NECP_025_Fuel_Bilge_Bypass_Tube_Seal_(2).pdf

United States Marine, Inc.

10011 Lorraine Road Gulfport, MS 39503

USA

(228) 679-1005

October 10, 2008

NECP025; RIB 08-075

Peter Depa

USSOCOM SOAL-M&RCC

7701 Tampa Point Blvd MacDill AFB, FL 33621-5323

Subject: 11 Meter NSWRIB; Contract No. USZA22-03-D-0003 NSWRIB Fuel Compartment Bilge Bypass Tube Sealant

Dear Mr. Depa:

Below please find background information on the sealing methods for the Fuel Compartment Bypass Tube.

History: The Bypass Tube connects the forward bilge to the aft bilge allowing liquids to flow between the two. Proper sealing of the tube prevents these liquids from intruding into the fuel compartment, and fuel from leaking into the bilges.

Findings: Historically, the bypass tube has been sealed using 3M™ 5200© Marine Adhesive Sealant.

In some cases, the 5200 sealant has been compromised, allowing fuel to leak into the bilge compartments.

Conclusion: USMI will begin using a two-part urethane foam to seal the bypass tubes in place. After the foam is cured, the entire tube/foam union will be sealed using fiber re-enforced plastics.

This will create a completely sealed fuel cell compartment, and prevent the transfer of liquids between the bilge and fuel compartments. See Attachment 1 for details.

If you have any questions or comments, please do not hesitate to call me by phone at (228) 679-1005 or e-mail at maleyd@usmi.com.

Sincerely, D.J. Malley cc: Sandy Smith Heather Stiller Ron Gospodarski Eric Griffith Phillip Navock

Andy Andrews

TANK COMP. BYPASS TUBE

FIGURE 1

Attachment 1

FIGURE 2 CUTAWAY

PROFILE OF THE

NSWRIB

FIGURE 3

Figure 3 shows the bypass tube in the floor of the fuel compartment. 5200 marine grade adhesive is used to seal the tube as it penetrates the forward and aft fuel compartment bulkheads. This installation procedure represents how the tube has been installed and remains the same for NECP 025.

Bypass Tube as installed in Fuel Compartment

Inside Stbd Fuel Cell Compartment

Forward Fuel Compartment

Bulkhead

FIGURE 4

Figure 4 shows the bypass tube penetrating the forward fuel compartment bulkhead into the forward bilge.

Bypass Tube penetrating the forward fuel compartment bulkhead, into the forward bilge.

FIGURE 5

Figure 5 shows the bypass tube penetrating the aft fuel compartment bulkhead into the engine room bilge.

Bypass Tube penetrating the aft fuel compartment bulkhead, into the engine room bilge.

FIGURE 6

Figure 6 shows a layer of Corecell foam above the bypass tube, creating a cavity to seal off the area occupied by the tube. The Corecell is bedded in a micro-sphere/resin mixture.

FIGURE 7

Layer of Corecell Foam covering the Bypass

Tube

Inside Stbd Fuel Cell Compartment

TANK COMP. BYPASS TUBE

FIGURE 7

Figure 7 shows 5 oz. fiberglass mat impregnated with resin layered on top of the Corecell foam, thereby sealing the fuel cell compartment. If fuel leaks, it will remain segregated from the bilge bypass tube. The fuel can then be drained from the fuel cell compartment using the fuel compartment drain plugs.

FRP Mat and Resin sealing the Corecell Foam and Bypass

Tube