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NavCal Marine Services LLC 865-765-3407

NavCal Tennessee River Information Source

This set of web pages will provide Tennessee River vessel operators and passengers useful information in a light and personal style from Captain Farmer (Licensed Coast Guard Passenger Vessel Master) based on over 50 years of boating experience. This page will be in a reverse chronological (blog style) order with both a table of contents and possibly an index. If you would like to use a particular post click on the title of that post and you will be taken to a pdf version that you are free to copy and use as long as you include the proper source credit shown at the bottom. To print the pdf version, right click inside the document and then select print. We welcome your comments on a post by post basis (please indicate which post) and suggestions for changes, new subjects, or which subject to include next by sending email to TNRiverInfo. We will include all appropriate comments as part of the referenced post.

AIS - Automatic Identification System & The Case for a Class C AIS, Transmit Only Device:
We need a less expensive AIS option to encourage more usage and increase navigational safety. Many recreational vessels operate without radar and/or do not use it properly. With the widespread availability of inexpensive GPS/chartplotters more nighttime operation is becoming common.

Class A vessel AIS transceivers must operate continuously at 12 watts. They are intended primarily larger commercial vessels including passenger vessels over 150 passengers. A class A AIS unit must maintain an updated time frame map in its memory such that it has prior knowledge of transmit time slots available (Self Organized Time Domain Multiple Access - SOTDMA). These transceivers must pre-announce their transmission by reserving their transmit slot in the available frame. This requires 2 receivers in continuous operation. By regulation, Class A AIS units must have an integrated display and interface capability with other ship systems. They transmit every few seconds and must be operational even when the vessel is moored (mode 5). They can be connected to most display systems where the received messages will be displayed in lists or overlaid on charts. They typically cost over $1,500.

Class B vessel AIS transceiver can operate using either carrier-sense time-division multiple-access (CSTDMA) or SOTDMA and are intended for smaller commercial and recreational vessels. CSTDMA transceivers listen to the frame map before transmitting and seek a slot where the noise in the slot is the same or similar to the background noise. Class B AIS’s transmit at 2 W and are not required to have an integrated display or operate continuously. They can be connected to most display systems where the received messages will be displayed in lists or overlaid on charts. Default transmit rate is about every 30 seconds. The Class B type standard requires integrated GPS and certain LED indicators. They are about $500.

These A and B units also often require a dedicated GPS device, using a special connector, which increases their cost even further.  Another disadvantage to Class B AIS's is that they require an external display on a chartplotter or similar device. Many recreational vessel chartplotters are small and screens are already crowded. Having a separate receiver like a combined VHF/AIS receiver is definitely better and safer option.

Class C vessel AIS transmitter (no receive output) should use CSTDMA to find a slot in the time frame and transmit at 2 watts or less only if valid GPS data is present. It should auto sense GPS data at either 4800 or 38400 baud and require a valid RMC sentence (see below). It should have two external terminal lugs for GPS NMEA0183 data input and a single SO-235 coax connector for switched RF I/O. Two additional lugs should accept switch closure, if entered, to override the default or stored basic navigational status and output the alternate default or stored alternate navigational status. A USB connector should accept the input setup data if entered or it should use the default (see below) and show all the stored setup data on receiving a “???” input. Windows, Mac and Linux terminal software should support the USB interface for setup or change.

Status indicator LEDs should include:
Power – None or Green
GPS OK – Red or Green
Receiver OK – Red or Green
Transmitter OK – Red or Green

The user is expected to be able to view his own data and that for other vessels on a separate AIS receiver (only). Thus there is no need for additional verification or an AIS data output from this device. The price point for this device should be under $200 to promote mass recreational use and thus enhanced navigational safety.

User data input via USB port and support software and defaults if not inputted:
MMSI – must be entered or device will not transmit
Vessel name – default NONE
Call sign – default NONE
Destination - 20 characters maximum - default NONE GIVEN
ETA - DD/MM and HH:MM using a 24 hour clock – default 01/01 00:00
Draught meters - format is xx.x m – default 00.0
Navigational status* - default 5 = moored
Dimensions in meters – default 1 x 1
Type of ship** - default 37 pleasure

Other accepted inputs via USB are:
*Navigational status
0 = Under way using engine – default alternate status
1 = At anchor
2 = Not under command
5 = Moored – default basic status
6 = Aground
8 = Under way sailing
11 = Power-driven vessel towing astern
12 = Power-driven vessel pushing ahead or towing alongside

