Author Topic: 2nd Generation US Navy Riverine Craft  (Read 4362 times)

Offline Abraham Gubler

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2nd Generation US Navy Riverine Craft
« on: May 06, 2011, 09:20:56 pm »
Most of the initial generation of the US Navy’s brown water force for VietNam were based on modified LCM6 craft. The second generation was to include purpose designed ships and capabilities improvements. The primary criticisms of the LCM6 based craft was high draft (>4 feet), low speed (<8 knots), vulnerability to mines and >12.7mm rounds and low manoeuvrability and seakeeping.

The late 1966 requirement for the ASPB Mk 2 [Assault Support Patrol Boat] was a max speed of 25 knots, range of 250 NM (while cruising 15-20 knots) and the same dimensions as the ASPB Mk 1. The additional speed was so it could tow a chain sweep in fast flowing rivers and tides. Proposals were received by the end of June 67 and orders for prototypes awarded to Sikorsky June 12, 68 and Sewart (Teledyne) June 28, 1968. Both vessels passed their operational evaluations and were declared surplus in 1980. The Sikorsky boat was appreciated for the firepower of the 105mm howitzer but had serious mechanical problems. The Sewart boat had a Navy 81mm mortar in a well right at the bow for bunker busting. It had three Mk 48 turrets each with a 40mm Bofors gun from the AC-130 Spectre gunship. The Sikorsky boat only had a single Mk 48 turret in the bow. The production plan for the ASPB Mk 2 was service prototype deliver in 12/68 with approval by 4/69. Contract signing in 7/69 for first deliveries in 3/70 and continuing at a rate of four per month for two years. Cost was estimated at $800,000 per unit and it looks like both Sikorsky and Sewart were to receive contracts to meet the demand.
« Last Edit: May 08, 2011, 06:53:57 am by Abraham Gubler »
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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Re: 2nd Generation US Navy Riverine Craft
« Reply #1 on: May 06, 2011, 11:31:35 pm »
Thanks Abraham. That bottom pic of the Sikorsky ASPB is the best one I've seen as far as determining scale.
There is more on the Sikorsky ASPB here.
http://www.sikorskyarchives.com/boat2.html

Are the weapons in the big turrets on the Sewart 30mm?


Offline Grey Havoc

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Re: 2nd Generation US Navy Riverine Craft
« Reply #2 on: May 08, 2011, 05:51:38 am »
So the first 4 photos are of the model, and of the prototype, of Sewart Seacraft's ASPB entry. Any idea where that prototype ended up? 

Offline Abraham Gubler

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Re: 2nd Generation US Navy Riverine Craft
« Reply #3 on: May 08, 2011, 06:56:14 am »
The 2nd generation of RAS craft was also to include a modular ATC (Armoured Troop Carrier).

The initial requirement for the new ATC was to carry 15-30 troops, down from 40 in the LCM(6) based ATC, but with the ability to rapidly disembark via a ramp or over the side. The CCB [Command and Control Boat] version was to carry a staff of five in place of the dismount unit. Speed of 25 knots was preferred but 20 knots was acceptable. Later the troop load was increased to 60 with supplies for two days and speed reduced to 15 knots with 15,000 lbs load or 12 knots at 20,000 lbs. Protection was to defeat RPG-2 and 75mm RCL. The ATC could be converted to a monitor with a variety of modules to be developed by Naval Ordnance Laboratory. The main monitor module was armed with the 152mm gun launcher turret of the Sheridan tank. Lighter modules carried either flamethrowers or the 106mm recoilless gun backed by MGs.

The Sewart ATC/CCB failed its operational evaluation in January 1969. It made a top speed of 26.2 knots but failed to meet the minimum sustained speed of 16 knots (only making 13.2 knots). Endurance was 170 NM instead of 250 NM and turning circle 75’ rather than 50’. It was also noisy, the coxswain had limited visibility, propulsion vulnerable to debris and no covered access to the gun turrets. It could carry 44 troops or a M113 APC.
« Last Edit: May 10, 2011, 03:53:20 am by Abraham Gubler »
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

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Re: 2nd Generation US Navy Riverine Craft
« Reply #4 on: May 08, 2011, 09:39:49 am »
Thanks for these Abraham: These are of particular interest given the current focus on litorral matters by the US and other navies.


