– The Effectiveness of Guards in Mitigating Propeller Strikes –

1. – The Effectiveness of Guards in Mitigating Propeller Strikes– William Daley, P.E. Mechanical Engineer wdaley@cedtechnologies.com 800.466.1090

2. Background • ABYC contracted CED to participate in a three-phase study into propeller-related injuries and their mitigation using propeller guards • Phase I consisted of CED’s analysis of the human factors involved in propeller strikes • Phase II of the propeller guard analysis involved on-water propeller guard performance testing conducted by MacNeil, Akers and Goudy • The current effort (Phase III) involved CED’s testing and analysis of commercially available propeller guards designed for use in the recreational boating industry

3. Testing Location • Performed at the University of Buffalo testing facility – the Center for Research and Education in Special Environments (CRESE) in July and December 2010 • Circular pool suitable for controlled testing • CED wishes to thank: • Dr. David R. Pendergast, CRESE Director • Andrew Barth, CRESE Technical Director for their support in this phase of the propeller guard study

4. CED Team • Program Manager – William H. Daley, III, P.E. • Mechanical engineer with over 30 years experience, including 20 years as a Naval Officer and Associate Chairman of the Mechanical Engineering Department, U. S. Naval Academy • BS, U.S. Naval Academy • MS, Aeronautical Engineering, U. S. Naval Postgraduate School • Patrick J. Hudson, Ph.D., P.E. • Naval architect with over 20 years of experience, including David Taylor Model Basin and U. S. Naval Academy faculty • BS, Naval Architecture, U.S. Naval Academy • MSEng, Civil Engineering, Johns Hopkins University • Ph.D., Ocean engineering, Johns Hopkins University • R. Gregory Lank, P.E. • Mechanical engineer with 9 years experience • BS, Mechanical Engineering, Penn State University • Corey M. Redmond, E.I.T. • Mechanical Engineer with 2 years experience • BS, Mechanical Engineering, Rensselaer Polytechnic Institute

5. Testing Protocol • Effectiveness of propeller guards studied with engine speeds of 15 mph, 5 mph, parked-in-gear, and reverse • Speeds representative of planing speed, no-wake speed and maneuvering • Test samples placed 90° from centerline of propeller at distances of 30-in., 24-in., 12-in., and 6-in. measured horizontally • Five test scenarios: (1) unguarded, (2) cage guard, (3) round ring guard, (4) octagonal ring guard, and (5) concentric ring guard

6. Guards: Cage &Round Ring Cage Guard Round Ring Guard

7. Guards: Octagonal & Concentric Octagonal Ring Guard Concentric Ring Guard

8. Test apparatus • CRESE circular pool 8-ft. wide, 8-ft. deep fitted with a rotating arm • 200 hp engine mounted on the rotating arm

9. Test apparatus • Two Deep Blue Pro color underwater video cameras mounted on extruded aluminum frame – approaching and departing perspective • Olympus iSpeed high speed camera mounted adjacent to an underwater observation window – 90° to engine path

10. Test apparatus • Test samples • Gelatin Innovations VYSE professional ballistic gel • 16-in. long, 3-in. diameter, cored with 1/2-in. schedule 40 PVC piping and a 4-way cross fitting centered within the sample (July and December 2010 testing) • 10-in. diameter, 16-in. or 30-in. long, cored with schedule 40 PVC piping in the same manner (December 2010) • Cured and hung from extruded aluminum frame • Frame design permitted movement of sample along line perpendicular to centerline of propeller

11. Test apparatus summary

12. Testing results • 112 runs in the CRESE pool in July 2010 and 107 runs in December 2010 • Recorded using three cameras • High speed video analysis and physical sample inspection after each run • Any degree of contact photographed • Notes taken to describe orientation (engine speed and test sample distance) and results • New sample after each verified contact

13. Unguarded: 15 mph • No contact with propeller • Distances • 30-in. • 24-in. • 12-in. • 6-in. Test sample 6-in. from propeller

