HSCG33-11-R-ADB013 Attach 4.docx

HSCG23-11-R-ADB013 Attachment 4 Cutter Boat Over-The-Horizon - Parent Cutters Launch and Recovery System Descriptions and Interfaces U. S. Coast Guard RFP HSCG23-11-R-ADB013 30 September 2010

Introduction

Cutter-Boat Over The Horizon-IV (CB-OTH-IV) will be launched and recovered from three classes of parent cutters; National Security Cutters (NSC), Fast Response Cutters (FRC), and Legacy Cutters. Two different methods of launch and recovery (L&R) are utilized on these cutters; stern ramp and side davit. The NSC’s utilize both the stern ramp and a single point side davit while the Legacy Cutters utilize a dual point side davit and the FRC’s will utilize a stern ramp. The characteristics and interfaces of the stern L/R systems, single point side davit and dual point side davit systems are provided as reference for the design of the CB-OTH-IV.

The information provided is the best available at this time. The first FRC is in the process of being designed and built. Additionally changes to the side davit and gantry crane systems on the NSC are under consideration. The characteristics and interfaces associated with these changes will be provided in future updates of this specification.

National Security Cutter Single Point Davit System

A hydraulically operated C-Frame davit is currently provided on the NSC for launching and recovering the CB-OTH-IV, from the side of the NSC. The davit is an Allied Systems Model DC-8600CTS, with a safe working load of 8,600 pounds. The davit has a cradle for storing the boat. A bridle for lifting the boat onto the davit cradle is required. The davit hook is a Vestdavit Hook rated at four metric tons. The bridle ring is required to be sized to fit the Vestdavit hook. The bridle length has to be sized to keep the CB-OTH-IV boat on an even keel while being lifted and sized so that the vertical distance between the bridle ring and the baseline of the boat does not exceed 94 inches. If the latter requirement is exceeded, the CB-OTH-IV boat will not be able to clear the davit's cradle and reach its storage position on the davit. A drawing depicting the single point davit and interfaces is shown below.

National Security Cutter Stern Launch & Recovery System

Launch Operations - For the launch operation, the NSC maintains headway into the seas to create reduced symmetrical stern wake turbulence. The deck crewmember opens the transom gate after the crew and passengers board the boat. The CB-OTH-IV boat engine is started prior to launch release. The coxswain signals readiness to launch, and a quick release on the centerline winch is released by the bowman and the boat safely slides down the ramp and is away under control of the coxswain.

Recovery Operations - For the recovery evolution, NSC assumes the best heading to shelter the OTH and maintain a seawater pool in the ramp. The designed nominal sill depth of NSC is 43 inches. When the stern gate opens, bright colored Ultra Poly on the ramp centerline provides the coxswain of the CB-OTH-IV with clear indication of the boat alignment as it approaches the ramp. The coxswain drives the boat into and up the notch to have NSC’s capturing rope fall behind CB-OTH-IV’s bow post. Boat recovery operations are illustrated in the photographs below.

Stern Door Configuration - The NSC stern door consists of two sliding door assemblies, one port and one starboard. The stern door system is provided for protection of the CB-OTH-IV boat in the stern ramp while backing and from waves in following seas. The doors are mounted on the transom of the NSC and slide open outboard along the transom.

Ramp Opening - The well entry of the stern ramp is flared 15 degrees to enlarge the opening. The flare provides an opening at the transom of 17 feet 10 inches narrowing to 12 feet 8 inches, approximately 10 feet forward of the transom.

Ramp Surface - The angle of the NSC stern ramp is 14 degrees. The stern ramp has 4 boat skids that allow for better control of the CB-OTH-IV boat when it enters the well. The two inboard skids are flared to match the 15 degrees of the ramp opening. The inboard skids are placed 24 inches off the center line of the NSC, while the outboard skids are placed 48 inches off the center line. The boat skids are 12 inches high and include a one and three-quarter inch thick layer of Ultrapoly with a one-half inch thick layer of Neoprene under the Ultrapoly for minimizing the boat impact on the skids. The ramp entry, which is fully plated, is covered with one and one-half inch of Ultrapoly on top of a one-half inch of Neoprene.

Ramp Side Fenders - The side of the ramp is protected with fenders as shown in the picture below. These fenders have a one and one-half inch layer of Ultrapoly over a half-inch of Neoprene.

Water Management System - The water management system includes ramp deck openings for capturing wave swells. A five degree slope in the bottom plate below the ramp, in addition to transverse diaphragms with drain snipes, allows for the gradual runoff of water out of the ramp as illustrated below. The ramp deck openings are covered with a grating to allow cutter personnel to safely walk around the ramp.

