Bearding and Rabbet lines

[shortgrass]

Can someone explain the actual procedure for cutting a bearding line and rabbet line for planking.  I understand the logic for cutting these lines to make the planking lie more evenly and smoothly.   I just have a difficult time understanding how deep to cut the bearding/rabbet lines; how close to the false keel, etc.  Would appreciate any and all feedback.

[druxey]

An appropriate reply would take a lot of electrons to answer your question in detail. Might I suggest a good volume on building a model like a full-size ship. Some suitable books:

 

The Anatomy of Nelson's Ships, Longridge

HMS Euryalus 1803, Volume I, Yedlinsky

The Naiad Frigate, Volume I, Tosti

The Fully Framed Model; HMN Swan Class Sloops 17670-1780, Volume I, Antscherl

 

 

 

[Gregory]

 

 

Here is a basic drawing from some of the  ModelShipways kits.

 

The idea, is that the final planking fits flush with the keel and stern post.  So the depth depends on the thickness of your planking material and whether or not you will be

doing single or double planking..

 

For instance, if the keel piece is 3/16  and your total planking material is 1/16, you would want the bearding line and rabbet  to be recessed 1/16 on each side of the keel piece.

Regardless of the thickness of the keel piece, the depth of the bearding line and rabbet needs to be the thickness of your planking.

 

There is tapering to be done, but you have to refine that as you go along.

[allanyed]

Also keep in mind that the shape of the rabbet is dynamic, never being the same angle along the length of the keel except in the area of the dead flat.  The angle should match that of the frames/bulkheads where they end at the keel/rabbet line.   There is more to it depending on the era as the keel itself changed over time as well.  For a kit, the same basic idea should apply, though.  The following was posted in the past but this may help you avoid a search.

Allan

 

[Bob Cleek]

No matter how you cut it, cutting the rolling bevel in a planking rabbet (sometimes called a "rebate") is a tedious process that takes some thought and care. You will find lots of theoretical instructions in boat building and modeling books about how to do it using the information that may be developed using lofting techniques. The exact angle of the rabbet can be developed for any point along the rabbet's length from the lofting (or lines drawings) and from that the rabbet, back rabbet, and bearding lines can then be developed and drawn or lofted. These varying angles define the shape of the rolling bevel that forms the rabbet. In small craft and model construction, there's an easier way to cut the rolling bevel without reference to the drawn or lofted the rabbet lines at all. Experienced boat wrights dispense with a lot of the lofting by "building to the boat," as  they say, rather than "to the plans." With the planking rabbets, this means that the angle and depth of the rabbet at any given point along the rabbet is developed using "fit sticks" and battens to define the rabbet lines and the bevel's rolling angles. It's easier done than said.

 

What you do is frame out your boat or model. Take care, as is always necessary, to fair the frame face bevels. This requires setting up the frames and sanding the faces so that a flat batten laid across the frames in a generally perpendicular relation to the frames, as well as at lesser angles, will always lay flat against the frame faces. (You may need to place temporary blocking between the frames or otherwise secure them well so they don't wobble when you sand across them.) Your frames should be cut and set up as in full size practice, with the corner of the outboard-most side of the face precisely cut and set up on the section lines such that when fairing wood is removed from the forward side of the faces of frames forward of the maximum beam and from the after side of the faces of the frames aft of the maximum beam. The accurately cut frame corner, the forward corner on frames aft of the maximum beam and the aft corner of frames forward of the maximum beam, is the reference point for fairing your frames. Use one batten for marking the faces of the frames and another, with a suitable sheet of sandpaper glued to its face, or a manicurist's emory board, to sand the excess off the faces until they are fair. The batten used for marking is chalked with carpenter's chalk and rubbed against the faces of the frames to mark the high spots. Where the colored carpenter's chalk transfers from the marking batten to the frame faces is where the frame face is too high and needs to be sanded down some more. When the marking batten lies flat in contact with all the frame faces, transferring chalk to the entire frame face, the frame faces are fair.

 

Now, with your frames faired, take a small stick of wood the same thickness as your planking and cut across at the ends perfectly square, which is called a "fit stick," and place it against the face of a frame and slide it down until the lower back corner of the fit stick (the inboard corner) rests against the keel. Accurately mark the point where the corner of the fit stick and the keel meet. This mark is where your bearding line is at that point.

 

Then take a second fit stick and place it on top of the first with the first in the position it was in when you marked the bearding line point and slide it down over the first fit stick until its lower back (inboard) corner touches the keel and mark that point. This mark is where your rabbet line is at that point.

 

Make these two marks at each frame. Spring a batten between all the upper and lower marks on the keel and draw lines through all the marks. These lines will be your bearding and rabbet lines. Extend them out as far as they will go, but, for the moment, they are relevant only for the span from the forward-most frame to the after-most frame.

