I find it interesting that a lot of the small boat aluminum designs seem to
say the main hull should be 3/16 and yet .100 is used in a heck of a lot of
commercially available small boats. .125 is considered heavy duty. Is it
just CYA?

No. Aluminum is very reactive. Corrosion will occur for a multitude of reasons. It is almost unavoidable and when it does, it is
FAST, but ultimately the scantlings of any boat is a product of size and hull design. Your comment of .125" as heavy duty, that
true if the boat doesn't exceed 18'.
Steve

"Bob La Londe" wrote in message ...
I find it interesting that a lot of the small boat aluminum designs seem to say the main hull should be 3/16 and yet .100 is used
in a heck of a lot of commercially available small boats. .125 is considered heavy duty. Is it just CYA?

"Steve Lusardi" wrote in message
...
No. Aluminum is very reactive. Corrosion will occur for a multitude of
reasons. It is almost unavoidable and when it does, it is FAST, but
ultimately the scantlings of any boat is a product of size and hull
design. Your comment of .125" as heavy duty, that true if the boat doesn't
exceed 18'.
Steve

"Bob La Londe" wrote in message
...
I find it interesting that a lot of the small boat aluminum designs seem
to say the main hull should be 3/16 and yet .100 is used in a heck of a
lot of commercially available small boats. .125 is considered heavy duty.
Is it just CYA?

I've been looking at some of the smallest boats, and there are some with
hulls as thin as .043. Holy cow. No wonder they are riveted. When I was
first practicing aluminum welding I discovered that was below the threshold
for my skills and/or machine. I could make two piece of .043 tube stick
together, but it wasn't pretty.

http://www.trackerboats.com/boat/specs.cfm?boat=3257

Holy cow. Its like tissue paper.

On Mon, 30 Nov 2009 18:42:10 -0700, "Bob La Londe"
wrote:

"Steve Lusardi" wrote in message
...
No. Aluminum is very reactive. Corrosion will occur for a multitude of
reasons. It is almost unavoidable and when it does, it is FAST, but
ultimately the scantlings of any boat is a product of size and hull
design. Your comment of .125" as heavy duty, that true if the boat doesn't
exceed 18'.
Steve

"Bob La Londe" wrote in message
...
I find it interesting that a lot of the small boat aluminum designs seem
to say the main hull should be 3/16 and yet .100 is used in a heck of a
lot of commercially available small boats. .125 is considered heavy duty.
Is it just CYA?

I've been looking at some of the smallest boats, and there are some with
hulls as thin as .043. Holy cow. No wonder they are riveted. When I was
first practicing aluminum welding I discovered that was below the threshold
for my skills and/or machine. I could make two piece of .043 tube stick
together, but it wasn't pretty.

http://www.trackerboats.com/boat/specs.cfm?boat=3257

Holy cow. Its like tissue paper.

I suspect that it is mainly a matter of cost, or how their particular
shop is set up to work. Certainly there isn't much of a trick to
welding 1 mm stuff and that is thinner then .043" stuff so I doubt
that it is the wielding itself that is a problem. My guess is that it
is warping that makes them rivet it as welding seams in flat aluminum
can result in some very exotic shapes if considerable effort isn't
taken to prevent it.
Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

"Bruce In Bangkok" wrote in message
...
On Mon, 30 Nov 2009 18:42:10 -0700, "Bob La Londe"
wrote:

"Steve Lusardi" wrote in message
...
No. Aluminum is very reactive. Corrosion will occur for a multitude of
reasons. It is almost unavoidable and when it does, it is FAST, but
ultimately the scantlings of any boat is a product of size and hull
design. Your comment of .125" as heavy duty, that true if the boat
doesn't
exceed 18'.
Steve

"Bob La Londe" wrote in message
...
I find it interesting that a lot of the small boat aluminum designs seem
to say the main hull should be 3/16 and yet .100 is used in a heck of a
lot of commercially available small boats. .125 is considered heavy
duty.
Is it just CYA?

