Any plywood design can be modified for aluminum. You need a design that
will be OK with some weight, as 1/8 aluminum weighs about the same as 3/4
ply. even 1/8 can be a bear to work with, I wouldn't be optimistic for the
chances of success with any thing lighter, unless you have a LOT of
experience.

I'm not sure what you mean by "semi tunnel" but I built an Atkin Rescue
Minor with fully protected prop and rudder. Or you can modify the transom
of any skiff to give you a bit of a tunnel effect with an outboard - at the
loss of some "lift".

Can you provide a link to pictures of the kind of boat (in wood or glass)
you are thinking of?

Sal's Dad


"Bob La Londe" wrote in message
.. .
Anybody know of any all aluminum designs (no wood composite or sandwich)
available for sale for a shallow draft semi tunnel for river running? I
can modify if need be, but I ain't gonna put no wood in it if I build it.
Well, maybe for totally non structural stuff, but I doubt it.

I'm trying to talk Mrs Santa into getting me a 60% duty cycle MIG w/ spool
gun for Christmas.


--
Bob La Londe
Fishing Arizona & The Colorado River
Fishing Forums & Contests
http://www.YumaBassMan.com

On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:

as 1/8 aluminum weighs about the same as 3/4
ply.

If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady

Richard Casady wrote:
On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:


as 1/8 aluminum weighs about the same as 3/4
ply.


If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady


plywood floats.

Aluminum don't.

What am I missing here?

On Thu, 06 Dec 2007 18:32:10 -0600, cavelamb himself
wrote:

Richard Casady wrote:
On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:


as 1/8 aluminum weighs about the same as 3/4
ply.


If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady


plywood floats.

Aluminum don't.

What am I missing here?

A clue.

Casady

Richard Casady wrote:

On Thu, 06 Dec 2007 18:32:10 -0600, cavelamb himself
wrote:


Richard Casady wrote:

On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:



as 1/8 aluminum weighs about the same as 3/4
ply.


If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady


plywood floats.

Aluminum don't.

What am I missing here?


A clue.

Casady


I thought most aluminum alloys weighed in at .1 pound per cubic inch.
Except 6061 which is only .09 lbs/cu.in.

Ply was .025 to .033 lbs/cu.in.

So clue me in.

On Thu, 06 Dec 2007 19:29:19 -0600, cavelamb himself
wrote:

Richard Casady wrote:

On Thu, 06 Dec 2007 18:32:10 -0600, cavelamb himself
wrote:


Richard Casady wrote:

On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:



as 1/8 aluminum weighs about the same as 3/4
ply.


If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady


plywood floats.

Aluminum don't.

What am I missing here?


A clue.

Casady


I thought most aluminum alloys weighed in at .1 pound per cubic inch.
Except 6061 which is only .09 lbs/cu.in.

Ply was .025 to .033 lbs/cu.in.

So clue me in.

I simply questioned if aluminum was in fact exactly six times as dense
as plywood. That is what you get with sheets six times as thick
weighing the same. That would make the density of plywood .017.lb/cu.
According to you it isn't. I simply opined that most plywood does not
have that particular density. What don't you understand? And I am
sorry about the cheap shot. It isn't really my style. I have the
'calculator that takes no prisoners',HP-48, and it isn't a problem but
it is usual to express wood density as pounds per cubic foot, in the
US, at least. Density figures in general are usually with reference to
the density of water.

Casady

Richard Casady wrote:
On Thu, 06 Dec 2007 19:29:19 -0600, cavelamb himself
wrote:


Richard Casady wrote:


On Thu, 06 Dec 2007 18:32:10 -0600, cavelamb himself
wrote:



Richard Casady wrote:


On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:




as 1/8 aluminum weighs about the same as 3/4
ply.


If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady


plywood floats.

Aluminum don't.

What am I missing here?


A clue.

Casady


I thought most aluminum alloys weighed in at .1 pound per cubic inch.
Except 6061 which is only .09 lbs/cu.in.

Ply was .025 to .033 lbs/cu.in.

So clue me in.


I simply questioned if aluminum was in fact exactly six times as dense
as plywood. That is what you get with sheets six times as thick
weighing the same. That would make the density of plywood .017.lb/cu.
According to you it isn't. I simply opined that most plywood does not
have that particular density. What don't you understand? And I am
sorry about the cheap shot. It isn't really my style. I have the
'calculator that takes no prisoners',HP-48, and it isn't a problem but
it is usual to express wood density as pounds per cubic foot, in the
US, at least. Density figures in general are usually with reference to
the density of water.

Casady


Accepted, thanks.

On Thu, 06 Dec 2007 23:22:23 GMT, (Richard
Casady) wrote:

On Wed, 5 Dec 2007 07:41:59 -0500, "Sal's Dad"
wrote:

as 1/8 aluminum weighs about the same as 3/4
ply.

If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

Casady

It may be.
Black ash 0.54
Birch 0.67
red cedar 0.38 (!!)
see the table here...
http://woodsgood.ca/woodDensity.htm

Regards

Brian W

There are lots of sources of materials density out there.

http://www.rfcafe.com/references/gen..._materials.htm
shows:

Aluminum at 171 lb/cu ft. Divide by (12*8) to get approx. 1.78 lb/SF for
0.125 aluminum.
Plywood (5/8 thickness construction grade) is 1.77 lb/SF (or 34 lb/cu ft)

So I stand corrected. 1/8 aluminum weighs about the same as 5/8 construction
grade ply. Maybe, when I calculated this a few years ago, I used a
different grade or species of plywood, or alloy of aluminum - I honestly
don't recall. But either way, it gets you into the ballpark. There are
relatively few elegant small boat designs using material this heavy.

Sal's Dad

--

as 1/8 aluminum weighs about the same as 3/4
ply.

If you divide 2.7, the density of aluminum, by 6, you get .45. I
thought plywood was heavier than that.

On Fri, 7 Dec 2007 15:33:51 -0500, "Sal's Dad"
wrote:

Aluminum at 171 lb/cu ft. Divide by (12*8) to get approx. 1.78 lb/SF for
0.125 aluminum.
Plywood (5/8 thickness construction grade) is 1.77 lb/SF (or 34 lb/cu ft)

So I stand corrected. 1/8 aluminum weighs about the same as 5/8 construction
grade ply

I thought a figure was a bit high. It is, slightly, but had I known
the difference was a small as it is[I will take your figures] I don't
think I would have bother to post anything. It did smoke out some
interesting figures. Plywood tends to be about as dense as the wood it
is made from, it seems. The texts seem to give the density of woods in
pounds per cubic foot but with a modern calculator[HP48] any and all
units are convenient.

Casady