Types of Hulls - 1 : The Planing Hull

Imagine making a sumo wrestler run a 100 meter-sprint...even the thought is hilarious and probably scary.

But why talk about sumo wrestlers running on blog a about boating!? - Simple...since boats have a body too - the HULL. And hulls are not only meant to keep the boat afloat, but their shapes and types have a reason too.


In our Types of Hull series, we are going to discuss only a drop-worth of what different kinds of hulls are about...the first being the Planing Hull.

With most of the boats in the harbour at the moment having these kind of hulls, it comes first on our list.

WHY 'PLANING' ?

The term 'planing' is given to any craft which is predominantly supported by hydrodynamic lift, rather than hydrostatic lift (buoyancy).

Simply put, it means that the boats weight is supported when in motion by the pressure of the water surface.


Planing allows the boat to go faster by using its speed and hull shape to lift the front part of the hull out of the water. The boat travels on top of the water, greatly reducing the hydrodynamic drag on the vessel.

The increase in aerodynamic drag is small by comparison, and can be compensated for by the increased power from the sails due to the faster speed of the craft, and by the crew trimming the sails.

HOW DOES IT WORK?

When a planing hull is either not moving or going very slowly it works like a displacement hull. However, by adding lots of horsepower, a planing hull will rise up over its bow-wave, causing the boat to displace much less water. As a result, there is much less wetted surface on the hull bottom, meaning less friction as well. The speed of the boat will now increase at a great rate. With this hull, the more horsepower you add, the faster the boat will go.


However, this great speed comes with some big downsides. The boat is now skimming over the waves which is great in flat water, but even in a mild chop the pounding and vibration become very severe. (ASK US, WE WENT FROM MUMBAI TO GOA...in 'slightly' choppy waters!)


At best, this is just uncomfortable for crew and passengers, but worse is that it greatly adds to wear and tear on the yacht. If the yacht slows down and reverts to displacement mode, the flat bottom of a planing hull and short waterline length make for a rolling and pitching ride.

The same can be said for the ride at anchor. The flat bottom of a planing hull also means that the yacht suffers greatly from windage, and so can be hard work to berth, even if fitted with bow and stern thrusters.

HOW TO GO FAST WITH PLANING HULLS ?

Again, its simple...MORE HORSEPOWER !

High speed planing yachts are often combined with Arnesen surface drives for yet more speed, which makes the captain's job even harder when manouevring at low speed.

And it is nigh on impossible to combine a planing hull with stabilisers because of the drag they cause.

Planing hulls are generally used by smaller dayboats, but some fairly large open yachts are designed to be fully planing hulls.
Read more...

'Look Ma! No Hands...!' - AUTOPILOTS

Planning on a long sea voyage? Surely if its a private sail with your family you wouldn't want one of you to always be at the helm and missing out on the fun with the family!


Or incase you want to rally through oceans solo and dont want to waste few hours on anchorage to catch a few winks...

Autopilots - inboard and outboard - give yachtsmen and sailors a lot of freedom of navigating through seas while saving a lot of effort and energy - in the bargain, less fatigue and more time to soak up the sun !

AUTOPILOTS

An autopilot is a mechanical, electrical, or hydraulic system used to guide a boat without assistance from the crew.


Most people understand an autopilot to refer specifically to aircraft, but self-steering gear for ships, boats, space craft and missiles is sometimes also called by this term.

HISTORY

The autopilots used on yachts are an adaptation of the ones used on aircrafts. In boats, an autopilot connects to your steering system and continually corrects your boat’s heading with information supplied by the compass, wind transducers or GPS.

The earliest autpilots used in aircrafts connected a gyroscopic Heading indicator and Attitude indicator to hydraulically operated elevators and rudder (ailerons were not connected as wing dihedral was counted upon to produce the necessary roll stability.) It permitted the aircraft to fly straight and level on a compass course without a pilot's attention, greatly reducing the pilot's workload.

In fact, in the early 1920s, the Standard Oil tanker J.A Moffet became the first ship to use an autopilot.

MECHANICS OF AN AUTOPILOT

Autopilots are designed to maintain an accurate course in various sea conditions with minimal helm movements. Because they steer so accurately, they will save fuel and get you to your destination faster, especially when connected to a chartplotter.


Autopilots consist of three main components:

1) heading sensor (usually a compass)

2) processor and drive controller (the brains)

3) drive mechanism (the business end)

There are two types of autopilot, Cockpit and Inboard (also called below-decks).

Cockpit pilots are simple to install and remain in the cockpit in all types of weather.


Inboard autopilots are permanently mounted below decks and are more powerful, more reliable, steer your boat better and can be supplied with a range of autopilot controllers.

MORE CONVENIENCE...

There are a lot of other yachting instruments that make your voyage more comfortable and the navigation more simpler. With the advance in technology you would see more and more of these in yachts around you.

1) Chartplotters

2) Fishfinders

3) Marine Radars

4) Satellite Television

5) Marine Cameras


Read more on these soon... Read more...