Light Weight

Designers and technically informed sailors all seem to agree that light weight is the fundamental driver of catamaran cruising efficiency. 

There is a virtuous circle.  A lighter boat:

• Is more easily driven and intrinsically faster 
• Needs a smaller rig to power it
• Smaller sails are easier to handle with lower loads
• Engines can be smaller and lighter (and anyway you’ll motor less and sail more)
• Smaller equipment means the boat is lighter… and so the virtuous circle goes round

And there are some great added win-wins:

• Improved motion Light cats with centralised weight pitch less, sail more smoothly and this increases their speed as well as comfort
• Safety Speed adds a major safety factor through the potential to outrun bad weather
• Simplicity A simple spec keeps the weight down and also reduces maintenance stress

We discovered it’s important to understand what “light” really means. In marketing driven times with so much material circulated by sponsored sailors, the terms “light” and “performance” seem to be applied to all sorts… 

We’re looking at boats of around 45 ft, so let’s compare the displacements of a few mainstream models and where they sit in the spectrum:

To put it in perspective, if you parked two VW Polos on an Outremer 45 it would still weigh less than the 11,000kg boats. Imagine that effect on performance!

I’m not suggesting that boats in one of these bands are better than the others. We all have our own priorities. Everyone understands that the heavier boats have correspondingly more voluminous accommodation and that’s absolutely fine if space is your main priority.

What’s less clear through some of the hype is that we found, by sailing various boats, you really have to look at the lightest sector if you want that feeling of effortless speed, or gliding along under sail when others are motoring. 

The light boat compromise 

Light boats, of course, compromise on volume and payload. Nevertheless, the step-up from the monohull space we’re accustomed to, to the space in a well-designed light cat, is huge. More than enough for our needs. We’re happy to forego the widest cabins for better handling, quick passages and weather routing safety. And… to be honest, pride of ownership of a real sailing boat is a big thing for us.

2000+kg payload is typically possible in the light boats and, after creating another spreadsheet, we estimate this will be plenty for us. Toys such as SUPs, bikes and a kite-board (on the have-a-go list) will be no problem in addition to spares and essentials. As Pogo said about the first Rush “We built the boat light enough so you can carry what you want”. That seemed a great philosophy and it worked. 

For us, the advantages of a boat that will sail in around 4 knots of breeze and be capable of good daily mileages using small sails, in comfort and safety mode, easily outweigh the compromises. An easily driven boat sailing at 10 knots, under lower loads from smaller sails, just feels better to us than a hard-pressed, heavier boat at the same speed.

Additional Key Features

Additional design elements that we conclude are important for us:

High bridge deck You can play around with shapes underneath, but fundamentally a high bridge deck, set well back from the bow, will reduce slamming and drag and improve comfort in waves. Less bridge deck area also reduces weight. 

Daggerboards They add cost and some complexity, but without them a boat points around 10 degrees lower and sails more slowly due to the drag from inefficient, long chord, short depth keel sections. VMG may be halved … upwind passages take twice as long. A respected designer of cats both with and without boards (for different brands / market sectors) pointed out the best way to get a cat without daggerboards upwind in adverse conditions is to run an engine… 

The ability to lift daggerboards and allow the boat to slide (rather than trip over a fixed keel) in big waves is another safety feature.

Rig set well aft This evolution has been handed down from race-boat development for: 

• A large foretriangle giving space for different size headsails to be set-up on furlers, ready for use 
• Efficient separation of downwind sails from the mainsail
• Centralised weight and less “pressure” on the bows allowing them to glide more smoothly.

Low windage / low centre-of-effort High topsides and square cabin tops increase windage, with disadvantages at sea and when mooring. Keeping the superstructure low keeps the rig low, with stability and efficiency benefits. 

High spec construction If you want to build a boat that is both light and strong, you have to use the best materials and build systems. I’ll talk through construction later so let’s just say that I believe construction is a hidden, but key factor. You can’t see what resin or fibre a boat is made from by looking at it… but it’s fundamentally important. Of course, cost is generally a downside to a higher tech boat…

Boat Size

Feedback indicates that 45 to 50 feet long is a sweet spot – big enough to achieve decent motion and space – small enough to be easily sailed by a couple. For budget, handling and complexity reasons we’re keen to keep the size down so we settled on the low end of that range.