DART_II_Hull_Specification.pdf

NDBC STANDARD SPECIFICATION FOR FABRICATION OF BUOY HULLS

USED IN THE DEEP-OCEAN ASSESSMENT AND REPORTING OF

TSUNAMIS (DART®) ARRAY

1.0 SCOPE

1.1 General. This specification describes the requirements for the fabrication of buoy hulls used in the Deep-ocean Assessment and Reporting of Tsunamis (DART®) array. This requirement also includes the buoy well, lid, cable pass-thru, and bumper mounts. The contractor shall provide all the necessary labor, material, equipment, facilities and services to fabricate and deliver the hulls to the National Data Buoy Center (NDBC). For the purposes of this specification the terms "payload compartment" and "well" are identical.

1.2 Government Furnished Property. The government will only provide molds for the buoy hull shell. The contractor shall provide the molds for the buoy well, well flange, lid, and cable pass-thru. The government will ship the molds to the contractor's facility. The contractor shall be responsible for any reconditioning required on the hull molds for the duration of the contract.

Upon completion of the contract, the contractor shall return the molds in the same condition as received to NDBC.

1.3 Precedence. Any ambiguity or conflict between this specification and other applicable documents shall be resolved by the following order of precedence:

a) The issued contract with any amendments or modifications

b) This specification

c) The drawings listed in paragraph 2.4

d) Other applicable documents listed in paragraph 2.0

2.0 APPLICABLE DOCUMENTS

2.1 General. The documents listed in this section are referenced in sections 3 and 4 of this specification. This section does not include documents cited in other sections of this specification, which are recommended for additional information or used as examples. While every effort has been made to ensure the completeness of this list, document users are cautioned that they must meet all specified requirements cited in sections 3 and 4 of this specification, whether or not the referenced documents are listed here.

2.2 Government Documents. The following documents form a part of this specification to the extent referenced herein. Suffixes denoting the specific issue of each document are omitted from future references to the documents in this specification.

STANDARD DATE TITLE

MIL-P-21929B 15 Jan 1991 Plastic Material, Cellular, Polyurethane, Rigid, Foam-in-Place, Low Density (2 pounds per cubic foot)

FED-STD-595B 7 Jan 1994 Federal Standard Colors

NDBC-8117 12 Feb 2009 NDBC Standard Test Procedure for DART II Hull Pressure Test

2.3 Industry Publications. The following documents of the issues specified form a part of this specification to the extent referenced herein. Suffixes denoting the specific issue of each document will be omitted from future references to the document in this specification.

STANDARD DATE TITLE

ASTM A666-03 1 Oct 2003 Standard Specification for Annealed or Cold-Worked

Austenitic Stainless Steel Sheet, Strip, Plate, and Flat Bar

AWS Dl.6/Dl.6M 10 Mar 1999 Structural Welding Code - Stainless Steel

2.4 Drawings. The following NDBC drawings form a part of this specification to the extent referenced herein and shall be referred to as "the drawings" throughout this specification:

Drawing Rev Title D020011 C DART II Buoy Payload Compartment Assembly D020012 C DART II Buoy Hull Assembly D030043 B DART II Internal Buoy Structure D030047 B DART II Fiberglass Hull Shell D030048 B DART II Fiberglass Hull Deck D030050 B DART II Buoy Well Flange D030052 B DART II Lower Hex Well D030053 B DART II Cable Pipe Deck Flange D030060 C DART II Mounting Block D030061 B DART II Buoy Well Threaded Socket Weldment D030062 B DART II Rubber Handle Mounting Tab D030063 B DART II Buoy Well Cable Pass Thru D030083 B DART II Rubber Bumper Attachment Nut D030095 B DART II Buoy Well Lid

3.0 REQUIREMENTS

3.1 General. The buoy shall be fiberglass over foam with Type 316 stainless steel framework and four attachment points on both the top and bottom.

3.2 Materials

3.2.1 Fiberglass. The fiberglass lay-up shall be layered with a combination of bulk fiberglass, applied by chopper gun, and 24 oz. roving. Equal bi-directional plus, minus, 45-degree strand material may be substituted for 24 oz. roving. Resin to glass ratio shall be 65 to 35. A smooth surface inside mold shall be used to form the fiberglass skin within which the bulk of the fiberglass shall be laid up. This shall be the required technique with the objective of producing buoys of consistent size and shape. Buoys with a surface finish consisting of dips or waves of greater than 1/4 inch may be rejected. All transitions must be fully feathered. Proper fiber glassing techniques shall be followed to prevent delamination.

