working fine after two seasons sailing. We have lots of seams, and last spring the hull dried as I was late launching, hence it takes lots of compound to launch.

As for a laid deck, logically it would be fine, as it is designed for exterior roofs and has a high resistance to UV. It is lots softer than polysulfides, however, and can't be finished as easily by sanding, etc. Still, it doesn't gum sandpaper. I would think it would end up difficult to finish a deck with a fine appearance. One advantage would be the elasticity, which is much greater than polysulfide, and might adapt to drying better. Might be worth a test block left outdoors for a year or so.

Lastly, a sister ship had deck surface covering strip-planked cedar that consisted of liquid neoprene troweled on, then painted, which lasted for about 30 years.

[JormaS]

Dan, how does it stick? Does it have a glueing capacity comparable to the polysulfides or the polyurethanes?

[Dan McCosh]

It seems to have good adhesion, based on the observation that it seems to glom on to a variety of surfaces--old bottom paint, old seam compound, etc. It's not a glue, however, since it doesn't have much substance as a material. It ends up pretty much like soft rubber, about as strong as a rubber band. The intrinsic stength of urethanes and polysufides is considerably higher.

[sdowney717]

Home Depot sells PL Premium polyurethane window and door sealant that stays pretty soft. Much softer than 5200. A little over 3$ per tube.
The tube says not for underwater use. I called them and they stated it was not marketed for that use and therefore not tested for that use. My own test gluing together 2 pieces of PT lumber for 6 months in salt water showed it held together fine. I plan on using this for all my seams simply as a backer seam filler for the permaflex polyurethane sealer which is 100% waterproof.
Also call those sanitred people up and talk to tech support, they will tell you you dont need a copper bottom paint to repel marine growth on top of the permaflex.

[JormaS]

Dan, how does it stick? Does it have a glueing capacity comparable to the polysulfides or the polyurethanes?

[Grouchy_Old_Coot]

I posted a few times on the merits of using liquid neoprene roofing sealant as a seam compound. Just pulled the boat for the second season after I began using the stuff, and it still looks good. It stays flexible, and bonded to the seams, despite a mixure of old compound in the seams. As I mentioned earlier, it sets up quickly, and is relatively inexpensive. Two drawbacks have merged. One is that thick sections take relatively long to cure, which can be problematic with wide seams. (a few gaps prior to launching were about 3/8 ins.) The other is that a sharp chisel doesn't cut it easily, due to its flexibility. It does sand and can be trimmed easily with a Fein power scraping blade. I still find it odd that the stuff isn't used commonly as a seam compound, as most of its characteristics are superior to most others I've tried.

Whatever happened with bottom sealing method?:confused:

I have scoured this site (and others) and have never seen much about the use of rubber type materials as a bottom bedding material. It seems on the surface that especially for a trailered boat, using the same material that has been time tested in the roofing industry may not be an insane idea!;)

And since there is so much emotion surrounding 5200, wouldn’t neoprene be a viable solution? Water repellant, elastic and not as tenacious as 5200 – what am I missing?:)

[Spissgatter W-9]

Dan,
Would you address handling the material? I looked at the sanitred website. Am I correct that it comes in a liquid to which a thickening agent must be added to make suitable for calking? In which case do you put in empty cartridges for application to seams?
Thanks
Geo

[skip g]

Dan, do you have an update on the neoprene compound in your hull seams? I guess this would be year 4? I would love to know how it is holding up and if it is... what the product is.

Thanks

[Dan McCosh]

As an update, the past winter we left the boat in the water for the first time in about 15 years. Pullng it in the spring, we trimmed off the surplus from the hull using a fein scarper blade. (As I noted above, the stuff is a little too stretchy to cut cleanly with a chisel, but the power scraper blade works very well.) This left us with a clean hull free from squeezed-out compound for the first time in a long while this spring. The hull stayed dry through the winter in the water, and is pretty tight this spring--dunno if this means much by itself, however.
It's worked very well overall, and I haven't noticed any drawbacks. Previously, we had been using thiokol for many years. Before that, I'd tried slickseam and ashpalt roofing tar--which still reside in some of the seams, causing adhesion problems. The thiokol worked well, but tended to fall out in strands when the hall dried. Also it is becoming kind of pricey--noticable because when the hull dries it takes 8-10 tubes to fill the seams.
The brand I have been using is DeWitts Neo-Seal. DeWitts is a Detroit-based company that makes a variety of roofing sealants, caulks, etc. In fact, I stumbled across the stuff when I bought a tube for my roof, thinking I had picked up a tube of ashpalt roofing cement. I would think other roofing suppliers handle the same material. I don't know if DeWitts is a national brand--it's very common around here, sold through hardware stores.
There is a note above that talks about sani-tread. This, I think, is a urethane similar to truck bed lining material. The liquid neoprene is not two-part; it is dissolved in a solvent that evaporates as it cures.
A potential drawback is that while Thiokol and ashphalt tar stick to wet wood, the neoprene seems work mainly on dry wood. I've never tried it on a wet hull. It does bond to old neoprene quite well, which means it is easy to fill a seam with some old compound in it.

