heavy weather and boat handling seattle safety at sea seminar 25 feb 2012 paul h. miller, d.eng....

Heavy WeatherAnd Boat Handling

Seattle Safety at Sea

Seminar25 Feb 2012

Paul H. Miller, D.Eng. P.E.Professor of Naval Architecture

United States Naval Academy

Is a “big boat” – let’s say a 45-foot boat, much safer than a “small boat” – around 29 feet?

a) Always, by a lot

b) A tiny bit

c) It depends

d) They are basically the same

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A Reality Check

It is relative…

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All boats are small compared to what the ocean can throw at us!

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But what is “heavy weather” for your boat and you?

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A short sea story

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A calm start turned in to a gale in one hour!

Wind Strength(“Heavy” is what you are not used to!)

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22-33 knots = Small Craft Advisory34-47 knots = Gale Warning48-63 knots = Storm Warning> 65 knots = Hurricane Warning> 52 knots = Severe Thunderstorm Warning

Sailing in a Gale40-45 knots

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Fetch

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Fetch is the distance the wind blows from the land.

Waves reach full potential at 1000 NM but wave >20 ft can be seen at 15 miles

A wind/wave nomogram can be used to predict wave height

Shallow Waters Create Steeper Waves

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Wave Height/Wave Length Ratio May Go from 1/14 to 1/7 and may create breaking waves.

Becomes worrisome when water depth is less than 2x wave length.

Wave Patterns

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Waves are generated mainly from wind. Different wind sources will send waves in multiple directions. This causes multiple, overlapping waves.

Wave Heights

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The normally reported wave height is the “significant wave height”, which is the average height of the top third highest waves.

This closely corresponds to what our eyes see.

The average of the top 1% highest waves is about double the height of the top third!“Wave heights of 3 to 6 feet…”

Rogue Waves

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Wave crests may “stack” up to create “rogue” waves, lasting for seconds or minutes.

Rogue waves may be over 100 ft!

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Tidal Waves (not Tsunami’s!)

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The wind blowing against a tidal current can produce very steep waves!

Some Sailboats Do Better Than Others In Heavy Weather

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What are the good characteristics?

1. Stability!!! (w/o human stability)

2. Deep draft (avoid surface drift)

3. Sufficient lateral plane for low speed

4. Maneuverability

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Ballast or Beam for Stability?“Ballast Stability” vessels tend to follow gravity! (They remain more upright in waves)

“Form Stability” vessels tend to follow the water surface! If the water surface is angled, the boat will be too! It may trip and capsize.

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Preparing the boat before you go!Think Watertight Integrity

1. Hatches/boards

2. Port lights (storm shutters)

3. Vents/Dorades

4. Through hulls

5. Mast

6. Rudder shaft

7. Control lines

8. Prop shaft

9. Locker covers

Hint: Give your boat a good shower!Watertight is good, airtight is not!

Preparing the crew and boat before the storm

1. Foulies/thermal

2. Hooking on – night, reefed, water temp <60

3. Lifejackets, whitecaps

4. Communications

5. PEPIRB

6. Review COBs

7. Stowage – think inverted! Batteries & Sails

8. Food – cooking, thermos

9. Jackstays

10. Visibility

11. Drogues

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Evaluate: Are you pushing the boat too hard?

Things to consider:

1. Risk vs reward

2. When to reef?3. Cruising –

think upwind (MOB)

4. Racing – your limits and recoverability

Strategies

1. Changing jibs

2. Reefing

3. Storm sails

4. Heave to

5. Sea anchor

6. Ahull

7. Drouges

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Consider slowing down!

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Practice Makes Perfect and Builds Confidence.

Be concerned but not afraid, it is not as bad as Hollywood makes it

out to be!

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