Naseby 1655 - reverse engineering the ship model

.​
DonatasBruzas said:
A list of tools you need to calculate a ship hull - an outline for a Treatise or a Doctrine:
Click to expand...

Personally, I think that algebra in common practice could then have been used primarily to define the main, longitudinal design lines in order to precisely determine the coordinates of only the main points for the individual frames (ie. floor, breadth, tops). In contrast, the contours of the frames themselves would already have been left to be traced geometrically on the mould loft. A kind of practical compromise. We have modern, high-speed tools to do the calculations fast, but they would then simply drown in calculations of many thousands of points. What do you think?

.​
 
-Waldemar- said:
.​


Personally, I think that algebra in common practice could then have been used primarily to define the main, longitudinal design lines in order to precisely determine the coordinates of only the main points for the individual frames (ie. floor, breadth, tops). In contrast, the contours of the frames themselves would already have been left to be traced geometrically on the mould loft. A kind of practical compromise. We have modern, high-speed tools to do the calculations fast, but they would then simply drown in calculations of many thousands of points. What do you think?

.​
Click to expand...
Yes, I agree. They needed center coordinates and radii to make life size templates. Maybe knowing where your arcs touch would help a lot as well and could even make it possible to work around the centers - as the radii are really large. The sagitta and chord length would help you then :)
As I do not have enough space on the floor - I generate points to create my own 'templates'.
 
.​
DonatasBruzas said:
The sagitta and chord length would help you then
Click to expand...

This very skill would also certainly be particularly useful for selecting curved timbers for construction as well. I've already posted this graphic from the early 18th century in another thread recently, but it's very fitting here too, as it shows the process you write about graphically.


inoruk_f266t8_128.jpg​

.​
 
OH BOY I AM GOING SAY IT AGAIN THE BEST INFO ON WHAT IS GETTING TO SOME BORING STUFF ON SOS. PLEASE KEEP IT GOING JUST LOVE THE VARIOUS TYPES OF SHIP CONSTRUCTION DUTCH, ENGLISH MAYBE COMINGT UP SPAIN, FRENCH, EVEN USA MEDITERRANIAN AQLSO. JUST KEEP- IT COMING. GOD BLESS STAY SAFE YOU AND YOURS DON
 
-Waldemar- said:
.​


This very skill would also certainly be particularly useful for selecting curved timbers for construction as well. I've already posted this graphic from the early 18th century in another thread recently, but it's very fitting here too, as it shows the process you write about graphically.



.​
Click to expand...
This collection is a very interesting resource. It took me some time to find it :D
 
.​

DonatasBruzas said:
This collection is a very interesting resource.
Click to expand...


Yes, I would also say: extremely interesting! Shows not only projects being done in a standard, "classical" ways then in practical use (as opposed to some sort of fantasies), yet at the same time it uncovers and explains so many design details, meaning ways of achieving the desired design effects that one would look for in vain elsewhere.

In addition to this fantastic collection, Martes also recently showed me two other very interesting designs for ships of the line (a 50- and a 60-gun ship) from this very period, made by a designer of English origin and reviewed by Peter I. Again, designed quite typically by standard English moulding, yet of an quite unprecedented tactical-operational concept, as they were intended to operate in difficult, shallow Finnish waters.

.​
 
.​
DonatasBruzas said:
Now I have a script which needs some meticulous work to translate drawings into a written form (like describing what you see by using a limited set of 'words'). It does not have any validation, so it would not tell you that your circles could not be reconciled if they radii were to small. But then it also does not require you to do any mathematical calculations at all - it will give you sets of 3D points automatically :)
Click to expand...

Donatas, I want to show you an example of a similar problem that I also sometimes encounter. This time it is about the line of the floor aft of a French frigate of 1686. It is interesting to note that an identical anomaly is also present in the definition of this line in the Royal Regulation of 1673. For the quarter frame aft, it prescribes 2/3 of the width of this line at the master frame. However, while maintaining geometrical rigour (that is, tangency at point B), it generates a concave arc between points A and B, and this in turn creates concave hull surfaces in this area, which was then as now obviously unacceptable.

