Flotation Introduction

Transcription

1 Flotation Introduction Why are small boats required to have flotation, and why are there different requirements? Back in the 1950's and 60's the old Boating Industry Association (now NMMA) and the Yacht Safety Bureau (now ABYC) realized that one of the main reasons people died in boat accidents was the boat sank out from under them. It sounds obvious, but at the time it wasn't. Then in the 1970's a lot of research was done into hypothermia, and the two came together. It was realized that if the boat did not sink, it would give the people something to hang onto, something that could be seen much better than just a head sticking out of the water, and if the boat, although full of water, did not sink, or roll over, then the people could actually stay in the boat. Most of their torso would be out of the water reducing the effects of hypothermia, and providing a much better rescue platform. So work started on developing a standard for flotation. Through testing and experiments, techniques were developed that would provide enough flotation to keep a small boat afloat, and floating relatively level. However, this did not work well for inboard boats, because the size and weight of the engines required far too much flotation material to float the boat level. Meanwhile the Federal Boat Safety Act passed in 1971 and went into effect in Even before that in 1969, the Coast Guard had begun collecting statistical data on boating accidents. Analysis of this data revealed that the most significant contributors to fatalities were capsize, sinking and falls overboard. Flotation in a boat could eliminate the sinking, prevent capsizing, and prevent some of the falls overboard. Many of the "falls overboard" were actually the boat rolling over and dumping everyone in the drink. Also, analysis revealed that by far the majority of these accidents occurred in monohulled boats under 20 feet in length, manually propelled or with outboard power. The inboards contributed some of the fatalities. NMMA, ABYC, and the Coast Guard determined that monohull boats under 20 feet with outboard power or manually propelled should have level flotation, and inboard boats, basic flotation. Basic flotation simply keeps the boat afloat with some of the boat sticking out of the water. 1

2 When the regulation was proposed many people in the classic and wooden boat community felt that the level flotation standard was too rigid to be applicable to small manually propelled boats or boats with tiny engines. So after testing and consultation with persons building these types of boats the standard was modified to allow some latitude in achieving the same performance. That is, these boats have to float level to the same degree as larger boats with bigger outboards, but the method of achieving it is different. It was called modified level flotation. Additionally small boats are allowed to carry a greater percentage of their weight capacity as persons than larger boats are and integral air chambers are allowed. This seemed to satisfy everyone. This particular standard has been very successful in preventing deaths. It is not clear and probably not quantifiable just how many deaths have been prevented but the fatalities have dropped dramatically since 1972, but in the United States, from about 19 per 100,000 boat, or about 1300 people, to less than 6 per 100,000 boats, about 600, annually in At the same time the boating population has grown to roughly 5 times what is was then. The drop in fatalities is a combined result of education, engineering and enforcement, so it is hard to say which has contributed more, but certainly flotation standards have had an effect. Finally; the flotation standard is a performance standard that is, your boat must perform in a certain way. Rather than make a rule that says something like, you must put so many cubic feet of foam in your boat for every 160 pounds per person, etc., this standard says how your boat must perform under specific circumstances. The circumstances are, loaded with an amount of weight determined by the weight of the boat, the engine and the people, this boat must remain afloat, in calm water, the way described in the rule or standard. How you achieve this is left up to you the builder. In the ISO Standard for flotation ISO Small craft -- Stability and buoyancy assessment and categorization -- Part 1: Non-sailing boats of hull length greater than or equal to 6m, and in the RCD, these test are performed in a different manner. The principles are the same but the procedure is different. For instance the weights used inside the boat in the USA, are hung over the outside of the boat in the ISO standard. In some instances this makes it more difficult to 2