3.2.2 Stainless Steel. All stainless steel components shall be ASTM A666 Type 316.

3.2.3 Floatation Foam. The floatation foam injected into the hull shall meet the requirement of

MIL-P-21929B.

3.3 Construction

3.3.1 Fiberglass. The fiberglass shall have the following nominal thickness:

Hull Location Thickness (inches) Bottom 1/4 Sides to vertical flat 3/8 Vertical flat on up including top 1/2

Hull shall be constructed using alternate layers of chopped reinforcement, bi-directional and 24

oz. woven roving.

3.3.2 Procedure. Set the proper height of the frames to the inside of the shell. (the critical measurements here is the distance the lower pad eyes protrude out of the bottom of the buoy, i.e.,

3.7 inches minimum). Apply a 3/8-inch alternating layer of mat and roving extending a minimum of 6 inches on each side of the internal framework's bottom plates to secure the frame to the inside of the buoy bottom. An additional 1/8-inch thickness of reinforcement must be applied to the inner and outer seams. Each 1/8 inch thickness band shall be approximately 14 inches wide consisting of chop, two layers of 1-1/2 oz. mat and two layers of unidirectional roving. This additional thickness must be feathered into the adjacent areas not in excess of 3 inches on top and bottom to provide a smooth transition. All voids shall be filled with Duraglass and covered with a gel coat with surface agent then sanded to fair and re-gel coated as required.

The entire finished surface of the buoy is to be coated with gel coat with an air inhibited polyester surface. Apply an 18-inch wide strip of 40-mesh sand with gel coat to give a nonskid texture to the top of the buoy.

Drill thirteen 7/8 inch holes through the buoy side wall. Fiberglass the stainless steel rubber bumper mounts to the inside wall of the buoy at approximately 29 inch intervals. They shall be centered vertically on the rubber bumper groove and layered with 3/8 inch fiberglass and three layers of 24 oz. roving. These must be watertight. Note: the 29 inch interval will mean that the first and last bumper mounts will not be near 29 inches but closer to 12 inches apart.

Apply a smooth bead of 3M 5200 Marine adhesive/sealant to where the stainless steel framework and fiberglass meet.

The vertical sides up to and including the top, well and lid gelcoat shall be colored with three coats of safety yellow with surface agent added to the last coat. Other surfaces remain white.

3.3.3 Welding. All stainless steel welding shall be in accordance with AWS Dl.6.

3.3.4 Flotation Foam Injection. The contractor shall have a procedure for injection and curing of the floatation foam that is in accordance with MIL-P-21929B and manufacturer's instructions.

4.0 QUALITY ASSURANCE

4.1 Welding Procedures and Qualifications. The contractor shall submit welding procedures and welder qualifications that conform with AWS D 1.6 prior to fabrication of the framework.

4.2 Flotation Foam Filling Procedure. The contractor shall submit the selected floatation foam that meets MIL-P-21929B and the procedure for filling the hull prior to beginning the hull fabrication.

4.3 Hull Pressure Test. The contractor shall perform a hull pressure test in accordance with NDBC-8117. Any leaks will require repair and a retest until the test is passed At least two weeks prior to performing this test the contactor shall notify the government so they can witness the test.

4.4 Structural Integrity Test. The contractor shall conduct a proof test of the buoy framework.

This test shall be completed prior to encasing the buoy framework within the fiberglass hull.

This shall involve securing the lower part of the framework and pulling on each corner of the upper part of the framework until a load of 9,000 lbs is indicated on the load cell. This load shall be held for a period of 5 minutes. Following the test all welds and materials shall be inspected for deformation and cracking. Any signs of cracking or deformation will require repair and a retest until the test is passed. At least two weeks prior to performing this test the contactor shall notify the government so they can witness the test. The contractor will submit a signed and dated certificate to indicate the date in which this test was successfully completed.

4.5 Material Certifications. The contractor shall provide vendor supplied material certifications for all materials used in the construction of the buoy framework.

4.6 First Article. The contractor shall produce and deliver a first article of the buoy assembly for inspection prior to commencing fabrication of the remainder of the articles. This requirement may be waived at the contracting officer’s discretion if the contractor has successfully completed a DART buoy hull contract in the past

5.0 DELIVERABLES

All deliverables shall be shipped to the following address:

National Data Buoy Center Attn: Property Officer Building 3203 Stennis Space Center, MS 39529