joining aluminum sheets techniques

[dirigible designer]

I'm making an eight-foot study model of a personal lifting body
dirigible design of mine. I believe the ribs will be made of
fiberglass and widely-spaced for lightness. I want the skin to be
aluminum sheet.
It would be desirable to avoid installing a rib for every seam
between sheets of aluminum. So, I would like some advice on what is
the state of the art with infallible glue joints between hard aluminum
sheets.
I imagine there is no alternative to crimping the meeting edges as
is done when sewing two sheets of cloth together.
No way am I interested in rivets.

[Rob Turk]

"dirigible designer" > wrote in message
oups.com...
> I'm making an eight-foot study model of a personal lifting body
> dirigible design of mine. I believe the ribs will be made of
> fiberglass and widely-spaced for lightness. I want the skin to be
> aluminum sheet.
> It would be desirable to avoid installing a rib for every seam
> between sheets of aluminum. So, I would like some advice on what is
> the state of the art with infallible glue joints between hard aluminum
> sheets.
> I imagine there is no alternative to crimping the meeting edges as
> is done when sewing two sheets of cloth together.
> No way am I interested in rivets.

How about using sheets that are half as thick as you need and then glue them
on top of eachother with full overlap? I've used some 3M aluminum glue that
is stronger than the metal itself..

Rob

[Morgans[_2_]]

"dirigible designer" > wrote in message
oups.com...
> I'm making an eight-foot study model of a personal lifting body
> dirigible design of mine. I believe the ribs will be made of
> fiberglass and widely-spaced for lightness. I want the skin to be
> aluminum sheet.
> It would be desirable to avoid installing a rib for every seam
> between sheets of aluminum. So, I would like some advice on what is
> the state of the art with infallible glue joints between hard aluminum
> sheets.
> I imagine there is no alternative to crimping the meeting edges as
> is done when sewing two sheets of cloth together.
> No way am I interested in rivets.

Wow, where to start.

First, I would think you need to do a reality check, here.

How big will your full sized lifting body be? Figure the surface area of the
full sized design, and then figure how much weight the aluminum to cover
that area would weigh.

Next, figure what the volume of the full sized model is, and how much
buoyancy the helium in that volume would provide.

I think you will find that the volume of helium in the full size model would
not come close to lifting even half of the weight of the aluminum sheeting.

Once you do this, and run the numbers, I think you will not even need to
mess with the study model. The numbers will not work.

There is a reason that balloons and dirigibles are not covered with
aluminum. The areas and volumes are huge, and the only way to make it work
is with ultra lightweight and strong "fabrics."

As for not even considering rivets, I doubt you have any idea of the costs
and technology of what it takes to join aluminum without rivets. You have
friction stir welding, or glues. Friction stir is high tec and expensive to
set up. Glues are temperamental, and takes many complex steps and chemicals
to prep and bond the surface, and is also expensive, if you can even reach
the reliability needed for such an application. I won't go into the idea of
having ribs so far apart that there is not even a rib for the length of an
aluminum panel. It will not have enough support to hold its shape under
flight conditions.

I don't want to rain on your parade, but it looks to me (from how you
described your concept) that the whole idea is unworkable. If you have
further explanations that could convince me (and others) differently, go
ahead.
--
Jim in NC

[Blueskies]

"Rob Turk" > wrote in message .. .
snip

I've used some 3M aluminum glue that
: is stronger than the metal itself..
:
: Rob
:
:

I would like to see what 3M product you are talking about...

Dan D.

[Dave[_5_]]

Reminds me of the time when I was working on a ship, and somebody
started a kitebuilding contest. One of the engineers built one like
the proverbial brick s##thouse - then put a long tail of rags on it
(which got wet in a puddle on the deck), No, it didn't fly, even in a
stiff breeze. He didn't have a clue - and soon got frustrated and
threw the kite over the side.