** Vessel type / must be exhibiting the proper lights at night
30 = Fishing / commercial
31 = Towing astern
33 = Dredge
34 = Dive Vessel
36 = Sailing Vessel
37 = Pleasure Craft - default
52 = Tug towing ahead or along side
60 = Passenger
70 = Cargo

Minimum received GPS sentence is:
$--RMC,, A, llll.ll,a, yyyyy.yy, a, x.x, x.x, xxxxxx, x.x,a, a*hh"CR""LF"
Number = Description
1 = Time of position fix (UTC)
2 = A Status: A = data valid V = navigation receiver warning
3 = llll.ll, a Latitude, N/S
4 = yyyyy.yy, a Longitude, E/W
5 = x.x Speed over ground, knots
6 = x.x Course over ground, degrees true
7 = xxxxxx Date: dd/mm/yy - NOT USED
8 = x.x, a Magnetic variation, degrees, E/W - NOT USED
10 = a Mode indicator:
=A = Autonomous mode
=D = Differential mode
=E = Estimated (dead reckoning) mode
= M = Manual input mode
= S = Simulator mode
= N = Data not valid

Small Passenger Vessel Capacity:
The number of passengers that can be approved for carriage aboard a U S Coast Guard certified passenger vessel is based on space (length of rail, square footage, fixed seating see 46 CFR123), and vessel stability criteria. The space regulations set the initial maximums and then stability tests must be performed to verify the safe maximum load.

For each 36" of rail space you get one passenger. For each 18" on a fixed bench or each separate fixed seat you get one passenger. For each 10 square feet of habitable deck space you get one passenger. You may be able claim rail space and the same area in square footage. This can get a little complicated but a competent naval architect can assist you with calculating the max that the Costies are likely to approve.

You must provide space for passengers and crew. The number of "safety sensitive" crew you have to carry will be specified by the Costies. You may, for instance, need two deckhands from 1 to 150 passengers actually aboard, three from 151 to 300 and four over 301. You will be allowed other crew billets for bartenders, wait staff, and other similar crew.

For the final stability determination you must prove your vessel is safe for x number of passengers and crew at 185 pounds (used to be 140 or 160) each. There are basically two types of stability tests. In the simplified stability test you put weights (55 gallon drums filled with water on wooden pallets) centered aboard and note how much freeboard you have. You then move the drums as far toward the railing as possible and see how much the freeboard is reduced. Things like ports capable of causing "down flooding" must be considered.

The other type of stability test is called an "incline experiment". In this test you suspend three special types of plum bobs on the vessel and move a fixed amount of weight in increments and plot the "area under the righting curve". This is a rather complex test that normally needs to be supervised by a naval architect. Approximate data can be obtained, usually during the vessel design phase, by putting vessel lines drawings data into appropriate design software. This software normally yields pounds needed to heel the vessel one degree. The final incline experiment must be witnessed by the Costies and then the many pages of documentation must be submitted for review.

Licenses for Passenger Vessel Operators:
As mentioned in our Classes/Types Small Passenger Vessels there are two main types of "lower level" captain's licenses available from the Coast Guard. The first is Operator of Uninspected Passenger Vessel (OUPV). This is often referred to as a "six-pack" license since it allows you to carry six or fewer passengers on an uninspected vessel, usually a small fishing boat. The next up is a Master's License and comes in 25, 50, 100, 150 and 200 Ton increments for use on inspected vessels.

The requirements for both are somewhat similar and include: 18(OUPV)/21(Master) years old, U. S. Citizen (not for OUPV), physical exam and corrected 20-20 vision, clean record (convictions), CG drug test must be negative, 360 days Sea Service (4-hour days) 90 within last 3 years, Sea Service self certified on your boat w/ proof of ownership or certified by Master or owner on someone else's boat (see Testing will include Inland Rules of the road closed book, 30 questions, 90 required score*, Deck general & safety open book, 60 questions, 70 required score, Navigation general open book, 20 questions, 70 required score, Chart navigation open book, 10 questions, 70 required score** (* Near Coastal license includes International rules,** Inland license requires charting (but not on Western Rivers Masters license) You must be certified in first aid and CPR and pay applicable fees (about $240).

The first thing you need to do is record your "Sea Service Time". It can be on anything and you don't need the log book but on your boat you do have to prove it was your boat with slip rent, fuel or license bills, etc. If you are going for a master's license the Tonnage you get is based on the boat or boats on which you got your time. Anything OVER 5 tons (my old 25 foot sailboat) gets you a 50 Ton license. You need at least a 100 Ton license to pilot most boats up to about 400 passengers.

