Bevelling the frames

Bevelling a batten notch in frame 1
You can see the notch in this frame for the batten is sloped at an angle to match the angle at which the batten crosses the frame.

After my last post, I had a few questions about how to handle the joint where pieces like the chine cross the frames.  The chine, battens and sheer clamp are notched into all the frames.  The notches are pre-cut at 90 degrees to the face of the frames.  But in certain areas, particularly forward of say, frame 4, these pieces cross the frames at an angle that is increasingly far from 90 degrees.  Ultimately, these pieces (chine, battens, sheer clamp) all need to be securely fastened to the frames.  A little old edge like the corner between the face and the thickness of a frame hardly makes for good construction.  So what to do?

There are two possibilities, right? You can either add wedges at the joint or you can cut away some of the frame so you have a solid landing for the piece over the full thickness of the frame.

I had to look up how to spell “bevelling” for this post.  While I was there, of course I noticed the definition of bevel: to reduce a square edge on an object to a sloping edge.  I couldn’t have said it better.  Bevelling is the right choice here.  Stay with me and I’ll explain why.

Let’s take a moment to re-visit the lofting process for this boat.  Lofting, you’ll remember, is taking the lines from the plans, and enlarging them to the actual size of the boat.  When we did that, we drew cross sections of the boat at 10 different “stations”.  We did it so we could make patterns for the frames.  The outline of these patterns is the exact shape (less the planking thickness) of the boat at each of these stations over the length of the boat.  So far so good.  But here’s the rub–our frames are 3/4 inch thick and the boat gets smaller towards the front and rear (forward and aft for the purists out there).  So where do you put the frames exactly? Forward of the station line, aft of the station line, or split the difference?

The answer is … it depends.  As you move from the front of the boat to the rear, you notice that the boat gets bigger until you reach about frame 4.5.  Then it starts to taper aft.  So you place the thickness of the frame forward of the station line for frames 1 through 4.  Frames 5 – 10 are placed aft of the station line.  In other words, you frame forward for 1 – 4 and frame aft for 5 – 10.  The aft face of frames 1 -4 creates your reference edge.  The forward face of frames 5 – 10 creates your reference edge.  Look at that again and make sure you get it.  It’s key.

The reference edge is the exact shape of the boat at that place along the length of the boat.  You do all of this so you can bevel the frame to provide a good joint between it and the hull.  So bevel the notches first, then use that as a guide to bevel the entire frame where it contacts the hull.

Now take another look at the picture.  It’s a picture of frame 1, which is in a frame forward section of the boat.  And the notch for that batten has been properly bevelled to contact the batten over the full thickness of the frame so you have a good surface to glue the two pieces together.

Tool for bevelling
This tool is intended to be used to grind off welds. But I find it works great for bevelling. And the belts last forever in wood as opposed to metal!

Incidentally, here’s a picture of the tool I use for most of my bevelling.

Easy peasy, huh?  Yeah, I know.

5 Replies to “Bevelling the frames”

  1. Got it, nice tip, thanks! Bevelling the notches is easy but bevelling the whole frame sounds like a tricky job with the concave profile of the forward frames. Are you planning to use an electric plane with a convex foot?
    I noticed from your previous post that you’ve also beveled the stem. Did you notch it also where the chine and battens join?
    Finally, I noticed some old batten notches that have been filled in, is there a lesson there for the rest of us?

    1. You’re right Steve — bevelling a concave curved frame with a block plane is worse than tricky. I’d say impossible is a better word! I use a pneumatic tool with a 1/2 inch wide belt to do my bevelling of the frames and frame notches. I’ll try to post a picture of it in the article above.

      I’ll notch and bevel the chines where they intersect the stem, and perhaps add a chine breasthook to make it extra stout. The battens will be bevelled where they join the stem.

      I’m glad you noticed that the stem is bevelled. This was done by developing the “bearding line” on the lofting and transferring it to the stem blank. You’ll remember we used the lofting board to glue up the stem to it’s proper curve. Check out that blog entry if you haven’t seen it yet. The result is that the outboard face of all the framing creates a smooth, fair plane that the inboard face of the planking fits to.

      As to the plugs in some of the notches, I pre-cut the notches because they were included in the digital plans I worked from. The traditional way to do this is to use a batten, and notch the frames in place after they’re already set. For some reason, the notches on the forward frames didn’t line up so I had to plug them and use the batten approach to work out the placement of those notches.

      1. Thanks Tim! I’m glad I asked you about the filled notches because we also used a set of digital plans to construct our 1/5 model and I was puzzled by the discontinuous batten run at the bow especially the one just below the chine. In my inexperience I assumed the plan was correct and pressed on and it looks bad. We now have the original Nelson Zimmer plans from The WoodenBoat Store so we can discover lofting (at 1/5 scale) and check the frames and discover the bearding line!

  2. Thanks for the blog, Steve above and I are embarking on building a model first, although I’ll be building the real thing. I’ll be investing in a decent band saw, although I was thinking of rough cutting the frames with my bench saw set at an angle then finishing with a hand plane. I must admit I’m a novice to boat building, but pretty handy with timber.

    1. Hi Mark,
      I didn’t bevel the frames before I set them, electing instead to bevel them in place a batten lying across the frames to give me the proper bevel angle. You can, of course cut the bevel into the frames when you make them and some builders do this. As a matter of fact, if you’re curious, see if you can find a youtube of someone using an old Ship Saw to cut a rolling bevel on large wooden ship timbers. It’ll blow your mind!

      If you haven’t already, you should get yourself a copy of “The Gougeon Brothers on Boat Construction”. It’s the best investment you’ll make. The chapter on Lofting is the best I’ve come across. They tell you how to determine the proper bevel angle from your lofting. Let me know how it turns out!

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