08 February 2010

Lining Off

Resuming our Tale of Two Boats...

The Blue Moon's hull being painted, I relaunched her, splashing half a bottle of Blue Moon beer on her bow (no need to waste the whole bottle!)

Then Bob and I motored her down to her temporary new home -- a dock in the Steinhatchee River. With her long bowsprit, the slip was a bit short for the Blue Moon, so we had to back her in. NOT an easy thing to do with her long keel and small motor.

The motor did manage to get her moving backwards... slowly... but turning was a whole other thing. Fiddle with the rudder as much as we might, her long, deep keel kept her moving in a straight line. There was no way I as going to be able to back her into the slip, even without the current and cross wind.

If I'd had Cabin Boy with me, I would have warped the Blue Moon into the dock, neat as you please. But being dingyless, we had to depend on the kindness of the 5 or 6 bystanders who had gathered on the dock to comment and watch the show.

It wasn't elegant, but we eventually manhandled the Blue Moon into her slip, without scratching her lovely new paint.

Blue Moon in her temporary berth
photo jalmberg

I still need to paint the deck -- with a combination of white and that nice Bristol Cream used on the rail and waterline -- but I was out of time. I needed to get back to New York where Helena, kids, and business concerns all needed attention.

So, leaving Blue Moon tied up and in the capable hands of the marina (with Bob available to check up on her occasionally), I headed back to the frozen north and Cabin Boy.

The next step in building Cabin Boy was to plane the chine logs flat, so a straight edge (in lieu of a bottom plank) lies flat on the chine logs and keelson. 

Before planing, the chine logs are edged inwards (see photo, below). A straight edge (2x4) doesn't lie flat on the chine log. It sits on the chine log's edge.  I needed to take off that edge.

Straight edge (top) sits on edge of un-planed chine log
photo jalmberg

The right tool for this job was my nice wooden plane. I didn't take a lot of time over this. I just planed the chine logs by eye so they 'looked' flat, and then checked then with a straight edge (the edge of a 2x4.) 

Planing the chine logs so they are flat and level with the keelson (in background)
photo jalmberg

And here's how one of the chine logs look after planing. See how the straight edge now sits flat on the chine log. It's not a lot of work. We're talking about 10-15 minutes with a hand plane. Easy peasy.

Chine log planed flat
photo jalmberg

That done, the next step was to 'line off' the hull. 

Now, if I'm honest, I have to confess that I didn't really need to plane the chine logs before lining off the hull. I was just procrastinating, because I really didn't know how to tackle this 'lining off' thing.

Lining off is the process of deciding where the planks on your boat are going to go. It is one of those "more art than science" parts of boat building. One of those chapters where the Boat Building Books all go fuzzy with talk like "if it looks right, it is right".

Okay, fine. I get that. That's how you know when you are done. But how do you begin? I had no idea.

Like many things, you just need to start and see how it goes. I've often noticed that you never really know how to do something until you've done it. It's a chicken-and-egg problem, and the only way to crack it is to start, even though you don't know how to start. You just need to jump in and start working at it, trusting (hoping?) it will all become clear in the end. 

To get rolling, I noticed that Cabin Boy's plans included a profile drawing that showed an exterior view of the 4 planks. This was a good clue. The profile did not show the whole plank -- in particular, it did not show the parts of the planks that were overlapped. This is a lapstrake (or clinker) design, remember. 

However, I reasoned that if I allowed a 'standard' overlap of, say, 1", then it would be possible to measure the width of the planks right from the profile drawing, using my architect's rule.

For some reason, this process was extremely time consuming. Mainly because I made every mistake possible, including forgetting that the profile plan was right side up, and the boat was up side down. Yes, I measured the dimensions of the shear strake (the plank at the top) and used them to measure the garboard plank (the plank at the bottom). Luckily, I wasn't holding a sharp tool when I discovered this error. Duh!

However, after numerous errors and false starts, I had the 'first draft' of my lines, laid out with battens on the forms. Whew!

(By the way, I still haven't found a way to cut battens that I'm satisfied with. I'm using my bandsaw to cut them out of reasonably straight-grained white pine, but its not easy to cut a perfectly straight, 8 foot line, so my battens are full of waves and bumps. I know they look straight in the pictures below, but believe me, they are not. 

