deck caulking - cotton around the edges as a bond breaker?

[imported_Jimmy]

My question is about the edges of the deck at hatches, cabin, etc. My deck hasn't been laid very well so where the ends of the planks butt up against the cabin (and similar areas) the ends of the planks are different distances from the cabin and have different bevels. It seems like you couln't effectively caulk this type of seam with cotton, but I have been doing so anyway with the idea that the cotton will act as a bond breaker and also make the black stuff (I'm not going to say which one I'm using that is a whole separate topic) easier to clean out at a later date if (when) I need to do it again. So is this a good idea or will the cotton just retain water and cause problems?

Other details: Deck is 1"x1.25" teak over old 3/4" x about 5" fir subdeck (deck was originally canvassed). Seams have a caulking bevel which is being painstakingly scraped and sanded down to clean wood then brushed with acetone, sealed with epoxy sealer, caulked hard with cotton (as recommended in a past article in Wooden Boat), and then filled with expensive black rubbery stuff.

[ 08-23-2005, 12:33 AM: Message edited by: Jimmy ]

[Donn]

.

[SandMaster]

I think the cotton is a mistake. It will retain any fresh water or salt that gets in and could cause rot.

What are you using for your calulking? I highly recommend sis from teak decking systems for deck caulk.

[imported_Jimmy]

Are you saying I shouldn't use it in the uneven seams or not at all? With hull seams you would paint it with red lead and not worry about rotting but in deck seams I get kind of nervous. I know the cotton is sopposed to keep the water out, but in the process it gets wet and probably stays wet for a while making it prone to rot?

So, should I just fill up the space with black goo? I thought you were supposed to only let the rubbery stuff bond to the sides or it will start to peel off at the bottom which is the reason they use bond-breaker tape when doing pretend teak decks. I can't think of an easy way to get tape to the bottom of a tapered seam.

[Andrew Craig-Bennett]

I did as you are proposing - used the cotton as a bond breaker - and have had no trouble.

(Mind you, I painted over the lot with Coelan, which is probably why!)

[T.A.R.]

Do yourself a favor use the cotton. They've been caulking decks for years with it.

[imported_Jimmy]

I guess I didn't explain my question very well, but after talking to some other people I decided not to use cotton in the seams in question. My question was whether it was a good idea to use cotton ONLY as a bond breaker in locations where there wasn't a proper or even caulking bevel. In this situation the only function of the cotton would be as a bond breaker, however, if water did get in, the cotton wouldn't be packed tight and wouldn't seal the seam, just retain water and probably rot. This was only around the edge of the deck, mostly along the dedge of the cabin. The rest of the deck was caulked properly with cotton.

[Jay Greer]

I am at a loss to understand your definition in refrence to a "Bond Breaker". In the past, prior to the use of poly sulfide seam compounds, deck seams were first primed with a mixture of bee's wax and turpentine. After caulking with cotton, the seams were given another dose of the same mixture, followed by oil based seam compound such as "Kuhl's Elastic Seam Compound" or
"Jeffrey's Marine Glue". These mixtures were more effective than the modern polysulfide compounds as the seam primer and the seam "paying" materials were compatable with each other as with the wood that they were intended to seal.
JMG

[islandteak]

By 'bond breaker' I expect that you mean a barrier between a polysulfide caulking and the subdeck. The caulking gap is irregular shaped so you want to use cotton to cram in . I would soak the cotton in raw linseed oil, just enough to coat the cotton and prohibit any potential moisture from absorbing into the cotton.In later years removing the polysulfide may be as easy as sliding a razor blade along each side of the seam and 'popping' the caulking out....hhmmm, it sounds good in principle.

...Ken

[islandteak]

Geez, I posted to quickly.
You're bound to get the linseed oil on the sides of the caulking groove and that will interfere with a polysulfide bond with the sides of the teak deck.

I'll just pass this over to the next in line.