 

Now, at each frame, with your two fit sticks stacked as when you marked the lower rabbet line, take a knife or chisel and using the lower edge of the upper fit stick as a guide, cut into the keel at the same angle as the face of the bottom edge of your upper fit stick, i.e. with the flat of your blade against the edge of your lower fit stick. This cut should be as deep as your planking is thick. (This first cut can be easily made with a small circular saw blade on a rotary tool if you know what you're doing. Mark the blade face with a Sharpie to indicate the depth of cut.) Cut down to the point of the rabbet cut you've made from above so that you end up with the back rabbet face of the keel at a right angle to the rabbet line cut.  Test your cut with a fit stick, which, when the rabbet section cut at that frame is done, should lie perfectly fair on the face of the frame with its bottom edge fit perfectly into the rabbet you've cut. Because the angle of your rabbet is defined by the lower edge of the top fit stick and it's depth by the thickness of your planking, there's no need to worry about where the back rabbet line is. You'll develop the back rabbet naturally when the two lines you are cutting to meet at right angles at the bottom of the cut.

 

Now, you simply "connect the dots" or rabbet "notches" you've created at each frame by carving out the wood in the way of the rabbet and bearding lines between the frames to form a continuous rabbet with a fair rolling bevel.

 

The stem, deadwood, and stern post are a bit trickier than the sections where the frames are set up on the keel, but the method of marking them and taking the rabbet angles off of fit sticks is the same and shouldn't need much further explanation. The main difference is that a batten of the same thickness as your planking is place across the frame faces, rather than perpendicular to the frame faces, and extended to where its bottom inboard edge touches the stem, deadwood or stern post and is marked there for the bearding line, and then another fit stick batten is placed on the first to find the rabbet line. You will find a chalked marking fit stick batten to be handy again in fairing up the dubbing on the wide deadwood rabbets. These techniques are a lot easier to learn by doing than to explain in writing. 

 

On a real vessel, cutting the planking rabbets is a very exacting process because the ease of caulking and the watertightness of these seams are dependent upon the perfect fit of these faying surfaces (where the planks and keel touch.) This isn't a big consideration in a model. What's important for a model is only that the visible rabbet lines and the planking are fair and tight. If the angle is off behind the planking and a bit too much wood is removed, it makes no difference because a sliver can always be glued in place to raise the plank to where it has to be and the rest filled with glue, or if too little is removed, the plank face can be sanded fair after it's hung. (The latter being the less preferable. It's generally better to remove wood from behind the plank than from the plank itself.)

 

This may seem like a tedious exercise and it is, but doing it correctly will make your planking a far easier task, particularly in hull forms where there is considerable twist in the planks at the ends. A final word of caution for the modelers with a machinist's background: This is a hand job. You won't find a way to do it more easily on your mill. Many have tried to devise some sort of jig which would permit cutting these rolling bevel rabbets with saws, routers, or other power tools. As far as I know, and those I know who know a lot more about it than I do, nobody's succeeded. Don't waste a lot of time trying to figure out what nobody else has been able to accomplish. I expect that it could be accomplished, in theory, at least, with very sophisticated CNC technology, but would probably take a lot longer to program and set up than doing it by hand will.

 

This video of full-sized construction illustrates the method described fairly well:  

 

 

 

[mgdawson]

Hi shortgrass, there are a few wooden boats being built / rebuilt with regular youtube updates. Two i’m following are the ‘Sampson Boat Co‘, where an english shipwright is rebuilding a 130 year old yacht, ‘Tally Ho’ in Oregan and ‘Acorn to Arabella’ where a couple of blokes are building a 1930s(?) yacht design from scratch, including harvesting most of the timber from their property. Both are explaining the how and why.

Look around episode 60 in the former and episode 45 in the latter for cutting the rabbet. I could be an episode out in either direction for the explanation you’re looking for, i watched those episodes quite a whiles back.

Mark

[shortgrass]

I am working on an older kit - the USS Independence by A/L  Seeing the mistakes in the kit (and the ones I have made), I am trying to get a better idea of how to approach my next build.

[wefalck]

I think there are two simple geometrical answers to the question - which doesn't mean they are easy to achieve. However:

 

- the rabbet has to be so deep that the planking lands on the keel/stem without step, i.e. neither the planks nor the keel may be proud of each other

 

- the included angle between the two surfaces of the rabbet should be around 90"

[vaddoc]

Take a small piece of plank material, rest it on the frame, slide it down on to the rabet line, cut the bevel so the plank thickness is all in the rabet groove, with the plank piece resting on wood in both surfaces. Do the same for all frames (the angle will constantly change). Connect all the rabet segments you ve cut eyeballing things and/or using pieced of plank material. Rabet done

[Gregory]

There is also the option when building a POB kit, of using an offset strip a'la Chuck, down the center of the backbone ..

 

 

Image from Chuck's Cheerful instructions.

 

 

Notice the groove created by the rabbet strip, that serves as the rabbet at the stem.

 

Of course, kits that haven't provided separate parts for the stem, keel and sternpost, would not lend itself to this method.

[Der Alte Rentner]

On 9/22/2020 at 5:33 PM, Gregory said:

There is also the option when building a POB kit, of using an offset strip a'la Chuck, down the center of the backbone ..

 

 

Image from Chuck's Cheerful instructions.

 

 

Notice the groove created by the rabbet strip, that serves as the rabbet at the stem.

 

Of course, kits that haven't provided separate parts for the stem, keel and sternpost, would not lend itself to this method.

 

[Der Alte Rentner]

What a fantastic shortcut.  I was planning on trying to cut a notch the entire length of both sides of the false keel, which would have required my making a couple of patterns and setting up a pattern bit on a routing table.  This is SOOOO much easier!

 

Thanks for the tip.