Why 4130 tube?

[Leon McAtee]

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.

Could the availability of cheap WWII surplus steel have created a
tradition that has persisted in spite of other possibly superior
options?

[Drew Dalgleish]

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.
>
>Could the availability of cheap WWII surplus steel have created a
>tradition that has persisted in spite of other possibly superior
>options?
I built a set of wheel skis for my plane last fall. They are welded
mild steel tube with 1/2" thick plastic bottoms. I couldn't see any
advantage to uing 4130. My cost for everything including rigging was
under $200
Drew

[Ron Webb]

I regularly use square ASTM A500 tube for all sorts of stuff. I like it a
lot, because MIG welding is much easier, it is very cheap.

It seems to resist corrosion much better. I left a rack on my pickup
unpainted all winter and there was very little rust when I painted it last
week. 4130 would have been badly corroded by now.

Square tubing also means that when I cut an angle with my cutoff saw, it
fits perfectly...no filing or joint jigger gadget needed.

My Adventurer Amphibian kit uses square tubing of some sort. I expect it's
just this same cheap structural stuff, even the engine mount and landing
gear are made of it. The Adventurer has a bad reputation (for such a cool
airplane), but not for THAT.
http://beta.communities.fr.msn.ca/AdventurerExperimentalAmphibian

I think the reason airplane types use 4130 is mostly tradition, and an
insistence that we need to have the best. But "the best" hasn't been
redefined since the 1950s.



> 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.

[Corky Scott]

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.
>
>Could the availability of cheap WWII surplus steel have created a
>tradition that has persisted in spite of other possibly superior
>options?

There's really nothing wrong with using mild steel tubing to construct
a fuselage with the following caveat's: 1. That you properly size the
tubing and wall thickness to give you the proper strength. 2. That
you can find it.

I've read several times over the last few years that mild steel tubing
is almost as expensive as 4130, but I don't know that from personal
experience.

The last thing I'd mention is that because 4130 is stronger and
stiffer, you can probably use tubing that is lighter than mild steel
to construct your fuselage and still have a strong fuselage. In
airplanes, saving weight is almost a formal religion. The more weight
you save, the more weight you can carry, or the better the performance
or both.

Corky Scott

[Kevin Horton]

On Thu, 18 Mar 2004 13:07:22 +0000, Corky Scott wrote:

> The last thing I'd mention is that because 4130 is stronger and stiffer,
> you can probably use tubing that is lighter than mild steel to construct
> your fuselage and still have a strong fuselage. In airplanes, saving
> weight is almost a formal religion. The more weight you save, the more
> weight you can carry, or the better the performance or both.
>
> Corky Scott

4130 is certainly stronger than mild steel, but the modulus of elasticity
of all steel is about 29-30 ksi, with very, very small variations
depending on alloy. So for a given tube diameter and wall thickness, the
mild steel tube and the 4130 tube will have the same stiffness. If you
increase the diameter of the mild steel tube to make up for it having a
lower strength than the 4130, then the mild steel tube will be stiffer
than the 4130 tube.

The following links show modulus of elasticity of 29 ksi for mild steel,
and 29.7 ksi for 4130 steel, or a 2.5% difference. Not really significant.

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=M1030F

http://www.matweb.com/search/SpecificMaterial.asp?bassnum=M4130A
--
Kevin Horton RV-8 (finishing kit)
Ottawa, Canada
http://go.phpwebhosting.com/~khorton/rv8/
e-mail: khorton02(_at_)rogers(_dot_)com

[Richard Lamb]

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.
>
> Could the availability of cheap WWII surplus steel have created a
> tradition that has persisted in spite of other possibly superior
> options?

I would think the 20 pound weight savings would be incentive enough.
But that's just me.

You know how hard it is to pull 20 pounds off of a bare airframe?

Or a girlfriend?

