I've written about this elsewhere, but feel I must keep going on about how complex boats can be to build. I know that building the hulls is usually the first step and its natural to want to make that as simple as possible, but in fact building the hulls is always the easy bit.

The last two large boats I built have been the Gypsy and Eclipse. I was day sailing my Gypsy after about 1000 hours work, although only 4' longer I've done more than 1000 hours work on the Eclipse since first sailing it and its still not finished.

One small example, which may sound a minor, silly point, but all these little extras soon mount up. My Eclipse has 23 interior lights, Gypsy had 6. Lights need wiring, conduits, circuit breakers, switches etc and all to be planned before building has progressed too far so that it can all be neatly hidden.

At least 30% of a monohull's displacement is a "go out and buy, then stick on the bottom" lump of steel or lead. On a multihull ALL its displacement will go through your hands. That means on a 40' cat you'll end up handling 5-6 tons of material. An Eclipse 3 tons, a Gypsy 2 tons.

Don't think that a slightly longer boat is not much more to build. Surface area (laminating, painting, sanding etc) goes up by the square of length. Weight (material that you have to handle, carry up ladders etc, eg timber, plywood, glass, resin) goes up by the cube.

If you really want an "easy build" boat the answer has to be - leave it out. Use an outboard engine not inboards, a tiller not a wheel. Don't fit a freezer or a shower. Keep the electronics to a minimum. Accept open fronted lockers, not drawers etc

By and large, boat building is not profitable, so when a boat is sold for £100,000 that means most of that money goes on materials and labour. Typically I'd suspect that 25% would be on materials. You don't get anything for nothing in life, so you will have to earn that remaining £75,000 by putting in the hours. Typically you work 2000 hours a year at your job. Think back over the last 3 years and work out how much you're done at work. Then think about spending 5-6000 hours building a 45' cat. Also think what else you could be doing in that 5000 hours, (have a social life? watch your kids grow up?).

On a 40' cat 5000 hours probably equates to 35,000 miles sailing. In other words, you will have to sail nearly twice round the world before you spend more time sailing a 40 footer than building it. I have built 18 boats in the last 20 years (all but two for my own use). I know first hand how hard it is to keep going on a project. The Eclipse has taken up most of my life for the last two years, I know I couldn't cope mentally with building anything larger.

Much worse than having a boat that's too small for you is spending years half building a boat and then giving up. So, please think very carefully about the length of time you are really prepared to commit to your boatbuilding project. I will say it again and again, there is no need to have a catamaran much over 35 feet for normal family sailing, while even a charter boat need not be more than 40 feet. Don't be seduced by the glamour of big boats unless you can afford to buy one complete or employ people to help you.

Update 2015: Here are some minimum rough times based on the boats I have built. So are for someone who knows what they are doing, to a basic fit out ready to sand/paint

Beach cats 120hrs
Strike 18 - main hull 150hrs
Janus 350 hrs
Strider/Shadow/Gwahir 550hrs
Wizard/Skoota 20/24 800 hrs
Sango 900 hrs
Surfsong/Windsong 1200hrs
Gypsy, Saturn 1500 hrs
Skoota 28, Jazz 30 2000 hrs
Mira, Mirage 2300 hrs
Romany 2500hrs
Vardo, Eclipse 2700 hrs
Flica 3000hrs

Bigger than that and I'll just say "a long time"