1. – The Effectiveness of Guards in Mitigating Propeller Strikes –
William Daley, P.E.
Mechanical Engineer

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.
Video 14
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.
Video 16
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
Video 11
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
Video 20
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
Video 24
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
Video 29
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
Video 35
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
Video 42
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
pvc core fully or partially removed
Video 54
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
Video 58
Test sample 6-in. from propeller

26. Concentric ring: 5 mph Test sample 6-in. from propeller
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
Video 62
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
Video 67
Test sample 6-in. from propeller

28. Concentric: reverse Test sample 12-in. from propeller
24-in. no motion of sample
12-in.
Pulled into guard
Multiple pieces
pvc core removed
Chunks
6-in.
Video 77
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.
Debris scattered
Video 105
Test sample 12-in. from propeller

31. Octagonal: cluster sample-parked-in-gear
Pulled into guard
Multiple pieces
pvc cores removed
6-in.
pulled into guard
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
Video 109
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
Video 111
Test sample 6-in. from propeller

34. Octagonal & Unguarded -15 mph comparison
Video 109, Video 111
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

51. Turning Point Prop: 15 mph
6-in: horizontal, 10-in. diameter, 30-in. long
Test sample 6-in. from propeller

52. Turning Point Prop: 5 mph
10-in. diameter, 16-in. long
24-in. & 12-in.: no contact
6-in.: two runs. Up to three cuts, some 3-in. deep
Test sample 6-in. from propeller

53. Turning Point Prop: Parked-in-Gear
10-in. diameter, 16-in. long
24-in.: no contact
12-in.: two runs. Cuts up to three inches deep
Test sample 12-in. from propeller

54. Turning Point Prop: Reverse
10-in. diameter, 16-in. long
24-in.: no contact
12-in.: two runs. One resulted in three slices, the other four slices
Test sample 12-in. from propeller

55. Octagonal Ring Guard: 15mph
10-in. diameter, 16-in. long
24-in. & 12-in.: no contact
6-in.: two runs. Large piece removed from sample and piece contacted propeller
Test sample 6-in. from propeller

56. Octagonal Ring Guard: 5mph
10-in. diameter, 16-in. long
24-in. & 12-in.: no contact
6-in.: guard shaped piece removed from sample
Test sample 6-in. from propeller

57. Octagonal Ring Guard: Parked-in-Gear
10-in. diameter, 30-in. long
24-in.: no contact
12-in.: multiple deep cuts, pieces removed, irregular cuts and tears, cuts to pvc core, and damage along full length of sample
Test sample 6-in. from propeller

58. Octagonal Ring Guard: Reverse
10-in. diameter, 16-in. long
24-in.: no contact
Testing with guard suspended due to unserviceable guard as a result of contact damage

59. Testing Summary – small samples

60. Testing Summary – large samples

61. Questions & Answers William Daley 800-466-1090