Richard

[Ron Webb]

>
> You know how hard it is to pull 20 pounds off of a bare airframe?
>
> Or a girlfriend?
>


Lessee...20 pounds heavier, but not as brittle or corrosive...cheaper to
acquire, and easier to work with...

Sounds like my kind of girlfriend too.

[VideoFlyer]

A wise man, I think!

[Leon McAtee]

Richard Lamb > wrote in message >...
> You know how hard it is to pull 20 pounds off of a bare airframe?
>
> Or a girlfriend?
>
> Richard

Depends on the girl............. one simple comment can do the job -
if your willing to be the recipient of the other reactions as well<G>

20 pounds may seem like a lot on a bare airframe but in the grand
scheme it's not really significant. My Aeronca for example lost a LOT
more than that with the change from Linen to Dacron. With the other
modern materials available to us now, that 20 lbs (if that) can be
made up for elsewhere. I know guys that have more than 20 lbs of junk
stashed in their planes that they haven't even looked at for years.

Other than weight - IS - there a reason not to use 1026 DOM? This
assumes of course that the design is based on the slightly lesser
strength and/or has adequate design margins to begins with.

==================
Leon McAtee

[Rich S.]

"Leon McAtee" > wrote in message
m...
>
> Other than weight - IS - there a reason not to use 1026 DOM? This
> assumes of course that the design is based on the slightly lesser
> strength and/or has adequate design margins to begins with.

I'll never forget the time I machined a new axle stub for a friend's boat
trailer. I bought a blank from the trailer parts company that was made from,
"1020 *Plow* steel". We installed it, lowered the jack and the axle
proceeded to slowly bend under the weight of the boat until the tire hit the
fender.

I bought a chunk of normalized 4130 and turned a new axle stub. He used it
for five years and never had a problem.

'Course this would never happen with that 1000 series steel from XYZ
company.

Rich "Mebbe you could save a buck on the leather jacket and silk scarf" S.

[UltraJohn]

Richard Lamb wrote:

> Leon McAtee wrote:

> You know how hard it is to pull 20 pounds off of a bare airframe?
>
> Or a girlfriend?
>
> Richard
>
Off of a dressed girlfriend is easy off a bare one is tought!

[Leon McAtee]

"Rich S." > wrote in message >...

> 'Course this would never happen with that 1000 series steel from XYZ
> company.
>
> Rich "Mebbe you could save a buck on the leather jacket and silk scarf" S.

Money saving is not my main motivation. In fact the local rusty stuff
purveyor wants - more - for local 10XX tube than AS+S 4130 W/shipping
would cost. From what I have been able to gleen from the Internet
1026 DOM looses a good bit of strength when welded (normalized state)
but something like 1040 DOM ends up with 92% of the yeild strength of
4130 N after application of fusing heat.

The down side of the 1040 seems to be that post heating is recomended
- the same as 4130 (says one Internet source). Does this mean that
1040 has similar problems with embrittlement in the HAZ as 4130? This
seems kind of odd considering the stuff is originally resistance
welded during fabrication. The same source says nothing about post
heating of 1020.

===================
Leon McAtee

[Richard Lamb]

Leon McAtee wrote:
>
> Richard Lamb > wrote in message >...
> > You know how hard it is to pull 20 pounds off of a bare airframe?
> >
> > Or a girlfriend?
> >
> > Richard
>
> Depends on the girl............. one simple comment can do the job -
> if your willing to be the recipient of the other reactions as well<G>
>
> 20 pounds may seem like a lot on a bare airframe but in the grand
> scheme it's not really significant. My Aeronca for example lost a LOT
> more than that with the change from Linen to Dacron. With the other
> modern materials available to us now, that 20 lbs (if that) can be
> made up for elsewhere. I know guys that have more than 20 lbs of junk
> stashed in their planes that they haven't even looked at for years.
>
> Other than weight - IS - there a reason not to use 1026 DOM? This
> assumes of course that the design is based on the slightly lesser
> strength and/or has adequate design margins to begins with.
>
> ==================
> Leon McAtee

I think it's the last assumption that won't let me let go here, Leon.
WAS that structure originally designed for mild steel of 4130.


