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Comparisons of Propulsion by Performance

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Last article, we compared different types of vessel propulsion by cost. Though costs are an important part of the decision on equipping a vessel, each type of propulsion has its’ strengths and weaknesses.

Though France Helices manufactures the SDS, we are the first to say when a surface drive system is not appropriate for a vessel’s use. The desire to make a sale is over-ridden by the duty to our customer to sell the proper equipment for a vessel. Indeed, the first question we ask potential customers is: “How is the vessel going to be used?”

This is, perhaps, the most important question that must be answered: Far more important than a mere question of cost constraints. Different propulsion systems perform better or worse under different conditions. Of course, there are exceptions, but in general:

Surface Drives

Perform Well:

  1. Speeds over 30 knots
  2. Situations requiring a high degree of maneuverability
  3. Shallow draft
  4. Dirty water
  5. Rough seas (articulated surface drives only)
  6. Reverse (despite a common misconception)
  7. Vessels under 200 tons
  8. Vessel types: Patrol boats, OPV, crew boats, racing boats, some recreational boats, RHIBs, some rescue boats (determined by use), landing craft
  9. Vessels in areas with poor maintenance
  10. Vibration-critical operations

 

Perform poorly to mediocre:

  1. Operating speeds 15-25 knots
  2. Bollard pull required
  3. Vessel types: Minesweepers, some rescue boats, dive boats, pilot boats
  4. Single engine installation
  5. Very small boats (at least the France Helices SDS is not really suited to vessel under 8m LOA)

Maintenance: Simple and low cost.

 

Water Jets

Perform Well:

  1. Vessel Types: Pilot Boats, minesweepers, passenger ferries, some race boats, OSV, most rescue boats
  2. Vessels over 200 tons
  3. Clean water (offshore) operation
  4. Regions with good maintenance
  5. Lower speeds
  6. Applications where propellers in the water are unsafe
  7. Single engine vessels

 

Perform Poor to Mediocre:

  1. Speeds over 50 knots
  2. Rough seas
  3. Shallow draft
  4. Dirty water
  5. Regions with poor maintenance

Maintenance: Complicated and expensive

 

Stern Drives

Perform Well:

  1. Small vessels under 8m
  2. Single engine vessels
  3. Lower speed applications (15-25 knots)
  4. Vessel types: Small patrol, RHIBS, small recreational

 

Perform Poor to Mediocre:

  1. Vessel over 12m LOA
  2. Poor maintenance regions

Maintenance: Complicated and expensive.

 

Outboards

Perform Well:

  1. Remote regions with poor maintenance / parts supply
  2. Smaller vessels under 12m LOA
  3. Shallow draft areas
  4. Rough seas

 

Perform Poor to Mediocre:

  1. Larger vessels over 12m LOA
  2. Speeds over 35 knots

Maintenance: Simple and expensive over the long term

 

Conventional Propeller

Perform Well:

  1. Speeds under 30 knots
  2. Bollard pull critical
  3. Dirty water
  4. Rough seas
  5. Heavy or large vessels
  6. Vessels with large differentials in displacement
  7. Vessel types: Recreational, Crew boats, OSV, passenger vessels (like harbor ferries)

 

Perform Poor to Mediocre:

  1. Shallow draft
  2. Speeds over 30 knots

Maintenance: Simple and low cost

 


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