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Preview: Carvel Planking a Wooden Boat, Part 1 – Spiling

January 14, 2014

“Spiling” is the technique boat builders use to determine the shape of a plank. In the abstract, it is a difficult process to understand.  Demonstrated by an experienced boatbuilder in a video, we think you’ll get it the first time through.

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– [Narrator] Figuring out how to curve the edges of a plank so it fits well and looks nice involves spiling, a process that is real tough to explain. But here thanks to Deer Isle’s Peter Buxton, the cloud of mystery vanishes and you really see what spiling is all about. Come along with us now while Peter marks out a new plank for the old oyster sloop that he’s rebuilding.

– Today we’re going to put a plank in the Nellie H. here. I’ve left all these old planks on the boat just to hold it together while I’m rebuilding it, to hold her shape and I really don’t have lumber wide enough to replicate exactly what they did before. So I’m going with a little bit narrower planks. We’re going to spile out a plank that’s gonna go from the bow down to about the seventh timber back. I’m putting this long, fair, straight batten onto the timbers here in order to get a mark where the bottom edge of the next plank wants to be. This batten is a piece of Doug fir that’s spliced in the middle of about an inch and a quarter by half-inch thickness. It’s about the right thickness and stiffness to bend fairly but not too stiff and so that’s a fine line. It’s also painted a dark color so that you can see it really well. I’ve got three points along the hull that I’ve marked out where I want a certain width, all the planks to be the same width. So I’ve got live five and three-eighths of an inch here that I want. So, I’m gonna mark that on the bottom edge of this. Clamp it off in those three different places and then stand back and eyeball it. The idea is to get this batten nice and fair. One of the most used tools in this shop is a good eye, so. Eight and a half, beautiful. I’m looking for about three inches to be even with the rest of these planks. So I’m just gonna put a little mark there at three and bring this batten in and I can’t really clamp it to the stem here so I’m gonna screw it. Good. Okay now is when you really want to start lookin’ at it. Bend right down and look at it, see that you’re happy with it. I’m hittin’ the marks that I’m after and that’s got a pretty good fair, fair craft to it so I’m pretty happy with that. And then we get a mark on the bottom edge here. Could’ve been the top edge but because of the room I have with the other plank, I’m using the bottom edge. I’m gonna take that batten off. I’m done with that for the time being. Gonna see how long a batten I need to spile over there. About 10 feet. This is a spiling batten. This can be made out of thin plywood, I’m using a piece of spruce strapping from the local lumber yard. It just needs to be flexible enough to bend around here easily but not too flexible so that is deflects edge-wise. It needs to be stiff enough so it doesn’t deflect too much and all we’re trying to do is get it between this mark that I put on and the edge of the next plank at each timber. Now, the planks in this boat have a lot of edge shape to them. As well as being curved around the shape of the hull here, they’ve got a lot of shape this way to them and so sometimes I have to use two battens to get them to go between the marks and screw ’em together. But I think, I think this one will work in one shot. That’s good. So as long as it falls between the two marks, the mark that I put on and the edge of the next plank, that’s all you need. Maybe a little bit of room between the two, you don’t want it to be too close. The most important thing with putting this on is to not get any edge set in it. So when it goes in here, just let it bend in naturally. You don’t want to force it up or down as it goes on. So I’m gonna make a little pattern because the front of this plank has quite a bit of shape to it. There’s a lot of angle and curve to it. I’m gonna make a little pattern that I’m gonna fasten onto the end of the spiling batten and in order to do that I’m just using a cheap pair of compass, pencil compass here and the idea here is to keep the compass in line with the edge of that plank. Because this pattern is going to move in this direction along the edge of this plank, after I cut it it’s going to move ahead in that direction, I want to hold my pencil compass in that same plane as the bottom edge of that plank and hold it throughout the whole marking process down across here in that same angle. If you don’t, if you do it like this which is your instinct to hold it 90 degrees to this edge, it’s not the same. You can see there that the gap is wider between those two marks on this end than it is up here and it won’t fit because the pattern is moving like this, it’s not moving like this. It’s not moving 90 degrees to this edge. It’s moving parallel to this edge. That’s a pretty good fit, I’m happy with that. That’s as good as you