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FFG-500 -- USS Fletcher -- Frigate Design for the US Navy https://111903.jhzobq.asia/forums/viewtopic.php?f=15&t=5104	Page 1 of 4

Author:	dwightlooi [ April 10th, 2014, 5:03 am ]
Post subject:	FFG-500 -- USS Fletcher -- Frigate Design for the US Navy
This is a very realistic design and it is done as a parametric model. The basic premise is that the US Navy can really use a proper, modern, frigate instead of a bunch of over-sized gunboats (LCS) and extremely expensive and heavily armed Destroyers (Burkes). The lead ship is hypothetically named for the historic Fletcher Class destroyers of WWII. The design paradigm can be summarized as follows:- 30+knots / 140m / 5000 ton vessel 1/2 the cost (~$950M) / 1/3 the manpower (106 crew) / 1/4 the missile load (24 VLS cells) of the Arleigh Burkes 57mm gun / ESSM as primary air defense weapon / ability to launch most existing and future USN weapons No new sensors / no new propulsion technology / no new weapons are to be designed specifically for this class Longer endurance and lower operating cost than traditional USN combatants through use of CODEG propulsion Unlike frigate centric navies, the US Navy does not really need this ship to pack be it's primary anti-air warfare platform or pack the majority of the fleet's firepower. There are plenty of aerial or shipboard sensors with 400+ km range when operating with a battle group and there are already plenty of VLS cells on the Burkes. Hence, the ship makes do without a long range volume search radar. relying instead on either the x-band AN/SPY-3 or the AMDR-X as it's sole active RF sensor. It also packs a very modest missile load of 24-tube. Steel is cheap, however, and with future growth and export potential in mind the ships do actually have space for 32 VLS cells and reserve power to support a SMART-L or event the AMDR-S, it is just that only 24 will be fitted for US Navy duties. I am completely new to Shipbucket, so I am having difficulty pinning down what exactly is "Ship Bucket Style". If someone will be so kind as to explain that, I'll post supplementary pictures that conform properly. This is a full 3D Parametric CAD model, so I can generate any view and any rendering on demand with relatively little pain. Note: Thanks to advice from forum members, I have revised the post with a "Shipbucket Style" Drawing!

Author:	klagldsf [ April 10th, 2014, 5:11 am ]
Post subject:	Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav
I have to admit I'm impressed but a few issues: - there is absolutely no need for a retractable sonar. It's already underwater, you don't need to hide it for stealth reasons. - I guess you can do a pumpjet, but for a ship this size and mission a more conventional set-up will work just as well. Sure you won't get the stupid cigarette-boat speeds of the LCS, but that's a very stupid requirement anyway. - it's also not a Shipbucket-standard drawing, which means it's going to get kicked to that forum that, you know, says non-Shipbucket drawings.

Author:	dwightlooi [ April 10th, 2014, 5:17 am ]
Post subject:	Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav
What is a shipbucket drawing?

Author:	Trojan [ April 10th, 2014, 5:22 am ]
Post subject:	Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav
In over simplified terms, its drawing using our scale, 1 foot = two pixels IIRC, and using a MS Paint or a similar program to create a 2D design.

Author:	dwightlooi [ April 10th, 2014, 6:20 am ]
Post subject:	Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav
Thanks! And, duly amended. I can't actually "draw" the model using MS Paint, but I have rendered and scaled the 2D projection drawings to a precise scale of 2 pixels : 1 foot

Author:

dwightlooi [ April 10th, 2014, 6:42 am ]

Post subject:

Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav

klagldsf wrote:

I have to admit I'm impressed but a few issues:
- there is absolutely no need for a retractable sonar. It's already underwater, you don't need to hide it for stealth reasons.
- I guess you can do a pumpjet, but for a ship this size and mission a more conventional set-up will work just as well. Sure you won't get the stupid cigarette-boat speeds of the LCS, but that's a very stupid requirement anyway.
- it's also not a Shipbucket-standard drawing, which means it's going to get kicked to that forum that, you know, says non-Shipbucket drawings.

The Retractable Sonar is for hydrodynamic reasons. When charging along at 30+ knots that knife edge and flat bottom rear helps get the ship to lose some displacement as the ship lifts ahead of the center of gravity more than it squats aft of it. Drag is reduced in part because effective displacement is reduced when the ship is partly supported by dynamic lift rather than just buoyancy. One can call this a "pre-planning" stage. This is how you get a 140m ship to a speed-to-length ratio of 1.6 and go 34 knots. A pure displacement hull will be around 1.3 and reach only about 27 knots even if you give it prodigious amounts of power. I many ways modern warships are all like that; this design is just a little more so than most. If you look at the tail end of the Burkes or the FREMM they have a flattened aft section rather than a one like the Titanic or Queen Mary. Unlike a planning hull hull with a speed-to-length ratio of around 2.5 (Eg. LCS Freedom) a mildly semi-displacement hull is still efficient at 15 knots. The retractable sonar is so you don't have a draggy pylon under the knife edge causing drag and pulling the front down. At above 25 knots, you won't be able to hear anything anyway, so whether the sonar functions doesn't really matter.

