BASIC POWERBOATING. SAFETY & RESCUE FOR SAILING INSTRUCTORS 9


As the boat continues to accelerate, it moves over the top of its bow wave, its bow levels off, and the boat starts to plane along the top of the water with less wave making and using less fuel. However, as the boat further increases its speed, wind and water friction on the hull also increase, causing a significant increase in fuel consumption. For most planing hulls, the optimum fuel consumption with respect to distance traveled is achieved just as the boat has come comfortably on a plane. When a planing boat encounters waves, its ride can often become uncomfortable and at times even dangerously unstable. It may have to be slowed back to the displacement mode where it doesn’t operate as well as its displacement cousin. There are several different shapes that can be used on a planing hull: flat-bottom, Vee-bottom and cathedral.


Flat-Bottom Hulls


Basically, most powerboat planing hulls are a variation of the flat-bottom hull. Their characteristics include: E Good load carrying E Below average in holding a course at low speeds - tend to slide or drift


E Inexpensive to construct E Rough riding in waves


Vee-Bottom Hulls


The Vee-shaped hull, although basically a flat-bottom hull, has a pronounced Vee-shape to its bow where it cuts the water.


Characteristics of this shape include: E Good ability to hold a steered direction at speed E Deeper Vees perform better in rough water E Deep Vees tend to roll at rest


Cathedral Hulls


Cathedral hulls have two or three Vee shapes forward which turn into basically a flat hull aft. This gives greatly improved stability, but with


some of the unpleasant rough water ride as the pure flat-bottom. Cathedral characteristics include: E Good tracking at low speeds E Good resistance to rolling even at rest E Good load carrying capacity E Uncomfortable at speed in rough water E Tend toward lower freeboard


Table of Contents


Cathedral hulls combine excel- lent stability and load carrying ability, but produce a bumpy ride in waves.


Vee-bottom powerboats have an angled bottom which improves ride and control in waves.


Flat-bottom powerboats plane easily, but produce a bumpy ride in rough water.


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98