Here in OZ there is a huge market for plate alloy boats compared with other parts of the world. I work at a boat building shop http://www.platemaster.com.au/ that builds plate alloy boats.
I personally want to build an expedition boat for myself. I want to be able to head up north and travel around the top of Australia by boat.
The main design criteria are
- 2.5m beam (maximum legal width to tow without oversize signs)
- 3500kg on the trailer (maximum tow weight of my Cruiser)
- diesel powered (just a fan of diesels, no other reason)
- accommodation for myself, wife and daughter
- long range capability
- self sufficient in terms of electricity, refridgeration, etc
- shallow draft
- ability to rest level on the bottom if the tide goes out (big tides up north, 8m+)
- hull strength (I've seen what happens when boat meets rockbar, not pretty)
Now I normally build plate boats so I am more than familiar with their strengths and weaknesses so I am definitely going to be going with plate alloy. I already own a BOC 250R MIG which is what we use to build most of our boats at work. We also use Eutectic MIGs and TIGs but in the spots I need these I'll borrow one of the welders from work.
I love the hull design we use at work too but I know that their might be a better hull for my needs than our normal one. I have been looking at Catamarans too.
A cat will sit on the bottom flatter than a monohull but the design we use has a planing plank so it is better than conventional hulls in this area.
The 7.3m boat we do comes in at about 3500kg on the trailer but that is with only normal amounts of fuel and water on board. I reckon I'll need to get down around the 6m mark to have enough weight spare for all the extras I want. The 6m is also cheaper to build, easier to tow, cheaper to power, cheaper to run, etc. We did one 6m hull (not on the website yet, I'll find some pics at work tomorrow) in a half cab and although it is a little cramped I reckon it would be big enough for my needs.
The max HP for a 6m (according to AS 1799) is 185hp so my preferences for engines are Yanmar 4BY180Z or a Steyr MO174V40. These are to be driven by a MerCruiser Bravo II leg.
I'll go into some more details tomorrow but it is bed time now.