This can be solved in basically four ways (assuming only circle arcs and straight lines are allowed):

– one can ignore the Royal Regulation and increase this 2/3 ratio to a slightly larger one, which will at least give a straight line between points A and B,
– one can simply draw a straight line connecting points A and B, but then a kink will occur at point B,
– one can increase the radius of the arc between points B and D, but then this arc BD will not be tangent to the horizontal line at point D (in other words, there will be a kink at point D),
– it is also possible to draw a straight line from point A to the tangent point C (in black), which will effectively increase the width of the floor at the quarter frame aft, quite like in the first solution.

In the end, I opted for the fourth solution in this particular case, but perhaps more interesting here is the reminder that sometimes taking these kinds of documents (regulations, ordonances, treatises, manuals, etc.) too literally can easily lead astray.


ViewCapture20240601_010001.jpg​

.​
 
Last edited:
.​

... naturally, it is still possible to reduce the width of line of the floor at the master frame, which is what the designer actually did when drawing the plan (see the arc well visible on the original plan just above the green arc), most likely for this very reason. But then there is no correspondence between the plan (19 feet) and the accompanying, written memorandum for this line (20 feet).

I have also found, again from a couple of other clues, that this plan, despite its appearance of naivety, was in fact drawn quite accurately and by contrast some of the values in the memorandum are rounded. On top of this, on the plan, the contours of the frames are also drawn according to the 19 feet value. Which raises the dilemma of which width of line of the floor is actually correct and should be chosen, the one taken from the written memorandum or the one read from the plan.

.​
 
Last edited:
-Waldemar- said:
.​


Donatas, I want to show you an example of a similar problem that I also sometimes encounter. This time it is about the line of the floor aft of a French frigate of 1686. It is interesting to note that an identical anomaly is also present in the definition of this line in the Royal Regulation of 1673. For the quarter frame aft, it prescribes 2/3 of the width of this line at the master frame. However, while maintaining geometrical rigour (that is, tangency at point B), it generates a concave arc between points A and B, and this in turn creates concave hull surfaces in this area, which was then as now obviously unacceptable.

This can be solved in basically four ways (assuming only circle arcs and straight lines are allowed):

– one can ignore the Royal Regulation and increase this 2/3 ratio to a slightly larger one, which will at least give a straight line between points A and B,
– one can simply draw a straight line connecting points A and B, but then a kink will occur at point B,
– one can increase the radius of the arc between points B and D, but then this arc BD will not be tangent to the horizontal line at point D (in other words, there will be a kink at point D),
– it is also possible to draw a straight line from point A to the tangent point C (in black), which will effectively increase the width of the floor at the quarter frame aft, quite like in the first solution.

In the end, I opted for the fourth solution in this particular case, but perhaps more interesting here is the reminder that sometimes taking these kinds of documents (regulations, ordonances, treatises, manuals, etc.) too literally can easily lead astray.



.​
Click to expand...

You may have a line going through points A and B and tangent at some point to an arc going through point D where the requirement of this arc being tangent at D persists. This could be had if your arc does not go through B.
 
.​

Yes, I tried this variant too, but it is only good for one special case, that is, when the AB curve is a straight line, which would be obviously insufficient for the other cases anyway. I have opted for a more universal approach, in which the AB curve can also be an arc of a circle, as in the below plan of a French ship of 1679. Then, in practice, one have to start by determining the BD section and only then add the AB curve.

Besides, this more universal solution correlates better with that mysterious correction of the width of the ‘flat’ at master frame, i.e. from 20 to 19 feet.


1679 - 1st rate ship of the line - project.jpg​

.​
 
You must log in or register to reply here.
Back
Top