I've been looking at some of the smallest boats, and there are some with
hulls as thin as .043. Holy cow. No wonder they are riveted. When I was
first practicing aluminum welding I discovered that was below the
threshold
for my skills and/or machine. I could make two piece of .043 tube stick
together, but it wasn't pretty.

http://www.trackerboats.com/boat/specs.cfm?boat=3257

Holy cow. Its like tissue paper.

I suspect that it is mainly a matter of cost, or how their particular
shop is set up to work. Certainly there isn't much of a trick to
welding 1 mm stuff and that is thinner then .043" stuff so I doubt
that it is the wielding itself that is a problem. My guess is that it
is warping that makes them rivet it as welding seams in flat aluminum
can result in some very exotic shapes if considerable effort isn't
taken to prevent it.
Cheers,

Well, of course its "possible" to weld. I imagine if I went to a smaller
(maybe .23) diameter wire and got feed rollers for my spool gun to handle it
I might even be able to do it with my big MIG rig. Might have to go to a
helium mix instead of straight argon so I could reduce material removal
during cleaning, and then of course I would have to lock stitch and then
back fill. It's a big pain though, and that's why:

"No wonder they are riveted."

Its just not worth the effort of welding for a low price "throw away" boat.

A small TIG torch could handle it easily enough, but it would be
slooooooooowww.

P.S. You do the lock stitch and back fill method on thicker material too.

On Tue, 1 Dec 2009 15:27:32 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
.. .
On Mon, 30 Nov 2009 18:42:10 -0700, "Bob La Londe"
wrote:

"Steve Lusardi" wrote in message
...
No. Aluminum is very reactive. Corrosion will occur for a multitude of
reasons. It is almost unavoidable and when it does, it is FAST, but
ultimately the scantlings of any boat is a product of size and hull
design. Your comment of .125" as heavy duty, that true if the boat
doesn't
exceed 18'.
Steve

"Bob La Londe" wrote in message
...
I find it interesting that a lot of the small boat aluminum designs seem
to say the main hull should be 3/16 and yet .100 is used in a heck of a
lot of commercially available small boats. .125 is considered heavy
duty.
Is it just CYA?

I've been looking at some of the smallest boats, and there are some with
hulls as thin as .043. Holy cow. No wonder they are riveted. When I was
first practicing aluminum welding I discovered that was below the
threshold
for my skills and/or machine. I could make two piece of .043 tube stick
together, but it wasn't pretty.

http://www.trackerboats.com/boat/specs.cfm?boat=3257

Holy cow. Its like tissue paper.

I suspect that it is mainly a matter of cost, or how their particular
shop is set up to work. Certainly there isn't much of a trick to
welding 1 mm stuff and that is thinner then .043" stuff so I doubt
that it is the wielding itself that is a problem. My guess is that it
is warping that makes them rivet it as welding seams in flat aluminum
can result in some very exotic shapes if considerable effort isn't
taken to prevent it.
Cheers,

Well, of course its "possible" to weld. I imagine if I went to a smaller
(maybe .23) diameter wire and got feed rollers for my spool gun to handle it
I might even be able to do it with my big MIG rig. Might have to go to a
helium mix instead of straight argon so I could reduce material removal
during cleaning, and then of course I would have to lock stitch and then
back fill. It's a big pain though, and that's why:

"No wonder they are riveted."

Its just not worth the effort of welding for a low price "throw away" boat.

A small TIG torch could handle it easily enough, but it would be
slooooooooowww.

P.S. You do the lock stitch and back fill method on thicker material too.

I know...

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Nov 29, 6:28*pm, "Bob La Londe" wrote:
I find it interesting that a lot of the small boat aluminum designs seem to
say the main hull should be 3/16 and yet .100 is used in a heck of a lot of
commercially available small boats. *.125 is considered heavy duty. *Is it
just CYA?