[skip g]

Thanks Dan. Seems like you have gotten some good service out of this product so far. If it is still rubbery and still sticking after 4 years, I would say that you found a good solution for your bottom seams. I will be cleaning out and refilling the seams on my boat in the next couple weeks just north of you and will try to find some of that goo locally (bay city). Thanks

[Dan McCosh]

I'm pretty sure Dewitts is distributed all through Michigan. Note, however, that they do make both the asphalt-based stuff and the neoprene and the tubes look pretty similar.

[Grouchy_Old_Coot]

Thanks Dan. Seems like you have gotten some good service out of this product so far. If it is still rubbery and still sticking after 4 years, I would say that you found a good solution for your bottom seams. I will be cleaning out and refilling the seams on my boat in the next couple weeks just north of you and will try to find some of that goo locally (bay city). Thanks

Dan - It seems like you may have enlightened us to a new sealant. Are you using this above or below the waterline?

If this stuff works better than 5200 what will the Old Farts have to complain about?:D

[Dan McCosh]

We've only been using it below the waterline. It only comes in black, and it's too stretchy and rubbery to take any kind of real finish for topside seams.
As for 5200, there is not much of a comparison. The neoprene is a sealant, considerably more elastic than 5200, without the bonding strength. Although it's irrelevant to seams below the waterline, the neoprene has a very high UV resistance, while 5200 has none. I've never used 5200 as a seam compound, but do use it as a bedding for some fittings where the bonding action seems appropriate. We also glued trim strips on the cabin edge with it. This was a controversial decision--done to elminate the screw holes and bungs which were causing problems with rot and varnish lifting. Removal of the strip will take sawing it off, but after six years or so, it is working fine. From what I've seen, as a seam compound, 5200 seems to harden with age, and sticks mainly where you don't want it to, falls out where you want it to stick. I also haven't used the neoprene as a bedding agent. It might work very well, but I usually prefer traditional oil-based bedding.

[Grouchy_Old_Coot]

We've only been using it below the waterline. It only comes in black, and it's too stretchy and rubbery to take any kind of real finish for topside seams.
As for 5200, there is not much of a comparison. The neoprene is a sealant, considerably more elastic than 5200, without the bonding strength. Although it's irrelevant to seams below the waterline, the neoprene has a very high UV resistance, while 5200 has none. I've never used 5200 as a seam compound, but do use it as a bedding for some fittings where the bonding action seems appropriate. We also glued trim strips on the cabin edge with it. This was a controversial decision--done to elminate the screw holes and bungs which were causing problems with rot and varnish lifting. Removal of the strip will take sawing it off, but after six years or so, it is working fine. From what I've seen, as a seam compound, 5200 seems to harden with age, and sticks mainly where you don't want it to, falls out where you want it to stick. I also haven't used the neoprene as a bedding agent. It might work very well, but I usually prefer traditional oil-based bedding.

Dan - Did you apply a paint over this material and if so how has the adhesion faired?

I think the concern is that if the material is too elastic, any top coat like paint would crack where it was used (seams).

________________

And if this off the shelf roof caulk works, then what about thin roofing neoprene membrane used as a bedding material along with this type caulk for "stiching together" membrane panels and through fastener holes? Just a thought.:D

If there is sooooooooooooooo..... much debate over 5200 (read - "Sealant Smackdown") - why not look at other industries that have similar operating environments as boats (roofs, basements, off shore drilling rigs, water parks, etc...) and what they use?