3 pass the test. In others the results are the same. The US Coast Guard and ABYC have done some comparison tests using both methods. The results can vary widely, so if you are using ISO or the RCD you will need to obtain a copy of their standard. Additionally t6he ISO standard covers stability and buoyancy for small sailboats lees than or equal to 6 m. See the Appendix C for links to various Standards. Goals: Learn the rules and flotation standards for small boats. Learn how to test a boat to for Flotation. I strongly suggest that to complete this course you obtain the US Coast Guard Boatbuilders Handbook (the URL is below) and the Canadian Rules (also given below). These are free and will give you a lot of additional information. You can purchase the others, but they will only benefit you if you are planning on building boats for the European market. The exception is the ABYC Standards. If you are building boats I can t recommend strongly enough joining ABYC and getting copies of the standards either through on-line access, or on CD, or printed. The US Rules can be found at The Canadian Rules can be found at The Recreational Craft Directive for the EU can be found at. There is a fee for these documents. The ISO Standards for recreational boats are at CS1=47&ICS2=80&ICS3=&scopelist= There is a fee for these documents. ABYC Standards can be found at htpp:// There is a fee for these documents for non-members. Members can access these documents on-line. 3

4 The USA rules for Flotation are found in Title 33 Code of Federal Regulations 183, Subparts F, G and H, beginning at to The ABYC standards for Flotation are found in H-8, Buoyancy In The Event Of Swamping. The USA and ABYC Flotation Standards are divided into three categories, Definitions: From ABYC H-8 Basic Flotation: For inboard and sterndrive boats: A flotation system that will keep a swamped boat from sinking when its passengers are in the water clinging to it, provided that the aggregate weight of the engine, passengers and equipment carried in or attached to the boat does not exceed that boat's maximum weight capacity. With basic flotation the swamped boat may float at any attitude Level Flotation: outboard powered boats over 2 HP (1.49 Kw); A flotation system that will keep a swamped boat and a specified quantity of the weights of its engine, equipment, and passengers floating in an approximately level attitude. Sufficient stability is provided to prevent the swamped craft from capsizing in calm water. Level flotation does not provide a self-righting capability. Modified Level Flotation: manually propelled boats, or boats with 2 HP (1.49 KW) or less. - A flotation system providing the same buoyancy as basic flotation but the flotation material is arranged to achieve an approximately level floating attitude. Monohull: US Coast Guard Definition. Monohull boat: A boat on which the line of intersection of the water surface and the boat at any operating draft forms a single closed curve. For example, a catamaran, trimaran, or a pontoon boat is not a monohull boat. ABYC Definition of Monohull Boat: Monohull boat A boat on which the line of intersection of the water surface and the boat at any operating draft forms a single closed curve. 4

5 Basic Flotation Applies to: Monohulls under 20 feet (6m) which are: inboards sterndrives airboats jetboats With inboard engines (gas, diesel, electric, stern-drive, etc.): Less than 20 feet (6m)(measured on the center line, including rub rails): This category includes most stern-drive and inboard motor boats. It does not include: canoes kayaks inflatables multihulls submersibles raceboats surface effect vehicles amphibious vehicles sailboats Exception Mini Jet Boats must meet either: FED REGS Basic (33 CFR ) Or: ABYC H-8, Level Flotation Requirements: The boat has to float when swamped, (that is; full of water), with some part of the boat out of the water. So how do I test the boat to see if it meets the standard? To test the boat you need to know the following: 5

6 The maximum weight capacity (the safe load covered in Lesson 3) your boat will carry. This can be found on the capacity label or taken from your capacity calculations. How much weight in people it will carry, that is, the persons capacity. The machinery weight: the weight of the engine. These will be used to determine the amount of weight to load into the boat to test it for flotation. Then measure the following reference areas on your boat. Reference areas are specific areas on the boat where weights representing the load are placed. Cockpit area: 40% reference area. Passenger area: 70% reference areas. Two foot reference areas fore and aft. Fig 1 6

7 Fig 2 Measuring reference areas: First determine what is the cockpit, or passenger carrying area of the boat. This is different on every boat. Measure the length of this area. Divide the length in half. Measure from one end or the other, to the mid point of the length. Then multiply the length by 0.20 (20%) and measure that distance aft of the midpoint and the same amount forward of the midpoint. That is 40% of the length of the passenger carrying area. Repeat for the width. Measure the width of the passenger carrying area. Divide by half and mark the midpoint. Then measure 20% to one side and 20% to the other side. This area can be marked off with duct tape, which won t damage the boat and can be easily removed after the test. (see photographs illustrating this in the section on level flotation) Then you need to load the boat with the following weights: 2/15 of the Person Capacity. 25% of the Dead Weight. Dead Weight = Maximum Weight Capacity - Persons Weight (this figure can be zero or negative. If negative use zero) 7

