1. Snag Boat Final Presentation
Eric Speight
Matthew Funk
Courtney Johnson

2. 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

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

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

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

6. Problem..
Crane failure due to an excessive load.

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

8. Problem..
Picture of Current snag boat.

9. 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

10. Proposal

11. 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

12. 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

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

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

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

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

17. Deck Strength Calculation
Assumed the deck to be made out of G 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

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

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

20. 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 = in^2
σ = W/A = psi
Therefore the deck can handle the stress

21. 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
∆ = in

22. Patran
Baseline

23. Patran
Proposed

24. 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

25. Baseline Isometric Displacement
Max Deformation Feet

26. Proposed Isometric Displacement
Max Displacement Feet

27. Baseline Stress Tensor
Maximum Stress 2.27e6 psf

28. Proposed Stress Tensor
Maximum Stress 1.88e6 psf

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

30. 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.

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

32. 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

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

34. Gantt Chart

35. Any Questions??

36. END