The "run angle" of a schooner hull form

Pete Culler wrote:

"...old time schooner men. They all more or less agreed, though each had his preference, that a vessel could be full forward, or fine, or somewhere in between, she could be flat-floored or sharp, wall-sided or not, deep or shoal, or have any of the other combinations and variations, and still be a good ship; but not one of these experts had ever seen a vessel with a poor run that was worth a damn!"​

Is the "run" the angle of the the keel along the length of the bottom? I'd like to understand what he's saying here.

Can anyone offer more insight into what he's talking about or explain with some examples?

 

If you look at the lines of a vessel in profile the buttock lines basically define the "Run" of the hull.
Flatter lines disturb the water less as the SL ratio goes up.
You can see that modern hull designs have "flat runs", particularly in the aft sections, this suppresses the stern wave thereby reducing drag.
Now look at the lines of a boat like a Westsail 32, it's commonly referred to as a slow boat, and its buttock lines are steep, almost like sections of a fat oval, (little "flatness" in the midship sections).

 

While the buttock lines tell the story, it is actually the diagonals that define "the run". This is because the diagonals define the "sailing lines" rather than the construction lines. I myself find that the aft quarter diagonals one of the most important set of lines used when designing a sailing vessel, and I put them in early in the design.

 

Every designer has their "methods", that said, diagonals were generally used as a "check" on the fairness of the curves that delineated the shape of the section curves on the loft floor, (did the loftsman "pull" the curve or compress it).
And their was no set pattern of their angle in respect to heights where they come off of the centerline.
Designers more-or-less stick them where they felt they were needed.

 

They are generally put in close to perpendicular to the skin. They have the advantage of being much smoother than the buttocks, especially with a counter stern.

 

After over 65 years of pouring over plans and reading what designers and commentators have to say and the terminology they used, I'll stand by what I've said; that diagonals were not generally used to define what was colloquially called the "Run" of a hull.

 

Whether buttocks, diagonals, or water lines, the general idea is to minimize acceleration and deceleration of a unit of mass as in a water molecule as it moves across the surface of the hull.. The designer has to reconcile that with buoyancy distribution and a whole mess of other desirable and/or necessary features of the hull. All the while, some consideration must be given to the interior accommodation such as cargo space, living arrangement, machinery space, crew comfort, safety, and all that sort of stuff.

 

^ Yes, you are correct, and no line drawn on paper can describe/define the path that those molecules take on their path when they "run" from bow to stern.

 

Ok, thanks everyone. I think I am learning here. So, the "run" is the concept of how water flows along the length of the hull, with the SL ratio being the direct analogue? It's not necessarily the static or heeled waterline when underway, but more the general shape that impacts drag on the wetted surface?

 

Pretty much, at low SL ratios even a barge can move along without disturbing the water, it's when speed increases that drag and wave making resistance starts going up quickly.
As speed increases a hull that's too fine forward can't raise her bow in the swells, too fine aft and and she drags a big stern wave.
Older yachts with "wineglass" sections were optimized for going to windward, (that's how you win races on a triangular course,) and their fine sections aft worked well as typically a sailboat will seldom get up to high SL ratios going to windward, but it hurt them downwind, as speed increases the quarter wave moves aft towards the area of the hull where the fineness reduces buoyancy and they can get "squirrelly" on the helm.
(How bow/stern overhangs affect sailing and "ratings" for racing is another issue).
More modern hulls do better downwind where the boat is moving at a higher SL ratio, the "run" is much more flat, and the wide sterns provide buoyancy and suppress the stern wave.
The rub with the modern shape in going to windward is that as the boat heels the waterplane shape becomes grossly asymmetrical, the bow sections lose buoyancy, weather helm builds, and the balance between CE, (center of effort,) and CLR, (center of lateral resistance,) goes out the door.
Good control with those hull shapes require they be sailed as flat as practicable, they don't like being "on their ear".

 

The "run" also refers to the shape or contour of a vessel's hull below the waterline, specifically towards the stern. A well-designed run allows the vessel to move smoothly and efficiently through the water by reducing drag.

 

On a long-keeled sailing vessel, the stern run develops a disproportionate amount of lateral resistance to leeway because of the ever-growing vortex that creates low pressure on the windward side of the hull. This pressure field is sensitive to stern geometry and the way the keel blends into the hull aft of midship. Done right, there was a definite groove where these vessels' long skinny hulls had low leeway and low added drag from leeway and could really hold their canvas. They also were from an era where hull and rig development was well ahead of rudder and steering development, and the run had a big impact on rudder effectiveness. Remember these beasts with 50,000 sqft of canvas were steered by hand.