Teaching Planing Speed on the Powerboat Level 2 course:
KNOWLEDGE OF:
- Loading: effect on handling & performance, effect on balance & trim, CE plate and manufacturers recommendations
UNDERSTANDS:
- Crew members: minimum number in faster craft, keeping a good lookout
- Awareness of other water users, including effect of wash
- Planing boats: propellor angle & immersion, shallow drive, planing handling
CAN:
- Handle a boat at planing speed
Instructor Briefing to cover:
- WHAT you / your students are going to do?
- WHERE you're going to carry out the activity?
- WHY we take so many considerations before and during planing speed activities?
- WHEN to speed up, slow down, turn etc
- HOW to achieve the aim (planing) then give a short demo.
Preparation:
- Are the conditions and area appropriate? (Visibility, Sea State, Other craft etc)
- Are you allowed to 'speed' in the area?
- Ensure all gear onboard is stowed away / Secure all loose gear
- Brief crew on correct positioning, lookout & communications
- Trim the engine down
- Ensure area is safe & clear
Crew Briefing:
- Ensure all crew / students are aware of what will be happening and what to expect
- All crew to keep a good lookout and make helm aware of any potential hazards / other craft in the area
- All crew / students to sit or stand in a secure position and hold on
Activity:
Each student in turn will have a go at all of the following:
Aim: Good crew communications
- Carry out good crew communications prior to any action i.e. when speeding up, turning or slowing down so there are no surprises !
Aim: Good throttle control
- Helm to bring powerboat gradually 'just' onto the plane and maintain a fixed speed i.e. 16 knots
Aim: Trim control
- Helm to adjust trim (trim tabs and/or power trim) to obtain optimum position
Aim: Turning (1 hand steer, 1 hand gear)
- Warn crew and carry out 360º check to ensure safe and clear prior to starting turn
- Perform wide, gentle turn/s maintaining a planing speed
Aim: Slowing down safely
- Warn crew and carry out 360º check (particularly behind) prior to slowing
- Trim engine down
- Reduce power gradually to reduce possibility of swamping
TOP TIP: Try to avoid engine ventilation (see info on what is ventilation & cavitation below)
Other Background Information to include:
- Propellor angle and immersion (see further info below)
- Ventilation vs. Cavitation (see further info below)
- Prop Slip (see further info below)
- Power trim (FYI we do not condone the lack of lifejacket in this video)
- Making a VHF distress (MAYDAY) call
- Cold Water shock & Immersion Hypothermia (+ see cold water shock info below)
- Avoiding & mitigating the risk of a hook turn
What is cold water shock?
What is the difference between Ventilation & Cavitation?
What is the difference between wash & wake?
Powerboat Prop Slip:
What is Prop Slip?
Propeller slip is the difference between the distance a propeller travels through water and the distance it should theoretically travel. It's a necessary part of a propeller's function, and is typically between 5% and 25%.
Slip and boat speed
Slip is not constant, and changes depending on the boat's speed. Slip is highest when the boat is transitioning from displacement to planing, and decreases as the boat reaches its maximum speed.
Slip and propeller efficiency
Too much diameter or blade area can reduce slip, but it can also lower the boat's overall efficiency and performance
Slip and propeller pitch
Lowering the propeller pitch can increase acceleration and thrust, while increasing the pitch can make the boat go faster.
Slip and propeller issues
If the slip is greater than 25%, there may be an issue with the propeller.
Powerboat Propellor Angle & Immersion:
A powerboat propeller's immersion and angle can affect its performance in several ways, including:
Immersion ratio
A propeller's immersion ratio can affect its hydrodynamic coefficients and efficiency.
Immersion depth
Propeller immersion depth can vary due to wave phase, which can cause a decrease in performance.
Pitch motion and tilt angle
A study found that the wave phase can affect a propeller's relative immersion depths and advance ratios.
Partial submerged propeller
A partial submerged propeller (PSP) has each blade enter and exit the water during rotation. This type of propeller is often considered one of the most efficient propulsive devices for high-speed vessels.
Rake
The rake is the angle of the propeller blades perpendicular to the propeller hub. The average rake angle for most outboard propellers is 15 degrees.