Are cant frames single or double

[Don Case]

See title😉

[Jaager]

I have not seen any that are double. 

 

The cants are generally single and mostly near straight, so one piece of timber will cover the length. No butt joints. Each heels to the deadwood at a different angle and all of the edges sit against the neighbor on either side.  A folding paper fan sort of effect when viewed from above. The goal is to have the face square with the main waterline.  This saves wood and the bevel is at the heel.  My money is on there being a liberal use of chocks in the space between each frame. 

 

I do not employ them. I stay with whole bends up to the FP.  In most of the zone where cants are, I use solid wood where the spaces would be.  There is significant bevel and a lot of loss of wood. At model scales, this does not matter.  With the chocks in the real ship, the side view was probably close to my solid wall zone - except that the bevel makes each frame appear to be much wider than a cant frame.

 

 

[druxey]

It all depends on country, era, etc.

[Bob Cleek]

1 hour ago, druxey said:

It all depends on country, era, etc.

And the shape of the bows, and what timber was on hand at the time, which decreased in size as the forests became consumed by a wooden navy's prodigious consumption of timber. When there came to be less large trees, ships came to be built of smaller pieces and hence scarfs and doublings increased. When it came to the point that ships became so large and the timber so small that the number of scarfs in a keel were insufficient to hold a ship's shape for long and her ends began to sag, or "hog," shipbuilding engineers like the famous Seppings began to devise ways to engineer construction to build rigidity into the hulls which was derived from devices like specialized knees and diagonal strapping. For a wonk, reconciling the changes in ship design and construction with the increase in the size of ships and the consequent decrease in the size of available trees is a fascinating study.

[Don Case]

2 hours ago, druxey said:

It all depends on country, era, etc.

Sorry, I keep forgetting that. England late 18th century.

[allanyed]

Jaager

When you say no butt joints, do you mean they were made of a single piece of timber or with futtocks but with chocks or scarphs?    Would love to see more contemporary information on this, especially  for the earlier part of the18th century when cants first came into use.   

Thanks  

[Mark P]

Good Evening Don;

 

In the English Navy, cant timbers continued the pattern of the main frames, in that (for example) two filling frames were followed by a double frame (I hesitate to call a double cant timber a 'bend') The pattern of scarph joints was continued from the square frames, except in the lowest timbers, which no longer had to straddle the keel, so the lowest scarphs were no longer needed. The uppermost joint was normally a plain scarph joint, without a chock, as with the square top-timbers.  

 

The longest futtocks of the double cants were called 'half-timbers'. This may also have applied to those of the filling frames, but my memory not powerful enough to recall this for sure (need a few more MB inserting) 

 

See below an excerpt from a framing plan which shows the bows of Andromeda of 1784

 

The dashed line is the station line of the cant, centred on the joining faces of the double frame. Note that the station line location, as drawn at the keel, did NOT give the position of the station line at the keel, but at the height of maximum breadth. For example, in the clip below, the 'S' near the boxing is not below the bottom end of the dashed line, but is vertically below the line of station 'S' at the foremost point, which is the maximum breadth (note that this does not work any longer as the maximum breadth becomes, in theory at least, the flared out part of the top-timbers)

 

All the best,

 

Mark P

 

[druxey]

Those joints were normally chocked at that time period. Chocks are more economic; not only do they uses up offcuts of timber but, with thoughtful layout, the individual floors and futtocks could be a little shorter than if they had been scarphed.

[Don Case]

17 hours ago, Mark P said:

Good Evening Don;

 

In the English Navy, cant timbers continued the pattern of the main frames, in that (for example) two filling frames were followed by a double frame (I hesitate to call a double cant timber a 'bend') The pattern of scarph joints was continued from the square frames, except in the lowest timbers, which no longer had to straddle the keel, so the lowest scarphs were no longer needed. The uppermost joint was normally a plain scarph joint, without a chock, as with the square top-timbers.  

 

The longest futtocks of the double cants were called 'half-timbers'. This may also have applied to those of the filling frames, but my memory not powerful enough to recall this for sure (need a few more MB inserting) 

 

See below an excerpt from a framing plan which shows the bows of Andromeda of 1784

 

The dashed line is the station line of the cant, centred on the joining faces of the double frame. Note that the station line location, as drawn at the keel, did NOT give the position of the station line at the keel, but at the height of maximum breadth. For example, in the clip below, the 'S' near the boxing is not below the bottom end of the dashed line, but is vertically below the line of station 'S' at the foremost point, which is the maximum breadth (note that this does not work any longer as the maximum breadth becomes, in theory at least, the flared out part of the top-timbers)

 

All the best,

 

Mark P

 

So in this case the station of the cant frame is the shape of the frame but not the actual ship? Does the body plan reflect this or is the body plan still the shape of the hull?

