New to the game. Aluminium or marine ply?

I am thinking of building a vessel of approximately 6m to 7m. I am new to boat building however, I am a Carpenter by trade and feel this would not be to difficult. I have been looking at kits from both Alucraft Boat Builders & Designers and Marine Kits Australia. I have only one problem. I have been told that a single-phase 240-volt MIG welder would not penetrate the 4mm to 5mm aluminium good enough for a quality weld. Can anyone clarify this for me please?

For this reason I would prefer to build a vessel in marine ply. I am very experienced with timber and would probably find this easier. Does anyone know if glass over ply would be heavier than aluminium or are they comparable in weight?

Many Thanks,
Jon.

 

I can't answer the question about the welder, but you may find that you can build a plywood hull as light or lighter than an aluminum hull in the smaller sizes. On small boats, the aluminum is sometimes made thicker than necessary in order to be able to weld it properly. This causes the boats to be a little heavier than if they were riveted. This is not a bad thing, as it also makes for a very sturdy boat. Plywood is actually a pretty light material and because of its thickness, pretty stiff as well. A lot of this will depend on the designs of the boats in question, so can't really be answered in a general way. If you are used to working with wood, and enjoy doing so, you may be better off building in ply. If you have experience in both, which would you rather spend an enormous amount of time doing? Don't rule out strip planking or cold-molding either. Both produce lightweight, sturdy boats. Your experience with wood could make these quite enjoyable methods of building. Good luck!

 

Dudley Dix http://www.dixdesign.com has some great looking ply boats and lots of information you might find useful. I would agree with Timm, unless you plan on regular interviews with rocks, go with what you know!

Paul

 

i´m in the same situation as you, but i am going for Alu.
I think you have to see to the demands. I agree with Timm , but if you want a long lasting boat with a minimum of maintenance - go for alu. (hope your water don´t eat alu) I work as a boat mechanic in Sweden and did recently a job on a couple of the Navy´s Alu boats. They sure are heavy and looks lake the have hit some rocks now an then. They are biult in the early seveties and have their third set of outboards, but they are still handling like they did as new. Those boats havent cost many hours in repair..
Some of the welding guys says you can build a boat vith a 190A MIG if you pre-heat the plating with a torch and have som spacing. Dont now, but im going too try. In Sweden we have a lot of rental shops who have some heavy welding mashinery. Maybe you can hire a maschine and give an experienced welder som money to do the hull in a weekend. And then complete the boat with the smaller MIG.

goodluck with your choise.


Staffan

 

Thanks for the information I have found it very informative. I think I will stick to what I know and go with PLY construction as I will not be hitting too many rocks, HOPEFULLY. I was hoping to build something like the vessel below in ply but I can't find anyone who would have the plans to build such a boat in ply with an epoxy finish. Can anyone help me with this?

Many Thanks,
Jon.

 

RE; aluminum welding

Hello

new here, but thought I'd weigh-in on the Aluminum welding issue.

I weld regularly with both a single phase MIG and TIG machine, and can tell you that either one will handle the thickness you are
reffering to. The Lincoln 300 I have will handle 3/8" easily.

Thanx

 

Re aluminum vs wood
I have built many boats with aluminum and helped others build with wood. Aluminum boats can be built two to three times as fast as wood because the joining of the sheets is easier. Your welder is big enough. When you join ply at say the chine you have to put a backing piece in, fair it to match the gunnel whose angle changes from stern to bow. Screws, glue, primer, finnish coat all add to the cost and time. A wooden boat will deteriorate over time and lose value. Almost all the tools that you use on wood can be used for aluminun. I would recommend purchasing
the book, Boatbuilding with Aluminum, by Stephen Pollard. I have been trying to find plans for a 34 foot and found a few down under that would have plans in you size range in a kit form.
An aluminum boat with a 1/4 bottom and 1/8 inch sides will be lighter than wood. The main trick when building a boat with aluminum is to ensure that your hull joints are almost light tight
before welding to ensure strength. buy the book and happy building.