boating safety circular 96

7/29/2019 Boating Safety Circular 96

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About 8:30 a.m. three men, ages 31, 37, and38, left for a day of fishing on a lake aboard a1988 18-foot, four inch bass boat. The weatherwas clear, the water was choppy (1.5 to 2 footwaves), the wind was seven to 14 miles per hourfrom the northwest, the air temperature was

about 65 - 70 degrees Fahrenheit. A countyemployee who had been fishing on the lake atabout 8:00 a.m. onthe same day,reported whitecapson the water andwinds of 16 to 17miles per hour.About 10:30 a.m.,

two people alsoboating on the lake noticed the unoccupiedopen fiberglass bass boat circling at slow speed.

The boat was retrieved and the identity of theowner was determined from State vesselregistration records. No witnesses had seenthe men in the boat after it got underway, orwitnessed the accident.

Shortly thereafter, a Civil Air Patrol aerialsearch and a county sheriff department watersearch commenced and continued for four days,with no results. About 8:00 a.m. five days afterthe accident, a boater found the body of onevictim. A water search located the two othervictims about three and one-half hours later.

None of the victims was wearing a PersonalFlotation Device (PFD)[a Coast Guard approvedlifejacket], and all were fully clothed. The autopsydid not indicate that alcohol or drugs wereinvolved, nor was trauma indicated. All threemen drowned.A decal on the outboard engine cover read

150 HP, but the engine markings indicated a200 horsepower outboard motor. The U.S.Coast Guard Maximum Capacities label,

permanently attached to the port console,showed a rating for six persons or 810 poundsand a 175 horsepower motor. Fishing gear andfive PFDs were found in seat lockers forward ofthe starboard console; one PFD had a cord withan engine kill switch clip attached to it.

According to a brother of one of the victims,who had been on the boat when it was being

operated on a riverabout four weeksprior to theaccident, the boattended to wobbleor rock from side toside, at a speed of65 miles per hour.

The boat builders customer service managerstated that the boat was rated at 70 miles per

hour with a 175 horsepower outboard motor.The National Transportation Safety Board

(NTSB) was unable to determine the probablecause of the accident; however, the NTSB statedthat the accident was likely the result of: (a) theboat striking a wave while chine-walking, (b) asudden turn by the operator at high speed, or (c)a sudden pitch or roll in response to striking awave at high speed, or a combination of thethree, throwing the occupants overboard.Contributing to the accident, according to theNTSB, was the operator's powering of the boat

beyond the manufacturer's recommendation andthe Coast Guard maximum guidelines.Contributing to the loss of life were the occupants'failure to wear PFDs, the operator's failure to

Inside:Fuel Tank Fill and Vent Systems .................................. 6

Explosion danger with recharging of ............................ 7

SVR gel cell batteries

U.S. Department

of Transportation

United States

Coast Guard

Boating Safety Circular 78

AUGUST 1996

"Contributing to the loss of life were theoccupants' failure to wear Personal FlotationDevices (PFDs) . . . Had [they] worn PFDs,they might have survived."

LIFEJACKETS - THEY FLOAT, YOU DON'T


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Boating Safety Circular2

use the boat's installed engine kill switch, and asticking accelerator pedal, which allowed theboat to continue to operate. The operator andhis two passengers may not have recoveredfrom the impact of entering the water in time toprevent their drowning or, if they did recover,they may not have been able to board the boat.Had the occupants worn PFDs, they might havesurvived.

In its report, the National Transportation SafetyBoard recommended "that the U.S. Coast Guardpublish aBoating Safety Circular that describesthe circumstances of this accident, stressing thedangers of operating a boat at high speed and the

phenomenon known as "chine-walking," theneed to wear PFDs, and the use of engine kill

switches.This accident demonstrates that all persons

may be unexpectedly ejected from a boat, leavingno one to stop it, and also the need to wear CoastGuard approved lifejackets. Today, the typicalhigh performance boat may be a bass boat, askiboat, a speedboat, or one of severalcombinations, and may be able to attain speedsas high as 70 to 100 miles per hour. Many highperformance boats also have accommodationareas for sleeping and a galley for cooking.

