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.

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

"Brian Whatcott" wrote in message
news
On Tue, 27 Nov 2007 20:54:32 -0700, "Bob La Londe"
wrote:

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

Uh-oh: you said "aluminum boat" and "MIG welder" really, really,
casually.


There are some things about mig aluminum welding that a lot of people don't
realize...

1st - Its really hard to do a good job with a cheap welder like the 120V
20amp 10/20% duty cycle things with only two heat ranges like they sell at
Harbor Freight. I'm looking at a Hobart Ironman 250. I already got one of
those cheap ones. Figured I'ld use the push feed gun for steel and a spool
gun for aluminum so I wouldn't ever have to worry about gun/tip
contamination.

2nd - You have to burn some metal to get it dialed in just right. I got
scrap laying around from some other things I can burn up.

3rd - Use a clean stainless brush on all surfaces just before welding to
break up and remove the oxidation. Never use your brushes for aluminum on
ANYTHING else. Brushes are cheap insurance. USE THEM EVERYTIME even if you
brushed it yesterday.

4th - A spool gun is the way to go, but even with a push feed gun its
possible to push aluminum if you swap out the V groove feed wheel for a U
groove feed wheel. The V groove wheels shave the soft aluminum wire causing
it to plug up the feed tube and your gun.

5th - There is no 5th item.

6th - if for ANY REASON the wire doesn't feed STOP. Otherwise you will you
will have a wad of crammed up aluminum wire someplace in your rig.

7th - Practice and warm up for a few minutes on some scrap EVERYTIME before
you start on your cut pieces. (Thats a good idea on steel too.)


Tell me you have MIG welded aluminum before - that you have the right
mask screen, that you can not only stitch thick aluminum castings
together, but you have seamed sheet as well.....

Nope, I'm not super experienced, but I got a pile of scrap aircraft aluminum
to practice on. I've played some with aluminum, and I don't plan on using a
cheap rig. I've used some of the torch alloy stuff too, but its really only
suitable for small work.

I have a variable shade autodarkening mask, and I use it for everything. I
even use it for cutting. I just lighten the shade up.

And worse comes to worse... I can alway learn to install blind rivets.
LOL.


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



--
Posted via a free Usenet account from http://www.teranews.com

"Sal's Dad" wrote in message
...

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".

There are some "tunnel" designs for running an outboard a few inches higher
that just have a small tunnel at the rear of the boat. When I was really
reading a lot about boat building a few years ago I recall reading about
some of them.


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



--
Posted via a free Usenet account from http://www.teranews.com

On Sun, 9 Dec 2007 19:16:34 -0700, "Bob La Londe"
wrote:

....
Uh-oh: you said "aluminum boat" and "MIG welder" really, really,
casually.


... I'm looking at a Hobart Ironman 250. I already got one of
those cheap ones.....
3rd - Use a clean stainless brush on all surfaces just before welding to
break up and remove the oxidation. Never use your brushes for aluminum on
ANYTHING else. Brushes are cheap insurance. USE THEM EVERYTIME even if you
brushed it yesterday.

4th - A spool gun is the way to go, but even with a push feed gun its
possible to push aluminum if you swap out the V groove feed wheel for a U
groove feed wheel....

5th - There is no 5th item

Bob La Londe

This seems like a plan to me: the story I hear quite often is that
the hot puddle will drop out given half a chance on thin stock.

A particular optical filter is said to be a big help in visualizing
the puddle's state.

Good luck!

Brian W

On Mon, 10 Dec 2007 02:38:44 GMT, Brian Whatcott
wrote:

On Sun, 9 Dec 2007 19:16:34 -0700, "Bob La Londe"
wrote:

...
Uh-oh: you said "aluminum boat" and "MIG welder" really, really,
casually.


... I'm looking at a Hobart Ironman 250. I already got one of
those cheap ones.....
3rd - Use a clean stainless brush on all surfaces just before welding to
break up and remove the oxidation. Never use your brushes for aluminum on
ANYTHING else. Brushes are cheap insurance. USE THEM EVERYTIME even if you
brushed it yesterday.

4th - A spool gun is the way to go, but even with a push feed gun its
possible to push aluminum if you swap out the V groove feed wheel for a U
groove feed wheel....

5th - There is no 5th item

Bob La Londe

This seems like a plan to me: the story I hear quite often is that
the hot puddle will drop out given half a chance on thin stock.

A particular optical filter is said to be a big help in visualizing
the puddle's state.

THere have been at least a million aluminum airplanes produced. All
were riveted. Wonder why?

Casady

Bob La Londe wrote:

"Brian Whatcott" wrote in message
news
On Tue, 27 Nov 2007 20:54:32 -0700, "Bob La Londe"
wrote:


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

Uh-oh: you said "aluminum boat" and "MIG welder" really, really,
casually.



There are some things about mig aluminum welding that a lot of people don't
realize...

