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bruce d

'sharp schooner' question

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What were the characteristics of a ‘sharp schooner’ in the late 18th century? I have found some later descriptions which anecdotally describe some of the features of individual vessels but so far none that actually say what makes a ‘sharp schooner’.

 

I may have overlooked a source. As an aside, it would be interesting if the definition varied in different countries...

 

If there is a proper definition from that time I would be grateful.

 

Thanks,

Bruce

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17 hours ago, grsjax said:

Might want to take a look at "The Search for Speed Under Sail" by Howard I. Chapelle.

Thanks, that was actually my starting point when I decided to dig into this. Although it is the best single source of clues so far it stops short of making the type of statement that would clear things up.

Having asked for input, perhaps I should explain. We have all seen vessels described as ‘clean’, ‘fast’, ‘sharp’ etc. but I have come across a couple of occasions where the expression ‘sharp schooner’ seems to be a complete description as if that phrase classified the craft, not merely pointed out a characteristic.

Also, some vessels are described as ‘sharp’ (rather than using the word to describe her bow or stern, either of which could be sharp). Where the descriptions are detailed, and The Search for Speed Under Sail is a good example, there are some common denominators such as ‘short keel’ and ‘heavy’ or ‘great’ drag.

My pedantic mind cannot ignore the fact that very knowledgable sources such as Chapelle made the distinction so there must be something there. I just need to find it, perhaps someone already has? Or am I chasing phantoms?

 

Thanks,

Bruce

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Sharp, I'm afraid, is probably a highly subjective term.  MacGregor offers some tantalizing thoughts about early written descriptions starting with Sutherland.  He doesn't offer a descrption of sharp just some related design concepts for fast ships. The most tantalizing is a reference to Bouger's rules for fast ships described in Fincham's Outline of Shipbuilding

 

Now to find my copy on Fincham...

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That’s right.  The Mid Nineteenth Century Clippers were often referred to as “sharp” as well as the earlier Baltimore Clippers even though they had completely different hull forms.

 

Roger

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3 hours ago, Roger Pellett said:

... you might wish to refer to is Chapelle’s Baltimore Clipper.

Thanks, good point. I am re-reading it now, first quick scan through drew a blank.

 

2 hours ago, Roger Pellett said:

The Mid Nineteenth Century Clippers were often referred to as “sharp” as well as the earlier Baltimore Clippers even though they had completely different hull forms.

... and this is the point my brain won't process without sending me back to the original thought: sometimes it appears to identify a ship rather than describe it. In 20th century context: all Destroyer Escorts were destroyers, but not all Destroyers were destroyer escorts even if they performed escort duties.

I appreciate any pointers, my attention is held by a comment from Wayne:

2 hours ago, trippwj said:

The most tantalizing is a reference to Bouger's rules for fast ships described in Fincham's Outline of Shipbuilding

 

Now to find my copy on Fincham...

Wayne, my fingers are crossed that you can find a book easier than I can!

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One thing to keep in mind is that ship design and building terms in the 18th and 19th centuries were often vague and different writers would refer to different things with the same term and vs versa.

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2 hours ago, bruce d said:

Wayne, my fingers are crossed that you can find a book easier than I can!

 

Found it in

Fincham, John. 1852. An Outline of Ship-Building. In Four Parts ... Whittaker and Company. https://books.google.com/books?id=FadWAAAAcAAJ.
 
From PDF page 46-47.
 
image.png.bd8d7c738d1bd05b6a6c3cb86e8e4280.png
 
I believe this is the treatise to which Fincham is refering
 
Bouguer, Pierre. 1746. Traité du navire, de sa construction et de ses mouvemens. Jombert. http://archive.org/details/bub_gb_lh1ZBtRvAb0C.
 

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hull design is a series of trade offs. Carrying capacity  vs speed is one of the biggest. A sharp ship in general is one thst the requirements for speed and performance were more heavily factored in than say crrying capacisty or stability.  Familiarize yourself with the concept of block co-efficient.  Generally a sharp ship of any rig(ship, barque, schooner) has a lower block co-efficient.