Also, there is a subtlety here that only applies to airplanes.

Building a truss structure with heavier tube probably doesn't ring
bells and wave red flags for you, but it really should.

It's not the actual increase in weight that's the issue, but the
distribution of that weight.

(everybody look blank for a moment and say "huh?")

But wouldn't the increased weight would be evenly distributed?
Very true.

The extra weight in the cockpit section is hardly noticeable
BECAUSE
it's all close to the center of lift.

But.

The longerons, verticals, diags, tail feathers, etc. in the aft section
all weigh more too.

And THAT increased weight can be a real serious BALANCE issue.

(Sorry for the caps, but I get loud when I preach
the Gospel according to Weight and Balance)

Can I get an Amen?


Richard

[Del Rawlins]

In > Ron Webb wrote:

> Lessee...20 pounds heavier, but not as brittle or corrosive...cheaper
> to acquire, and easier to work with...

There is no difference between mild steel and 4130 as far as corrosion
resistance is concerned, and in a traditional welded tube aircraft
structure any increase in brittleness is going to be a non-issue. If
you hit something hard enough to break (not just bend) it, you probably
wouldn't have survived anyway. I've flown in an aircraft with a 4130
tube fuselage that was rebuilt following a stall/incipient spin incident
from (very) low altitude. Some tubes were bent but as I recall nothing
actually separated. Pilot and passenger both walked away.

----------------------------------------------------
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[Del Rawlins]

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

>>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.

To add to Corky's comments, 4130 can be TIG welded with little worry
about the HAZ as well, which is how I am welding the steel components of
my Bearhawk together. I may do some stress relief of critical clusters
and attach points using a rosebud torch, not because I think it is
necessary, but only because it is easy and I haven't seen a convincing
argument that it hurts anything to do so. MIG welding of aircraft steel
components is generally not recommended, not because of the alloy so
much as it is difficult to control the heat applied throughout the weld.
What an amateur can end up with using MIG, is a weld that starts cold
and finishes burning through. It is also possible to lay down a nice
looking bead with MIG that doesn't have any real strength to it. This
is less likely with TIG, and darn near impossible with oxy/acetylene
welding.

While it is true that we don't typically heat treat 4130 to obtain the
ultimate stength that it is capable of, the normalized condition that it
is generally supplied in is a heat treat which is optimized to provide a
good compromise between strength and toughness. This is what makes a
steel tube fuselage hold together and protect its occupants during an
accident.

Finally, any cost difference to be had using mild steel instead of 4130
is totally insignificant compared to other costs incurred during a
homebuilt project. The 4130 for my fuselage should run a little over
$1000, while I may end up spending 20 to 30 grand on an engine package.
Even if it only saves me 20 pounds, that is 20 pounds that I won't have
to carry for the life of my airplane. That is also 20 pounds more of
gear, fuel, or whatever than I can carry for the life of the airframe.
I don't know about you, but I'm planning on keeping my plane for a long
time, considering the trouble I am going to in order to build it.
Figure that I am 29 now, hope to fly it before I turn 35, and plan to
fly it as long as I am medically able to do so. I'd have to truly be a
retard to want to skimp on materials in this fashion, even if the parts
were resized to maintain equal strength.

----------------------------------------------------
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[Leon McAtee]

Del Rawlins > wrote in message >...

> To add to Corky's comments, 4130 can be TIG welded with little worry
> about the HAZ as well, which is how I am welding the steel components of
> my Bearhawk together. I may do some stress relief of critical clusters
> and attach points using a rosebud torch,

Seems to be a contradiction here. If TIG works so well why bother
with the "stress relief of critical clusters and attach points"? This
either implies that the welding process is not completely acceptable,
or the rest of the structure has been over built and less than ideal
welds are acceptable. If the later is the case why not use something
like 1026 DOM and forget the post heat alltogether?