14. Unguarded: 5 mph • No contact when sample at 12-in. • Sample struck during 2 of 3 runs at 6-in. Test sample 6-in. from propeller

15. Unguarded: parked-in-gear • No contact at 24-in. • Drawn into propeller at 12-in. on each of two runs Test sample 12-in. from propeller

16. Unguarded: reverse • No contact at 12-in.; two runs • 6-in. - struck during each of two runs. Multiple cuts Test sample 6-in. from propeller

17. Cage guard: 15 mph • No contact at 12-in. • 6-in. - blunt force strike on each of three runs • Multiple cuts 8-1/2-in. apart centered about center of sample • Fractured about center connection during one of three runs Test sample 6-in. from propeller

18. Cage guard: 5 mph • 12-in. – sample pushed by guard with no observable contact damage • 6-in. - sample pushed by guard with no observable contact damage Test sample 6-in. from propeller

19. Cage guard: parked-in-gear • No contact with the guard when test samples were as close as 6-in.

20. Cage guard: reverse • 6-in. • Test sample was observed to rest on the guard • No observable cuts or tears in the sample

21. Octagonal ring guard: 15 mph • 12-in. – no contact • 6-in. • Pulled into guard • Captured • Cut into multiple and irregular pieces • Discharged out aft end • pvc core pulled from sample and cut into multiple pieces Test sample 6-in. from propeller

22. Octagonal ring guard: 5mph • 12-in. – no contact • 6-in. • Pulled into guard • Multiple strikes • pvc core pulled from sample and cut into multiple pieces Test sample 6-in. from propeller

23. Octagonal: parked-in-gear • 30-in. – no sample motion • 24-in. – pulled into guard with multiple cuts, pvc core removed • 12-in. – pulled through guard with multiple cuts, pvc core fully or partially removed • 6-in. – pulled into with multiple cuts, chunks and pvc removed Test sample 6-in. from propeller

24. Octagonal ring guard: reverse • 24-in. – no sample motion • 12-in • Pulled through guard • Cut into multiple pieces • pvc core removed • 6-in. • pulled through guard • Cut into multiple pieces • pvc core fully or partially removed Test sample 12-in. from propeller

25. Concentric ring: 15 mph • 12-in. no contact • 6-in. • Blunt force contact • Split into multiple pieces • Cuts • pvc core partially removed Test sample 6-in. from propeller

26. Concentric ring: 5 mph • 12-in. – no contact • 6-in. • Gel split to core • Gel tearing • pvc core dislocated • Pulled from suspended connection, captured and dragged upstream with guard Test sample 6-in. from propeller

27. Concentric: parked-in-gear • 24-in. – horizontal, no contact • 12-in. – horizontal and vertical, no contact or rested on guard • 6-in. • Horizontal: drawn through guard, multiple pieces, core removed • Vertical: Drawn into guard, no prop contact Test sample 6-in. from propeller

28. Concentric: reverse • 24-in. no motion of sample • 12-in. • Pulled into guard • Multiple pieces • pvc core removed • Chunks • 6-in. • Pulled into guard • Multiple pieces • Chunks • pvc core removed Test sample 12-in. from propeller

29. Round ring guard • Substantially similar results to octagonal ring guard • Contact made with similar results at the same orientations • 15 mph: 6-in. • 5 mph: 6in. • Parked-in-gear: 24-in., 12-in. & 6-in. • Reverse: 12-in. & 6-in.

