Doug,
Your question is not so silly, but it is impractical. Welding long aluminum seams would cause way too much distortion. 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. Using less than 2 mm
would make the boat susceptible to corrosion that would be too expensive to repair economically. Lapstrake construction would look
silly at 2 mm or less scantlings. 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

"DougC" wrote in message ...
Recently I have gotten the urge to build a small rowing boat. The size would be 15 feet or less, as I want it car-toppable.

I like the looks of the wineglass-transom rowing boats, but so far haven't seen anything that quite matches what I think I'd
want.

This web page shows one example of something that is /somewhat/ similar to what I'd like:
http://www.clcboats.com/boatbuilding_classes/59.html
-although what I want differs greatly from this.

I may eventually hang a very small engine on it, but only 2 or 3 hp or so.

---------

One question I have is if the individual strips/planks usually change in width from one end to the other. On most boats it
appears they do not, but on a few (such as the one linked above) it looks like they do.


Another matter I've noticed is that boats using this "strip" construction are always wood. I would think that I would rather use
welded aluminum for easier maintenance, but I cannot find any commercial or amateur boat manufacturer using this method for
these plank-style boats. The aluminum boats all look like the plywood boats -- using large fairly-flat pieces with simple
curves.
.....
Is there some reason that strips of aluminum cannot be joined this way? -Aside from requiring welding a lot of thin pieces of
aluminum, that is.


Lastly if there's an online site that shows photos of the different types of boats, it'd be real nice. What other sites seem to
call a skiff or a dory, this page calls a yawl.
~

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.

~

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.

~