I'm not from Missouri but I still need to be shown that TIG is truly
acceptable for welding 4130. (I have a TIG and could use it, but
don't) I know some certified plane builders do it this way, and have
heard that at least one uses MIG, but to me it seems that heat is
heat, no matter how it is introduced to the metal. From my limited
understanding of metallurgy it's not the quantity of the energy put
into the metal it's the energy density, or peak heat, that is the
determining factor, coupled with the rate of cooling. The HAZ may be
smaller and closer to the weld with TIG but it - is - still there.
Isn't it? Maybe because the TIG HAZ is closer to the weld, and
therefore has a larger area than than the HAZ would have after being
chased out into the tube, one can get a stronger overall stucture by
not post heating a TIG weld?

Just to clear up a possible misconception from another poster - I am
NOT suggesting to, or wishing to, substitute ERW DOM mild steel for
4130 in an existing design. I'm well aware of the cascade effect of
changing something on an existing design.

If TIG, or MIG (I'm real good at MIG of thin metal, done lots of it)
welding of 4130 results in an overall better airframe then I'll stick
to 4130. But if there is a substitute, like 1040 DOM, that has a
strength only slightly less than 4130 N, that can be welded with out
any worry of developing a critical HAZ (not 100% sure about this),
then to me that would seem to be a better option for the average
homebuilder.

I'm not trying to be argumentative and have no desire to ignite any
flame here. I do like to occasionally challenge the accepted
traditions to see if there might be a "better" way of doing things.
Even if there isn't a better way I, and maybe some others, will get a
better understanding of just why "we do it that way".

=================
Leon McAtee

[Rich S.]

"Leon McAtee" > wrote in message
om...
>
> I'm not trying to be argumentative and have no desire to ignite any
> flame here. I do like to occasionally challenge the accepted
> traditions to see if there might be a "better" way of doing things.
> Even if there isn't a better way I, and maybe some others, will get a
> better understanding of just why "we do it that way".

Understand where you are coming from, Leon. It seems that you are walking
awfully close to the line between "builder" and "designer" - one which I
avoid like STD's. :o)

The pitfalls of changing a design are many and legendary. One thing seems to
lead to another and it is my opinion that it takes an aeronautical design
engineer who is specifically trained in the field of homebuilt light
aircraft to fully comprehend and integrate changes to proven designs. You
say, "it's only 20 pounds"; but that may have far-reaching effects which are
not evident to a builder.

That being said, I would think that a change from 4130 steel to 2024
Aluminum would have many more advantages than from 4130 ---> 1026. I was
given the option on the plans for my airplane to use either 1/4" 4130 or
3/8" 2024 Al for the wing joining plates. The 2024 was stronger and lighter,
so I chose to use aluminum. The difference here was that it was written
right there in the plans. I would not have elected to do this myself.

From what I've heard, the builder of John Denver's Long Eze had a better
idea for the location of the fuel selector valve. . .

Regards,
Rich S.

[Del Rawlins]

In > Leon McAtee wrote:
> Del Rawlins > wrote in message
> >...
>
>> To add to Corky's comments, 4130 can be TIG welded with little worry
>> about the HAZ as well, which is how I am welding the steel components
>> of my Bearhawk together. I may do some stress relief of critical
>> clusters and attach points using a rosebud torch,
>
> Seems to be a contradiction here. If TIG works so well why bother
> with the "stress relief of critical clusters and attach points"? This
> either implies that the welding process is not completely acceptable,
> or the rest of the structure has been over built and less than ideal
> welds are acceptable. If the later is the case why not use something
> like 1026 DOM and forget the post heat alltogether?