With the innovations in boat and engine designand the greatly increased boat speeds,recreational boat operators have had to learn awhole new terminology, previously used onlyby raceboat drivers:

Chine-walking is a phenomenonassociated primarily with V-bottom hulls,which are operated at high speed with only a

minimum amount of hull area in the water.When chine-walking, the hull may have atendency to roll or fall off to one side thenthe other. This rolling action must be stoppedor controlled if the oscillation appears to beintensifying. Unchecked, the boat may goout of control and flip over or eject the

occupants. Chine-walking is controlled bysmall, properly timed, and continuoussteering corrections, by trim correction, orboth. It also helps to have a very tightsteering system with minimal backlash.

The chine of a boat refers to the edge oneach side of the hull where the bottom meets

the hull sides. When you hook a chine, thechine dips down far enough to dig into the

water, usually in a turn. This can cause theboat to suddenly turn more sharply thananticipated and/or roll up on its outside edge.In severe cases, the boat can roll over and theoperator and any passengers might beejected.

Porpoising is a continual rhythmic up anddown motion of the boat's bow, not causedby wave action. Porpoising is usuallyassociated with over trimming the engine(too far out), weight distribution (center ofgravity too far aft) or hull bottom design.

When a boat which is on plane suddenlyturns sharply,it spins-out, often reversingdirection. This is usually caused by a forward

YEAR CAUSE VESSELS INVOLVED FATALITIES

1994 .............. High Speed Maneuver .......................... 71 ...................................... 18...................... Speeding ................................................ 733 ...................................... 46

1993 .............. High Speed Maneuver .......................... 69 ....................................... 9

...................... Speeding ................................................ 536 ...................................... 27

1992 .............. High Speed Maneuver ........................ 110 ...................................... 17

...................... Speeding ................................................ 429 ...................................... 27

1991 .............. High Speed Maneuver .......................... 73 ...................................... 32

...................... Speeding ................................................ 206 ...................................... 35

See related story on pages 4 and 5


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area of the hull digging into the water andveering to one side allowing the aft end ofthe boat to rapidly pivot around the bow.Spinning out can be associated with startingan intended turn, then compounded by a bowsteer situation, running bow down, hookinga chine, or even hooking an inside sponson

of a true tunnel hull boat.

When a high speed boat is squirrelly, ithas unpredictable running characteristicswhich may give the operator an uneasyfeeling as to the handling and control at aspecific speed, balance and trim setting.This condition requires the boat operator's

water surface. Then, with a small steeringcorrection by the boat operator, the boat willfall off to the chine on the opposite (starboard)side. This oscillating motion (chine-walking)will continue until the operator either slowsdown, or makes some other change to the trim ofthe boat, like lowering the outboard motor back

in the water a small amount with the power trimswitch or hydraulic jack plate. Several otherfactors can cause chine-walking, such as motorsetup, propeller design, play in the steeringsystem and soft or loose motor mounts.

While many slower runabouts can be equippedwith single cable steering systems, high-speedbass boats and other performance craft must use

undivided attention at all times.

When there is steering backlash there isplay or lost motion in the steering systembetween the engine steering arm and thesteering wheel. Minimization of steeringbacklash is always desirable, but particularlywith high performance boats. Dual steeringcables, correctly adjusted, used withoutboards and single sterndrives, or hydraulicsteering systems are excellent installationsfor minimizing backlash.

High performance V-bottom hulls often havea tendency to chine walk or rock from side toside at high speeds. As speeds increase there isless boat hull in the water, and with V-bottomhulls, the supporting surface becomes narrower.Depending upon the design of the boat and theload it is carrying, at some point the hull falls offto one side, the port side for example, and the aftend of the boat's chine on the port side strikes the

a more precise dual-cable system. Dual-cablesteering reduces the slop or "play" inherent in a

single helm and cable merely by adding a secondcable which is in tension against the other.Mostengine manufacturers offer solid motor mountsthrough their high performance divisions.

Passengers usually have a disadvantage theoperator doesn't have -- the operator knowswhen he or she is going to make a sharp turn --passengers usually do not. Passengers who aremoving about a boat, or who are improperlyseated on the bow, a gunwale or a seatback, areejected from the boat or fall overboard when

boat operators are wake jumping, are in sharpturns or are performing other maneuvers atspeeds which are dangerously fast for theprevailing conditions. Some victims are ejectedfrom boats by collisions with another boat or asubmerged or fixed object. Ejections from a

boat are also caused by sudden acceleration or

deceleration.