The next thing is learning plotting on a marine chart with compass corrections and doing time speed distance calculations. The United States Power Squadron teaches these skills in four courses up to "Advanced Piloting". This needs to become second nature before you test or go to a school. If you need help send email to we can assist you and no you can't claim you will only need your GPS.

You will need to memorize a lot of the "Rules of the Road" (COMDTINST M16672.2D) and many people use flash cards to drill and drill again on the rules, lights, sound signals, etc. The tests are multiple choice but open book means their books! 33 and 46 CFRs come in several sections and cover a lot of pages. You won't have time to look up much. It isn't always easy to find something even if you are thoroughly familiar with each book section. You need to know how to use marine charts, light lists, coast pilots, tide tables and similar publications and you must know which one has what that you might need.

Once you get a license it allows you to stand in the corner of the pilothouse until the owner AND the insurance company decides you can actually touch the wheel. Licenses are good for five years and for renewal you mush show minimum time using it (360 days in five years) or you will have to retest on some subjects. You can go to a certified school (can give the test) or go to a Coast Guard Regional Exam Center and test their. For the REC you must submit application, etc. and have an appointment.

Classes/Types of Small Passenger Vessels:
If a vessel carries any passengers for hire (they pay anything to ride) the captain/master must be licensed and in all but one case the vessel must be inspected and certified by the U. S. Coast Guard. Failure to comply with any part of the regulations carries severe penalties. See 46 CFR114.400 for the definition of passenger for hire. There are several different classes of passenger vessels that we will cover in this post.

Six-Pack: Vessels that carry six or fewer passengers are uninspected but their captain must hold at lease an Operator of Uninspected Passenger Vessel (OUPV or six-pack) license. These vessels have to meet certain minimum requirements detailed in 46 CFR24 to 28 but they are not inspected annually by the Coast Guard as all other passenger vessels are. You have to take the operator's word that the boat is in full compliance with all the requirements of the CG safety guidelines. If you have ever been charter boat fishing you may have noticed that boats carry either 6 or fewer passengers or 15 or so more but nothing in between. There isn't much reason to have a seven or eight passenger boat. It would have to be inspected every year ($300 fee) and meet stringent requirements shown below so why bother. Typically passenger vessels are just not practical to design, build, and operate for between 7 and 15 or so.

T-Boats: Vessels that carry over 6 but less than 150 passengers are classified as T or Subchapter T boat. Their master must hold a Master's license of the correct tonnage/area (25, 50, 100, 150 or 200 Tons, (see vessel operator license requirements in a later post), the vessel must meet the subchapter T (46CFR175 to 185) requirements, and must be inspected and rectified every year. These vessels must have a current certificate of inspection (COI) prominently posted where it is clearly visible to the passengers. As a passenger the COI is your assurance that the vessel meets the Coast Guard safety criteria. T-boats must have bilge pumps and similar safety equipment (see equipment and requirements for vessels) not required on six pack boats. Almost all T-boats must have at least one deckhand in addition to the master to help safely handle the boat and its passengers. There are minimum crew training requirements (training foe vessel crew in a later post) in areas like fire and man overboard recovery.

K-Boats: Vessels that carry more than 149 passengers or more than 49 passengers on overnight voyages are classified as K or Subchapter K boat. Their master must hold a master's license (see vessel operator license requirements in a later post) of the appropriate tonnage/area. These vessels must meet still more stringent equipment requirements ( see 46CFR114 to 122) like redundant bilge and fire pumps, no wooden hulls or superstructure, and must have a Mate or Senior Deckhand (see deckhand requirements) capable of getting the vessel safely back to the dock if the master is incapacitated.

K-Boats and above must also have an approved vessel and facility security plan and conduct security training, drills, and exercises. On these vessels, on a certain percentage cruises all boarding passengers must be screened prior to being allowed aboard the vessel. There are other security procedures that must be followed including restricted areas on the vessel and/or facility. K-Boats generally range from 300 to 500 passengers. Again there is not much justification for a 160 passenger boat under United States rules.

H-Boats: Vessels that exceed 100 Gross Registered Tons (see GRT in a later post) are classified as H or Subchapter H Boat. They must comply with still more stringent equipment and training requirements (see 46CFR70 to 80) such as monthly crew training (see training for vessel crew in a later post).

OUPV and T-Boats are based on the number of passengers carried. The maximum number of passengers that can be safely carried depends on space (length of rail, square footage, fixed seating see 46CFR176.113, and vessel stability criteria (stability for passenger vessels in a later post).

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Mail to NavCal Marine Services, 8016 Ellisville Lane, Knoxville, TN 37909.
We may be reached by phone at (865) 765-3407.  (c) NavCal Marine Services LLC

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