Seam compound vs. roofing cement [Archive]

Wayne Jeffers

09-10-2002, 08:41 AM

If the original seam compound is still good, and the boat has simply opened up due to being dried out for three years, a product called Slick Seam is probably what you want. It's a waxy compound you put in the open seams to keep water out (mostly) until the wood takes up and the seams tighten. As the seams tighten, it will squeeze out without crushing the edges of the planks.

Wayne

WWheeler

09-10-2002, 09:04 AM

Roofing cement? That's original. Comes in a tube, it's cheap, and keeps the water out. Come to think of it, roof patch-in-a-tube is just tar, which has been used to seal wood boats in days gone by. (of course it can be as messy and hard to remove as 5200...)

Allen Foote

09-10-2002, 09:56 AM

Yes, WWheeler, but it also sets up hard and won't allow closure of the seam like a softer polysulfide (such as BoatLife) will. After 3 seasons, that hulls got to be dry. Do not use anything that sets up hard...niether 5200 or roofing cement. Slick seam is fine if the boat won't be in cold water or is hualed out seasonally. It turns to wax and falls out in cold temps.

Bayboat

09-10-2002, 01:51 PM

In my experience still the best seam compound is oil-based, like Interlux. Brown for the bottom, white for topsides. Too bad Kuhls is no longer available. I haven't used a polysulphide seam compound much but one like BoatLife gets a good press. I have never tried stuff that is intended for some other use, except for Portland cement in old, wide seams on workboats where the planking is damp. A product that comes in a tube on which the label claims it is a "caulk" isn't. The only proper caulking material is cotton or oakum.

WWheeler

09-10-2002, 03:33 PM

Point taken. Roofing tar would be a permanent mess. Boat Life I've heard is for above the waterline - what about below?

bugeye

09-10-2002, 08:41 PM

hi,
I think some of you are thinking of something else when you're thinking of roofing cement. The stuff that comes in five gallon steel buckets takes years to become solid, and it never gets hard. It's a great thing to use on the bottom, because it's really cheap and effective, albeit messy. Dont use it for topsides because it will bleed through paint. I use the stuff on all kinds of things. Alot of workboats use it mixed with portland cement as seam compound right from the start. The cement thickens it, but when encapsulated in the tar, it doesn't harden. And worms won't touch it.

Stan Derelian

09-10-2002, 10:32 PM

A lot of old timers around here say the best thing to use in a mixture of roofing patch compound and portland cement mixed until it has a good plastic consistency. It stays flexible, and holds in place.

Ian McColgin

09-11-2002, 08:20 AM

Around here we use the roofing goop as a squeeze-out on underwater seams on boats that have been dried out too much. A well baked boat that's been on the hard for a few years can well take a few months to approach full swelling. After the first year, you'll not need it since the drying over one normal winter is pretty managable.

JormaS

09-11-2002, 06:03 PM

Roofing tar is an old product that comes in many varieties intended for a number of uses. Mostly I think it is called bitumen. In a more solid form it´s sticky and it practically never hardens which makes it usable as a seam compound.

Hempels and Interlux both sell a bitumen compund where butylene rubber has been added in order to make it even more elastic. Both are packed in cartridges that can be used with a normal goop gun, and also in tin cans so you can apply it with a spoon or whatever.

These products as well as regular "roofing tar" can, at least in my view, very well be used as underwater seam compound. They have a moderate glueing capacity so they will stick to wood. However, when the boat is hauled for some time and the planks start shrinking there is not necessarily enough glueing capacity nor elasticity to follow the movement. The seam will then open up but the goop can be warmed with a heat gun and then pushed to accommodate the new seam width. It will stay soft enough, even in cold water, to be pressed out by the swelling planks.

The down side with bitumen is that it is hard to do a neat and tidy seam job with it because its stickyness makes it difficult to remove mechanically from surfaces adjacent to the seams.
Also, it bleeds into wood which means you have to rout the seams if you want e.g. polysulfide or polyurethane (Sikaflex, 3M 5000 series) to stick to the wood later. I don´t know about linseed oil putty. Maybe it would stick, I haven´t tried.

I have used polyurethane/polysulfide in underwater seams (over cotton), but I won´t do it again. Or maybe if the boat stays all year in the water. Bitumen in one form or another is my favourite. It´s messy but it´s easy to apply and easy to patch when needed. If it´s allowed to skin a little before painting it won´t bleed through the paint if you touch it with the paint brush only once or twice.