...Ken

[imported_Jimmy]

Well, this is mostly achedemic for me now since most of the seams are filled. Jay, by "bondbreaker" I was refering to something people do with newer pretend teak decks that are usually only about 1/4" thick and have straight sided seams with no cotton. In this case many people believe it is better to have the sealant stick only to the sides and not the bottom of the seam. I think the theory is that when the deck planks shrink it pulls evenly on either side of the sealant. If the sealant is also stuck to the bottom, the force will be greater in some areas and the bond between the sealant and the wood will fail and once it fails in one place it will continue to separate until it isn't attached on one side and it leaks. In the case of a v-shaped seam I think it would probably fail at the bottom first and then peel upward. On thes straight sided seams they just put tape along the bottom of the seam (called bondbreaker tape) on my v-shaped seams there is cotton in most of them which will serve the same purpose in addition to its primary purpose of keeping the water out. What I was wondering is whether it is a good idea to put it in seams that you can't caulk properly just as a bondbreaker.

Jay, I like your description of how to do it the traditional way. If I have to do it again I will seriously consider doing it that way. Hopefully I don't have to do it again for a long time.

[Jay Greer]

I might add, that there are some other advantages to a traditonal caulked deck over the newer style deck that utalises a thin overlay of planking over a plywood subdeck. A traditional deck is made up of staves (planks) that are nearly square in cross section. Thus planks that are an inch and a half in width might be an inch and a quarter in thickness. Here the advantage is in the ease of installation. If one is building a sprung deck, the planks are much easier to edge set if they are closer to being square in cross section. A thin rectangular plank is hell to edge set! Additionally there is little longevity to a thin overlay planked deck and it will, most likely require replacement in a few years as it will rapidly become too thin to be of service. It is difficult to keep plugs from popping in a thin layed deck as well! Additionaly, a cotton caulked deck creates a stronger structural panel , resiting wracking (twisting) strains in a seaway under the loads transmitted by the rig and ballast keel. This is due to the tension created by the caulking and deck crown. The covering boards, if installed correctly resist the caulking tension, much in the manner of the rings used to build the Arnolfo di Cambio Dome in Florence Italy. Once a cotton caulked deck starts to take up during the caulking process, the whole hull begins to ring like a giant bell if the caulker knows his stuff.

[Bob Cleek]

Yes, the traditional laid deck is superior, as said above. The greatest advantage, however, is its tightness. When the deck planks are roughly square in section, and properly butted against one another, only the top portion of the plank exposed to the sun will dry most. The lower portion of the plank will retain its moisture better and stay tightly butted against its mate. It is then a simple matter to simply wet down the deck and soak the upper portions of the plank which swells and shrinks in the area of the caulked plank seam.

[imported_Jimmy]

Yes, I'm sold on a traditional deck. The problem is I have one that isn't quite done right or well. Mine was just laid over the original deck without a covering board so that the outside seam is up against the toerail instead of a covering board and instead of the plank ends going under the hatch coamings, they butt up against them (badly). So, for the bennefit of any future readers who might encounter a similar situation if the search tool ever works again, can anybody answer my question?

[ 08-25-2005, 10:45 AM: Message edited by: Jimmy ]

[Andrew Craig-Bennett]

Well, Jimmy, I rather thought that I already did.

[imported_Jimmy]

sorry Andrew, you did answer the question, you were one of the few, however, your lack of details made me suspect you may have not fully understood the question (no offense intended). So do your teak deck planks really butt unevenly against your cabin and hatch coamings? How much cotton did you put in and how hard did you caulk it? Did you use anything else in the seams? Why did you paint(?) over a teak deck? Thanks

[ 08-25-2005, 03:45 PM: Message edited by: Jimmy ]

[JormaS]

Jimmy, from your description I gather that in the places you mention, the seams will be wider than normal and have a depth equal to the plank thickness. Is this what you mean?

If so, then maybe you can´t pound the cotton enough to make it sit tight. Question is, what purpose would the cotton then serve. To my mind, it would mainly serve to fill the bottom of the seam, thus making the seam shallower. Of course it would also serve as a bond braker for the sealant.