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Chapelle (The Baltimore Clipper, Edward W. Sweetman Company, New York, 1968, page 4), in speculation on the origin of the Baltimore clipper, describes an earlier 1770s French lugger Le Coureur. "The lines show a powerful and fast craft with ... great deadrise and rather sharp waterlines."

 

The faster ships being built at the end of the 1700s had very sharp lines below the waterline with hollow "cheeks" and a great deal of deadrise amidships. By "sharp lines" I mean small angles between the lines at the bow and stern relative to the ship centerline, and waterlines that were concave (curving inward) forward and aft, and convex (curving outward) midships. This is in contrast to the "bluff bow" that was common on larger merchant and warships of the 1600s and 1700s where the waterlines were convex from the bow.

 

The bluff bow designs had waterlines that began at the stem almost perpendicular to the centerline. This created a lot of drag, but it was a necessary feature to keep the bow afloat.  Buoyancy (the forces that keep the ship afloat) is proportional the amount of water displaced. These forces are greatest amidships where the beam is widest and the greatest amount of water is displaced. But at the bow and stern the forces are less because less water is displaced. This is the major factor causing "hogging" of a ship, where the bow and stern sag lower than amidships because the forces lifting them are weaker. With the weaker structural designs in early ships the bluff bow and square sterns were necessary to support these parts of the ships.

 

By the late 1700s ship designers were learning how to build very strong hulls. Think of the diagonal members in the Constitution's hull, and the diagonal metal straps used in the later clipper ships. This allowed the "sharp entry" into the water, both bow and stern.

 

Another factor was the deadrise. This is the angle of the cross section lines to the horizontal. Most large ships of the 1600s and 1700 had nearly flat bottoms amidships to maximize cargo space. But this created a large cross section area, and that meant high drag. The French lugger Chapelle mentions was unusual because it had fairly high deadrise - the bottom formed a "V" rather than a "U". This had two effects. It reduced drag, but it also reduced buoyancy amidships.

 

The combination of sharp lines fore and aft and high deadrise amidships evened out the differences in buoyancy along the length of the ship, creating less strain and hogging. This made for lightweight and very fast ships with smaller cargo capacity - sort of the FeDex of the day. It is these features that come to mind when I see references to a "sharp" ship.

 

I would add one more thing here. These effects of deadrise and sharp lines were not unique to older ships. Modern steel hulled ships suffer from the same hogging effects, and some designs were especially at fault. American cruisers of the late 1930s and 1940s were prone to structural failures because of extremely sharp and long hulls with relatively broad midships cross sections and very little deadrise. This had the effect of magnifying the hogging stresses. Several of them lost their bows in heavy seas, and many were scrapped after the war because of structural failures instead of being mothballed for future use.

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Thanks for the responses. I am certainly better informed now on this obscure point and have enjoyed re-re-reading a bunch of Chapelle. His 'Baltimore Clipper', 'Search for Speed Under Sail' and 'The History of the American Sailing Ships' all provide pieces of the puzzle. One piece of the puzzle that started me of was this from United States Bureau of Fisheries Report, Volume 14, of THE COMMISSIONER FOR 1886.

About 1815 the "half sharp" schooner made its appearance, and from this date rapid changes were made, and a few years later, about 1850, the "sharp-shooter" (as the clipper schooner was at first called) was introduced.”

The theme of this part of the report is the traditionally slow working boats in the mackerel industry and the introduction of faster craft.

7 hours ago, popeye2sea said:

The only reference I found in Falconers Marine Dictionary referred to sharp as in sharp bottomed as opposed to flat or full bottomed.

 

However, it is easy to believe I am not the first to ask this question. In her MA thesis published online (NEWASH AND TECUMSETH: ANALYSIS OF TWO POST-WAR OF 1812 VESSELS ON THE GREAT LAKES), Leeanne Gordon makes a detailed study of the hull forms of her subjects and states:

There is no definition of a sharp vessel, even in terms of these various coefficients. These terms are used only for comparison of different hulls.

I think she is right. I found pretty much the same in Steel and some other English language publications of the period but nothing that nails it down. So I will keep the subject in mind when reading old stuff but, for the moment, it looks like the phrase was a general term with no specific implications. 

Thanks for the input, will post if anything changes.

Bruce

 

 

 

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