[Drew Dalgleish]

On 13 Mar 2007 14:47:13 -0700, "dirigible designer"
> wrote:

>I'm making an eight-foot study model of a personal lifting body
>dirigible design of mine. I believe the ribs will be made of
>fiberglass and widely-spaced for lightness. I want the skin to be
>aluminum sheet.
> It would be desirable to avoid installing a rib for every seam
>between sheets of aluminum. So, I would like some advice on what is
>the state of the art with infallible glue joints between hard aluminum
>sheets.
> I imagine there is no alternative to crimping the meeting edges as
>is done when sewing two sheets of cloth together.
> No way am I interested in rivets.
>
Marine sealants like sikaflex or 3M 5200. would probably work but you
would have to come up with some very fancy clamping fixtures to let
it cure. blind rivets would be way easier. But like Jim said it will
be too heavy to fly.

[dirigible designer]

Thanks for the suggestions to my question of how to join aluminum
sheets [without rivets] for making a dirigible.
The advice that an aluminum dirigible won't fly is not borne out by
reality. Do a websearch for Schwarz airship. It was aluminum and flew
in 1897. That's right, eighteen ninety seven. Then there was the Navy
ZMC airship which flew for ten years back in the forties.
One "advantage" of an aluminum skin is that the skin holds the lift
gas, saving the weight of internal separate bags. Also, aluminum,
being stiff, can add some monocoque strength to the frame.
I'm thinking of employing some corrugated alum. for added stiffness
and reduced drumming. It doesn't look nice but might work well.
Any ideas? [negatives not needed ;-]

[cavelamb himself]

dirigible designer wrote:
> Thanks for the suggestions to my question of how to join aluminum
> sheets [without rivets] for making a dirigible.
> The advice that an aluminum dirigible won't fly is not borne out by
> reality. Do a websearch for Schwarz airship. It was aluminum and flew
> in 1897. That's right, eighteen ninety seven. Then there was the Navy
> ZMC airship which flew for ten years back in the forties.
> One "advantage" of an aluminum skin is that the skin holds the lift
> gas, saving the weight of internal separate bags. Also, aluminum,
> being stiff, can add some monocoque strength to the frame.
> I'm thinking of employing some corrugated alum. for added stiffness
> and reduced drumming. It doesn't look nice but might work well.
> Any ideas? [negatives not needed ;-]
>
>
>
>
He didn't say it wouldn't work.

Just that at this scale it would ne too heavy to fly.

double - square - cube relationship...

Richard

[Jim Logajan]

"dirigible designer" > wrote:
> Thanks for the suggestions to my question of how to join aluminum
> sheets [without rivets] for making a dirigible.

Hi "dd" (Allen?). I am familiar with the history of aluminum airships.

One remote possibility it to look into/experiment with aluminum
soldering. Once upon a time I did not think it was possible to solder
aluminum, but if you do a Google search on the subject you should find
some information on the subject. It's not impossible, merely difficult.

As to glues, I would suggest going to McMaster-Carr's website
(http://www.mcmaster.com/) and browse some of the categories under
"Fastening and Sealing". Perhaps a mix of some blind or solid rivets (to
provide structural strength) combined with a construction adhesive (to
provide a seal and some shear strength) might work?

Anyway, I'd suggest you try buying some likely candidates and try some
small-scale experiments.

Also, I believe there is a patent for the rivet machine that was invented
in order to build the ZMC airships, but I don't have the patent number
handy. But check patent 1,706,830. It is the main patent related to the
ZMC airship design. It should also hopefully provide a starting point for
finding the other patents related to the work done on the ZMC airships.

> I'm thinking of employing some corrugated alum. for added stiffness
> and reduced drumming. It doesn't look nice but might work well.

Well, the ZMC-2 used something like 0.006 inch thick aluminum. You can
now get hard-temper aluminum foil from MacMaster-Carr that is 0.002 inch
thick. But wider rolls (less joining needed for the same surface area)
are available down to 0.003 inch thick. Soft-temper of course can be had
down to 0.0007 inch thick. About the temper of house-hold aluminum foil,
though.