Anyway, getting back to my original point. A lot of commercially
available boats seem to be made out of a lot light sheet than the
designers are reccomending in the boat plans they are selling.

http://www.seaarkboats.com/boat.php?...&boat=Big+Easy

For example: The link above is to a medium V design 24 footer. The
specs says .125 thick sheet. I can't buy a plan to build a boat that
size designed for .125 sheet. Most of the ones I have seen want to
spec .1875 which basically means .190. Now why is that? Is it just
the typical over building to cover your dearie aere, or are all those
commercial boat builders building inadequate boats and damn the
liability?

On Wed, 9 Dec 2009 13:08:20 -0800 (PST), Bob La Londe
wrote:

On Nov 29, 6:28*pm, "Bob La Londe" wrote:
I find it interesting that a lot of the small boat aluminum designs seem to
say the main hull should be 3/16 and yet .100 is used in a heck of a lot of
commercially available small boats. *.125 is considered heavy duty. *Is it
just CYA?

Anyway, getting back to my original point. A lot of commercially
available boats seem to be made out of a lot light sheet than the
designers are reccomending in the boat plans they are selling.

http://www.seaarkboats.com/boat.php?...&boat=Big+Easy

For example: The link above is to a medium V design 24 footer. The
specs says .125 thick sheet. I can't buy a plan to build a boat that
size designed for .125 sheet. Most of the ones I have seen want to
spec .1875 which basically means .190. Now why is that? Is it just
the typical over building to cover your dearie aere, or are all those
commercial boat builders building inadequate boats and damn the
liability?

I wonder whether you are comparing designs that could be in one case
simply a covering attached to a structural frame where the skin only
keeps the water out while the structure provides the strength versus a
design where the skin provides some of the total structure strength?

Think of the original kayak design versus a stitch and glue dinghy
with no internal frames for exaggerations of this concept.

I remember reading that some of the British Steel 70-footers found
dented plating around the bow after leaving the Southern Ocean. the
answer was to add frames to the bow section for the next year's race,
not increase the thickness of the plating. In other words the
thickness of the plating was not considered a factor in the strength
of the bow portions. The frames provided the strength while the
plating kept the water out.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

"Bruce In Bangkok" wrote in message
...
On Wed, 9 Dec 2009 13:08:20 -0800 (PST), Bob La Londe
wrote:

On Nov 29, 6:28 pm, "Bob La Londe" wrote:
I find it interesting that a lot of the small boat aluminum designs seem
to
say the main hull should be 3/16 and yet .100 is used in a heck of a lot
of
commercially available small boats. .125 is considered heavy duty. Is it
just CYA?

Anyway, getting back to my original point. A lot of commercially
available boats seem to be made out of a lot light sheet than the
designers are reccomending in the boat plans they are selling.

http://www.seaarkboats.com/boat.php?...&boat=Big+Easy

For example: The link above is to a medium V design 24 footer. The
specs says .125 thick sheet. I can't buy a plan to build a boat that
size designed for .125 sheet. Most of the ones I have seen want to
spec .1875 which basically means .190. Now why is that? Is it just
the typical over building to cover your dearie aere, or are all those
commercial boat builders building inadequate boats and damn the
liability?

I wonder whether you are comparing designs that could be in one case
simply a covering attached to a structural frame where the skin only
keeps the water out while the structure provides the strength versus a
design where the skin provides some of the total structure strength?

Think of the original kayak design versus a stitch and glue dinghy
with no internal frames for exaggerations of this concept.

I remember reading that some of the British Steel 70-footers found
dented plating around the bow after leaving the Southern Ocean. the
answer was to add frames to the bow section for the next year's race,
not increase the thickness of the plating. In other words the
thickness of the plating was not considered a factor in the strength
of the bow portions. The frames provided the strength while the
plating kept the water out.

