Jiggery-Tackery

I'm practicing making joints.

I built a simple jig to hold two pieces of tubing parallel and about
6" apart and have notched and placed a third piece of tubing,
connecting the two parallel pieces at 60*

To minimize warpage from the heat (I'm using gas) I know I should tack
one side of the joint, then the other, then repeat at 90*

So how do I get to the other side of the joint (for the second tack)
if it's lying flat against the board? Certainly the folks building a
fuselage don't take it out of the jig after doing only one of the four
tacks per joint - Mike

On Jun 7, 9:32*am, Michael Horowitz wrote:

So how do I get to the other side of the joint (for the second tack)
if it's lying flat against the board? Certainly the folks building a
fuselage don't take it out of the jig after doing only one of the four
tacks per joint - Mike
..--------------------------------------------------------------------------------------

Dear Mike,

I believe the most common method is to cut a 6" dia circle in the jig-
board. Of course, that could leave the intersecting piece supported
by air. So you modify the hole -- use something other than a true
circle, such as a D-shape. Or you might cut away the wood and replace
it with metal (on the back-side of the board), to which you've tack-
welded scraps that will hold the intersecting piece in position. Of
course, if you are building just one copy ALL of the traditional
methods can be tossed out the window... so long as what's wheeled out
the door is an accurate copy of the original fuselage.

Michael Horowitz wrote:
I'm practicing making joints.

I built a simple jig to hold two pieces of tubing parallel and about
6" apart and have notched and placed a third piece of tubing,
connecting the two parallel pieces at 60*

To minimize warpage from the heat (I'm using gas) I know I should tack
one side of the joint, then the other, then repeat at 90*

So how do I get to the other side of the joint (for the second tack)
if it's lying flat against the board? Certainly the folks building a
fuselage don't take it out of the jig after doing only one of the four
tacks per joint - Mike




The way I did mine was to tack front and back sides while in the jig.
Tack left and right after it's out.

On Jun 7, 1:49*pm, cavelamb wrote:
Michael Horowitz wrote:
I'm practicing making joints.

I built a simple jig to hold *two pieces of tubing parallel and about
6" apart and have notched and placed a third piece of tubing,
connecting the two parallel pieces at 60*

To minimize warpage from the heat (I'm using gas) I know I should tack
one side of the joint, then the other, then repeat at 90*

So how do I get to the other side of the joint (for the second tack)
if it's lying flat against the board? Certainly the folks building a
fuselage don't take it out of the jig after doing only one of the four
tacks per joint - Mike

The way I did mine was to tack front and back sides while in the jig.
Tack left and right after it's out.

Heating metal to cherry red tends to shrink it. I will measure parts
as each tack is cooled to see where it needs to be shrunk to walk it
back into alignment and add the next tack there. I continue this
process as the welds are completed. With experience, a welder can
produce tubular parts within a few thousandths of spec.

Gas welding tends to heat a larger area than say TIG so parts can
suffer greater warpage. However, I've carefully reheated TIG welded
tubular structures with a gas flame to remove warps.

I love gas welding but if I were to do another welded fuselage, I'd
bite the bullet and buy a TIG welder. It's much faster and cleaner.

On Jun 7, 1:34*pm, bildan wrote:

I love gas welding but if I were to do another welded fuselage, I'd
bite the bullet and buy a TIG welder. *It's much faster and cleaner.
---------------------------------------------------------------------

Not a good idea, in my opinion. Usta be, buy a TIG,er you'd get a CD
with about 800megabytes of arguments as to WHY you did so, which you
would have to read & memorize before you could return to the
internet. Today, you buy a TIG.er you get the CD plus a DVD showing
pitchers of the 'critical heating zone'... which is also the critical
cooling zone, depending on who you're arguing with.

Bottom Line: Use o/a, you'll have the fuselage on its gear by the
time the TIG'er people are still arguing about who shot John, why the
sky is blew and other matters of Dire importance.

Or... you could do your tacking with MIG! MIG doesn't set anything on
fire so's you don't need to cut holes. And you can make a one-sided
tack that's strong enough so you can drag the thing all over the shop
without having anything bust loose. Kinda whippy of course, what with
all the shrinkage on just the one side, but that'll go away when you
use your MIG'er to tack the OTHER side... before you put the thing in
the rotisserie, find your scooter an' get the right tip on your o/a
rig to do all the FINISH welding. (Or Finnish if that's where you come
from.)

Now, ain't you glad you got all us instant Internet experts to give
you all this good advice?

-R.S.Hoover

On Sun, 7 Jun 2009 15:10:00 -0700 (PDT), Veeduber
wrote:

On Jun 7, 1:34*pm, bildan wrote:

I love gas welding but if I were to do another welded fuselage, I'd
bite the bullet and buy a TIG welder. *It's much faster and cleaner.
---------------------------------------------------------------------

Not a good idea, in my opinion. Usta be, buy a TIG,er you'd get a CD
with about 800megabytes of arguments as to WHY you did so, which you
would have to read & memorize before you could return to the
internet. Today, you buy a TIG.er you get the CD plus a DVD showing
pitchers of the 'critical heating zone'... which is also the critical
cooling zone, depending on who you're arguing with.

Bottom Line: Use o/a, you'll have the fuselage on its gear by the
time the TIG'er people are still arguing about who shot John, why the
sky is blew and other matters of Dire importance.

Or... you could do your tacking with MIG! MIG doesn't set anything on
fire so's you don't need to cut holes. And you can make a one-sided
tack that's strong enough so you can drag the thing all over the shop
without having anything bust loose. Kinda whippy of course, what with
all the shrinkage on just the one side, but that'll go away when you
use your MIG'er to tack the OTHER side... before you put the thing in
the rotisserie, find your scooter an' get the right tip on your o/a
rig to do all the FINISH welding. (Or Finnish if that's where you come
from.)