30. Octagonal: cluster sample -reverse • Three sample bound together • 24-in. – no contact • 12-in. • Pulled into guard • Cut into multiple pieces • pvc cores removed • 6-in. • Pulled into guard • Cut into multiple pieces • pvc cores removed • Debris scattered Test sample 12-in. from propeller

31. Octagonal: cluster sample-parked-in-gear • 12-in. • Pulled into guard • Multiple pieces • pvc cores removed • 6-in. • pulled into guard • Multiple pieces • pvc cores removed Test sample 12-in. from propeller

32. Octagonal: cluster sample -15 mph & 5mph • Similar results at both speeds • 6-in. • Pulled into guard • Multiple cuts • Multiple pieces • pvc cores removed Test sample 6-in. from propeller

33. Unguarded: cluster sample -15 mph • 6-in. • Cluster remained intact • One piece sustained a cut • One piece sustained a tear Test sample 6-in. from propeller

34. Octagonal & Unguarded -15 mph comparison Test sample 6-in. from propeller

35. Environmental Safety Prop: 15 mph • No contact with propeller • Distances • 24-in. • 12-in. • 6- in. Test sample 6-in. from propeller

36. Environmental Safety Prop: 5 mph • No contact when sample at 24-in. and 12-in. • Sample struck during 2 of 3 runs at 6-in. Test sample 6-in. from propeller

37. Environmental Safety Prop: Parked-in-Gear • No contact at 24-in. • Drawn into propeller at 12-in. on each of two runs Test sample 12-in. from propeller

38. Environmental Safety Prop: Reverse • No contact at 24-in. • 12-in. – struck during each of two runs. Multiple cuts and pieces removed Test sample 12-in. from propeller

39. Environmental Safety Prop: 15mph • 10-in. diameter, 16-in. long • No contact at 24-in. & 12-in. • 6-in. – struck during each of two runs. Cuts as deep as pvc core. Test sample 6-in. from propeller

40. Environmental Safety Prop: 15mph • 10-in. diameter, 30-in. long • No contact at 24-in. & 12-in. • 6-in. – struck during each of two runs. Cuts up to 3-in. deep. Test sample 6-in. from propeller

41. Environmental Safety Prop: 5mph • 10-in. diameter, 16-in. long • No contact at 24-in. & 12-in. • 6-in. – struck during each of two runs. Three principle cuts. Test sample 6-in. from propeller

42. Environmental Safety Prop: 5mph • Horizontal orientation -10-in. diameter, 30-in. long • No contact at 12-in. • 6-in. – five slices along length Test sample 6-in. from propeller

43. Environmental Safety Prop: 5mph • 10-in. diameter, 30-in. long • No contact at 12-in. • 6-in. – two cuts. Test sample 6-in. from propeller

44. Environmental Safety Prop: Parked-in-Gear • 10-in. diameter, 16-in. long • 24-in.: no contact • 12-in.: three runs w/cuts to lower portion of sample • 6-in.: three slices on 1 of 2 runs Test sample 12-in. from propeller

45. Environmental Safety Prop: Parked-in-Gear • Horizontal orientation -10-in. diameter, 30-in. long • 12-in.: two runs. 3 cuts on one run, 4 cuts on the other Test sample 12-in. from propeller

46. Environmental Safety Prop: Parked-in-Gear • 10-in. diameter, 30-in. long • 24-in.: no contact • 12-in. & 6-in.: two at each distance. Minor knicks to one sample; no evidence of contact on other. Test sample 6-in. from propeller

47. Environmental Safety Prop: Reverse • 10-in. diameter, 16-in. long • 24-in.: no contact • 12-in.: two runs with multiple cuts • 6-in.: two runs, one w/extensive cuts to pvc core Test sample 12-in. from propeller

48. Environmental Safety Prop: Reverse • 10-in. diameter, 30-in. long • 24-in.: no contact • 12-in.: two runs. Contact with no evidence of damage • 6-in.: two runs. One with up to seven slices Test sample 6-in. from propeller

49. Turning Point Prop: 15 mph • 10-in. diameter, 16-in. long • 24-in. & 12-in.: no contact • 6-in.: two runs – two cuts, some as deep as 3-in. Test sample 6-in. from propeller

50. Turning Point Prop: 15 mph • Horizontal, 10-in. diameter, 30-in. long • 24-in. & 12-in.: no contact • 6-in.: two runs. One resulted in fours slices, the other five slices Test sample 6-in. from propeller