8 62.4 times the volume of the 2 largest air chambers in cubic feet, if you used air chambers. If air chambers are used; the 2 largest will be punctured and flooded during the test. (I cubic meter = 1 metric ton or 1000 kg or 1 liter= 1 kg) Air chambers integral with the hull are not allowed. (33 CFR (b)) Note: The weights you use do not weigh the same under water, so they must be multiplied by a factor to compensate for their loss of weight when submerged. For instance, iron weights have to be multiplied by a factor of A ten pound iron weight would weigh 8.6 lbs (4.53 kg X.86 = 3.9 kg) under water. So you must then add weights to make up the difference. For instance, if your persons weight is 1124 pounds, then 2/15 that is 150 pounds. So you need to put 150 pounds in the boat. But 150 pounds of iron does not weigh 150 pounds under water. To get the correct amount divide the weight by 0.86 to get how much you actually need to put on the boat. 150 lb/ 0.86 = lb. (68.04 kg x 0.86 = 58.5 kg) This is the amount you would load into the boat. However if the weight will be dry (even though the boat is swamped) do not compensate. Use the actual weight. In some cases the weight for the engine may stay completely out of the water, and weights placed on seats or on top of fuel tanks may be out of the water. All of this depends on how much flotation the boat has and how high it sits when swamped. At the end of this lesson in Appendix C is a table of Material Conversion Factors. You will also use this table extensively in Lesson five when calculation amounts of flotation. Initially the boat is flooded with water and allowed to soak for 18 hours. Then the weights for the basic flotation test are added, and if any part of the boat is above the water it passes. With this weight aboard and the boat fully swamped, it must float with some part of the boat out of the water. ABYC H , SAYS THAT IN ADDITION TO THE ABOVE: WEIGHTS THAT, WHEN SUBMERGED, EQUALS 75% OF THE DRY WEIGHTS OF THE PROPULSION SYSTEM AND BATTERIES." 8

9 ABYC assumes you will test without the engines and sterndrive installed. The Coast Guard tests the boat with the engines installed but removes the sterndrive and batteries, and substitutes weights. The biggest difficulty with the basic flotation test is finding a test tank or pool that is deep enough. Often the boat is almost vertical with only the bow out of the water. If the pool is only 6 or 7 (2.13 m)feet deep the stern of the boat will be resting on the bottom of the tank. Sometimes by shifting weights forward you can level out the boat so it can be tested in a shallower tank. 9

10 Level Flotation: Applies to: Mono-hull outboard boats (not catamarans, trimarans, or pontoon boats. Mono-hull means that if you can draw a continuous line around the hull at the waterline when the boat is at rest it's a mono-hull. If it makes two or more footprints in the water it's a multi-hull. Greater than 2 Horsepower (1.49 kw): Less than 20 (6 m) feet (measured on the center line, including rub rails): It does not include: canoes kayaks inflatables multihulls submersibles raceboats surface effect vehicles amphibious vehicles sailboats This category includes most outboard motor boats. Requirements: The boat has to float when swamped, (that is; full of water), in an upright level attitude. See the diagrams in each test for specific requirements. At the end of this lesson in Appendix B, are tables of weights for outboard motors, batteries and portable fuel tanks. Table 4 is from The US CFR 183, and Tables 1a and 1b are from ABYC Standard S-30. These tables must be used for calculating capacity, and flotation, and for doing the flotation test. Do not use the actual weight of any particular outboard. The weights of the heaviest outboards are included in the tables. This is so no matter which brand the owner of the boat uses, they will have enough flotation to float level. To test the boat you need to know the following: 1. The maximum weight capacity (the safe load covered in Lesson 3) your boat will carry. 10

11 2. The weight of the persons. This comes from the persons weight on the capacity label or your capacity calculations. 3. The machinery weight: the weight of the engine from Table 4 or the ABYC tables These will be used to determine the amount of weight to load into the boat to test it for flotation. Then measure the following reference areas on your boat. Reference areas are specific areas on the boat where weights representing the load are placed. The cockpit area. 40% reference area. The following photos illustrate measuring the 40% reference area Photo #1 11