Corrugated is going to drive your raw material cost up (unless you build
equipment to corrugate the raw sheets or foil yourself). And I would
expect it would impose a large drag penalty, too.

Lastly, it is really hard to build working reduced-scale prototype
airship designs. They don't scale down well.

Good luck!

[Gig 601XL Builder]

Jim Logajan wrote:
> "dirigible designer" > wrote:
>> Thanks for the suggestions to my question of how to join aluminum
>> sheets [without rivets] for making a dirigible.
>
> Hi "dd" (Allen?). I am familiar with the history of aluminum airships.
>
> One remote possibility it to look into/experiment with aluminum
> soldering. Once upon a time I did not think it was possible to solder
> aluminum, but if you do a Google search on the subject you should find
> some information on the subject. It's not impossible, merely
> difficult.
>

What about welding it?

[Jim Logajan]

"Gig 601XL Builder" <wrDOTgiaconaATsuddenlink.net> wrote:
> Jim Logajan wrote:
>> "dirigible designer" > wrote:
>>> Thanks for the suggestions to my question of how to join aluminum
>>> sheets [without rivets] for making a dirigible.
>>
>> Hi "dd" (Allen?). I am familiar with the history of aluminum airships.
>>
>> One remote possibility it to look into/experiment with aluminum
>> soldering. Once upon a time I did not think it was possible to solder
>> aluminum, but if you do a Google search on the subject you should find
>> some information on the subject. It's not impossible, merely
>> difficult.
>>
>
> What about welding it?

Might work with joining sheets to ribs, but sheets-to-sheets? Don't know
either way, actually. :-)

I never got around to experimenting with it, but I had considered trying to
use a flux of some kind (something to deal with the formation or thickening
of the oxide layer) applied between two overlapping sheets and then
applying heat using a high-temperature heat gun. Some of the heavy-duty
heat guns claim air temperatures near the melting point of some alloys of
aluminum.

[Ernest Christley]

Jim Logajan wrote:
> "Gig 601XL Builder" <wrDOTgiaconaATsuddenlink.net> wrote:
>> Jim Logajan wrote:
>>> "dirigible designer" > wrote:
>>>> Thanks for the suggestions to my question of how to join aluminum
>>>> sheets [without rivets] for making a dirigible.
>>> Hi "dd" (Allen?). I am familiar with the history of aluminum airships.
>>>
>>> One remote possibility it to look into/experiment with aluminum
>>> soldering. Once upon a time I did not think it was possible to solder
>>> aluminum, but if you do a Google search on the subject you should find
>>> some information on the subject. It's not impossible, merely
>>> difficult.
>>>
>> What about welding it?
>
> Might work with joining sheets to ribs, but sheets-to-sheets? Don't know
> either way, actually. :-)
>
> I never got around to experimenting with it, but I had considered trying to
> use a flux of some kind (something to deal with the formation or thickening
> of the oxide layer) applied between two overlapping sheets and then
> applying heat using a high-temperature heat gun. Some of the heavy-duty
> heat guns claim air temperatures near the melting point of some alloys of
> aluminum.

I just tried my hand at welding aluminum this past weekend. I'm putting
a fuel tank together. Unless you have some major jigs, the sheets will
warp all to hell before you get halfway down a joint.

[Andy Asberry[_2_]]

On 13 Mar 2007 14:47:13 -0700, "dirigible designer"
> wrote:

>I'm making an eight-foot study model of a personal lifting body
>dirigible design of mine. I believe the ribs will be made of
>fiberglass and widely-spaced for lightness. I want the skin to be
>aluminum sheet.
> It would be desirable to avoid installing a rib for every seam
>between sheets of aluminum. So, I would like some advice on what is
>the state of the art with infallible glue joints between hard aluminum
>sheets.
> I imagine there is no alternative to crimping the meeting edges as
>is done when sewing two sheets of cloth together.
> No way am I interested in rivets.

