Snag Boat Final Presentation Eric Speight Matthew Funk Courtney Johnson

Outline Introduction Problem Proposal Solution Accomplishments Center of Mass Calculation Buoyancy Force Calculation Structural Properties Deck Strength Calculation Patran Analysis of Proposed Changes Conclusion Complications Gantt Chart Questions

Introduction What is a Snag boat? Traditional use of the ROS Snag boat was to clear debris from rivers for safe navigation.

Introduction The JRRF is located at FT. Eustis in Virginia.

Introduction JRRF use To maintain and inspect moorings. e.g. Anchors, chains.

Problem.. Crane failure due to an excessive load.

Problem continued.. Non-operational snag boat due to broken crane No usable space for the JRRF to operate

Problem.. Picture of Current snag boat.

Proposal Make the vessel more usable Remove second level Remove portion of first floor Move wheel house to rear on first floor Relocate crane to accommodate deck space for mooring inspection. Assure that integrity of vessel is uncompromised

Proposal

Solution We needed to see if these modifications were even possible without seriously damaging the structural integrity of the boat. We calculated the center of mass of the boat, as well as the upward buoyancy force. Deck strength Analysis Patran Analysis of section before and after modifications

What we have accomplished Developed website Center of mass before and after modifications Buoyancy force Gathered information regarding structural analysis of ships Determined beam properties applicable to our ship

What we have accomplished Analyzed the deck strength Analyzed the proposed modifications in Patran

Center of Mass Calculation Baseline (82 , 5, 21) Proposed(81, 4 ,21) Baseline with Load (93, 6, 21) Proposed with Load (93, 6, 21)

Buoyancy Force Calculation Buoyancy is an integral part of determining still water moment 1170 tons

Structural Properties Information for all L beams on ship Steel plating thickness, weight, etc.

Deck Strength Calculation Assumed the deck to be made out of G10180 Cold Drawn Steel Width = 40ft Thickness = .25 in Compared it to stress calculated using F/A Force is weight of chain link and anchor Calculated the cross sectional area of a chain link and anchor on the ship deck

Chain Link Used a 5-1/4 open link chain Weight of 1 Link = 440lbs Width of link = 31 inches

Anchor Assumed a 10,120 lb anchor Width of anchor: 94.0625in

Comparing Results Max yielding strength value: Maximum Yield Stress = 54 kpsi Modeled the deck as a simply supported beam with a cross sectional area of: A = (width of chain + width of anchor)*(deck thickness) A = 31.265 in^2 σ = W/A = 337.75 psi Therefore the deck can handle the stress

Deflection of the Deck Modeling the deck as a simply supported beam where: ∆ = 5PL^4/384E*I Calculated moment of inertia by using deck thickness/width I = 2.304e 6 E = 30 e 6 psi ∆ = .10569 in

Patran Baseline

Patran Proposed

Force Divided buoyant force by the foot print of the ship. Yielded 344 lbs/sqft Applied 100 lbs/sqft to the bottom 5 ft of the sides of the hull Applied the density of A-36 steel to the model

Baseline Isometric Displacement Max Deformation 0.184 Feet

Proposed Isometric Displacement Max Displacement 0.0936 Feet

Baseline Stress Tensor Maximum Stress 2.27e6 psf

Proposed Stress Tensor Maximum Stress 1.88e6 psf

Safety Factors A36 Yield Stress of 5.22e6 Baseline 2.3 Proposed 2.9

Structural Pro’s Removing weight but maintaining integral parts of the structure No beams will be swapped out for smaller ones Estimated weight removed would be 63,000 lbs Hull beams will remain untouched. They have the highest load on them.

Structural Con’s Stress Stress concentration located right on the section where we stopped modeling

Structural Recommendations/Final Thoughts Entire ship needs to be modeled in ten foot sections Safety Factor is low, a ship that is loading and unloading should have a high safety factor (approx 6) due to fatigue

Complications Initially no clear direction After some discussion we came to the realization of what we needed to be done.

Gantt Chart

Any Questions??

END