Bulbs on the Front of Yachts

Bulbs

Ron,

Great question, and a lot of Yachts and designers put the bulbs on hulls to act as "wave breakers" and also for hydrodynamics of the water flowing over the hull. Typically the slower yachts, Mazu for example, will have a bulb, and Cakewalk, which is faster than Mazu doesn't have one, it also depends on the angle of entry of the hull into the water.

I'm by no means a Naval Architect, but this is how it's been explained to me.

Hi,

The whole bulbous bow concept is rather misunderstood by many who fit them.

They are designed to work at a set speed which is usually full speed for the hull and load condition (draft) the best.

Here is what Wikipedia has to say.

Bulbous bow - Wikipedia, the free encyclopedia

This is true. Case in point, Captaintilt's description.

Wiki's description & illustrations leave a little to be desired too. The illustration below better explains the basic concept, however the shape and size of the bulb plays an equally critical role as well, such as a semi-symmetrical or inverted bulb.

But the Bulbous bow is not not only about efficiency is it not?! I mean as you said there is a certain hull speed you can compute with the formula 2,42 x √LWL.
So when you want to go faster than the hull speed you need an bulbous bow to keep the ship balanced (trimming factor). So more horsepower alone does not lead to a higher speed. (?)

A bulbous bow reduces wavemaking resistance, but the increased surface area increases frictional resistance.

It's only worth fitting one when the net change in resistance is a decrease.

One benefit on smaller displacement yachts, say 70-150 feet, is reduced pitching.