Several horse trailer manufacturers attach the outer skin with
adhesive and double sided tape.

--Andy Asberry--
------Texas-----

[Stuart & Kathryn Fields]

I welded 4 aluminum gas tanks ( I busted the first two in an incident) and
one oil tank for my Baby Belle. I don't remember having much warpage, but I
also recall someone telling me to tack the things in a lot of places before
finishing the seam welds. The things pressure tested to 14' of water the
first time with no pin holes. Now if that doesn't prove luck is better than
skill I'll eat a welding rod. I also welded some aluminum beer cans
together, but they wouldn't hold mashed potatoes after I finished with them
let alone a liquid.
--
Stuart Fields
Experimental Helo magazine
P. O. Box 1585
Inyokern, CA 93527
(760) 377-4478
(760) 408-9747 general and layout cell
(760) 608-1299 technical and advertising cell

www.vkss.com
www.experimentalhelo.com


"Ernest Christley" > wrote in message
...
> Jim Logajan wrote:
> > "Gig 601XL Builder" <wrDOTgiaconaATsuddenlink.net> wrote:
> >> Jim Logajan wrote:
> >>> "dirigible designer" > wrote:
> >>>> Thanks for the suggestions to my question of how to join aluminum
> >>>> sheets [without rivets] for making a dirigible.
> >>> Hi "dd" (Allen?). I am familiar with the history of aluminum airships.
> >>>
> >>> One remote possibility it to look into/experiment with aluminum
> >>> soldering. Once upon a time I did not think it was possible to solder
> >>> aluminum, but if you do a Google search on the subject you should find
> >>> some information on the subject. It's not impossible, merely
> >>> difficult.
> >>>
> >> What about welding it?
> >
> > Might work with joining sheets to ribs, but sheets-to-sheets? Don't know
> > either way, actually. :-)
> >
> > I never got around to experimenting with it, but I had considered trying
to
> > use a flux of some kind (something to deal with the formation or
thickening
> > of the oxide layer) applied between two overlapping sheets and then
> > applying heat using a high-temperature heat gun. Some of the heavy-duty
> > heat guns claim air temperatures near the melting point of some alloys
of
> > aluminum.
>
> I just tried my hand at welding aluminum this past weekend. I'm putting
> a fuel tank together. Unless you have some major jigs, the sheets will
> warp all to hell before you get halfway down a joint.

[Rob Turk]

"Blueskies" > wrote in message
t...
>
> "Rob Turk" > wrote in message
> .. .
> snip
>
> I've used some 3M aluminum glue that
> : is stronger than the metal itself..
> :
> : Rob
>
> I would like to see what 3M product you are talking about...
>
> Dan D.

Hi Dan,
This is 3M DP 490 Scotch Weld. We used it to bond our aluminum leading edge
to the spar on area's where we were not allowed to use pop rivets.
Rob

[dirigible designer]

Thanks for all the ideas for joining aluminum sheets. I was amazed at
all the different versions of 3M epoxy there are. Should be one to
suit my needs. http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs66Sum5COrrrr Q-
I'll be back in touch after I gather some materials and put a few
pieces together. high flight, Allen

[Blueskies]

"Rob Turk" > wrote in message .. .
:
: Hi Dan,
: This is 3M DP 490 Scotch Weld. We used it to bond our aluminum leading edge
: to the spar on area's where we were not allowed to use pop rivets.
: Rob
:

Thanks!

[Blueskies]

"dirigible designer" > wrote in message
oups.com...
: I'm making an eight-foot study model of a personal lifting body
: dirigible design of mine. I believe the ribs will be made of
: fiberglass and widely-spaced for lightness. I want the skin to be
: aluminum sheet.
: It would be desirable to avoid installing a rib for every seam
: between sheets of aluminum. So, I would like some advice on what is
: the state of the art with infallible glue joints between hard aluminum
: sheets.
: I imagine there is no alternative to crimping the meeting edges as
: is done when sewing two sheets of cloth together.
: No way am I interested in rivets.
:



Stir weld it...