DROWNINGS AS COMPARED TO OTHERFATALITY TYPES

IN RECREATIONAL BOATING ACCIDENTS 1989 - 1994YEAR DROWNINGS OTHER DEATHS TOTAL

1994 ....................... 613 .................................................... 171 ......................... 784

1993 ....................... 667 .................................................... 133 ......................... 800

1992 ....................... 673 .................................................... 143 ......................... 816

1991 ....................... 739 .................................................... 185 ......................... 924

1990 ....................... 707 .................................................... 178 ......................... 865

1989 ....................... 753 .................................................... 143 ......................... 896

(continued on page 6)


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While preparing this article for the Boat ingS a f e t y C i r c u l a r, we contacted MercuryMarine engineer, Mr. Richard Snyder, arecognized expert on hydrodynamics, boattesting, and high performance boating andracing, and asked him a number of questionsabout the operational phenomenon calledchine-walking. What follows are Mr. Snyder's

answers to our questions:What is chine walking?Chine walking is a rhythmical roll from side

to side (chine to chine) encountered usuallyat higher on-plane speeds on some V-bottomboats, more often when powered by a singleoutboard motor. It might be thought of as thelateral version of "porpoising" which islongitudinal, on-plane pitching or rhythmicalbouncing (up and down bow motion) that canbe encountered with many boat bottomdesigns.

What causes chine walking?As any planing boat, but in particular a V-

bottom boat, is powered to higher speeds, the

boat is supported increasingly by the velocitypressure of the water touching the hull, anddecreasingly by the static pressure ofdisplacement. With a V-bottom boat, thatmeans that the center portion of the bottomtouching the water is becoming narrower.

There will finally come a point where the boatwill roll or fall to the side, away from itsformer balanced position. This imbalancecan be initiated by a simple slight movementof the steering wheel when putting the boat,intentionally or not, into a slight turn.

Now comes the part not well known.Because the center of gravity of the outboard(or sterndrive) lies behind the steering (swivelor rudder) axis, the outboard will want to fallin the direction of the roll. This fall, due togravity, will accentuate or magnify the rollsince in a small way it's trying to make theboat turn slightly in that roll direction.

Because of the spring in the steering systemand often some counter input to the steeringwheel by the operator, the hull will bounce

back over center to roll in the oppositedirection. Then the outboard, due to gravity,flops back over center to the opposite side,thus accentuating the opposite roll. Thisaction can continue to cycle and grow to agreater and greater magnitude if nothingdifferent is done.

What does the operator feel when a boat is

about to start chine-walking?What the operator originally feels, usually,

is a very mild, rather stable level of this cyclicroll if the operator does not increase speed,change boat trim, or put incorrect input intothe steering wheel.

What can the operator do?Plenty. The novice operator can reduce

speed a little or trim the bow down a little.But what just about all faster V-bottom driversquickly learn is how to make little rhythmicalcorrections to the steering wheel which canlevel the boat out immediately and permit theoperator to safety continue to increase speed.

This proper steering technique coupled with

a simple search for the optimum engine trim,and thus boat trim, will allow the boat to besafely operated at its maximum speed, giventhe existing engine height, propeller and boatload.

But of course there is one major adjustmentthat can greatly help the chine walkingsituation. And that is taking all practicalsteps to remove the free play from the steeringsystem. The usual first step, if it isn't present,is to install dual cable steering and correctlyadjust out as much of the free play as possible.

There are also relatively new hydraulicsteering systems (both manual and power)that have addressed the free play problemvery well.

On the lighter, faster boats the outboardmotor (or sterndrive) installation height canbe raised a little to reduce the amount ofrudder in the water. As boat speed increasesthe most desirable size of rudder decreasesand excessive rudder definitely adds to the


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likelihood or severity of chine walking.Are certain types of boats or boats with

various types of propulsion more susceptibleto chine walking than others?As discussed earl ie r, V-bottom boats

possess the only bottom design where theboat can ultimately fall off a narrowing centerstrip of water contact. Although single

outboards are the most common propulsorwhere chine walking is present, multipleoutboards and single or multiple propulsorsof other types are not exempt, if sufficientspeed and steering free play is present.

Will power trim equipment or after-marketequipment such as hydrofoils or trim tabsmake a boat more susceptible to chinewalking?

