Why 4130 tube?

Ron Webb wrote:
There is no difference between mild steel and 4130 as far as
corrosion resistance is concerned,

Now you have got my curiosity in gear. As I said, my personal
experience is that I have seen a significant differance.

I went looking for some quantized data on the subject. I have not
found what I was looking for on the net, and may run up to the
University library later on. For now I found http://www.armycorrosion.
com/summit2001/DAY_1_PM/schario.pdf

It does not have much in the way of quantized data, comparing 1010 to
4130 corrosion properties, but there is enough to refute the claim
that there is no differance.

The stuff in my garage doesn't seem to notice any difference. It is
more than happy to rust if I don't do anything to protect it. It could
be that it happens slower; I haven't done any sort of scientific testing
to see. But the bottom line is that rusty is rusty.

----------------------------------------------------
Del Rawlins-
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But the bottom line is that rusty is rusty.



Agreed...but if it took 30 years to rust out the back of the longerons on
your new float equipped Bearhawk to the point of them being unsafe, since
they are .049" 4130 - but it would take 100 years to do the same thing to
..063 1010 --that might be enough to tip the scales if the weight differance
was 20 pounds or so...

OK, I'll admit it...I made the longerons on my MoHawk out of 1/2 x.032
4130 too, just like the plans say...but there are MANY things I'd do
differently if I was starting over...like start with a set of Bearhawk plans
for instance;^}

In Ron Webb wrote:

Agreed...but if it took 30 years to rust out the back of the longerons
on your new float equipped Bearhawk to the point of them being unsafe,
since they are .049" 4130 - but it would take 100 years to do the same
thing to ..063 1010 --that might be enough to tip the scales if the
weight differance was 20 pounds or so...

My position is that if the lower longerons are getting rusty, there are
other parts in there that I need to be just as concerned about. Beefing
up parts doesn't make the airframe any stronger necessarily, it only
shifts the weak point elsewhere. I would expect that to be true of
corrosion issues as well as overall strength. I would rather go the
extra mile with corrosion protection measures NOW while the plane is
under construction, than add a bunch of unneeded weight by making
everything thicker. In 20-30 years I will most likely want to tear the
fabric off and inspect everything closely no matter what anyway. I've
got a sandblaster and I'm not afraid to use it.

OK, I'll admit it...I made the longerons on my MoHawk out of 1/2 x.
032 4130 too, just like the plans say...but there are MANY things I'd
do differently if I was starting over...like start with a set of
Bearhawk plans for instance;^}

I hear that a lot. 8^)

----------------------------------------------------
Del Rawlins-
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A building material that is less expensive and more available may in
practice end up building a lighter airframe. The reason is that
you're more likely to be able to use the exact right stock instead of
just over building because you couldn't find or afford the expense to
buy a special piece of the lighter guage material.

Bend versus break. Old cars were build on rigid chassis, the safety
argument was that you want something really strong. But modern cars
are generally built uni-body designated crush zones to dissipate some
of the energy instead of transfering it to the passengers.

"In theory, practice and theory are the same. But in practice, they
are often very different."

In Jay wrote:
A building material that is less expensive and more available may in
practice end up building a lighter airframe. The reason is that
you're more likely to be able to use the exact right stock instead of
just over building because you couldn't find or afford the expense to
buy a special piece of the lighter guage material.

Speak for yourself. If my plans call for a specific material, that is
what I use. On the couple of occasions where I have deviated, I placed
long distance calls to the designer to get his okay on the changes.

Bend versus break. Old cars were build on rigid chassis, the safety
argument was that you want something really strong. But modern cars
are generally built uni-body designated crush zones to dissipate some
of the energy instead of transfering it to the passengers.

I'm all in favor of less rigidly constructed car chassis for other
people. That way, when I get into a collision with one of them, they
will serve as a crush zone for my rigid chassis and heavy duty bumpers.
If I get into an accident where (for example) my '73 pickup truck isn't
sufficient to protect me, chances are I wouldn't want to survive that
anyway. Not to say I won't try to improve my chances where it makes
sense; I just finished fabricating a set of brackets to convert the old
beast from lap belts only to lap with shoulder belts.

"In theory, practice and theory are the same. But in practice, they
are often very different."

"No plan survives contact with the enemy intact."

----------------------------------------------------
Del Rawlins-
Remove _kills_spammers_ to reply via email.
Unofficial Bearhawk FAQ website:
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"Ernest Christley" wrote in message http://www.ernest.isa-geek.org/

What is a typical critical angle of attack for stalling on the Dyke Delta?
I'm thinking it's somewhat higher than most because of the low aspect ratio.

D.

Capt.Doug wrote:
"Ernest Christley" wrote in message http://www.ernest.isa-geek.org/


What is a typical critical angle of attack for stalling on the Dyke Delta?
I'm thinking it's somewhat higher than most because of the low aspect ratio.

D.