Just a point of order. Except for the last photo of the ASPB, the source seems to be Norman Friedman's US Small Combatants an Illustrated Design History
http://www.amazon.com/Combatants-Including-Pt-Boats-Subchasers-Brown-Water/dp/0870217135
I had a copy before it was lost with my house in Hurricane Ida.


Offline Abraham Gubler

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Re: 2nd Generation US Navy Riverine Craft
« Reply #5 on: May 08, 2011, 09:31:35 pm »
Just a point of order. Except for the last photo of the ASPB, the source seems to be Norman Friedman's US Small Combatants an Illustrated Design History

They are all US Navy copyright images. But of course Friedman’s book is my source for all of them and the information.

http://www.amazon.com/Combatants-Including-Pt-Boats-Subchasers-Brown-Water/dp/0870217135

$170 to $570…. Thank God for the library system.

I had a copy before it was lost with my house in Hurricane Ida.

What the sea giveth, the sea taketh…
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Abraham Gubler

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Re: 2nd Generation US Navy Riverine Craft
« Reply #6 on: May 08, 2011, 09:48:38 pm »
Tabulated Data for the boats:

Sewart ASPB Mk 2

Length: 50’, Beam: 21’4”, Draft: 2’9”, Displacement: 90,310 lbs, Engines: 2 Avco-Lycoming TF-1260, Power: 1,050 hp (950 hp continuous), Speed: 25 knots, Fuel: 2,000 gallons, Range: 250 NM, Armament: 3 20mm, 1 40mm 1 81mm, Hull Material: Aluminium, Cost: $2.7m

Sikorsky ASPB Mk 2

Length: 48’8”, Beam: 19’8”, Draft: 3’5”, Displacement: 74,537 lbs, Engines: 3 P&W Canada ST6-570, Power: 565 hp (443 hp continuous), Speed: 25 knots, Range: 250 NM at 15 knots, Armament: 1 105mm (M101), 1 twin 20mm, 1 Mk 48 Mod 2 turret, Hull Material: GRP , Cost: $2.6m

Sewart ATC Mk 2

Length: 49’9”, Beam: 24’, Draft: 3’3”, Displacement: 97,023 lbs, Engines: 2 Avco-Lycoming TF-1260, Power: 920 hp (800 hp continuous), Speed: 20 knots, Range: 250 NM at 15 knots, Armament: 2 Mk 48 Mod 2 turrets, Tactical Diameter: 35 yards at 6 knots, Cost: $1.5m
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline Jschmus

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Re: 2nd Generation US Navy Riverine Craft
« Reply #7 on: May 09, 2011, 10:53:53 am »
I don't know if they would be of any interest here, but I have photos of some of the current generation of US riverine craft.

Offline Abraham Gubler

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Re: 2nd Generation US Navy Riverine Craft
« Reply #8 on: May 09, 2011, 05:50:38 pm »
I don't know if they would be of any interest here, but I have photos of some of the current generation of US riverine craft.

Please post them, especially if you have any more images of the Safe Boat built CB90, but in a new thread in this part of the forum:

http://www.secretprojects.co.uk/forum/index.php/board,41.0.html

These threads are for historical projects that never made it into service or off the drawing board.
"There is a tendency in our planning to confuse the unfamiliar with the improbable." Thomas Schelling

Offline JFC Fuller

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Re: 2nd Generation US Navy Riverine Craft
« Reply #9 on: May 10, 2011, 01:02:09 am »
Just a point of order. Except for the last photo of the ASPB, the source seems to be Norman Friedman's US Small Combatants an Illustrated Design History
http://www.amazon.com/Combatants-Including-Pt-Boats-Subchasers-Brown-Water/dp/0870217135
I had a copy before it was lost with my house in Hurricane Ida.

Brickmuppet,

Thanks for that, I thought all this looked familiar.