12 Photo #2 The passenger carrying area: 70% reference areas. The two foot (61 cm) reference areas fore and aft. There are three tests to do. The first is the level flotation test, after an 18 hour soak. Put your boat in the water. Put half the persons weight in the boat assuming the maximum persons weight is less than 550 pounds. If over 550 pounds (249.5 kg), add (1/8) times persons weight minus 550) in the 40% reference area. The Center of Gravity of all the weights needs to be in the 40% reference area. That doesn't mean all the weights have to be in the 40% area, just the Center of Gravity of all the weights. Place weights to simulate the engine in a basket on the transom. You get this weight from table 4 column 2, Swamped Engine weights, or column 4 from the ABYC table. Why swamped? Because only the lower portion of the engine will 12

13 be underwater. The center of gravity of the engine weights must be no more than three inches aft of the transom and no more than three inches above the top of the transom. Place weights to simulate the battery in the position where the battery is normally mounted. This weight comes from Table 4 Column 4, Submerged Battery Weights, or ABYC table column 8. If no position for the battery is indicated, put them on the centerline of the boat. Place weights to simulate the full portable full tank, also from Table 4 or the ABYC table, in the position where the tank would be placed or if no position is indicated, on the centerline. If the boat has a permanently installed full tank, either fill the tank ¾ full of water, or use weights to simulate the weight of the tank. These weights should be place so their center of gravity is a close to where the tanks center of gravity would be. Pull the plug! Let the boat fill up with water. Leave it that way for 18 hours. Fig 3 13

14 The 18 hour soak is primarily designed to get trapped air out of areas on the boat. To test the boat properly you should drill small holes in areas where air may be trapped, open up the backs of upholstered seats and open hatches or covers to compartments. All areas of the boat should be flooded. The easiest way to do the 18 hour soak is to prepare the boat in the afternoon, put it in the water at four or five pm, and let it sit overnight. You can then test it first thing in the morning. Test 1. After the 18 hour soak the boat should float in the following way: One end out of the water. The other end 6 (15.24 cm) inches or less under water (or out of the water too) measured at the 2 foot (61 cm) reference area. No more than a 10 degree heel angle. (You can buy a device at a hardware store that measures this. See Photo #4). TEST 2. The second test is the stability test. You need to do this one twice, once on each side of the boat. Place half the weight for persons on one side of the boat. The center of gravity of these weights has to be in the 70% reference area on that side of the boat. You have a lot of lee way here. You can move the weights from front to back, or back to front to get the boat to pass as long as the Center of Gravity is in the 70% area, and 30% of the total passenger weight is in the 70% area. Take the other half of the passenger weight out of the boat. Leave the engine, batteries, fuel and control weights where they are. WARNING! Make sure you have some ropes or straps attached to the boat to keep it from rolling over. If you don't have enough flotation to keep it upright, that's what it will do. Then the weights will fall out and go to the bottom of the pool or lake. When it settles down it should float like this. (See diagram) 14

15 Fig 4 The final results should be: One end out of the water. The other end 12 inches (30.48 cm)or less under water (or out of the water too) measured at the 2 foot (61 cm) reference area. No more than a 30 degree heel angle. Experience has shown that if it goes 30 degrees it will probably roll all the way over. 15

16 Photo #3 above, Photo #4 below REPEAT THIS TEST ON THE OTHER SIDE. 16

17 TEST 3. The final test is without the passenger weights. Take all of the passenger weight out of the boat. Leave the engine batteries and gear weights where they are. Let the boat settle Fig 5 The final result should be: One end out of the water. The other end 6 inches (15.24 cm)or less under water (or out of the water too) measured at the 2 foot reference (61 cm) area. No more than a 10 degree heel angle. 17

