|
See
Ike's List
For Everything Boatbuilding! Don't tell me that I can't. Tell me how I can! |
Custom Search
|
|
|
|
See
Ike's List
For Everything Boatbuilding! Don't tell me that I can't. Tell me how I can! |
|
Custom Search
|
|
|
Printer Friendly Page HOME SUBJECT INDEX SITEMAP IKE'S LIST IKE'S STORE HOT TOPICS ABOUT THIS SITE CHART OF REGULATIONS HULL ID NUMBERS LABELING SAFE HORSEPOWER SAFE LOADING FLOTATION ELECTRICAL SYSTEM FUEL SYSTEM VENTILATION RECALLS NAVIGATION LIGHTS _________________ Basic Electricity DC Basic Electricity AC Business Of Boatbuilding Legal Considerations Quality Management Production Management Federal Regulations Statutes and Regulations: How they are made Environmental Carbon Monoxide Marine Engines Marine Toilets Boat Myths Boating Quotes Standards Documents Available Free online
Please Report
|
HOW TO CALCULATE FLOTATION NEEDS
The following are simplified methods to calculate the amount of flotation needed for a boat. The notation used, such as Boat Weight = Wb , is the same as used by ABYC, the Coast Guard and NMMA, so if you have problems you can call them and they will recognize what you're talking about. If everybody is speaking the same language it makes life a little easier. The first method is for outboard motor boats over 2 hp. The procedure is basically the same for all boats. You need to find three things; The boat weight and how much flotation you need to support it. The machinery(engine) weight and how much flotation to support it. The persons weight and how much flotation to support it. I have simplified the calculations but in real life there is much more that goes into a boat than fiberglass and wood. Things such as screws, fittings, glue, paint, windshields, consoles, seats, etc. all add weight. There are several ways to determine the weight of each of these. The simplest way is to weight each item before you install it and add up the weights. But you need to know that different materials have different weights under water. That's what the table is for. It provides factors for determining what something weighs submerged. For instance; Fiberglass; weighs about 1/3 under water what it weighs dry. So the factor is 0.33. You need to determine where everything will be when the boat is swamped. If it will be dry, use the full weight; if wet the submerged weight. The engine will not be fully submerged on an outboard so you need to use a swamped weight. That is what it would weigh if it were only partially submerged. For that you need to take the swamped weights from the table. Use Table 4 for outboard motor weights. You can also use Table 4-2 at the bottom of the table page for metric weights, or use ABYC Standard S-30,Outboard Engine and Related Equipment Weights Available from ABYC. If using Metric the value for water is 1000 kg/cubic meter If you use S-30, the engine weights are heavier (because they are more up to date) than in the USCG table. S-30 also includes both 2 cycle and 4 cycle engines. This results in heavier engine weights than the USCG table. So you will come out with slightly amounts of flotation. Additionally there is
a different formula to calculate flotation for persons weight for boats
with over 550 pounds of persons capacity. You will see this in the
examples. Method of Calculation with example: OUTBOARD MOTORBOATS OVER 2 HP:14 Foot outboard
Factors for the Specific Gravity of
materials: Calculate the amount of
Flotation required, Ft, for The boat using: Boat (Hull) weight(Wb)
= 800 lb
Fiberglass
Wood Recalculate total Boat Weight The following is the method for Modified Level flotation: OUTBOARD MOTORBOATS LESS THAN 2 HP & MANUAL PROPULSION:
See Example Calculating Capacities and Making Labels Note: The requirement for flotation for persons weight is 2/15 of the persons weight or 0.1333 times the persons weight. But in the Guidelines the USCG uses 1/4 or 0.25 times the persons weight to provide a safety factor. This provides a safety factor of 2 or twice the amount of flotation for persons weight. If you use 2/15 you will have a lower amount of flotation.
Flotation for persons Weight (Fp): over 550 lb persons capacity The following method is for Basic Flotation: INBOARD MOTORBOATS: Factors for the Specific Gravity of materials: Factor: K = Fiberglass = 0.33 Aluminum = 0.63 ABS Plastic = 0.11 Oak, white = -0.18 Oak = -0.56 Mahogany = -0.72 Plywood = -0.81 Flotation for persons Weight (Fp) over 550 lb persons capacity Fp = (0.5 X 550)+0.125(Wp-550)+.25(Wdw) / 60.4 = 275 + ________ + _______ / 60.4 Flotation for persons Weight (Fp) Fp = _______ boats with less than 550 lb persons capacity Fp =(0.5 X Wp)+.25 (Wdw)/60.4 = ______ + ______ / 60.4 = Fp = _______ Flotation for swamped machinery (Fm) = (Wm) / 60.4 = _______ / 60.4= Fm = _______ Amount of Flotation (in cubic feet) = Fb + Fp + Fm = Ft = ______ +_______ + ______ + _______ = _______ Weight of Flotation in pounds (Fw) = 2 lb/cu ft x Ft = 2 X ____ = _______ Total Boat weight = Weight of Flotation + Boat weight = Fw + Wb = = ___________ + ___________ = ______ Keep track of total boat weight over a production run. If total boat weight increases significantly (say more than 50 lb) you need to add flotation.
|
|
||||
|---|---|---|---|---|---|---|
 
|
||||||
| This Web site may contain copyrighted material the use of which has not always been specifically authorized by the copyright owner. I am making such material available in my efforts to advance understanding of educational, economic, and scientific issues, etc. I believe this constitutes a "fair use" of any such copyrighted material as provided for in section 107 of the US Copyright Law. In accordance with Title 17 U.S.C. Section 107, the material on this Web site is distributed without profit to those who have expressed a prior interest in receiving the included information for nonprofit educational purposes. For more information see: www.law.cornell.edu/uscode/17/107.shtml. If you wish to use copyrighted material from this Web site for purposes of your own that go beyond "fair use", you must obtain permission from the copyright owner. | ||||||
|