Well, it seems except for S&G conversions most of the aluminum plans I have
seen call for building a frame. Atleast in the 20 foot size range. Here is
an example from the Glen-L design catalog. 230 Max HP. The Sea Ark in my
previous post is rated at 225 so similar in stresses.

http://glen-l.com/designs/hankinson/...snakeshtr.html
SNAKE SHOOTER VEE between 17-1/2' and nearly 23'

Plating
1/8" 250 sq. ft.
3/16" 200 sq. ft.
1/4" 40 sq. ft.
3/8" 10 sq. ft.

Based on a once over that looks like 3/16 plating for the hull bottom and
1/8 for the sides to me. I have not looked at just one or two designs.

On Wed, 9 Dec 2009 18:16:52 -0700, "Bob La Londe"
wrote:

"Bruce In Bangkok" wrote in message
.. .
On Wed, 9 Dec 2009 13:08:20 -0800 (PST), Bob La Londe
wrote:

On Nov 29, 6:28 pm, "Bob La Londe" wrote:
I find it interesting that a lot of the small boat aluminum designs seem
to
say the main hull should be 3/16 and yet .100 is used in a heck of a lot
of
commercially available small boats. .125 is considered heavy duty. Is it
just CYA?

Anyway, getting back to my original point. A lot of commercially
available boats seem to be made out of a lot light sheet than the
designers are reccomending in the boat plans they are selling.

http://www.seaarkboats.com/boat.php?...&boat=Big+Easy

For example: The link above is to a medium V design 24 footer. The
specs says .125 thick sheet. I can't buy a plan to build a boat that
size designed for .125 sheet. Most of the ones I have seen want to
spec .1875 which basically means .190. Now why is that? Is it just
the typical over building to cover your dearie aere, or are all those
commercial boat builders building inadequate boats and damn the
liability?

I wonder whether you are comparing designs that could be in one case
simply a covering attached to a structural frame where the skin only
keeps the water out while the structure provides the strength versus a
design where the skin provides some of the total structure strength?

Think of the original kayak design versus a stitch and glue dinghy
with no internal frames for exaggerations of this concept.

I remember reading that some of the British Steel 70-footers found
dented plating around the bow after leaving the Southern Ocean. the
answer was to add frames to the bow section for the next year's race,
not increase the thickness of the plating. In other words the
thickness of the plating was not considered a factor in the strength
of the bow portions. The frames provided the strength while the
plating kept the water out.

Well, it seems except for S&G conversions most of the aluminum plans I have
seen call for building a frame. Atleast in the 20 foot size range. Here is
an example from the Glen-L design catalog. 230 Max HP. The Sea Ark in my
previous post is rated at 225 so similar in stresses.

http://glen-l.com/designs/hankinson/...snakeshtr.html
SNAKE SHOOTER VEE between 17-1/2' and nearly 23'

Plating
1/8" 250 sq. ft.
3/16" 200 sq. ft.
1/4" 40 sq. ft.
3/8" 10 sq. ft.

Based on a once over that looks like 3/16 plating for the hull bottom and
1/8 for the sides to me. I have not looked at just one or two designs.

I don't think you can tell from the materials list. The plywood boat
for example uses 1/4" for the bottom planking and 3/8" for side
planking. Looking at the aluminum list it appears that 1/8" is for
bottom and 3/16" for side, which assumes that the two versions are at
least similar in design.

Given that Glenn-L makes a meal of saying that anyone that can weld
can build one of these boats I would suggest that thickness of plating
may well be selected from sizes that the designer expects that
"everyone" can have some hope of welding successfully.

Again assuming that the basic design is at least similar the aluminum
thickness doesn't seem to relate to the plywood sizes given that
aluminum has an ultimate tensile strength of somewhere around 90 MPa
while plywood is in the region of 30. If it were simply strength
bottom aluminum plating would be in the region of 0.083, based on
plywood strength.

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)