Let's take a look outside that boat, I mean "box" and open out minds to (dare I say it?) modern technology. (not all of it is bad guys....):cool:

[Dan McCosh]

Bottom paint works fine--including painting over the surplus on the planking outside the seams. I'm not sure why you would want to use the roofing membrane for bedding. I do know one guy who used neoprene roofing for a cabin top, on a modified commericial boat he is converting to a liveaboard. The cabin top is fairly large, covering what used to be a hold, more like a big hatch cover. It's durable, but pretty rustic for most small boats. The material I am using for seam compound is mainly used as a sealant for the neoprene membrane roofing. It is also troweled on roofs--available in 5-gallon cans. If you are thinking of doing something like this on a hull bottom, I always remember a book I read once on survival at sea in a life raft. It started out with a guy discovering someone had used some kind of a stick-on coating on his boat that began to peel off 500 miles out in the Atlantic. That's when the liferaft survival story began.

[Dan McCosh]

Another thought on new alternatives. The marine industry is so small nothing much is developed specifically for it. The commercial sealant, caulks, urethanes, polysulfides, resins, composites, etc., find their big markets in commercial construction and automotive applications. You find urethane sealants used as concrete caulking, window sealants, etc. The marine versions can be simple labeling and packaging, or modified compositions that refine the properties somewhat. I've experimented a lot, but usually end up back with some fairly traditional materials. I started this thread mainly because this stuff seemed so good as a seam compound I thought others had been using it. The reality is that there are so few wooden boats today, no one is going to be doing much to develop a new compound. It's not anything new, however--it's a pretty standard roofing material that's been in common use for about 50 years.
Might add I also was surprised to see anyone had dug this thread up, considering its age.

[Grouchy_Old_Coot]

I contacted Dewitt Products (dewittproducts@sbcglobal.net (dewittproducts@sbcglobal.net)) about Neo-Seal and this was their reply:


We have never tested this product for extended use under water, therefore we cannot make a recommendation. Sorry we could not be of more help, but if you have any further questions please feel free to contact us.

Jared McClellan
DeWitt Products
313-554-0575


Although this doesn't mean anything, if you are having great success with it.

Heck Viagra isn't being used for its original intent!:rolleyes:

[Dan McCosh]

Post-it notes is another. It's interesting, but not surprising that they hadn't tested it for this use--as far as I know, they don't market anything for marine use. I would be interested in some data on how salt water affects it, particularly if it is submerged only partly cured. I've used it up to about an hour before launch in fresh water and it seems to cure OK. That alone is kind of pushy, as unlike the urethanes and polysulfides, I don't think water is involved in the curing process. You would think it might be used as a lining for some kind of industrial tanks.

[mariner2k]

Dan,
I recaulked a couple of years ago with neoprene. (found it at Lowe's).
So far I think it is the best caulking I ever used and will probably stay with it from here on in. I find it to be a couple of steps up from roofing tar. Regarding problems with wide seams and staying soft....if your cotton or oakum is in place there should be no problem.
I know......I have some pretty wide ones.
Great product..low cost....it has my vote.

[Texas Boater]

Dan,
I recaulked a couple of years ago with neoprene. (found it at Lowe's).
So far I think it is the best caulking I ever used and will probably stay with it from here on in. I find it to be a couple of steps up from roofing tar. Regarding problems with wide seams and staying soft....if your cotton or oakum is in place there should be no problem.
I know......I have some pretty wide ones.
Great product..low cost....it has my vote.

This is GREAT! :D This is exactly the type of open minded informative discussions I had hoped to find at this forum all along. While every NEW idea may not be a gem, STATUS QUO is also not a guarantee for best practices. :rolleyes:

I am sure the standard bottom bedding/sealant materials (they shall go unmentioned at least by me!) are excellent but I am also confident that sealant chemistry has made a few strides since the “standard’s” invention.:p

Thanks for the thread….
:)

[skip g]

Dan, What are you using for bottom paint... this is my first year on Huron and would like to know what has worked for you. Tx.

[Dan McCosh]

We've been using West Bottomcote for the past couple of years, and it hasn't worked very well. This year, we got a deal on the ACT bottom paint, and are trying that. We've used Petit, and others. None do much to retard the algae that is the main problem in Lake St. Clair. The soft stuff is difficult to clean, as it come off completely when scrubbed underwater. The hull looked like it was covered in green astroturf when it came out this spring. The race guys keep scrubbing, and I once shared a dock with a guy who used an air supply and wet-sanded his bottom before a race. The stuff we have been using does seem to work well against barnacles. So far we haven't had any.