by gerinc » Sat Feb 16, 2008 12:31 pm
ar wrote:To guest,
SEveral points.
Hood, Renown and Repulse do NOT have bulbous bows or flared forefoots. Hood appears to have one but that is in fact a continuation of the built-in bulge that carries up to the bow.
You say that the flare of the SS United States runs up tp the bulwark. NOT so, the flare goes up to a KNUCKLE. This knuckle is at the point where the black colour of the hull meets the white. VERY difficult to see in photos except at just the right angle. I tale this from the builders body plan with photo confirmation.
Flare; Too much and you get slamming which gives a much wetter ship further along the ships structure such as the bridge, and excessive strain on the hull. US ships had a greater flare than their RN counterparts. British ships tended to actually be drier in heavy weather as they slammed less in a heavy sea at the same speed. Also less strain on the hull. This came to the fore when US ships operated with the HOME FLEET in the Artic during the war.
I hope this helps a little.
SS United States' flare does go to a knuckle, you are correct. I have seen the ship in person. The paragraph containing my reference to the United States was talking about clipper bows in general, and not specifically to hers.
With the flared forefoot, I see we're either defining things differently or it's a subjective opinion as to what qualifies as a "flared forefoot." Hood, Renown, and Repulse all have greater breadth at their forefoot than they do at their waterline. This is the definition of a flared forefoot. The the narrowest part is at the design waterline, and the bow widens down towards the baseline. Indeed, even in the American cases like the SS United States or any of the ten WWII built battleships, the forefoot only swells relative to the stem, not the run aft. No military ships had bulbous bows through WWII except the Yamato class, that I am aware of.
You're also correct that US capital ships were wet, frustratingly so at times, but it was not from plunging through the wave, rather being splashed by the ship's bow pounding the wave. However, the earlier ships (pennsylvania and earlier) went into the seas, as opposed to over them. The clipper bow was intended to fix this. A ship going through a wave takes a lot of water on her decks, and this creates a lot of weight above her metacenter which can cause stability problems if the water isn't shed very quickly, especially in heavy seas. This is also why the US ships had a very pronounced sheer running from fore to aft, to shed any water shipped aboard. Very few ships today are built without flare on their bows (topsides, I mean, not forefoot). Pounding (slamming as you call it) is best combated by changing course slightly or slowing down. Even the British ships couldn't steam at flank speed into a substantial swell. I also feel compelled to point out (all in fun, of course) that when the British ships were serving with the US Pacific Fleet, the fuel economy and endurance of HM's ships were inferior to that of the american ones. Ship design is always a trade-off.
But I don't want a tit-for-tat US/British discussion here. Clearly, as in the case of the US ships, the desired result wasn't always achieved. However, ships on both sides of the pond were built with this style of front end for long after the war, both commercially and militarily. In the US, the Navy has only recently begun using the bulbous bow with the last two Nimitz class carriers. Testing has shown that the sonar bulges on the bows of some ships (which are under the baseline) do not have any effect on efficiency, so those aren't considered bulbous bows.
Gotta run now, but I look forward to hearing your opinions further!
Cheers!
[quote="ar"]To guest,
SEveral points.
Hood, Renown and Repulse do NOT have bulbous bows or flared forefoots. Hood appears to have one but that is in fact a continuation of the built-in bulge that carries up to the bow.
You say that the flare of the SS United States runs up tp the bulwark. NOT so, the flare goes up to a KNUCKLE. This knuckle is at the point where the black colour of the hull meets the white. VERY difficult to see in photos except at just the right angle. I tale this from the builders body plan with photo confirmation.
Flare; Too much and you get slamming which gives a much wetter ship further along the ships structure such as the bridge, and excessive strain on the hull. US ships had a greater flare than their RN counterparts. British ships tended to actually be drier in heavy weather as they slammed less in a heavy sea at the same speed. Also less strain on the hull. This came to the fore when US ships operated with the HOME FLEET in the Artic during the war.
I hope this helps a little.[/quote]
SS United States' flare does go to a knuckle, you are correct. I have seen the ship in person. The paragraph containing my reference to the United States was talking about clipper bows in general, and not specifically to hers.
With the flared forefoot, I see we're either defining things differently or it's a subjective opinion as to what qualifies as a "flared forefoot." Hood, Renown, and Repulse all have greater breadth at their forefoot than they do at their waterline. This is the definition of a flared forefoot. The the narrowest part is at the design waterline, and the bow widens down towards the baseline. Indeed, even in the American cases like the SS United States or any of the ten WWII built battleships, the forefoot only swells relative to the stem, not the run aft. No military ships had bulbous bows through WWII except the Yamato class, that I am aware of.
You're also correct that US capital ships were wet, frustratingly so at times, but it was not from plunging through the wave, rather being splashed by the ship's bow pounding the wave. However, the earlier ships (pennsylvania and earlier) went into the seas, as opposed to over them. The clipper bow was intended to fix this. A ship going through a wave takes a lot of water on her decks, and this creates a lot of weight above her metacenter which can cause stability problems if the water isn't shed very quickly, especially in heavy seas. This is also why the US ships had a very pronounced sheer running from fore to aft, to shed any water shipped aboard. Very few ships today are built without flare on their bows (topsides, I mean, not forefoot). Pounding (slamming as you call it) is best combated by changing course slightly or slowing down. Even the British ships couldn't steam at flank speed into a substantial swell. I also feel compelled to point out (all in fun, of course) that when the British ships were serving with the US Pacific Fleet, the fuel economy and endurance of HM's ships were inferior to that of the american ones. Ship design is always a trade-off.
But I don't want a tit-for-tat US/British discussion here. Clearly, as in the case of the US ships, the desired result wasn't always achieved. However, ships on both sides of the pond were built with this style of front end for long after the war, both commercially and militarily. In the US, the Navy has only recently begun using the bulbous bow with the last two Nimitz class carriers. Testing has shown that the sonar bulges on the bows of some ships (which are under the baseline) do not have any effect on efficiency, so those aren't considered bulbous bows.
Gotta run now, but I look forward to hearing your opinions further!
Cheers!