There are so many options when it comes to yacht propellers that the choices and variations available can be overwhelming, particularly to beginners. The confusion comes in the ‘balancing up’ of different factors, for example, drag versus usefulness of the propeller versus cost.
Inboard auxiliary engines are more or less standard on sailing yachts these days; the benefits of having an engine are considerable when it comes to safety and manoeuvrability. However, these benefits do come at a cost- the sailing performance of any yacht is adversely affected by propeller drag.
If you’re trying to choose a propeller for your yacht, there are some things you should bear in mind to make this ‘balancing up’ successful:
How Important Is Speed?
If you’ve spent money on making your yacht as fast and streamlined as possible, don’t waste all that effort by sticking a great big propeller on it, particularly since the drag effect increases with the square of the speed. Did you know that the drag of an exposed fixed three-blade propeller can be responsible for up to 35% of the total resistance of the hull through water?
If you’re a racer, speed and therefore a lack of drag, is going to be really important to you. This means that a folding propeller, although it might be less durable and less efficient, is worthy of some serious thought.
How Important is Manoeuvrability?
The solution to the drag experienced with an exposed fixed blade is a folding blade. However, this type of propeller has a lot less thrust, particularly in reverse (about half due to the various forces needed to keep the blades unfolded), so it won’t work for your yacht if, for example, you value the ability to navigate around the marina with ease. Folding propellers are also typically much more expensive than fixed blade propellers.
How Much Can You Afford?
It’s always worth keeping in mind that different propellers have different types of costs associated with them. For example, a basic fixed blade propeller is the cheapest propeller at face value, but take into account the costs associated with the frequent damage to these blades and the likely chance that you’ll need to re-pitch it more than once; and it suddenly becomes a less sound investment.