Power trim has long been an essential toachieving the most efficient, comfortable, evensafest ride as the many recreational boatingvariables change. However, as an operatorreaches for higher speeds, this is achieved byboth throttle and hull attitude adjustments.

throttles, e.g., foot throttles?Kill switches ("lanyard operated ignition

interruption switches" or more simply"lanyard stop switches") are contained inmost manufacturers' control boxes and as adash mounted accessory. We think that theyare generally a good safety device to use.

Although Mercury has made them a part of

our control boxes for 17 years, operator usageis not very high.

Foot throttles are generally thought of as aplus for boat control in that, obviously, bothhands are then available for steering control.However, foot throttles do create thepossibility of shifting into gear with too muchthrottle (RPM), and have thus been involvedin serious gearcase damage. Also,occasionally when coming down hard off of awave, an operator's foot may inadvertently,though briefly, depress the foot throttle, givingthe boat an unexpected burst of speed.

Among the materials in the appendices tothe National Boating Safety Advisory Council

Basic hull physics dictates that a boat bottomwill run most efficiently (achieve the greatestlift to drag ratio) when the bottom is operatingat a four to five degree angle to the water.Faster boats tend to run flatter than that.

Thus power trim plays a major role in givingthe operator a tool to trim the propulsor outthus lifting the bow.

Generally, add on "hydrofoils" are notconsidered to be much of a chine walkingfactor. However, at some trim settings,

"hydrofoils" can cause some V-bottom boatsto roll sharply over on one side creating ahazardous condition.

While the Coast Guard does not havesufficient accident statistics to justify aregulation requiring the use of kill switches,many engine manufacturers, including yourcompany, offer them as optional equipment.Does Mercury Marine have any specificrecommendations about the use ormaintenance of kill switches or dead man

(NBSAC) Report of the Propeller GuardSubcommittee is a pamphlet published byMercury Marine titled "Hi-Performance BoatOperation," which contains a variety ofimportant information which might be ofintertest to our readers. Is the pamphlet stillpublished, and how might interestedindividuals obtain a copy?The Mercury pamphlet entitled "Hi-

Performance Boat Operation" now in its 4thedition is, I believe, a useful teaching tool. I

wrote this booklet originally in 1977 andhave updated it on several occasions. It isincluded with every engine sold (outboardand sterndrive) by Mercury's HighPerformance Division. A copy can bepurchased through Mercury, Mariner, Forceand MerCruiser dealers. A copy can also bepurchased from Mercury Marine in Fond duLac, Wisconsin by writing to: Mercury Marine,Publications Department, P.O. Box 1939,Fond du Lac, Wisconsin 54936-1939. Thecurrent price is $0.40.


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Coast Guard Approved Lifejackets:

In 1994, the Coast Guard received reports of6,906 recreational boating accidents whichresulted in 784 fatalities, 613 of which weredrownings. Coast Guard Approved lifejacketscould have saved the lives of at least 550 boaterswho drowned in 1994, including approximately

30 children who were 12 years of age or younger.The primary causes of the accidents wereoperator inattention or carelessness andspeeding.

During this year's National Safe BoatingCampaign, the Coast Guard and otherrecreational boating safety organizations areurging all recreational boaters to wear theirlifejackets, instead of simply storing them onboard for the purposes of meeting minimumequipment carriage requirements.

Historically, the major obstacle to encouragingthe recreational boating public to wear lifejacketswhile boating, was the fact that the currentlyCoast Guard approved, inherently buoyantlifejackets were too bulky and thereforeuncomfortable. On March 28, 1996, the CoastGuard published a final rule in the FederalRegister establishing structural and performancestandards for inflatable lifejackets forrecreational boaters, as well as the proceduresfor Coast Guard approval of inflatable lifejackets.The regulations in the final rule are intended toallow approval of lifejackets which may bemore appealing to boaters, than currentlyapproved, inherently buoyant lifejackets, therebyincreasing the percentage of lifejackets actuallyused by the boating public and saving lives.Several manufacturers will have Coast Guardapproved inflatable lifejackets on the marketthis summer.

Kill SwitchesEmergency shut off switches otherwise known

as kill switches have been in use on racing boats

for many years. Several companies offer killswitches for sale to the public or as optionalequipment. Kill switches can be attached orwired into most engine control systems whichare equipped with remote electric starting.