Water Management System

Capture Mechanism - The NSC is equipped with a mechanism that automates the capture of the boats. The capture mechanism consists of dual carriages, one port and one starboard, connected together with a double nylon net and a capturing line. The net prevents the small boat from traveling too far up the ramp while the capturing line captures and holds the boat. The CB-OTH-IV boat enters the ramp and impacts the net, pushing the carriages up the ramp until the boat stopped. The carriages are connected to two electric winches with clutches via wire ropes. These winches control the forward and aft motion of the carriages. Once the boat stops and begins to slide back down the ramp, the bow-horn of the boat snags on the nylon capturing line, and the side winches are automatically activated to bring the boat up the ramp. The figure below shows a notional bow hook arrangement stating 30” being the maximum separation of the aftmost portion of the bow hook to the foremost portion of the boat. It should be noted that because of catenary in the capturing line and net, stretch of the capturing net, and possible deflection of the boats collar an accurate dimension cannot be provided. It has been demonstrated that 30” will provide for enough separation of bow hook to bow for the capturing line to snag. Other details of the capture mechanism with its interfaces are provided on the next page.

Bow Post Distance (Notional Bow & Bow Post)

Gantry Crane – A Gantry Crane is provided for transferring the small boat from the ramp to the boat stowage area or vice versa. The boat stowage area is just port and starboard of the NSC stern ramp. The system consists of two independent trolleys with winches, port and starboard on NSC. The two aft winches on the trolleys are fixed, while the forward winches can be moved 16.5 feet to 20.5 feet forward of the aft winch cable.

Fast Response Cutter Stern Launch & Recovery System

Launch Operations - For the launch operation, the speed of FRC is reduced to 5 knots while utilizing both propulsors to produce a reduced, yet symmetrical stern wake turbulence as the CB-OTH-IV boat launches. A deck crewmember opens the transom gate after the crew and passengers board the boat. The CB-OTH-IV boat engine is started prior to launch release. The coxswain signals readiness to launch, and the safety line is released by the bowman. The CB-OTH-IV boat is then held only by the winch cable. With the CB-OTH-IV boat under power and control by the coxswain, upon the command to launch the boat, the winch cable quick release lanyard is pulled by a boat bowman, and the boat safely slides down the ramp and is away under control of the coxswain.

Recovery Operations - For the recovery evolution, FRC assumes the best heading with a 20-40 degree offset to wave heading to reduce motions, and maintain a seawater pool in the ramp. The designed nominal sill depth is 24.4 inches. FRC speed will be held at 5 knots using both propulsors to produce symmetrical stern wake turbulence for safe CB-OTH-IV boat approach to stern notch. When the stern gate opens, bright colored Ultra Poly ramp skids fixed to the ramp deck provides the coxswain with clear indication of the boat alignment as it approaches the ramp. An artist rendering of the boat recovery on FRC is shown below. The CB-OTH-IV boat is then driven onto the ramp and captured by the mooring capturing line dropped over the bow post by a FRC deck crewmember.

Stern Gate - The transom of the FRC is fitted with a non-tight aluminum stern gate that, when closed, protects the CB-OTH-IV boat in the stern ramp while backing and from waves in following seas. The stern gate is non-tight allowing the water level at the lower end of the ramp to vary.

Stern Ramp - The stern ramp system is 12 degree inclined plane installed with Ultra Poly fendering which is located along the centerline of the stern ramp to provide a self centering operation. Ultra Poly is bolted to the ramp bottom creating a low friction surface which protects the ramp and CB-OTH-IV boat bottom’s surfaces from impact and abrasion and also permits the boat to slide down the ramp easily. The ramp extends below the water line within the FRC hull to create a seawater pool, or wet sill, at its base.

Recovery Winch System - The FRC stern winch is rated at 5,500 lbs. The winch has a drum spooled with CRES wire rope, 13.3 meters in length, that can extend 5m beyond the aft edge of the stern ramp to pull the CB-OTH-IV boat onto the ramp if a loss of power occurs on the boat. A quick release hook is connected at the working end for launching operations.

The CB-OTH-IV-FRC interface requirements are provided in the figure below.

Recovery on FRC (Artist Rendering)

Legacy Cutters Dual Point Davit System

A hydraulically operated Twin Pivot Arm Davit system is currently provided on the 378’, 270’, and 210’ Legacy Cutters for launching and recovering the CB OTH boat, from the side of the cutter. The davit is a Welin Lambie Type TW.PIV.5.OB, with a safe working load of 11,000 pounds. In order to accommodate different hook centers, the fwd davit arm position is variable between 17’ 8-3/4” and 20’ 3-1/2”. The davit has cradles for storing the boat. Bridles for lifting the boat onto the davit cradles are required. With a 6” clearance above the cradles the bridle ring heights should be no greater than 6’-1” from the keel of the boat where the hook centers are located. A drawing depicting the dual point davit and its interfaces is shown below.

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