No contradiction. I haven't been convinced that stress relief is
necessary, but neither have I been convinced that it hurts anything, and
it only takes all of a few minutes to accomplish. From what I can tell,
even experienced welders can't agree on whether or not it is desirable.

> I'm not from Missouri but I still need to be shown that TIG is truly
> acceptable for welding 4130.

Over and above 50 odd years of experience in the aerospace industry?
I'm going to say Arkansas, but that's only a guess.

> (I have a TIG and could use it, but
> don't) I know some certified plane builders do it this way, and have
> heard that at least one uses MIG, but to me it seems that heat is
> heat, no matter how it is introduced to the metal. From my limited
> understanding of metallurgy it's not the quantity of the energy put
> into the metal it's the energy density, or peak heat, that is the
> determining factor, coupled with the rate of cooling.

Speaking of contradictions, if heat is heat, why do you still need to be
shown that TIG is acceptable for welding 4130?

> The HAZ may be
> smaller and closer to the weld with TIG but it - is - still there.
> Isn't it? Maybe because the TIG HAZ is closer to the weld, and
> therefore has a larger area than than the HAZ would have after being
> chased out into the tube, one can get a stronger overall stucture by
> not post heating a TIG weld?

That's possible, I don't know.

> Just to clear up a possible misconception from another poster - I am
> NOT suggesting to, or wishing to, substitute ERW DOM mild steel for
> 4130 in an existing design. I'm well aware of the cascade effect of
> changing something on an existing design.
>
> If TIG, or MIG (I'm real good at MIG of thin metal, done lots of it)
> welding of 4130 results in an overall better airframe then I'll stick
> to 4130. But if there is a substitute, like 1040 DOM, that has a
> strength only slightly less than 4130 N, that can be welded with out
> any worry of developing a critical HAZ (not 100% sure about this),
> then to me that would seem to be a better option for the average
> homebuilder.

To play devil's advocate, I would like to be shown instances where
amateur TIG welding of 4130N resulted in homebuilt aircraft falling out
of the sky. Also, before deciding to switch from 4130 to something else
based on price, check out the prices at Dillsburg Aero in Pennsylvania.
Members of the Bearhawk list who live nearby to ACS in California, have
reported that it is still significantly cheaper to have 4130 shipped
from Charlie Vogelsong at Dillsburg than to buy it locally at ACS.

> I'm not trying to be argumentative and have no desire to ignite any
> flame here. I do like to occasionally challenge the accepted
> traditions to see if there might be a "better" way of doing things.
> Even if there isn't a better way I, and maybe some others, will get a
> better understanding of just why "we do it that way".

Understood. As a relative newcomer to aviation, I get sick and tired of
the deeply held beliefs of many of the mechanics and pilots I encounter,
which often have no basis in reality, or are based on obsolete
information.

----------------------------------------------------
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[Ernest Christley]

Del Rawlins wrote:
> In > Leon McAtee wrote:
>
>>Del Rawlins > wrote in message
>...
>>
>>
>>>To add to Corky's comments, 4130 can be TIG welded with little worry
>>>about the HAZ as well, which is how I am welding the steel components
>>>of my Bearhawk together. I may do some stress relief of critical
>>>clusters and attach points using a rosebud torch,
>>
>>Seems to be a contradiction here. If TIG works so well why bother
>>with the "stress relief of critical clusters and attach points"? This
>>either implies that the welding process is not completely acceptable,
>>or the rest of the structure has been over built and less than ideal
>>welds are acceptable. If the later is the case why not use something
>>like 1026 DOM and forget the post heat alltogether?
>
>
> No contradiction. I haven't been convinced that stress relief is
> necessary, but neither have I been convinced that it hurts anything, and
> it only takes all of a few minutes to accomplish. From what I can tell,
> even experienced welders can't agree on whether or not it is desirable.
>
>
>>I'm not from Missouri but I still need to be shown that TIG is truly
>>acceptable for welding 4130.
>
>
> Over and above 50 odd years of experience in the aerospace industry?
> I'm going to say Arkansas, but that's only a guess.
>


It was my understanding that the problem with TIG is that it doesn't put
in ENOUGH heat. That is, it melts the steel at only a very limited
section, as soon as you move on all the surround steel sucks the heat
out, basically quenching the weld and making 4130 brittle.