18 Modified Level Flotation: Applies to: Mono-hull Boats (not catamarans, trimarans, or pontoon boats): Mono-hull means that if you can draw a continuous line around the hull at the waterline when the boat is at rest it's a mono-hull. If it makes two or more footprints in the water it's a multi-hull. I am repeating this definition because a lot of small pedal boats and small fishing boats are not mono-hulls until you put the passengers in them. With this load they are monohulls and must meet this standard. Less than 2 Horsepower (1.49 kw), gas or electric outboard motor, or: Manually propelled. (Oars, sculls, paddles or pedals, etc.) This category includes most dinghies and rowboats, and some small john boats. Requirements: The boat has to float when swamped, (that is; full of water), in an upright attitude. See the diagram in each test for the specific requirements. To test the boat for modified level flotation, you need to know the following: The maximum weight capacity (the safe load) your boat will carry. This is taken from the capacity label or from your capacity calculations. How much weight in people it will carry. This is also taken from the capacity label or from your capacity calculations. If you want to use 2 horsepower (1.49 kw) or less you need the engine weight: = 25 lb. (11.34 kg) Then measure the following reference areas on your boat: Cockpit area. 40% reference area. Passenger area 70% reference areas. 18

19 Two foot reference areas fore and aft. These are the same as the reference areas for Basic flotation and level flotation. There are three tests to do. TEST 1. The first is the level flotation test after an 18 hour soak. Put your boat in the water. Put half the persons weight in the boat assuming the maximum persons weight is less than 550 pounds. If over 550 pounds (249.5 kg), add (1/8) times persons weight minus 550) in the 40% reference area. The Center of Gravity of all the weights needs to be in the 40% reference area. That doesn't mean all the weights have to be in the 40% area, just the Center of Gravity of all the weights. Pull the plug! Let the boat fill up with water. Leave it that way for 18 hours. When done it should float like this: Fig 6 19

20 One end out of the water. The other end 6 (15.24 cm) inches or less under water (or out of the water too) measured at the inner side of the 2 foot reference (61 cm) area, at the centerline of the boat. No more than a 10 degree heel angle. (You can buy a device at a hardware store that measures this). TEST 2. The second test is the stability test. You need to do this one twice, once on each side of the boat. Place half the weight for persons on one side of the boat. The center of gravity of these weights has to be in the 70% reference area on that side of the boat. You have a lot of lee way here. You can move the weights from front to back, or back to front to get the boat to pass as long as the Center of Gravity is in the 70% area, and 30% of the total passenger weight is in the 70% area. Take the other half of the passenger weight out of the boat. If this is a 2 HP 1.49 kw)or less boat, leave the 25 lbs (11.33 kg) where it is. WARNING! Make sure you have some ropes or straps attached to the boat to keep it from rolling over. If you don't have enough flotation to keep it upright, that's what it will do. Then the weights will fall out and go to the bottom of the pool or lake. 20

21 Fig 7 One end out of the water. The other end 12 inches (30.48 cm) or less under water (or out of the water too) measured at the 2 foot (61 cm ) reference area. No more than a 30 degree heel angle. Experience has shown that if it goes 30 degrees it will probably roll all the way over. REPEAT THIS TEST ON THE OTHER SIDE. TEST 3. The final test is without the passenger weights. Take all of the passenger weight out of the boat. Let the boat settle 21

22 Fig 8 One end out of the water. The other end 6 inches (15.24 cm) or less under water (or out of the water too) measured at the inner side of the 2 foot (61 cm) reference area, at the centerline of the boat. No more than a 10 degree heel angle. Some procedures to be used during testing Permanently Installed Fuel Tanks: 20 Gals (75.7 L) or Less. Place weight of fuel on deck over CG of Fuel Tanks. Greater Than 20 Gal. (75.7 L) : Initially same as above. If boat fails fill tank to ¾ level with water. If still fails fill tank full with water. Time Allowed to stabilize between tests: 15 minutes. Hull to Deck Joint: Seal Hull to deck Joint with tape on all boats prior to test. 22