I think it is important to make the seam shallow enough if you put in a polyurethane or a polysulfide sealant. The sealants´ manufacturers normally prescribe seam dimensions where the depth is less than the width, except when the seams are very narrow, like e.g. 1/4". In that case they seem to suggest a rectangular seam. I´m talking about the part of the seam that will accommodate the sealant, of course.

As an aside, my understanding is that the modern sealants are not intended for beveled, V-formed seams. The reason is that the width at the bottom then tends to be so small that the sealant will be hard stressed at elongation, and will tend to let go of the plank edges.

But in the seams that you mention (if I have understood it right), you have two alternatives: Either you fill them with the sealant all the way up from the sub-deck, or you fill the bottom first with something else, like with cotton (maybe impregnated with some glue if necessary). It could also be a cell foam rod, like in house construction.

The main thing is that the tightness of those seams will depend solely on the sealant. Therefore the prescriptions should be taken seriously. The modern seam compounds depend on their elongation and glueing capacities. They need clean and primed surfaces and preferably they should have only two glueing edges, hence the bottom tape. But cotton or a cell foam rod works fine, too. Seam dimension is crucial. The worst dimensions are in a deep and narrow seam, because then the elongation capacity will not be utilized, and the glue line will not hold.

It´s not rocket science, as has been stated many times over. But also remember, that after alcohol, these sealants are the most widely miss-used stuffs on boats. :D

[imported_Jimmy]

Thanks Jorma. It sounds like you understand the situation pretty well. I wish I had thought of filling the bottom of those seams with something like that cell foam rod you were talking about. Yes the seams in question went right to the sub-deck (one inch). They're done now. I did some with cotton in places wher I could get it relatively tight and didn't use anything in others. I guess in a few years I will know which worked best. I think next time (hopefully that is a long time away) I will go the more traditional route and use marine glue. I may even get rid of the teak altogether and go back to canvas decks which she had originally. I canvased the cockpit of my boat and it is a lot easier and so far has lasted better and kept the water out better than teak.

[JormaS]

OK, good luck Jimmy.

On a general note, I´m beginning to think that teak decks bring us more trouble than we deserve, especially when they consist of ribs glued/screwed to a sub-deck. Surely they are nice to look at and to walk on. But in the long run, a teak deck is hardly a rational choice when compared to the less complicated alternatives...as your canvassed cockpit seems to prove! ;)

[Jamie Hascall]

Hi Jorma,

Nothing like a teak deck thread to somehow find me poking around the forum again.

Jimmy, I think you've gotten the best answers that you can on this one. I will confirm that using a bond breaker makes removal of the old caulk easy. However, in my thinking it gives a great avenue for spreading of moisture down the seam when failure does occur. Jorma and I (and others)hashed this all out a number of years back and here we are again. Sadly it sounds like searching is no longer an option but if it becomes one again, try looking for something with a title about the horse not being quite dead yet.

Sadly, I think that Jorma's last statement about teak decks being mostly a pain is the most pertinent one of the lot. I was just looking at bungs needing replacement and a few seams that never quite got done... :(

Good luck
Jamie

[JormaS]

Jamie, nice to hear from you!

The name of the thread was "Deck Caulk (grab that stick, this horse is only kinda dead)". Google finds it when using that whole phrase as a search word, but it does´t open the page. :( The WBF "official" advice on how to use Google does not work at all for page-specific search.

It´s a pity, because there is a wealth of information on that thread.

[imported_Jimmy]

Yes, it sucks that the search thing doesn't work anymore (and I haven't had any luck with that "work around"). I think I remember the dead horse thread, but not anything about this topic. I read almost everything to do with teak decks over the last few years. The only reason I posted was that I don't remember this specific topic being covered (and of course I can't do a search to find out). I sanded the deck last night and it looks wonderful enough to make me foreget all the worries about where to caulk it with cotton, or not, and whether I caulked it evenly, or too hard, etc. Hopefully it doesn't remind me in the winter when it gets wet and swells up again. Wish me luck.

[JormaS]

As I recall, your topic was not specifically addressed in that thread. But you´ve done it, the skipper sounds happy and that´s what counts. smile.gif