Most kill switches have a lanyard with a snapor hook which is intended to be fastened to somepart of the operator's clothing or lifejacket. Ifthe operator falls overboard, or leaves the helmstation without disconnecting the lanyard, it

NEW FUEL TANK FILL AND VENTSYSTEMS REDUCE WATER

POLLUTION

Several boat manufacturers are now using asingle fitting which incorporates both the fuelfill and the fuel tank vent. If fuel comes out ofthe vent, it simply flows back down the fuel fill.Some boat owners have complained aboutoverfilling tanks on boats equipped with newfuel fill fittings.

Because gasoline spilled into a boat can leadto a significant fire or explosion hazard, the

Coast Guard Fuel System Standard in Subpart Jof Part 183 requires manufacturers of boats withpermanently installed gasoline engines (exceptoutboards) to design fuel tank fill and ventsystems so that if there is an overflow from thefill or the vent, gasoline doesnt go into the boat.The American Boat and Yacht Councilsvoluntary industry standard, H-24, has the samerequirements, and they also apply to manyoutboard powered boats.

For many years the typical fuel tank fill andvent system has consisted of a fuel fill locatedsomewhere on the deck or gunwale, and a ventfitting located on the topsides. When the tank isfull, liquid fuel squirts out of the vent. Manyboat owners look for overflow from the vent asan indication that the tank is full. However,some States have recently passed laws makingfuel spills as small as these illegal, and theEnvironmental Protection Agency (EPA) isconsidering similar regulations.

will turn off the ignition or open a special switchin the ignition circuit, thereby stopping theengine.

In general, it can be expected that a boat willcome to a stop within 50 to 75 feet of an operatorwho goes overboard with the kill switchoperating properly. In such a situation, some

persons would still drown due to the lack ofswimming ability (failure to wear a lifejacket)or injuries received while being ejected from theboat.

Although accident data does not support theneed for a Federal regulation requiring theinstallation or use of kill switches, the CoastGuard recommends the use of such devices.


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Boat owners who have been using overeflowfrom the vent to determine when their tanks arefull are contributing to water pollution and riskcreating an explosive condition. Low cost after-market devices are available (such as an in-linewhistle) which will indicate when a fuel tank isalmost full.

There are obvious advantages for boatmanufacturers who use the new fittings:

(1) one fitting, instead of two, reducesinventory and costs; and

(2) repairs are cheaper, because only one partneeds to be replaced.

Owners and operators of boats equipped withthe new combination fuel tank fill and ventfittings are reminded to be careful and to avoidoverfilling the tank when they are refueling.

CONSUMER ADVISORY -DANGER OF EXPLOSION IF

SEALED VALVE REGULATED (SVR)GEL CELL BATTERIES IMPROPERLY

RECHARGED

The American Boat and Yacht Council(ABYC) Project Technical Committee for DCElectrical Systems recently informed the CoastGuard that an explosion can occur when gel cellbatteries are recharged with battery chargerswhich are not automatic temperature-sensingvoltage-regulated chargers.

According to East Penn, a manufacturer of gelcell batteries, SVR (Sealed Valve Regulated)batteries work on the "recombination principle."This means that the hydrogen that is normallyproduced on the negative plate in all lead-acidbatteries, recombines with the oxygen producedon the positive plate to form H

20 or water. This

water replaces the moisture in the gel.The oxygen is trapped in the cell by special

pressurized sealing vents. If an SVR gel cellbattery is overcharged, the hydrogen and oxygenwill be produced faster than they can recombine,and will be driven out of the sealing vents andlost to the atmosphere.

Hydrogen gas released by a battery isextremely flammable and requires only a

source of igniton to set it off. Some explosionshave occurred.

SVR gel cell batteries are advertised as"maintenance free" and as "sealed," which maylead boat owners to believe that gel cell batteriesdo not emit hydrogen gas during charging andare completely safe to put anywhere on a boat.These claims are true as long as themanufacturers instructions for charging are

carefully followed.Automatic, temperature-sensing, voltage-

regulating battery chargers must be used.Charge voltage must be limited to 13.8 to 14.1

volts maximum. Constant voltage chargersmust never be used.

In addition to the explosion dangers associatedwith recharging with the wrong equipment,overcharging or undercharging an SVR gel cellbattery also reduces performance and batterylife. Before using and recharging gel cell

batteries boat owners should read theinstructions, or contact the manufacturer, to besure they have the correct type of battery charger,and are recharging it in accordance with themanufacturers specifications.

boating safety circular 96

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