If you have a system for cutting nice, straight battens, please share it with me by leaving a comment below, or emailing me at john@unlikelyboatbuilder.com.)

Lining off by science and mathematics... a good first draft
photo jalmberg

Anyway, I call the above 'first draft' because this is as good as I could get the lines using science and mathematics. And it wasn't quite good enough. If you study the photo above carefully, you'll see what I mean. The lines just aren't right.

Yes, I measured the profile plan as carefully as possible, and I laid out the measurements using as much precision as possible. But, apparently, science and math can only get you so far when lining off. I needed to turn to art.

By 'art', I mean eye. I had finally reached the point where the Boat Building Books made sense to me. The only way to finish the job was to move the battens around until they 'looked' right. 

Amazingly, this was much easier than I expected. After pulling a few tacks and letting the battens 'flow' around the molds as they wanted to do, rather than forcing them into my mathematically 'precise' locations,  they suddenly looked 'right'. 

Lining off by eye... better!
photo jalmberg

So, once again, I have to report that olde-time Boat Building Masters knew what they were talking about. Your eyes and your battens will tell you what to do if you just give up a bit of control and let them speak. Don't fight them.

Tomorrow, another frighting task: spiling the planks. I have no idea how to do this, but apparently I'm not going to let that stop me.


Next Episode: A Garboard Tragedy - Act 1

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  1. That's right; go with the flow. The nice thing about straight grained battens is that they will generally help you find the right curve if you don't constrain them too much.

    On getting straigt battens ... It's very unlikely you'll ever saw then straight, even with a table saw. Too thin and whipity-whipity. I found a good technique was to saw as closely as possible, and then let that nive long jointer plane do the rest of the work. Only takes a couple of passes per side and you have a collection of nice battens in less than 30 minutes.

    If you would like a bit of moral support with spiling, let me know. It's not that hard and we could talk through it by phone. You have my email address.

    See page 160 in Greg Rossel's Small Boats book for a detailed approach to spiling carvel planks. Then, move to page 178 for the lapstrake equvialent.

  2. Re: straight battens - why not take a board, plane one edge flat, rip to just over the finished width on the table saw, and then run it through a surface planer to finished width? Perhaps that is more power tools than you would like to deal with, but I think the same thing could be accomplished with hand tools, especially since the batten you want is not terribly long.

  3. As a novice boatbuilder with limited tools, i found a method of cutting battens on a table saw that works for me. I cut battens from a 2x4x8, setting my rip fence at 1/8", and use a feather board to keep the 2x4 true against the fence. Use a good blade, ideally with stiffening discs installed, go slow, and make sure you work is supported on both ends of the saw. In 10-15 minutes you'll have 12-14 battens, depending upon the kerf of your saw.

  4. If I only had a table saw... I should probably get me one of those :-)

    Planing the curvy side(s) of the batten after cutting just might work. The tricky bit will be to clamp it to my bench firmly enough so it doesn't wriggle out from under the plane.

    Will have to try that and see how it works.

  5. I just read through the entire blog, it is fascinating, you are doing a very nice job and the improvement in your workmanship is very easy to see. I'm a carpenter with some marine carpentry experience so it's not entirely empty praise!

  6. Thanks! I've been working on this spiling problem for a couple days now, and think I've just about got it licked.

  7. Hi, I'm about to start my first boat building project, probably on about the same scale a boat as the 'Cabin Boy'.
    Yesterday I was reading Iain Oughtred (Clinker Plywood Boatbuilding Manual) and he describes a somewhat mathematical approach to dividing the strakes over the girth :)
    His rule of thumb is the width of the sheerstrake is some 70% of the width of the garboard. The other topside strakes equal the sheerstrake and the ones in between (the broadstrake and eventually some one or two more) are narrower than the garboard but wider than the sheerstrake. And all this depends on the bilge form... Then he comes up with a kind of graph to lay it all out nicely.

    Anyway; if you like to study upon planking, the book is recommended.

  8. Erwin: there's lots of ways to skin this cat, but in the end, it's how it looks that counts. Enjoy your build!


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