can do. So the idea behind spiling a plank is to get the inside face of the plank. That’s what you’re after here is the inside face, the face of the plank that’s going to be on these timbers. Here are my spiling calipers. You can pick these up anywhere at used tool barns and whatnot but the special thing about these though is he heated this tip up and bent it out like this, which is imperative to get into this top corner when you’ve got a plank there. If it’s straight, sometimes you can’t get that very tip into that corner. So, the idea here is to just start by pushing the straight part of it into the spiling batten, adjusting it and sweeping it in an arc until that tip just touches the plank up in there. Just like that, it’s just scraping the inside edge of that plank. All right and then gonna make a mark out here. Circle it and put a little line pointing whether it’s up or down and then do the same down here to this pencil mark. I’m going to adjust it and then sweep it in an arc and make sure that the bottom of the arc is on the line where I want it and do the same, circle it, put a little line and arrow pointing down and then circle this middle one too and usually I just connect ’em like that so there’s no confusion. The same back here. Sweep it in an arc. Keep adjusting it until it just scrapes that upper plank. So the top of that arc is just right on the line just right and then I’ll work my way all the way down the plank at each timber, doing that. Doing the same thing. I think we’re ready to stick that on. Now we’ll just remove it. I marked the aft end of where I want the plank to go on this batten. The batten’s a little bit longer than what the plank’s gonna be so I put a mark where I want the end to go and then I’m gonna cut the plank just a little bit long for now and we’ll cut it again later. What we’re trying to do here now is just find one of these planks throughout my pile here. Pick out a plank that will work with the shape I’ve got to get out, the length of course. I’m looking for one without too many knots which is sometimes hard to do, almost always end up with a knot or two. So I’m just doing a little preliminary measuring right at the moment and making sure this is even gonna work with this board and if it does, then I’ll screw the spiling batten down to the plank and mark it off and I think that’s gonna work so screw it down. Now the idea is to just transfer those same marks that I had before. So here’s the mark where the straight one went into. Let the calipers out until it just goes into that little hole there and then what I want to do is scribe a bit of a sweep just like I did before with that arc and pick the apex of that sweep, the highest point away from this mark and circle it. Just like that. Then do the same all the way along. So now I’ve reversed the process and marked, transferred all these marks onto the plank out here, circled ’em with my pencil so I know where they are at each point and then I’m gonna take my pattern here and… try to mark that 90 degrees to the edge of the pattern down onto the plank because the pattern of course is half an inch up off the plank. And if you wanted to get fussy with it, you’d probably want to take and do something like that. Put a couple marks, make sure that you’re getting, getting it 90 degrees from this face. So now I’ve got this nice, fair, again Doug fir thin batten that’s quite flexible that I’m going to use to mark the edges of this plank with. So I’ve got my little points here and I’m just going to nail that on the outside of the plank. You can use the inside if you have to but the outside is nice just because you don’t end up with nail holes in your plank. Here again you really want to use your eye. Bend down and eyeball that batten up and adjust it if it needs. That’s a little kink. On the top edge of this plank where it’s going to fit up to the next plank, you can’t adjust it too much ’cause it really has to go by your marks. But the bottom edge, because it’s not fitting against another plank, you can play with the batten until it really looks nice. I’m gonna let that go just a little bit right there just so it looks nice. Good. So that’s the end, that’s the end of the plank there but I’m gonna just mark it at the edge. And do the same on the other edge. Even though this is my last mark here and I don’t have any more out here, I’m going to pull this batten down just a little bit and tap another nail in there to kinda complete that curve. If you don’t, the end will kind straighten out on you and make a flat spot in this curve up in here. Looks good. Okay, so there we are. So there now we have the shape of the plank. You can see it’s quite wide at this end, tapers down on that end and has a gentle curve to it. As often is the case, the top of the plank is bowed up instead of what you’d think. Normally when you look at boat you’d think the top would bow down but often that’s not how it ends up.

– [Narrator] In Part Two, Peter will show you how he cuts and shapes a plank now that it’s edges have been drawn out, so stay tuned.



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