Allen Foote

09-12-2002, 11:29 AM

Roofing tar is one thing, fiber reinforced roofing cement is another. The ONLY advantage to using tar on boats is the fungiside properties for both dry rot and toredo worms and the only time it should be used for seam filler is UNDER COPPER SHEATHING. If you have a workboat and just want another season...go for it. BUT, regardless of the sentiments here, it does not belong on a "well found yacht" and I can imagine what a surveyor (especially one versed in fiberglass) would write about it. "Mess", for charectorising seams after being filled with tar is an understatement. WWheeler,...A soft polysulfide should be used under the waterline and a seam filler such as white Interlux or trowel cement above. The white BoatLife doesn't take white paint well above the waterline and the seams become discolored. The Interlux seam fillers ARE NOT FLEXIBLE! You DO NOT want an inflexible material in the seams of a flexible wooden boat.

WWheeler

09-12-2002, 01:16 PM

As it happens, I'm acquiring a boat that has copper sheathing, with tar and felt underneath. It's new copper, replacing what was there. (owner stalled out on the project when his house burnt down.)

bugeye

09-12-2002, 07:52 PM

Allen,
I really don't think that you know excrement from shinola. Have you ever used a roofing tar-portland cement mix? It's isn't yachty, that's for sure, but it is in many ways the best thing there is, and after a brief education period, you learn to not make such a mess. And also, regular brown seam compound does stay flexible as long as the boat isn't allowed to dry out. If you put it in within a few weeks of launching, you'll find that it stays soft for years and years, as long as the boat isn't on the hard for a long time

Concordia..41

09-12-2002, 08:27 PM

Allen Foote

09-14-2002, 02:49 PM

BUGEYE, give me a break! How many chunks are missing in your seams? "Stays fexible as long as it doesn't dry out?" SO, everytime that boat is hualed, it has to be reputtied? and recualked? because it drys overnight? How long before it drys out 2 days? how long does it take to paint your boat bottom? Don't tell me 2 hours...and that seam compound sets up hard overnight. You cannot cotton caulk a hull and fill the seams with putty AND reluanch before Interlux brown sets up. CAN"T DO IT! What about the guy rebuilding his hull over the course of a years weekends? Your telling him to put "concrete" in his seams! WE are not talking a 16 foot punt. Every boat hualled here for bottom painting stays out a WEEK! I've yet to see a boat hung in slings for painting and then put back in....nice theory but it doesn't happen. AND what goes between the hard Interlux and the other side of the seam (which gets bigger every day)? more hard putty? Just becuase its in your seams does NOT make it the right thing to use. With the amount of it sold...obviously, people need to know the damage it does do, the problems it does cause and that there IS a better course of action. smile.gif The same things can be said about these "tar based seam fillers", there is a better filler to use that does not have those distinct disadvantages. Lets draw a line of distinction here....are you saying that these tar/portland cement seam fillers are good for 1) 40 foot power boats? 2) 20 foot daysailers? 3) 300 foot copper clad tall ships? or 4) 60 foot traditional built carvel planked work boats no longer working and sitting at the dock 350 days of the year? BUT the main reason you want a MORE FEXIBLE filler is that the filler STAYS in the seams while the vessel's planking works(moves and flexes) while in a seaway! The Interlux seam fillers ARE NOT flexible and will harden and crumble when dry.

[ 09-14-2002, 04:06 PM: Message edited by: Allen Foote ]

bugeye

09-14-2002, 07:40 PM

Hi Allen,
I honestly don't know what you're talking about. Right now, I'm doing some planking on an 82' sardine carrier that has been on the railway for going on two months. The seams are payed with regular brown seam compound. Seams that were payed several years ago are still flexible. It's not rubbery, but you can squish it with your finger without it breaking. Similar compounds have been used for decades if not centuries. It works. It is not a maintenence-free method of paying seams, but it is easily servicable. If you have serious problems with putty falling out, my guess is either that your cotton or oakum is not set deeply enough, or you have a boat that works too much. Another possibility is that the caulk seams aren't large enough and cannot cope with the movement.
My boat is in a plastic shed which has been frightfully hot this summer. I will spend time in purgatory for subjecting it to such heat, but new topside seams that I paid in the beginning of the summer with Interlux white seam compound are still soft. I just don't understand why you've had such troubles with traditional seam compounds.

Hughman

09-14-2002, 08:22 PM

Another inexpensive possibility for smaller boats is window putty, sometimes mixed with bottom paint. It does harden, but it takes a few weeks, and is easy to remove. costs about $20.00 a gallon

J. A.Tones

09-14-2002, 09:15 PM

If I may insert a few facts regarding "roofing tar" and cement - you do not use "roofing tar" least not here in the Pac. N/W. What is used all the time on both older pleasure and working commercial boats is a mix of "FibreGum" - a roof patching product and Portland Cement. You get the Fibregum in tubs at most any home hardware type outlet and mix it with cement untill it gets even thicker than it was when you started. Best done when you can warm the tub to get the Fibregum to soften. I don't know what the cement does in the mix but every wooden commercial fishboat around here uses this mix over the normal cotton caulking including well respected shipyards.
I re"filled" the seams on the garboard plank 3 years ago and right now I am cleaning all the seams for a total refastening and recaulking job. This mix is still somewhat soft in that it must be scraped out of the seams rather than chipping it like I have to with the lead based putty in the other seams.
The thru hulls , rudder stock and most everything on my boat underwater is bedded with this mix and it all is still "soft" after up to 12 years.
Maybe Fibregum is not available in the USA but I am certain there is an equivalent product.

