Weight saving exercise.

ORVAL FAIRBAIRN
sednews
In article ,
Matt Whiting wrote:

Fortunat1 wrote:
"Cy Galley"
sednews:4V41e.103754$r55.32258@attbi_s52:


I would check with a Van's builder. RVs have aluminum riveted tanks
with pro-seal. If you know a good tig welder, then a welded tank
can be built.



OK, thanks.There are two down the road from me, in fact! I'll
probably try and weld it myself, though I've never welded aluminum
before. Then again, most ofthe things I've done on this contraption
I've never done before. I'm assuming baffles (and I think I'd
need them in a long shallow wing tank) aren't welded, though. I'm
supposing that the tank would be assembled, but the back left open
until the baffles are all riveted, and then closed up and welded?

I see no reason not to weld the baffles as well. Probably less messy
than sealing the rivets.

Matt


that depends on the aluminum alloy used -- and, how much warping you
can tolerate. Van's tanks are "wet" cells -- part of the wing and are
2024-T3, which is NOT weldable. The nice thing about wet cells is that
they add only the weight of the ProSeal to the airframe weight, while
separate tanks add their own weight to the plane.

6061 and 5052 are common weldable alloys, but you will get some
distortions from the welding process.

I still don't see how I would weld the baffles in place before the tank is
closed up. This tank would be about 48" by 24" by 5" The top has a bevel at
the back to conform to an airfoil shape. I reckon I'd need two baffles
(strictly eyeball engineering here) to minimize sloshing from side to side.
maybe just one. If I were to make the tank out of a single wrapped piece
with ends stitched on afterwards, how would i go about welding the baffles
in place? Put the ends on last? Presumably, the baffles would only need to
be tacked as opposed to a continuous seam all the way around..

"Rich S."
:

"Montblack" wrote in message
...

Aluminum will weigh 5 x the mahogany? Wow.

Specific gravity of Aluminum = 2.7
Specific gravity of Mahogany = ~.5

What's the cost difference between aluminum and wooden props?

New Ed Sterba Birch prop ~ $600. New Sensenich Aluminum $2,000.
These are rough figures.

Why do people buy birch instead of mahogany?

Birch has a specific gravity ~ .7 and is a lot stronger per pound than
Mahogany when used for a prop.



Might go to a wood prop if the one I have doesn't work out. But it is quite
a good prop, and it's absolutely gorgeous, to boot!

"Fortunat1" wrote

I still don't see how I would weld the baffles in place before the tank is
closed up. This tank would be about 48" by 24" by 5" The top has a bevel
at
the back to conform to an airfoil shape. I reckon I'd need two baffles
(strictly eyeball engineering here) to minimize sloshing from side to
side.
maybe just one. If I were to make the tank out of a single wrapped piece
with ends stitched on afterwards, how would i go about welding the baffles
in place? Put the ends on last? Presumably, the baffles would only need to
be tacked as opposed to a continuous seam all the way around..

Keep in mind that the baffle need not be attached to both the top and
bottom. Its job is to slow the fuel, not be a perfect seal.
--
Jim in NC

Fortunat1 wrote:

I still don't see how I would weld the baffles in place before the tank is
closed up. This tank would be about 48" by 24" by 5" The top has a bevel at
the back to conform to an airfoil shape. I reckon I'd need two baffles
(strictly eyeball engineering here) to minimize sloshing from side to side.
maybe just one. If I were to make the tank out of a single wrapped piece
with ends stitched on afterwards, how would i go about welding the baffles
in place? Put the ends on last? Presumably, the baffles would only need to
be tacked as opposed to a continuous seam all the way around..

Yes, you would wrap the sheet to form the overall tank shape, weld in a
baffle or three working from the open ends and then weld on the ends to
close things up.

Matt

"Morgans"
:


"Fortunat1" wrote

I still don't see how I would weld the baffles in place before the
tank is closed up. This tank would be about 48" by 24" by 5" The top
has a bevel
at
the back to conform to an airfoil shape. I reckon I'd need two
baffles (strictly eyeball engineering here) to minimize sloshing from
side to
side.
maybe just one. If I were to make the tank out of a single wrapped
piece with ends stitched on afterwards, how would i go about welding
the baffles in place? Put the ends on last? Presumably, the baffles
would only need to be tacked as opposed to a continuous seam all the
way around..

Keep in mind that the baffle need not be attached to both the top and
bottom. Its job is to slow the fuel, not be a perfect seal.


Mmm, OK. I had considered that, but figured that the baffle would flex if
it weren't nailed to each of the four sides. I'm thinking now it might be
possible to get in from either end of the tank. I'd only have to get in
about 16" throug a 5"X24" opening and make a few tacks to the top. I know a
guy who welds aluminum boats up. I'll ask him what the deal is with those.