[allanyed]

Don,  simply put the station lines that you see in the body plan are not the shape/size of any frame except for those square frames that happen to fall on a station line.   For the cant frames, none of the station lines are the shape of a cant frame as the cant frames are, well  ...... canted.....  and the station lines are not.  If you read Wayne Kempson's article in the Articles Data Base here at MSW, he explains in more detail on pages 74-79 how to draw the cant frames.

Edited April 25, 2021 by allanyed

[Mark P]

Good Evening Druxey;

 

You are quite correct about the rationale behind the use of chocks, they do enable the use of shorter or less curved timber. However, by reason of the top-timbers having little curve, and, especially towards the stern, being almost straight, the use of chocks conferred little advantage from the point of saving timber, and actually involved more work, in that cutting chocks and their mating joints involves four angled cuts, whereas a scarph involves cutting only two. 

 

John Fincham, who was headmaster of the Naval Academy at Portsmouth, illustrates this very clearly in the plates which accompany one of his books (can't remember which, unfortunately!) His plate shows the practice in the time shortly before Seppings' reforms introduced the dowelling together of futtocks, but is certainly applicable to much earlier decades, for the reasons outlined above. I have also seen earlier illustrations showing the same thing, and have seen it in written descriptions. 

 

All the best,

 

Mark P

 

 

Edited April 25, 2021 by Mark P
apostrophe in the wrong place!

[Mark P]

Good Evening Don;

 

To expand upon Allan's quite correct explanation, the dashed line shown in the framing plan in my earlier post is the profile of the station line of the double cant timber, when viewed from a point square to the keel. It does not represent any line shown on the body plan, and is obtained by extrapolating from the cant timber lines as drawn on the half-breadth plan.

 

The dashed lines of the cant stations are never shown on the main draught of the vessel, and only appear on the framing plan. 

 

All the best,

 

Mark 

[Jaager]

I was describing some of the English 18th century versions of cants that I have seen.  The "no butts" part was about a model shortcut, as I was flashing on how to do the timbers.  It was not about actual practice -sorry for the misinformation.

Not many of the Navy Board framed models from the later 17th century seem to have replicated cant frames -I take my inspiration from them, so I do not model cant frames.  Flying a black flag here, I will admit that I have little interest in modeling any structural part not visible from a completely planked and completely decked hull.  The below the wale open framing is an obsession of mine, but I do that with an eye towards Art, rather than literal replication.  My money is on the actual internal structure of most ships being a lot irregular and not all that pleasant to look at.  The regularity and neatness of the plans was probably more of a wish.  There was probably a focus on economy and practicality and making do with the stock on hand.

Building demonstration models for shipbuilding  classes of teenage midshipmen I will leave to others.

[druxey]

Mark: Certainly some toptimbers were scarphed, but I repeat that I've not seen too many delineated this way (with the 'X') on disposition of frame drawings. The ones that show this are later rather than earlier.

[Mark P]

Good Morning Druxey;

 

I don't possess as many disposition of frame drawings as I would wish, most regrettably, mostly dating from the 1780s. On the majority of these, while the joints in the lower futtocks are indicated by a single line, the uppermost joints, to the shorter top-timbers, are indicated by two lines, the correct distance apart for a scarph, with the lower line frequently dashed. This difference in treatment can only indicate a scarph joint as opposed to a chocked joint. The earliest of those which show this is Bombay Castle, dated Navy Office 1779. On only one frame plan are Xs drawn between these two lines, though, which would indicate to me that an X was not always shown.  

 

This has also been described in writing, but I cannot recall if this was in a modern or contemporary work. It would certainly be interesting to know how far back this method extended. 

 

All the best,

 

Mark P 

[druxey]

Mark: I agree that the solid line/hatched line is another way to delineate a scarph joint (without the 'X'). Also, that there are regrettably few early examples of disposition of frame.

[allanyed]

21 hours ago, Jaager said:

Not many of the Navy Board framed models from the later 17th century seem to have replicated cant frames -I take my inspiration from them, so I do not model cant frames. 

Thanks Jaager,

I agree as I don't believe there are any 17th century ship models with cant frames as they did not come into general use until the 18th century (about 1715, according to Goodwin)   

[Mark P]

Good Evening Allan;

 

1715 it was; surprisingly, although saving timber was one reason for adopting this measure, the main consideration seems to have been to prevent decay, which was more prevalent in these areas. Perhaps because a square frame with a large bevel results in a much longer mating surface between the frame and the planking, thereby trapping more moisture than would a canted frame with its shorter mating surface.

 

All the best,

 

Mark