John Tones MV Penta
Sidney BC

Bayboat

09-14-2002, 11:13 PM

Bugeye is right. Interlux seam compound, meant principally for small boats and yachts, does not harden quickly, certainly not overnight. The surface may resist a bit, but the bulk of it stays malleable for a long time and will squeeze out as the planks take up. It is specially formulated not to harden and specifically for filling seams on top of cotton or oakum, and has been used for many years. It is still the seam compound of choice for small boats and yachts. Allen, I don't understand your difficulty with it. Perhaps you got hold of an old can from which the oil had evaporated. The other compounds mentioned, various versions of "roofing tar", Portland cement and the like, lauded by the "old timers," are for workboats and fishboats, and are often used, not because they are the best, but because they are economical when used on a large boat with wide seams. It doesn't make sense to use them on small boats and yachts. It is not the way to save a little money on something on which you should be using only the best materials.

bugeye

09-15-2002, 09:27 AM

Hi, There seems to be a great deal of ambiguity with the words "roofing tar". When I say "roofing tar" I'm speaking of the gooey stuff that takes years and years to even start to stiffen, and comes in one and five gallon cans or buckets. I'm wondering if some of us are thinking that I'm talking about asphalt steeps, which comes it big blocks and is a solid until heated. I just call this pitch. Anyhow, we all seem to have strongly formed opinions on this subject and we arent getting anywhere. I'm going to keep using things like gooey tar and white putty, because it's appropriate to the boat that I own. And Allen, I'm sure that you'll keep using whatever rubber goopety-goop you've been using all along, and you'll be sure that you're doing what's best. That's what is great about owning you're own boat. You get to do whatever you want with it. No hard feelings. I apologize if my comment regarding your ability to recognize shinola was a little too much.

Seppo

09-15-2002, 12:58 PM

Hi

Just some practical happenings that I've had and heard about concerning this goop stuff...

I've put some goop called 'Proof' into the underwater seams and that seems to work ok, it's pushed out as the seams get tight when swelling.

I'd anyway keep the boat moist a week or two before applying...:
I've spoken with a fellow who got into trouble using this stuff on too wide seams - they had no time to wait or something - so somebody applied the stuff on the seams. They put the boat into water and the goop came in... needed a couple of bigger pumps and bilges got rather messy with the stuff getting spread all over the place...

BR
Seppo

HOWdie

09-15-2002, 05:37 PM

Seppo is on the right track. If at all possible put her in the drink for a week. If not you still need to find a way to increase the mositure content of the planking. Then button her up and put her overboard. Don't expect to get bristol topsides the early in the season. Let her settle down first then ya can make her prudy.

Stan Derelian

09-15-2002, 08:01 PM

OK, OK, I stand corrected. I said roofing tar. I meant "fiber gum". But I believe that fiber gum in the States is the same as "wet patch" roofing compound--and that takes a long time to harden if it ever does.

I know that it has been used on boats up here in the NW that are NOT fish or work boats, and the owners have been very happy with the results.

JormaS

09-16-2002, 05:33 PM

I´m trying to make sense of this discussion. Most of us have used one goop or another with better or with worse results and we´re trying to communicate our wisdom to somebody who posed a clear question.

But we´re having a problem here. We mention products and materials supposing that everybody knows what we´re talking about. But we don´t.

Take Interlux Seam Compound for example. What is it? Must be manufactured by International Paint but is probably sold under a dozen of names in many different countries. What about Boatlife? Could be a polysulfide sealant but I´m not sure. And "roofing tar"? I´m pretty sure that is a class of more or less modified bitumen/asphalt products including Proof 10 by Hempels, Tremcoverall by Tremco and many, many more. And then we have trowel cement, 5200 and glazing putty...

Now I know why they have Latin names in the natural sciences. It´s in order to know what the other guy is talking about. One man´s Oregon Pine is another man´s Douglas Fir, as we all may know.

I´m convinced that everybody is trying to be helpful here and we´re all curious to learn, but
PLEASE, try to give some specifics of the products whenever possible. Also, I find it very helpful when you state the exact reasons why you find a certain product helpful.

Thanks for a good thread. Let´s go on.

WWheeler

09-17-2002, 07:37 AM

Good point, Jorma. Some of the products being mentioned here, like the Fibregum roofing cement, I've never seen before. When I was thinking of roofing tar, I was thinking of a roofing compound (roof patch?). It comes in a tube, just like the yacht seam goop, and it's used for patching asphalt shingle roofs, sealing shingles to valleys etc.