23 Location Of Outboard Motor Weight 3 Inches aft of transom. (+/- 1 inch) (7.62 cm) 3 inches above transom. (+/- 1 inch) (7.62 cm) Flooded Bait Wells During Flotation Tests Remove riser from drain hole and let bait well flood /drain naturally. Trolling Motor Weight for Flotation Test. If equipped with or wired for a trolling motor, the trolling motor and battery are to be considered gear weight. Kicker Motors: If the boat is equipped with a pad or wiring for a kicker motor then flotation must be provide for the submerged weight of motor and controls. If the manufacture of the boat does not specify the horsepower for the kicker motor the the horsepower will be assumed to be 10% of the main motor s horsepower. Weights will be from table 4. How do I know it works? Test it! The best way to find out if your boat passes is to test it. You can do the test yourself, or have a laboratory do it, or if you are newly in business as a boat builder the Coast Guard will do it for you. Call the Coast Guard at

24 Questions 1. The level flotation standard applies to: a. Outboard boats of two horsepower or less b. Inboard and sterndrive boats c. Manually propelled boats d. Outboard powered boat over 2 hp (1.49Kw) *** 2. Level flotation will keep a swamped boat afloat when loaded with specified weights. It will also; a. Make the boat self righting b. Keep the boat from heeling more than 30 degree in calm water *** c. Allow the boat to float with a heel angle greater than 30 degrees. d. None of the above. 3. A steel weight weighs 55 lbs out of the water. If there are two 55 lb steel weights, and during the test one is submerged and the other is out of the water, what is the combined weight. a lb (46.89kg) *** b lb (46.39kg) c lb (43.9kg) d. 110 lb (49.88kg) ( )=103.4 (21.95kg kg=46.89kg) *** ( ) = (21.45kg+24.94kg=46.39kg) ( ) = 96.8 lbs (21.95 x 2 =43.9kg) ( ) = 110 lbs (24.94 X 2 = 49.88kg) 4. When a boat has basic flotation it may float: a. In a level attitude with one end out of the water b. At any attitude with any part of the boat out of the water *** c. Must float at less than 30 degree heel angle and upright d. None of the above. 24

25 5. A 19 foot catamaran with an outboard motor under the US CFR, requires a. Level Flotation b. Basic Flotation c. Modified level flotation d. No Flotation. *** 6. A 16 foot outboard motor boat is tested for flotation with the following results. The first test after the 18 hour soak with persons and gear weight; The heel angle is 11 degrees, the bow is out of the water and the stern is 4 inches underwater at the 2 foot reference area measured at the centerline. Does this boat pass or fail? a. Pass b. Fail *** (10 degrees is the limit) 7. The minimum flotation standard that would apply to a small dinghy with a 2 hp (1.49 Kw) motor would be? a. Basic Flotation b. Modified level flotation *** c. Level Flotation d. This boat is not required to have flotation. 8. Which of the following must have flotation? a. canoe b. kayak c. pedal boat with two hulls d. rowboat *** 9. A single 150 Hp ( Kw) engine is used on an outboard boat. What is the total swamped weight of the engine. Use Table 4 from the US CFR, and the value for fresh water. a. 540 lb(244.9 kg) b. 450 lb(204.1 kg) c. 380 lb(172.4 Kg) **** d. 405 lb, 6.7 cu ft (183.7 kg,.184 cu meters) 25

26 10. An outboard boat is tested for level flotation. On the stability test, when measured at the aft 2 foot reference area the measurement must be at least. a. 6 inches b. 12 inches ***** c. 30 degrees d. 10 degrees 26

27 Appendix A Table 4 from 33CFR183 Weights of Outboard Motors and Related Equipment For Various Boat Horsepower Ratings Boat Horsepower Rating Motor and Control Weight Battery weight Full Portable Fuel Tank Weight column Dry Swamped Dry Submerged to to to to to to to to to to and up Transoms Designed for Twin Motors 50.1 to to to to to and up Below are tables 1a and 1b published in ABYC Industry Conformity Standard S-30, Outboard Engine and Related Equipment Weights. It is updated on a five year cycle and contains the weights for four stroke outboards.. 27

28 28

29 29

30 Appendix B 2004 American Boat & Yacht Council, Inc. 30

31 Appendix C The US Rules can be found at The Canadian Rules can be found at The Recreational Craft Directive for the EU can be found at. There is a fee for these documents. The ISO Standards for recreational boats are at CS1=47&ICS2=80&ICS3=&scopelist= There is a fee for these documents. ABYC Standards can be found at htpp:// There is a fee for these documents for non-members. Members can access these documents on-line. 31