Ship designs - why such a tubby look?

[RedLeif]

Hi
Do any of you know why the big warships of this period had such rounded bows? When I look at modern ships most have much more angled bows. What was the biggest influence or factor in the 'look' of these designs? Was it a limitation of construction materials? They must have realized that a tapered narrow hull moves faster than a wide blunt shape. I do realize part of the answer has to do with the armaments of the day. One needs quite a bit of room to accommodate the recoil of the smooth bore cannon fired out the side of the ship. But one could surely have designed the needed wide body yet with a tapered bow? Without a long lesson in naval architecture I'm just curious if a short answer is handy to any of you.

Thanks,
Leif

[RichardPF]

While I am not a naval architect by trade I did complete a program from the Westlawn School of Marine Technology some years ago so can probably answer this to at least a first pass level.

Some of the shape does have to do with the structural strength of the materials available at the time, but for the intended application the shape is not that far off of what the best possible design would look like today constructed with modern materials.

For a displacement hull, as opposed to a planing hull that skims the surface of the water, the drag from the water increases incredibly beyond a speed known as the Hull speed. This point is where the bow and stern waves are in sync and add together. This speed is roughly 1.34 times the square root of the waterline length. Carrying full sail, the ships of that period can reach hull speed quite readily and these principles were known at the time. For a racing displacement sailboat (or just for a boat to look racy), you will get a tiny bit more speed from a shape roughly resembling a teardrop with the pointy end forward, but the difference is minimal. If you look at the "old" America's Cup boats before the age of catamarans and trimarans, you wil see that the bow is quite vertical and the stern at the waterline extends to or beyond the deck. The rounded bow of the older designs was to include the maximum length at about the maximum beam (width) possible as a fighting platform and for cargo space with a slight concession to the materials of the day. These vessels also do not have deep keels, so having the largest area at the deepest point also helps with stability. If you look at the shape of the displacement part (underwater part) of modern large ships such as cargo ships, you will see much the same shape.

[Volunteer]

Really good explanation even an old pipeliner can understand. Thank you Bruce.

[RedLeif]

Your explanation is very much appreciated. Thank you Bruce.

[7eat51]

This is one of the reasons I appreciate this community - the diversity of knowledge and interest bases. Some folks are into tactics, some into history, some into people, some into technical specs, some into modelling, etc. I always sign-off having learnt something. Thanks for such an informative answer, Bruce.

[Sea Gull]

Look at the photos of the dreadnaughts of WW1. More modern materials, but they certainly were also a bit on the wide side.

[David Manley]

"Hull speed" may have been one of the factors in the design of smaller ships, but when you get up to two and three deckers with lengths in the order of 180-200' or more that "hull speed" works out at about 18 knots, which none of these ships reached. If you look at the underwater form they are actually quite a bit finer than most people realise. But anyway, the full bodied designs tended to be a compromise between a variety of factors, including structural strength, directional stability (which drove the underwater form aft to a great extent), intact vertical stability (which drove the tumblehome element of the design of 2 and 3 deckers), carrying capacity (remember these ships were often stored for voyages of many, many months and so they needed an enormous carrying capacity) and speed. Speed often lost out to the others, which were required to provide rugged, survivable warship designs.