Yes, two conventional propellers will work. But the idea is to keep the propulsion design as simple as possible, hence the desire to go single shaft. Delivering 72,000 shp on one shaft will require CVN sized screws which won't fit under the a ship with a 6m draft. Using a pumpjet allows for a big impeller to be buried in the bowels of the ship. A pumpjet also has the added advantage that it can be made to resist cavitation to a higher operating speed. This is in part from the ability to increase the pressure of the water at the impeller by narrowing the duct work at that point and/or increasing back pressure by changing the nozzle cross section. Higher pressure = less cavitation; the same reasons submarines are quieter at higher speeds when they run deep. For an ASW platform this allows for a higher "silent running speed". When rigged for silent running, the Fletcher class will probably run the Gas Turbine (even if it's not fuel efficient at low loads). She'll likely shut down the diesels down to eliminate the vibrational noise from reciprocating engines, discharge a curtain of bubbles from two or three bands of the "masker" system around the hull to reduce acoustic conductance. Finally, it'll draw the discharge flap in to increase pressures in the pumpjet system to minize cavitation and retract the stabilizers to reduce flow noise. Should be able to glide around at 12 knots with no more detectability than a diesel-electric sub chugging along on it's AIP system at half that speed. With a dual-band hull sonar and stringing that SQR-20 towed array (under the thermal layer if needed), submariners should be very, very scared. Chances are the first thing you'll hear will be an ASROC or Helo dropping a torpedo or two above you.

Author:	heuhen [ April 10th, 2014, 7:20 am ]
Post subject:	Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav
ONE shaft was done before, but it was founded to give to bad ship control at lover speed. Something those type of vessel often do. They normally travle at 12-16 knots, and us to sprint very rarely. An sonar under hull do not make noise so you can forget that retractable sonar.

Author:

acelanceloet [ April 10th, 2014, 10:19 am ]

Post subject:

Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav

heuhen wrote:

ONE shaft was done before, but it was founded to give to bad ship control at lover speed. Something those type of vessel often do. They normally travle at 12-16 knots, and us to sprint very rarely. An sonar under hull do not make noise so you can forget that retractable sonar.

tell that the perry.

anyways, dwightlooi, I believe there is an shipbucket drawing of this ship made already. should be possible to dig it up.

I have some comments on the design, but those will come later, after I have taken an good look at the design

EDIT:
well, I have them now

- interesting hull shape. I think that is one of the best ways I have seen an tumblehome hull merged to an conventional bow.
- I wonder how an propeller fits IN your hull but not outside of it. as it is impossible for the propeller to be above the waterline (lower underneath it will actually be a bit better, even in this configuration) and you can stick the propeller a bit underneath the keel level (look at the perry class) so why can it not be done here? while it looks less vulnerable, anything sucked into the intake will literally destroy your powerplant, as it gets stuck somewhere along the way.
- the propeller inside the hull will result in more cavitation then outside it. waterjets are never, ever, more efficient then propellers, except in 30 knots+ speeds. exception might be the advanced waterjet that was tested on that zumwalt technology demonstrator, which might be an better option for you.
- the helideck looks extremely far aft. do you have space for 2 helicopters? if not, I would create it using a bit of that aft deck space. if VLS cannot be at the side of the helideck, moving some of them to the bow seems not an bad idea.
- why the 57mm in visby style instead of the mount build for the zumwalt?
- the sonar dome retractible is an good idea. the shape of it however....... note that sonar domes need to let the water flow as much indisturbed as possible. this means they are mostly teardrop shaped in all directions except the one they are connected to the hull with. the sonar itself is an dome or an sphere, which you want as much at the front as possible for the drop shape.
- the stabilisers would work better if perpendicular to the hull.
- where are the air intakes for your gas turbines?
- I think the exhausts penetrate your hangar.
- the superstructure seems huge for what is in it. the zumwalts looks cramped with stuff, yours looks empty. with some movement of the exhausts and the addition of intakes, that might be fixed though.
- try to place your rudders in your propulsion stream. that will make them more effective.
- your waterline is stepped. try to avoid that

EDIT 2:
found the sb style drawings of this ship.
http://www.shipbucket.com/images.php?di ... 1%20AU.gif
http://i284.photobucket.com/albums/ll31 ... FG-500.png
the second one is an AU modification, and the first one seems to be not entirely accurate with your current rendition.

Author:

TimothyC [ April 10th, 2014, 1:53 pm ]

Post subject:

Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav

It's been done. I tweaked Martin's work for an exercise in underwater hull shading.

[ img ]

I don't like Tumblehome.

Although, I give you credit, that the version above is less bad than the prior version.

dwightlooi wrote:

Note: Thanks to advice from forum members, I have revised the post with a "Shipbucket Style" Drawing!

You've got one that is the right size, now you need to draw it in Shipbucket style (which is a pixel art style). Take a look at other drawings on the site to get a feel for it, and don't be afraid to ask questions.

Author:	acelanceloet [ April 10th, 2014, 1:59 pm ]
Post subject:	Re: FFG-500 -- USS Fletcher -- Frigate Design for the US Nav
ow just rechecking, this hull has none of the characteristics of an semi-planing hull.

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