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Preview: Caulking a Wooden Boat Part 1, Tools and Basics

May 3, 2013

Geno Scalzo is a master caulker out of Owls Head, Maine. He has over 30 years experience caulking wooden boats, and he’s taken the time to help us demystify the process and purpose of caulking properly. Here in the first video of the series, we are with Geno as he works on caulking the deck of the Jacob Pike, a very impressive 83′┬ásardine carrier that is undergoing some repair. Chances are that your boat is smaller than the Jacob Pike, and so it’s important to adjust the technique and force you use with your own caulking endeavor. Stay tuned for more from this series and enjoy!

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– [Narrator] One of the big mysteries in wooden boat building has always been caulking. Caulking is what fills the seams between two planks and keeps the water out. On this video series on caulking, Geno is gonna walk us through the steps. And at the end of this series, the mystery should be gone.

– We’re doing a little work on the deck of the Jacob Pike. 83-foot sardine carrier that was originally built at the Newbert and Wallace yard, Thomaston in the late ’40s. She had a bit of a collision and we’ve done some repair work on her and some of that repair involved laying parts of the new deck and we have to caulk that. Not a very involved process. Involves just the usual technique, I suppose, but pretty simple and straightforward once you get used to doing it. To caulk that deck that you’re gonna, or I’m gonna require needing tools of this nature. This unusual looking mallet. Solid hardwood with inner and outer rings which keep the end of the mallet from mushrooming in when you’re hitting it constantly. Inner rings pretty much just hold the mallet together. So you got these nice little slots in it which provide an ungodly obnoxious ring that most people describe as wonderful and some people describe as really deafening. Why it’s like this, hard to tell, pretty much evolution is what created tools like this. It does the job perfectly well. It’s a well-balanced tool. It goes up and bounces back. The wood always comes back at you. So you never have to lift the mallet back up. It comes right back to you. Thus allowing you to do this repetitive task pretty much all day long without having any fatigue in your arm. The other item involved in this are these nifty little irons which come in various shapes and sizes and have various different configurations for different things. This little iron is the one you most, you would be using most often and it’s a threading iron. It’s the iron that you actually lift the cotton and tuck it back underneath itself as you caulk. Generally they are fairly thin. This one being a bent iron, very thin tip to be able to get those tucks. Which I’ll show you in a minute. Tight and close together. Now these other irons, as I said, have different configurations, different thicknesses. Some of them have small grooves in them. And that generally allows the material to be gathered and concentrated in the center of the caulk and seam. Some of them don’t have the grooves, some of them are just strictly flat, blunt irons, which are used in the process of setting the material to the bottom of the caulking seam. Now what we’ve just done is we’ve taken this soft cotton and we’ve tucked it in one thread onto another to fill the seam. And we’re filling the seam to the bottom of the caulking seam. And then we’ll come back and set this material to the depth that we need to have to fill that seam up properly. Most boats’ caulk and seam would probably be, whether it’s a small skiff or schooner, probably about 60% of the thickness of your planking. So if you have one-inch planking thickness your caulk and seam would probably be no more than 5/8 of an inch thick. And probably for planking that thin, a single strand of cotton like this or even possibly a half a strand. You can split this material very easily. And get the thickness that you need probably based on practice. Now this cotton has no real strength. It’s merely a vehicle for the planks once they’re wet to swell against. And that will always give you watertight integrity. It gives you some structural integrity. Everything is in compression at that stage and holds the vessel together. Keeps things from moving around. And the boat’s working in a sea way, there’s a lot of adverse forces under play. Caulking with proper joinery keeps the vessel tight and rigid and watertight. One of the things that you wanna pay close attention to when you start to caulk or if you’re caulking your own boat or you’re just lucky enough to be able to do this for a living, is you have to determine the difference between seams. This seam is a little bit narrower than this seam here. So you have to kind of approach how you’re going to tuck the material in one seam or the other. Generally, I like to caulk all my narrow seams first so that I could apply a little bit more pressure on the wide ones, thus putting the boat in the same amount of compression wherever I work. So this seam is a little bit wider. It’s required that I tuck my cotton in a bit closer so that all the material that I put in there will end up at the same depth on each seam and have the same amount of compressive force as all the other seams. So caulk the narrow ones first and go to the wide ones. If you have a seam that’s really narrow, you may have to just spread your tucks out a little bit. And that still provides you with the same amount of compressive strength. One other aspect that’s sometimes confusing to people that haven’t done this job is what happens when you’ve got a seam that’s huge, that’s very wide, how do I keep the material from going through the planking? Well, if the seam has got a back to it, if it’s still a wood to wood joint, then you really don’t have a problem, because you just caulk to the bottom of that seam as if you’d caulk any other seam. But if it doesn’t have a back to it, then what you’re gonna be required to do is to work all your narrow seams to put as much pressure against that seam as possible. If you still, when you’ve done that, caulked your narrower seams such as this one, and I’m gonna caulk this one really hard with a lot of material. If after you’ve done that and you’ve crowded these planks a little bit to the widest seam, then ideally you should still be able to go back and caulk this seam with the same amount of material gagged a little bit tighter, threaded a little bit closer. And then very gingerly only set this material to the proper depth. One-inch planking, 5/8 of an inch deep. Two-inch planking, inch-and-a-quarter deep. Don’t come onto it with a lot of force. Just let all the compressive strength of all the seams together help push this one so it tightens up once the boat starts to swell in the water. One thing that’s very important to bear in mind when you do this, if you’re caulking your own vessel or you’re caulking a deck, particularly a deck, but if you’re caulking a small boat and you’re unsure about how much to set the material, it’s always best to set all your seams if you can after you’ve threaded all of them. And that way you can get a better feel for exactly how well you’ve caulked the boat but you can also tell that I’m not gonna overpack one seam and drive it closed. If I put a lot of material in this seam and I close this seam up, then I’ll never be able to thread material into it. So if you come along and set your material to the depth after you’ve got a number of seams caulked in a particular area maybe it’s three feet, maybe it’s five feet, maybe you’ve got eight seams on the side of the boat, thread them all, get them loosely set to the proper depth and then go back and set them all as a gang. You’ll find that you’ll have two things will take place then the first is you won’t be pushing one seam tighter than the others. And the other thing is that you’ll have an opportunity to keep the edges of your plank from wobbling up, which often happens when you have one caulking seam on an edge rather than a caulking seam on both edges, which is common in most hull configurations. I should probably talk to you a little bit about what actually a caulking seam is. Now the caulking seam on this deck is composed of a slight bevel on the upper edge of the plank and then the same on the other side of this decking. There’s a bevel on each edge. Thus creating a caulking seam as two planks made together. Unfortunately, not all decks are created equal and some decks only have one caulking bevel on one plank edge coming against a square section on the next one. Why is that less than ideal? Well, if you’re caulking and you’ve got sheer to the vessel or crown to the vessel, you have to search for the caulking seam. That sounds pretty ridiculous, I realize, but if the seam is facing away from you on this side of the plank, you actually have to rise up over the edge to find it. So the best way to work a deck is to have the caulking bevel on both edges. Now you won’t be confronting this when you’re caulking hull, there’ll only be a caulking bevel on the top edge of your plank. And your next plank as it comes down will have a square edge. So that bevel should be easy to identify if you’re doing any caulking or plank replacement.

– [Narrator] Be sure and join us for the next caulking video where Geno will dig deeper into the mysteries of caulking.



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