I'm similarly confused about the Interlux compound. What's the chemical composition etc. Perhaps a more knowledgeable person could do a comparison chart ie. Brand name -- Composition -- Use. (Heck, this could be a whole WB article.) For example: BoatLife -- Polysulfide -- Above waterline seam sealing. And what the heck is polysulfide anyway, and why is it used here.

[ 09-17-2002, 08:38 AM: Message edited by: WWheeler ]

Dan McCosh

09-17-2002, 09:34 AM

I feel compelled to contribute to this debate. I've used slick seam, roofing tar, and polysulfide on two boats over a 25-year period. The slick seam is easiest to apply in the spring. Problem is it squeezes out, and if the planks dry the next year even a bit it has to be completely redone. Another odd effect--I once hit a rock and all the seam compound squeezed out all over the hull. The roofing tar approach is actually pretty good. Goes in easy, sticks to anything, even when wet, and stays flexible in the seams. Main problem is the goo on the planks, which ends up making it very tough to sand or work with the bottom finish. Last is polysulfide, which i have been using for the past 9 years or so. It's expensive, and doesn't like to stick to the previous goos. It' easy to finish off, with a scraper or sander, and is far superior when the hull works under load.

Jamie Hascall

09-17-2002, 11:53 AM

Ah yes, if only there were latin names for product to really identify them past their brand or common names. It's great to hear from Jorma on this as we got into a great discussion of deck caulks a couple of years ago with the additional wisdom of The Chemist. It does much to explain the makeup and economics of many of the available marine goos. http://media5.hypernet.com/ubb/ultimatebb.php?ubb=get_topic;f=1;t=001376
I'm very interested in this topic at the moment as a friend has just hauled his old motor cruiser and this roofing tar solution may be perfect for some last ditch sealing of its old and pretty sorry hull.
Lets keep this discussion going with as much specificity as possible.

Jamie

Eddiebou

10-23-2011, 02:08 PM

I realize this is an old thread but it's worth looking at again. So here goes my experience with black roof goo in a tube.
I used Plastic Roof Cement as bedding for a small cross planked skiff last year. It wasn't like tar, it skimmed over quickly. I got thinking, this stuff isn't like the old "Alcatraz" roofing tar you used to be able to get. Then I found an old (empty) can of Alcatraz. To my surprise, it said, "Plastic roof cement".
So what is a good source for the good "Tar"?

Soundman67

10-24-2011, 06:22 PM

I used a product called roof patch to fill in some overly large gaps in the dried seams last spring. It sure doesnt dry too quickly. It did do what I wanted it to do, which was to make the hull mostly watertight until the planks took up. I will be going onto a tidal grid in a few months to have a look at what has happened with the product. I am interested in how this will work long term. The cracks in the seams werent big enough to mix up the roof patch with cement but when I re-caulk the whole bottom next time I will use the fibergum and cement mix. So far the roof patch on its own has worked for me. It was put in just hours before I launched. Only trouble I have seen so far is that bottom paint didnt want to stick to the roof patch too well. again I will see how that has held up in a few months.

Ian McColgin

10-24-2011, 07:28 PM

I mix roofing goo -stuff in a tub - with the brown underwater seam compound at 50/50. Neatest to load it in a caulking gun or grease gun. G'luck

Bob Cleek

10-24-2011, 07:45 PM

I would like to know the makeup of Dolphinite bedding compound. I know it has whiting, linseed oil and some form of dryer. I looked through a lot of the old boatbuilding books to see if I could find a recipe for it to no avail. At one time you could buy it by the gallon and 5 gallon cans. This made it inexpensive to use, as a gallon was just a little more than a quart. I can only buy it in quarts and pay $21.69. The local supplier did say he would give it to me for $18.60 by the case.
I plan to use it to bed the cast iron ballast and the dead wood when we go back together. I found a recipe that mixed 1 gallon of dolphinite, 1 quart of red lead paint and 1 pint of white lead to use for this purpose. This appeared to be what they used on Sarah 47 years ago and I plan to go back the same way. If you break up a piece of the old bedding you can still smell the linseed oil, see the white and red lead.

Dave

Sun over the foreyard.

Probably too late to do you any good, but if anybody else is wondering, bedding a ballast keel with Dolphinitei isn't the accepted practice, around here, at least. Dolphinite is for bedding joints and fittings, but ballast gets another treatment. From all the keels I've seen bedded by master wooden boatbuilders in yards in the SF Bay Area, the practice is to make a gasket of Irish felt that goes between the ballast keel and the wooden keel and that is set, top and bottom, in "Henry's." Yes, the roofing patch compound is a bit messy, but you only have to clean it off the one seam. Scrape off the excess with a putty knife and wipe it clean with a rag wet with paint thinner.

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