Matt Whiting
:

Fortunat1 wrote:

I still don't see how I would weld the baffles in place before the
tank is closed up. This tank would be about 48" by 24" by 5" The top
has a bevel at the back to conform to an airfoil shape. I reckon I'd
need two baffles (strictly eyeball engineering here) to minimize
sloshing from side to side. maybe just one. If I were to make the
tank out of a single wrapped piece with ends stitched on afterwards,
how would i go about welding the baffles in place? Put the ends on
last? Presumably, the baffles would only need to be tacked as opposed
to a continuous seam all the way around..

Yes, you would wrap the sheet to form the overall tank shape, weld in
a baffle or three working from the open ends and then weld on the ends
to close things up.

'Kay. makes sense. Al I have to do now is learn to weld aluminum!

"Fortunat1" wrote in message ...
Yes, you would wrap the sheet to form the overall tank shape, weld in
a baffle or three working from the open ends and then weld on the ends
to close things up.

'Kay. makes sense. Al I have to do now is learn to weld aluminum!

Or, you can drill holes in the outer skin where the baffle flanges are
located and then weld them from the outside. It's a lot easier than trying
to get a stinger in the tank.

Learn how to weld Aluminum? After a couple thousand in dedicated equipment,
and a hundred hours of practice, you'll certainly be qualified. It's a
little easier than turning crankshafts, I suppose. If it was me, I'd spend
my time doing fun things and leave the 20 minutes of welding to the pros.

Rich S.

"Rich S."
:

"Fortunat1" wrote in message
...
Yes, you would wrap the sheet to form the overall tank shape, weld
in a baffle or three working from the open ends and then weld on the
ends to close things up.

'Kay. makes sense. Al I have to do now is learn to weld aluminum!

Or, you can drill holes in the outer skin where the baffle flanges are
located and then weld them from the outside. It's a lot easier than
trying to get a stinger in the tank.

Learn how to weld Aluminum? After a couple thousand in dedicated
equipment, and a hundred hours of practice, you'll certainly be
qualified. It's a little easier than turning crankshafts, I suppose.
If it was me, I'd spend my time doing fun things and leave the 20
minutes of welding to the pros.


Mmm, maybe. Plan was to borow my buddie's TIG, though! I do know someone
who can do it for me, alright. On the other hand, ACS have atank for this
airplane.
By the way, I'm hurt! I learned to weld steel and it only took me a few
months! And it was fun, too..

"Fortunat1" wrote

Mmm, maybe. Plan was to borow my buddie's TIG, though! I do know someone
who can do it for me, alright. On the other hand, ACS have atank for this
airplane.
By the way, I'm hurt! I learned to weld steel and it only took me a few
months! And it was fun, too..


Welding Al is indeed much harder to master than welding steel. The melting
point of the filler and the melting point of the filler is the same, or very
close to it. Get it got enough to flow the puddle, and if you are just a
little too hot, it blows through.

And of course, a tank has to be perfect to not leak. Many pros still get a
few leaks. Make sure that whoever does the welding does a pressure test,
before any gas goes in it.
--
Jim in NC

Having just finished the tanks for my RV-7, I agree with Cy. If you're
in the USA, call Van's A/C & get the name of a builder near you & go
look at the plans for the tank/leading edge to get an idea of how they
go together.

If you can handle cutting & fitting the aluminum, the rest is pretty
simple & you can build with a drill & a cheap 'pop' rivet tool using
closed end pulled rivets. AD41H aluminum body steel mandrel is what's
used to attach the back baffle to the ribs. You'll need at least a
couple of internal ribs to stiffen the 2x4 foot top & bottom panels.

The hardest thing will be bending up the 'box' but a good sheet metal
shop can do that for you. (Be sure to tell them to use the proper radius
on the bends.)

You will be amazed at how light it will be.

Charlie

Cy Galley wrote:
I would check with a Van's builder. RVs have aluminum riveted tanks with
pro-seal. If you know a good tig welder, then a welded tank can be built.


"Fortunat1" wrote in message ...

"Rich S." sednews:_fydnZvUOMpYONnfRVn-
:


"Fortunat1" wrote in message


. . . so I'm going to have to learn to build an aluminum
tank..

Anyone know of a resource to show me how?

The books by Tony Bingelis have excellent tips on this.
http://www.amtbooks.com/sport_plane_...on_techniq.htm


Mm, have all of his books and I don't remember seeing an article about
ali
tank construction, but I did find this article from SA on the net..
http://members.eaa.org/home/homebuil...About%20An%20A
luminum%20Fuel%20Tank_.html