I think it is somewhere up around 90. 8*)

Actually, it doesn't stall in the conventional manner. I will slow down
and descend like a leaf once you hit MCR (minimum control rate), but at
that point there isn't enough elevon authority to pull it to a stall.

I have heard that it will spin, though.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

"Capt.Doug" wrote in message
...
"Ernest Christley" wrote in message http://www.ernest.isa-geek.org/

What is a typical critical angle of attack for stalling on the Dyke Delta?
I'm thinking it's somewhat higher than most because of the low aspect
ratio.

D.

It isn't the aspect ratio that gives it the high angle of attack. It is the
delta characteristic, that all delta wings have.
--
Jim in NC


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On 17 Mar 2004 18:19:11 -0800, (Leon McAtee)
wrote:

Why do we homebuilders use 4130 tube? My old Aeronca does just fine
being made of mild steel. A bit of napkin calcs says that going up
just one tube diameter for the size tube we normally use, the area,
and the strength/weight goes up between 15% and 20%. This pretty
much offsets the difference in tensile strength between 4130 N and
1026, and more than offsets it for something like 1040. The "mild
steels" can be welded using MIG or TIG with little worries about HAZ
and since we are not heat treating the 4130 to obtain its strength
advantage it seems to me to actually be a poorer choice for amateur
aircraft construction.

For a typical rag and tube plane, properly choosing the tube sizes
should result in a weight gain of less than 15% for the same strength
which is, what, around 20 pounds for something like a Tailwind or
Aeronca. This to me seems like a good trade off to eliminate the
possibility of cracked welds due to poor technique. Not to mention
maybe saving a few bucks and being able to get the steel locally.


you are probably correct there.

I'm slowly restoring an Auster built from T45. that is an alloy which
preceeded 4130 and has a tensile strength of 45 tons to the square
inch.
you get to appreciate lots of things beadblasting a 50 year old
fuselage. the thing I appreciate most is that the alloying components
have protected the steel from corrosion so much that a simple bead
blast and a repaint is all that 99% of the entire fuselage requires.

you get the same corrosion resistance with 4130.
moisture that only sees light surface corrosion in 4130 will probably
deeply pit a mild steel component.

my tailwind fuselage is 4130 and has no discernable rust in 18 years.

for corrosion resistance alone I'd go the extra mile for the
recognised alloy.
Stealth Pilot
Australia

Gentlemen,
I have no real experience and very little formal training. The
absolute reliance on 4130 is a wives tale. Very serviceable aircraft
were and are built regularly with mild steel tube. For amateur
construction mild steel makes more sense than 4130. On the Yahoo
Piper Cub site in the files section is a factory drawing of a Super
Cub fuselage. It is predominently mild steel in the sizes of 3/8-7/8
..035 wall. These planes did not rust away or disappear from tubing
failure. The US military materials book from WW2 notes that after
welding 4130 is reduced substantially in tension, 74 thousand #/ as
compared to mild steels 54 thousand #/, and the compression of tubes
is a minor difference in the lengths we deal with. Please reference
Bob Whittier's book on tubing for this discussion.

The problem of weight moving backward is real but not a reason for not
using mild steel. The Circa Nieuports with thier aluminum tubes work
fine, it is a matter of design. A second coat of paint, a big swivel
tail wheel, or balancing the elevator will be as much of a change and
many homebuilts have these changes made over the plans regularly. If
a guy can't keep control of his C of G then he needs help. I have
done a design study using .049 mild steel to replace .035 4130 in a
standard low wing Warren truss fuselage. The effect on the C of G was
neglidgeable due to the increased weight in the forward fuselage were
the largest and more cocentrated collections of tubing existed. The
added weight in the tail feathers was compensated for with a movement
of the speced A65 forward 2-3 inches. I've decided to use wooden tail
feathers and actually save a lot of weight.

Many homebuilts do not come close to the designers empty weight and
operate over stated design grosses all the time, even those built from
4130. Or the guy who puts an extra hundred #'s of Lyc. and electrics
in an A65 design is never questioned so severly as a guy who wants to
use mild steel tube accepted and certified for aircraft construction
by civil and military specs for 70 years.

Many fine planes were built and designed using common sense, alternate
materials and the engineering from established designs. Pete Bowers
discussed this in his book on Homebuilts he wrote in the seventies
prior to the litigation era we now live in. In fact I have a
collection of fuselage plans from the past and they would appear to be
designed in 1930 out of light gauge mild steel and copied since.

Recently I saw some sitka from an established aircraft supplier. I
wouldn't have used it for ladder rails. I have hand picked perfect
quarter sawn Western Hemlock for a fraction of the cost at a local
building store that was far superior to the aircraft grade stuff that
cost more in brokerage fees than my wood. Get educated about
inspection and alternatives using established experts and build around
the limitation. A can of line oil or linseed oil used according to
Tony Bingelis in a properly ventilated fuselage will take care of
rust. Probably good idea with 4130 as well.