3mm or 4mm bottoms difference?

[Stuart]

I built my own plate alloy boat and I can testify to the fact that this was an eye opening experience. Dealing with a good naval architect was a learning experience that overturned many old wives tails.
One issue that I always believed in was the structure in the hull determined hull strength more than hull plate thickness.
Most people seem to rattle on more about the virtues of having thicker hull plate and never do you see the structure that the hull relies on to keep its shape under extraordinary pressures.
Off course thicker plate such as 5mm over 4mm is going to have a bit more impact resistance but not heaps more. Plenty of good structure to support the sheet such as close spaced frames and plenty of stringers will see a hull made from even 3mm resist high impacts over a more sparse hull structure using 4 or even 5mm bottom sheets. I have seen enough plate alloy boats in all sizes with Bowes in between the frames. Most of the owners said the same thing, the plate isn’t thick enough, but on just about every boat this happened to the frames where to far apart and there simply weren’t enough stringers to support the pressures.

I happened to be driving a plate alloy when this very thing happened, upon taking the boat back to the factory they dropped a frame straight in to the spot where the hull had bowed in after much manipulation. It spun me out because they had a frame in stock that would fit that very spot in the hull. I did a bit of asking around and found that was a fault with that brand of hull and design.
It seems any hack can start an alloy boat company these days with next to no experience building boats or even fishing. Some of these guys I have spoken to don’t fish or neither have they owned a boat previously. It seems nuts that this can happen in this day and age.
Some poor guy goes out and buys and XYZ boat but unawares to him and his family fishing many miles offshore that the thing is a potential lemon and they loose there lives.
It’s happened before and unfortunately it’s going to happen again. In my experience there is bugger all good plate alloy boat builders around that I would trust, hell that’s a major part of the resone I built my own boat, built like a brick crapper and heavy.
For a 7.3 meter centre console the bare hull weighs 1.5 tonnes then I have the engine and another 700kg to drop in it. Why people want light weight boats for offshore work is beyond me, weight always means softer.

Stu

[BenAllen82]

For a 7.3 meter centre console the bare hull weighs 1.5 tonnes then I have the engine and another 700kg to drop in it. Why people want light weight boats for offshore work is beyond me, weight always means softer.

Stu

Yeah absolutely, weight does help with the ride of a boat and structure of the internals as well. But really if the design of the hull is done right, structure is sound and not skimped on you really shouldn't have any problems. Weight will always make a hull work better, it gives you more momentum to drive the hull shape into and through the water.

Weight can have its inherent problems though, usually requires more horsepower which increases the setup/maintenance costs. More running costs with fuel etc.. Four-strokes are a good alternative for fuel usage reduction but power to weight becomes and issue, especially when the likes of evinrude are getting very good at what they do with emissions and 300H first service intervals. Other dramas can be the weight "setup" in the boat, put your weight in the wrong place can change the whole dynamic of the boat and the way she handles, especially if you get in to some dramas in some big swell, 2T of boat has a fair bit of momentum when it starts to rock and roll. I've heard of people say "oh shes got 400L of fuel and 200L water in the hull...." thats like an extra 600kg of weight. Sure but after being out on a weekend trip how much is really left, and coming home in a following sea is the worst time "NOT" to have that weight there!! If your boats riding higher in the water shes got more chance of rolling. I reckon Surtees "locking flood tube" is such a great idea for that reason.

Stu I gotta take my hat off to someone who really sets out and builds their own boat the way they want mate well done!!. 7.3... that's no easy task!! Did you get it in kit form or start from scratch?? Have you got any pics mate, i'd be interested to take a look.

Ben

[Stuart]

It was a big job on my own, seems a bit of hard work and my list of freinds vanish. The boat wasnt a kit, although it did turn up on a flat pack but then all plate alloy boats do. I payed a naval architect to design the hull, once that was done it was a matter of back and foward untill it was just perfect for me. That took around 2.5 months to get just right and then the CAD designes where sent to me and the cutting file off to the alloy company to be router cutt. I have since changed a few things to better suite my needs, as the build progresed It become more apparent for a few changes, not to the hull but inbuilt eskies and a 2 seat passanger seat at the front of the console which also doubles as a 150 ltr eskiy. Im spraying it at the momment but I intend on putting up some pics when done. Would I do this again, hell ya? And the first question many ask is do you save any money doing this yourself...Yes, plenty.

Stu

[BenAllen82]

Yeah it is a bit easier if you've got the help of someone who's being doing it for a while and have access to the gear required, were into a build on a 6.2 M Platey at the moment with a new hull, should be interesting to see the results...

Ben