The technique of tapering planks is called spiling....look it up. I didn't say this wasn't possible. I said it is impractical.
5052 is marine grade aluminum. Planks are not necessary with metal because it is possible to form metal with compound curves,
which is impossible with wood. If compound curves are required in wood then strip plank, cold molding, carvel or lapstrake
construction is required. In all those cases the shape is created with multiple pieces bonded together in some form. In the case
of the shape you wish for and the size you want. The material of choice would be Cedar using cold molding or lapstrake. If a metal
boat is really what you want, pick another shape or be prepared for a very difficult, time consuming task that will require both
equipment and skills you most likely do not possess. People who build boats successfully do not do so to save money. It isn't less
expensive. The reason production boats are built the way they are with the materials you have observed is economics.

As far as on-line builders of sheet metal boats.....I do, but not that small.
Steve


"DougC" wrote in message ...
On 7/22/2010 2:20 PM, Steve Lusardi wrote:
Doug,
Your question is not so silly, but it is impractical. Welding long
aluminum seams would cause way too much distortion.

It would seem like it, but then again, very complex aluminum shapes are welded up from sheet by car-body shops and airplane
shops. With bass-boats and jon-boats it goes both ways; the better ones are fully-welded while the cheaper ones are riveted.

The thickness of the
aluminum in a boat that size could not be more than 2 mm at most or it
would be too heavy.

One canoe company online says their metal canoes are .050", or 1.27mm thick. A (different) bass boat company indicates that they
use 5052-alloy sheet.

I can tell you that welding very thin metal is not that difficult, with the proper equipment and a bit of practice. Aluminum
isn't as easy to work with as steel, but it certainly isn't impossible.

Using less than 2 mm would make the boat susceptible
to corrosion that would be too expensive to repair economically.

One thing I can say for certain is that this is a freshwater-only boat, as I live near the geographical center of the lower-USA.
Considering that, I would not think that corrosion would be a problem with aluminum at all, but the boat wouldn't even be left
overnight in the water anyway.

Are you referring to ocean/marine use, in this instance?

Lapstrake construction would look silly at 2 mm or less scantlings.

I don't know anything about boat construction in particular, so I dunno what you mean there. I mean--I looked up what "lapstrake
construction" was, so I understand that bit. The part about "looking silly" I don't get.

The lapstrake is one answer to the question of if the planks are tapered or not, in that they may not need to be. But I can
imagine a method for tapering the planks accurately and reliably, too. It is a method that would work for thin sheet metal but
wouldn't work very well with (thicker) wooden planks though, leaving me wondering how wooden-boat builders do it.

The
shape you want is achievable with both aluminum and steel sheet, but
would be very labor intensive and that labor would have to be very
highly skilled sheet metal people. They are very scarce and expensive.
Those are the reasons they are not made. People would not pay those
costs for the end product.......but as a hobby, you could do it in about
10 years, after you gained the required skill set.
Steve


I cannot seem to find much of anyone online doing DIY (small) metal boats. I think all I've found was wood plank, plywood,
skin-on-frame or composite construction. Is anyone building welded sheet metal boats at all?

---------

This is a rather preliminary discussion. This whole project might not happen, just because I've got plenty of other things to
take up my time and money.

First I guess I'll have to get a smaller sheet of aluminum and try making a model.

~