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well, if you do not make the weather deck the strength deck you have to put expansion folds in all decks above. you also have to have to put more material then you would have put in the hull until the weather deck now into the hull below the waterline.

in other words, making a deck running the full length of the ship not part of the longitudinal strenght of the ship is actually quite a stupid idea.

EDIT: again a quick calculation: getting the hull to the same strength will require a hull 3,5 times as heavy (this is only counting the 'strength' part, the additional weight of the hull on top, now counting as superstructure, must be added to that) so a weight increase of your hull of 4 to 5 times as heavy would seem likely now.
if I assume your hull to be of similar construction to that of the perry, of which 30% of the weight is hull steel, your ship would thus have at least 100% of the ships displacement being the steel construction.

EDIT 2: dwigthlooi, don't get me wrong. your ship, as a drawing, makes a lot of sense and has only a few small flaws in my opinion. the specs you are giving afterwards though (center of gravity, strength deck, upgrade options) do not make a lot of sense to me, and I hope you do not hate me for pointing them out .

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None taken.

One thing I would like to suggest is that you look at the newer 76mm mounts in place of the 57mm gun. There are some indications and some RUMINT that the Mk110 doesn't quite work as well as the marketing would indicate, most notably in that the first two Zummwalts (which have huge margins*) lost the mounts.

Another thing I would do after the first change is I would bump up the aft 25mm to the 30mm that is going on the LPDs and Zumwalts. It would offer a bit more range, which is nice.

On the USCG ships, I'd just break apart the large doors you've marked out into two smaller doors. The super-long ones you have just don't make sense relative to two smaller ones with a pillar between them. Otherwise you've got a long section that has to take the weight of the helos above it. Much better to reduce the stress with supports near the sides of the ship leaving the center section free for movement. A secondary radar on these units would be good to see as well. It doesn't have to be an expensive system, but you want to be able to use something other than your SPQ-9.

As a final note, I've got to go with Ace, and recommend that the bow thruster is dropped in favor of the keel azimuth thrusters similar to those on the OHPs. It not only improves relative maneuverability, but it also provides a get-home capacity that the current set up does not offer.

*I don't know exactly how large the margins are, but they are large enough that the third is getting the steel deckhouse in place of the composite one that is going on the first two ships.

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yes the 57mm.

Norway was originally going to us it on there Skjold class, but they found out that the gun had an slow respons time, and the weight of the stealth housing was so that it made the original turret it was build on slower. (Sweden took just the Standard 57mm turret and replaced it with the more heavy stealth housing, the new housing had also an little of-center CG), It ended up with Norway using the 76mm instead. (more range, and sharing ammo with there frigates... cost saving)

Added rednerings of the underwater profile for the Coast Guard variant. Basically, the bow sonar pod is dropped and the bow is reverted to the original knife shaped profile. The idea is that as the ship approaches hull speed, the bow -- being extremely slender, sharp and with minimal flare will cut into the bow wave more than it rides on it.

The doors over the bow thruster, whose role is mostly to reduce flow noise more than reducing hydrodynamic drag, is dropped. The Prairie-Masker system is also eliminated since the MHECs are not particularly worried about announcing their presence to undersea foes -- not that any of the cartels' cocaine smuggling submersibles have passive sonars anyway.

I don't think ANY of the current crop of medium caliber guns are particularly effective at sinking anything more than small crafts with their gun(s). Trying to sink a container carrier or cruise ship with them will be like trying to sink a fishing boat with a 5.56mm or a 7.62mm rifle. After you expend the magazine, there will be time to take a vacation before there's enough flooding to effect an actual sinking. Basically, the A turret is there for rudimentary stuff like small craft defense and firing warning shots over the bow of non-combatants in a failure to yield situation at the range and wow factor which machine guns and small caliber cannons do not provide.

The situation with the US Navy and US CG is the reverse. The 57mm is here to stay on the new LCS and the NSC ships. The rest of the fleet use the Mk45 5" gun. The 76 Oto will be gone once the Perrys and Hamiltons retire. Using one of these two allows for simpler logistics and commonality, the caliber's effectiveness is really secondary. So it comes down to the 5" or the 57... and the Mk45 127mm/62 will actually fit. However, I believe that in a Frigate which may more often be tasked with littoral policing and escort duties, a fast firing 57 with decent fast boat engagement capability and a plausible if limited CIWS mode, is a better choice than the 5" with a 20 rpm ability to lob tiny shells to the horizon and beyond.

That is an incredibly Bad Idea. Not only will all of the flow calculations have to be redone (likely resulting in a different hull shape to maintain the same characteristics), but many of the hull calculations as well (the dynamic forces are going to be different with the new flow). This is on top of the changes that need to be done for the larger hatches (which will need to be done, because the strength deck can not be the mission deck).

A further impact of the loss of the bulb is that you'll loose bow bouyancy, which is going to impair sea keeping characteristics - something you don't want in a coast guard ship.

Heck, the Mk 57 PVLS removal isn't going to result in directly usable space anyway. The PVLS is built on an inner strength frame and an outer frame that is designed to blow away in the event of damage (from outside the ship or a direct missile explosion). You can keep the volume as void spaces certainly, possibly as ballast (as needed with equipment deletions) and maybe even as stores space, but this is again a place where what looks like a minor change can have significant impacts.

Furthermore, the lack of sonar ignores that the USCG is tasked with long ranged national security missions for which a high frequency sonar unit is a requirement. One of the most common missions that the sonar is used for is blackbox recovery - sonar isn't just about finding subs.

As for the gun, there is some indication that the 57mm won't be on the next flight of LCSes, as the USN isn't totally satisfied with it and the 76mm has a bit longer reach. If you've got the space for it, I would strongly consider the Mk 45. The 5"/62 is a very nice gun to have, and with a 30mm backup would be great for any ship that can carry it without a lot of extra cost simply because the gun is already in use on so many USN ships which means the supply lines are open and will continue to be open for decades to come.

Please don't get me wrong, I do like the idea of the common hull (witness my love of CPCX), but every change you make the to the USN version for the USCG does have an impact that could cause the hull to be less common, and therefore more expensive - and at some point you're better off with a custom USCG hull that shares electronics and subsystem commonalities, with a totally different hull.

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Personally I'd just mount the light gun on the deck. Exposed elevators are a royal pain the butt to maintain, especially if they have to be reasonably watertight.

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Actually, the ship was designed specifically to reduce bow buoyancy... that's how you get bows to pierce waves instead of ride them. The bulbs BTW are filled with water not air... the SQS-60/61 sonars as well as the new sonar on the Virgina class are water backed arrays not air backed.

- a volume closed off from the water outside it creates bouyancy, if there is water in it or not. (following Archimedes' law)

- whatever the bow design, removing volume requires balancing. if you remove the volume but keep the (relative) weight, the bow will dive in deeper, and even without waves the ship will be trimmed forward. and that reduces speed (or increases the required power) increases draft, and changes the way the ship moves. that is the seakeeping refered to above.

also....... "reduce bow buoyancy... that's how you get bows to pierce waves instead of ride them" is not entirely true, reducing bow bouyancy actually stops waves from pushing the ship out of the wave and reducing the bow wave, but it is not the only factor to getting a wave piercing bow.

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Drawings are credited with J.Scholtens
I ask of you to prove me wrong. Not say I am wrong, but prove it, because then I will have learned something new.
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