1st - Its really hard to do a good job with a cheap welder like the 120V
20amp 10/20% duty cycle things with only two heat ranges like they sell at
Harbor Freight. I'm looking at a Hobart Ironman 250. I already got one of
those cheap ones. Figured I'ld use the push feed gun for steel and a spool
gun for aluminum so I wouldn't ever have to worry about gun/tip
contamination.

2nd - You have to burn some metal to get it dialed in just right. I got
scrap laying around from some other things I can burn up.

3rd - Use a clean stainless brush on all surfaces just before welding to
break up and remove the oxidation. Never use your brushes for aluminum on
ANYTHING else. Brushes are cheap insurance. USE THEM EVERYTIME even if you
brushed it yesterday.

4th - A spool gun is the way to go, but even with a push feed gun its
possible to push aluminum if you swap out the V groove feed wheel for a U
groove feed wheel. The V groove wheels shave the soft aluminum wire causing
it to plug up the feed tube and your gun.

5th - There is no 5th item.

6th - if for ANY REASON the wire doesn't feed STOP. Otherwise you will you
will have a wad of crammed up aluminum wire someplace in your rig.

7th - Practice and warm up for a few minutes on some scrap EVERYTIME before
you start on your cut pieces. (Thats a good idea on steel too.)



Tell me you have MIG welded aluminum before - that you have the right
mask screen, that you can not only stitch thick aluminum castings
together, but you have seamed sheet as well.....


Nope, I'm not super experienced, but I got a pile of scrap aircraft aluminum
to practice on. I've played some with aluminum, and I don't plan on using a
cheap rig. I've used some of the torch alloy stuff too, but its really only
suitable for small work.

I have a variable shade autodarkening mask, and I use it for everything. I
even use it for cutting. I just lighten the shade up.

And worse comes to worse... I can alway learn to install blind rivets.
LOL.



Trust me, you can't really push aluminum well enough to weld a decent
seam. I have the Ironman210, and even with the teflon liner, it balls
and birdsnests easily unless the gun is straight out from the welder.
Even then, it'll only skip once, and then you gotta get out the cutters.

Spoolgun is the way to go.

I don't care what they told you.

--
“TANSTAAFL”
__________________________________________________ __________________________

America: Ironically, the safest place to be anti-American.
__________________________________________________ __________________________
"A prudent man foresees the difficulties ahead and prepares for them;
the simpleton goes blindly on and suffers the consequences." - Proverbs 22:3

Jeff Burke wrote:

On Mon, 10 Dec 2007 03:36:36 GMT, (Richard Casady)
wrote:

On Mon, 10 Dec 2007 02:38:44 GMT, Brian Whatcott
wrote:


On Sun, 9 Dec 2007 19:16:34 -0700, "Bob La Londe"
wrote:

...

Uh-oh: you said "aluminum boat" and "MIG welder" really, really,
casually.


... I'm looking at a Hobart Ironman 250. I already got one of
those cheap ones.....
3rd - Use a clean stainless brush on all surfaces just before welding to
break up and remove the oxidation. Never use your brushes for aluminum on
ANYTHING else. Brushes are cheap insurance. USE THEM EVERYTIME even if you
brushed it yesterday.

4th - A spool gun is the way to go, but even with a push feed gun its
possible to push aluminum if you swap out the V groove feed wheel for a U
groove feed wheel....

5th - There is no 5th item

Bob La Londe

This seems like a plan to me: the story I hear quite often is that
the hot puddle will drop out given half a chance on thin stock.

A particular optical filter is said to be a big help in visualizing
the puddle's state.

THere have been at least a million aluminum airplanes produced. All
were riveted. Wonder why?


Lowest bidder?


not hardly.

Best fastner for the material.

I modified my Bolger Diablo along those lines - It had a 20" transom, and I
wanted to run a "short shaft" outboard. It worked ok 90% of the time, but
ventilated like h3!! when accelerating. So I cut a notch out of the
bottom - maybe 2 or 3" high into the transom, 16 " forward into the bottom
panel, and 8" wide. Sort of a mini-tunnel. I'm sure this causes a small
degradation in performance, but gains me a few inches of draft.

I'm sure you could take any skiff design, with a flat bottom, and play
around with this. I would start with a really deep tunnel, and high
transom. If that seems too much, just cut down the transom (and glue foam
into the top of the tunnel) until you get the desired performance. You
might be surprised.

But, if you are going to cut a big notch in the bottom, make sure there is
enough bottom left at the transom to provide lift. Maybe extend the panels
out beyond the transom, on either side of the tunnel - you can always cut
them off. If there is a good high-speed tunnel design for home-builders, I
haven't seen it. Atkin had a bunch of low-speed tunnels, you might take a
look at the Atkinboatplans.com website for ideas.

Sal's Dad

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".

There are some "tunnel" designs for running an outboard a few inches
higher that just have a small tunnel at the rear of the boat. When I was
really reading a lot about boat building a few years ago I recall reading
about some of them.