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George Jung
01-12-2008, 11:04 AM
for our Navy Seals.

http://www.omaha.com/index.php?u_page=1115&u_mod=ap.online.headlines.us&u_sid=10230450

Sounds as if our elite military fighters are pretty well worn out by the time they get to the fighting;

"Fighter jet pilots are subjected to forces up to 10 times the pull of gravity, but the Mark V has produced forces upward of 20 Gs slamming against waves, said Lt. Damon Shearer, senior medical officer of Naval Special Warfare Group 4.

Navy SEALs are tough by nature, but they take a beating from their patrol boats: bruises, bumps and sore backs, even sprained ankles and chipped teeth.

Powered by a pair of diesel engines, the vessel is propelled to a top speed of about 60 mph by twin water jets.... The idea is to build a boat out of the best carbon-Kevlar composite that we can build to reduce those slamming forces,"

They didn't mention the 'per unit' cost, but suspect it'll be significant. Wonder how long before the drug runners start using something similar?

Paul Pless
01-12-2008, 11:30 AM
One of the things mentioned at the Phil Bolger tribute dinner at the WoodenBoat Show this past summer was that he and his wife had been designing a multitude of landing craft for the Navy and the Marines over the last few years.

LeeG
01-12-2008, 11:38 AM
All they need to do is slow down.

There's gotta be something else going on than just switching to carbon/glass composites. I bet they've got hull lined with Spenco heel cushioning inserts.

For anyone familiar with bicycles check out Specialized TriCross, it's got a carbon front fork with the most amazing dampening for an unsprung fork. It really is amazing.

George Jung
01-12-2008, 11:42 AM
Interesting, LeeG; but I suspect that, given their purpose, speed figures significantly in the operation. I'd wonder about radar capabilities, ie, 'stealth' with a composite hull. Maybe Chuck or one of the other military types here know more.

Memphis Mike
01-12-2008, 11:43 AM
A friend of mine is a former Navy seal. He's jumped out of an airplane, from thirty thousand feet, at night....... and landed in the ocean.:eek: He said it's pitch black. All you can see is the glow in the dark altimeter on your wrist to tell you when to deploy your chute.:eek:

rbgarr
01-12-2008, 11:46 AM
One of the new carbon/kevlar Mark V.1 "Makos" was launched just yesterday here in East Boothbay. Two of the older versions rumbled through our anchorage this summer on their way to the Hodgdon yard. The foam created by the water jets took a long time to disappear. I'd think that would create an awful lot of phosphorescence at night.

http://boothbayregister.maine.com/2008-01-10/navy_boat_launching.html

LeeG
01-12-2008, 11:54 AM
I know, I was joking George. I'm guessing there's a lot more going on than just a more expensive hull made out of composites to reduce ringing g forces, isolating the area where the Seals stand from the hull, dampening masses.

Given the amount of carbon used in the new destroyers superstructure there must be a some extra laying around for the little boats.

paladin
01-12-2008, 12:03 PM
Carbon is/acts like a metal where radar is concerned without special coatings...I suspect other reasons....

BrianW
01-12-2008, 02:27 PM
Is it just me, but wouldn't a lighter version of the same hull tend to pound even worse?

Paul Girouard
01-12-2008, 02:38 PM
Just to add onto George Jung's USN lesson for the day this boats , and those like it , would be part of what's referred to as "The Gator Navy". Small craft are commonly Skippered( commanded ) / Captain-ed by enlisted sailor's who would be in fact "Captains " of their vessel , they'd wear "Craft-master" pins / insignia's on thier uniforms , most of these vessels would be a in a "Squadron " type unit I'd think and deploy either as such , or individually with a SEAL team. Most would be based at 32nd st Naval ship yard in San Diego and or Little Creek Naval base I believe.

ishmael
01-12-2008, 03:40 PM
I wonder the same thing Brian does. This link to a local article says the hulls are only lightened slightly--though considerably stronger.

http://tinyurl.com/2zs7mm

Same weight, same hull form, it seems to my novice understanding the behavior in a seaway ought to be pretty much the same. What am I not seeing?

Paul Girouard
01-12-2008, 03:49 PM
Same weight, same hull form, it seems to my novice understanding the behavior in a seaway ought to be pretty much the same. What am I not seeing?



Maybe this line,

Maine’s congressional delegation secured $14 million for the project through a series of earmarks over several years. If the prototype is successful, the Navy could end up buying $200 million worth of the patrol boats from the Maine shipyard, Collins said.

It really doesn't matter to those elected officials IF it doesn't work better in the Field/ at sea . It only has to gather votes.

Look at the F-18 it's a piece of crap as far as fuel load , bomb carrying capacity. Yes it fly like a dream they say , but if you either can't get to the target or can't carry the payload to destroy it with a reasonable # of asset it's not a very good asset/ aircraft.

Bob (oh, THAT Bob)
01-12-2008, 04:21 PM
I'm also not seeing the design advantages of the new design yet, unless they are going to make a carbon hull that is flexible. That is one of the advantages of carbon fiber, the ability to design flex in a single direction; it can be anisotropic. Carbon fiber bike frames, as well as leaf springs and fishing rods take advantage of this property. But given that they said the hull is cored, which adds stiffness, I doubt it.

Both old and new designs are planing hulls, right? A planing hull is gonna hit big waves mighty hard. The article mentions they have already tried seat suspensions (heavy trucks use air-suspension seats that can soak up quite a bit more displacement and shock than standard seats, but even heavy trucks drivers don't see 20g's).

Heavy trucks often suspend the entire cab. Colin Chapman once built a Lotus F1 car where the driver's pod was suspended for good ride, allowing the wheel suspension to be completely optimized for good handling (and also squat quickly under aerodynamic forces to get into ground effect). Perhaps the new boat has a suspended cockpit. Electronically controlled dampers would take very little power. With a LOT of power consumption, it could even have an active suspension, like the stabilized gun on an M1 tank.

Sounds porky to me, but the sea trials (with subjective instrumentation, I hope) will tell the tale. "One valid test is worth a thousand expert opinions."

ishmael
01-12-2008, 04:44 PM
"But given that they said the hull is cored, which adds stiffness"

Yup. We're not talking a flexing hull, at least not intentionally. A bonded foam core as I saw in a few of the pics is going to be stiff.

I don't pretend to understand a tenth, a twentieth, of the dynamics involved here, but from what I do understand we're talking a planing hull, with a V of some sort(it looks sort of medium deep) up front. Same measurements in vital dimensions in same weight is going to give the same performance no matter the material, seems to me.

Kinda sexy in a Miami Vice sorta way, from the pics I've seen. Rakish! This is not your father's PT boat. LOL.

I dunno. If the Seals were basically happy with the design except that it pounded the crap out of them at speed in a seaway, I don't see how this is going to fix that.

P.S. I'm quite sure Mr. Giroud is correct in some ways. Maine's is a small economy, and if building these can come to Maine(assuming they have to be built at all) then I'm all for it. But those sorts of questions, bleeding into the political threads, are the questions? Maine has a large pool of skilled people who can build this sort of creature. As a taxpayer here, if they need to be built, Mainers can build them as well or better than most other states. If it's another "maker work" program then I'm agin it. But then, that's one small reason I've never been elected to office. LOL.