Now, ain't you glad you got all us instant Internet experts to give
you all this good advice?

-R.S.Hoover

I'd stick with TIG. or oxyacetylene. or whatever welding technique the
welder is personally best with.

if you can sample test your welded joints to destruction and find that
they are stronger than the parent tube then stick with what you do
best.

it isnt the method that is important; it is the structural strength of
the completed welded joints.

ps dont forget the hole that will allow all the tube seal to work
through and corrosion protect the final job from the inside.

when I couldnt get a hold of any more competent welding service on a
remote airfield I was forced to repair my tailwheel assembly by arc
welding with 2mm rods.
I used a lot of heat treating appreciation to lay the order of the
welds and it has given flawless service for more than 4 years now.

it is the weld strength that is important not the method.

btw my brother in law tells me that welding the joints in a spiral
path around and along the fuselage nose to tail will result in the
least distortion. ...as will a rubber mallett :-)
Stealth Pilot

On Jun 7, 4:10*pm, Veeduber wrote:
On Jun 7, 1:34*pm, bildan wrote:

I love gas welding but if I were to do another welded fuselage, I'd
bite the bullet and buy a TIG welder. *It's much faster and cleaner.
---------------------------------------------------------------------

Not a good idea, in my opinion. *Usta be, buy a TIG,er you'd get a CD
with about 800megabytes of arguments as to WHY you did so, which you
would have to read & memorize before you could return to the
internet. *Today, you buy a TIG.er you get the CD plus a DVD showing
pitchers of the 'critical heating zone'... which is also the critical
cooling zone, depending on who you're arguing with.

Bottom Line: *Use o/a, you'll have the fuselage on its gear by the
time the TIG'er people are still arguing about who shot John, why the
sky is blew and other matters of Dire importance.

Or... you could do your tacking with MIG! *MIG doesn't set anything on
fire so's you don't need to cut holes. *And you can make a one-sided
tack that's strong enough so you can drag the thing all over the shop
without having anything bust loose. *Kinda whippy of course, what with
all the shrinkage on just the one side, but that'll go away when you
use your MIG'er to tack the OTHER side... before you put the thing in
the rotisserie, find your scooter an' get the right tip on your o/a
rig to do all the FINISH welding. (Or Finnish if that's where you come
from.)

Now, ain't you glad you got all us instant Internet experts to give
you all this good advice?

-R.S.Hoover

Dunno about that. I took a TIG. I found OA skills generally applied
to TIG so it wasn't hard to learn. The big thing is that TIG is just
a lot faster and produces cleaner welds. I think I can do a 10" bead
with TIG in the time it takes me to do 1" with OA. I get a lot less
warping with TIG.

The showstopper is TIG rigs cost too much.

bildan wrote:

Dunno about that. I took a TIG. I found OA skills generally applied
to TIG so it wasn't hard to learn. The big thing is that TIG is just
a lot faster and produces cleaner welds. I think I can do a 10" bead
with TIG in the time it takes me to do 1" with OA. I get a lot less
warping with TIG.

The showstopper is TIG rigs cost too much.


The old argument _against_ TIG (and I've no experience to back it up)
is that it does not heat up the base metal much beyond the the bead
thereby locking in a lot of stress that an OA weld would show as warp.

Some people suggested (sometimes strongly) that TIG welds on thin wall
4130 should be reheated with OA to relieve those localized stresses.

On Jun 8, 10:33*am, cavelamb wrote:
bildan wrote:

Dunno about that. *I took a TIG. *I found OA skills generally applied
to TIG so it wasn't hard to learn. *The big thing is that TIG is just
a lot faster and produces cleaner welds. *I think I can do a 10" bead
with TIG in the time it takes me to do 1" with OA. *I get a lot less
warping with TIG.

The showstopper is TIG rigs cost too much.

The old argument _against_ TIG (and I've no experience to back it up)
is that it does not heat up the base metal much beyond the the bead
thereby locking in a lot of stress that an OA weld would show as warp.

Some people suggested (sometimes strongly) that TIG welds on thin wall
4130 should be reheated with OA to relieve those localized stresses.

There's probably a smidgen of truth in that - I heard it from an old
timer OA welder 45 years ago. Then again, he might just have been
grumbling about 1960's "new technology".

Since then there's a lot of field experience with highly stressed TIG
welded 4130 and if there's any loss in weld strength, it doesn't seem
to be a problem people worry about. However, if it was a real "bet my
ass" part, I might have it heat treated and magnafluxed.

"bildan" wrote

There's probably a smidgen of truth in that - I heard it from an old
timer OA welder 45 years ago. Then again, he might just have been
grumbling about 1960's "new technology".

Since then there's a lot of field experience with highly stressed TIG
welded 4130 and if there's any loss in weld strength, it doesn't seem
to be a problem people worry about. However, if it was a real "bet my
ass" part, I might have it heat treated and magnafluxed.

I thought that I remember that a small aircraft (Bearcat?) manufactured by
"Budd" (I want to say Davidson, somehow formerly involved in this group?) in
Mexico was using TIG as their primary welding method, and having no
problems. Anyone remember anything like that, or know more of it?

The Ag metal shop in the high school I teach at got a very nice TIG welder
this past year, so now I need to learn how to use it, if for no other reason
just to learn something new. Perhaps this summer will give me an
opportunity to play with it. It has always fascinated me, after seeing it
used so much on car and motorcycle "how to do it" TV shows. It certainly
does produce very neat welds, and on many different metals and widely varied
situations.

Jim in NC