[Tom Frey]

"Stuart & Kathryn Fields" > wrote in message
.. .
>I welded 4 aluminum gas tanks ( I busted the first two in an incident) and
> one oil tank for my Baby Belle. I don't remember having much warpage, but
> I
> also recall someone telling me to tack the things in a lot of places
> before
> finishing the seam welds. The things pressure tested to 14' of water the
> first time with no pin holes. Now if that doesn't prove luck is better
> than
> skill I'll eat a welding rod. I also welded some aluminum beer cans
> together, but they wouldn't hold mashed potatoes after I finished with
> them
> let alone a liquid.
> --

I have welded a lot of aluminum, including successful welding of beer cans.
And I second all of Stewart’s advice. When welding .030 and up, you will
want to tack weld even as close as every two to three inches before
beginning your finishing welds. Skip welding helps as well, meaning weld
between two tacks, skip between two tacks, and weld between the next. It
will all help to avoid distortion. Also, clean, clean, clean. Scrape or buff
everything with stainless steel rotary brushes, cleaned thoroughly in
acetone or eqv. If you pick up any oil or grease anywhere, clean your
scrapers and brushes and start all over. It even helps to handle everything
with clean cotton gloves. You can leave enough oil from your bare hands to
affect the quality of your welds, unless you keep your hands washed in
acetone, which I certainly don't recommend.



As for thinner than .030 or so, good luck without good fixtures. I have seen
some soldering techniques advertised the might be very workable, but have
never tried any of them.



As for glue, I haven't tried many, but have had pretty good luck with 3M -
2216BA. I don't know how it compares to the others mentioned above, but it
has worked well for me. On a seam of .010 with a half inch overlap, I
personally think it might be workable, but haven't done it my self. And if
you plan to glue, don't for a minute underestimate the value of cleaning,
preparation and a good primer. When done correctly under aircraft
conditions, actually mixing the epoxy and gluing your seam is only about 10%
of the battle. Proper cleaning, priming and curing of the primer is actually
more critical.



Free advice, your results could easily vary.


Max

[J.Kahn]

dirigible designer wrote:
> Thanks for all the ideas for joining aluminum sheets. I was amazed at
> all the different versions of 3M epoxy there are. Should be one to
> suit my needs. http://multimedia.mmm.com/mws/mediawebserver.dyn?6666660Zjcf6lVs6EVs66Sum5COrrrr Q-
> I'll be back in touch after I gather some materials and put a few
> pieces together. high flight, Allen
>
Bonded lap seams should be fine since the loads are certainly going to
be extremely low. You should make some sample lap joints with different
adhesives and pull test them. Grumman light singles are all bonded
aluminum joints, including skin laps, and have been going strong for 40
years since the first Yankees were produced.

Your biggest problem will be having even clamping pressure on the joints
during gluing.

Bonded metal joints are not super strong in tension; the strength is all
in the shear plane. That means the parts will peel apart fairly easily
and there should be a mechanical fastener at any corner of a skin.
There was an AD to do this on the Grummans.

John

[dirigible designer]

http://www.staplaultrasonics.com/products/seam-welder.htm

That url is for a company that makes ULTRASONIC WELDERS which work on
aluminum. I was reading in Wikipedia where the aluminum foil rolling
mills use ultrasonics to splice the rolled sheet back together when it
breaks in process.
The beauty of this method is that it generates very little heat and
so the al workpiece doesn't warp, which is a huge improvement over
thermal welding. Ultrasonics appear to be a lot simpler, with more
reliable seams, than the exotic Friction Stir Welding.
I haven't yet researched how adaptable this method, and its
machinery, is for homebuilders. It's just an exciting method to know
about. high cheers, Allen