Don't know if it was my lack of skill, the cheap TIG contraption I was
using, or misaligned stars, but the few test pieces I TIGed together
came apart with my bare hands. I'm strong, but not like that. I
decided to stick with OcyAcet.

Luckily, I'm almost done with it.

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

[Ron Webb]

> 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.

Anybody got a link that does a better job with this?

[Del Rawlins]

> 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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[Ron Webb]

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;^}

[Del Rawlins]

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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[Jay]

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."

[Del Rawlins]

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-
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[Capt.Doug]

>"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.

[Ernest Christley]

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

[Morgans]

"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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[Stealth Pilot]

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

[Bob Babcock]

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.

[Veeduber]

To All:

Bob Babcock's conclusions closely match my own.

I believe anyone wishing to become airborne safely and at least cost should
devote a bit of time to the areas Bob has mentioned, then draw your own
conclusions.

On close examination a great deal of the aviation information available on the
internet turns out to be one novice parroting another. Tracked back to its
source, many of the Conventional Wisdoms espoused by the novice as fact turn
out to be tainted with commercialism, fallacious data meant to promote a
particular product or dealer.

Due to the anonymous nature of the internet I think the wiser course is to
assume EVERYTHING you read here is bull**** (yes, even this :-) and to not
accept any opinion as valid simply because it is popular.

Think for YOURSELF.

-R.S.Hoover

[Stealth Pilot]

On 27 Mar 2004 23:12:41 GMT, (Veeduber) wrote:

>To All:
>
>Bob Babcock's conclusions closely match my own.
>
>I believe anyone wishing to become airborne safely and at least cost should
>devote a bit of time to the areas Bob has mentioned, then draw your own
>conclusions.
>
>On close examination a great deal of the aviation information available on the
>internet turns out to be one novice parroting another. Tracked back to its
>source, many of the Conventional Wisdoms espoused by the novice as fact turn
>out to be tainted with commercialism, fallacious data meant to promote a
>particular product or dealer.
>
>Due to the anonymous nature of the internet I think the wiser course is to
>assume EVERYTHING you read here is bull**** (yes, even this :-) and to not
>accept any opinion as valid simply because it is popular.
>
precisely.


.....but I have this 1951 Auster fuselage out in the workshop that I
have beadblasted all myself and it did have one or two areas of
corrosion.
take the rudder for instance.
someone forgot to put in the bottom two drain holes.
that rudder had something like 50 tide lines formed in rust on the
inside of the cotton covering. the entire bottom steel bow of the
rudder was corroded almost totally away.
a quarter of an inch above the rust I hacksawed it through. there was
not one hint of rust inside the sound tube.
the combinations of alloy and surface passivation advocated over the
years actually do work.
the bow is repaired in 4130 and the bottom rib is stainless steel tig
welded.

4 reasons to use 4130.
the design was stressed for it.
it offers better strength to weight ratio
bare surfaces of it have better corrosion characterstics.
it is available in tube sizes which are neat fits inside each other.

if your design was intended for mild steel then go for it.
typically all the homebuilts by Roger Druine were designed for mild
steel fittings. make sure they are adequately corrosion proofed.

if your design was competently stressed for mild steel then go for it.

in either steel dont be stupid and use square tube. it is needlessly
heavier. (calc the amount of steel in an inch square with 1/8" wall
thickness and do the same for inch round with 1/8" wall thickness. the
reason isnt rocket science)

btw every time my tailwind does a heavy arrival I'm thankful that the
fuselage is 20% stronger than mild steel.
ymmv.
Stealth Pilot