Have you guys ever noticed the void?

On Tue, 10 Jan 2006 11:24:24 GMT, Matt Whiting wrote:

Ron Wanttaja wrote:

I have to admit he does bring up a good point. I have often wondered
what the difference in strength's and weakness would be if I used
different wood in my plane, or enlarged the components for a larger
pilot.


Which is probably one reasons designers don't provide the equations. Many hate
it when folks make changes.

Most equations for light airplane design are well established and have
been around for decades. What unique equations could a typical designer
provide?

Not the equations per se, but the precise values and the design margins of the
design in question, the non-designer's lack of understanding of the
interrelationships between design elements, and the legal implications of
*providing* the information.

Remember, the poster I responded to specifically referred to the substitution of
one material for another. It's sometimes more than a mere comparison of the
strengths of the materials.

Ron Wanttaja

On 10 Jan 2006 03:59:39 -0800, "Lou" wrote:

The designer may hate it when you change a few things, but as many
people have pointed out, every pilot is different. Some changes are a
need and some are for want. Is this any different then a person
customizing a harley to their liking and calling it a Harley?

Not at all, it's exactly the same. Now, point out where Harley-Davidson
publishes the design data that one can use to make modifications.

Homebuilding *is* about experimentation, no question. I just feel that if
someone wants to make changes to an existing aircraft, they shouldn't be
offended if the original designer declines to help. If one owns the plans to
the aircraft, you have all the information you need to compute the effects of
your changes, using standard aircraft design books.

Ron Wanttaja

On 9 Jan 2006 12:05:59 -0800, wrote:


So fill the void yourself. Slide rule, #2 yaller pencil and the back
of an envelop, you're half way there. (You may use a calculator, if
you wish.)

I'm in the process of doing exactly that. ...and beyond that trying to
get a book written targetted to the amateur designer.

The other half has to do with the basic purpose of the 'Experimental -
Amateur Built' licensing category, in that it exists to foster
aeronautical education, which implies the need to know what you're
doing, if not from the outset, at least before first-flight.

the weakness in the argument is that there is no way for someone
learning to verify their calculations.
the absolute absence of calculations available for learning or
developing from means that while our building skills and confidence
may be in the second century of aviation our design skills are right
back there with the wright brothers.

And if that sounds slightly fey, as I'm sure it will to most of the
kit-assemblers, consider the other side of the coin: If the designer
provided you with detailed data, how would you know they were correct
without duplicating his calculations?

my point exactly. I want to verify the calculations. the aircraft I am
building is aerobatted by some and declared by others to have a 3.8g
ultimate wing. only access to the designers numbers will allow me to
sort the bs from the advertised claims and see what the actual
situation was when designed and now.

Even then, weight -- that is,
ACTUAL weight -- is a critical factor in those calculations. A lot of
home-builts were designed by midgets for others of their kind and often
cite weights and g-factors that are wildly fallacious if not out-right
lies. Stuff a two hundred fifty pound lard-ass in the cockpit, use
real numbers and the calculations for some of the most popular designs
are liable to read 'Lawn Dart.'

again if the original calculations were available the folly would be
easy to establish by running the calculations with the actual weight
against the design strengths.

Expecting the EAA to do something about your 'void' is wishful
thinking, in my opinion.

the eaa dont design aircraft. this is something that the eaa cant do.
this is however something that each and every designer can assist in
easily. I think that this black void in the homebuilding area actually
covers up a lot of ignorance. while it is easy to pretend that you
understand, in very many cases I have found that fear of ridicule is
behind keeping what calculations have been made secret.
we need to modify our environment to make the publication of design
calcs a part of creating a design. that way we will develop more
competent design knowledge in the community.

come to think of it the eaa I'm sure would be more than happy to add a
section to the members area to hold sets of design calcs.

I suggest the wiser course is to think for yourself If that requires
cracking a few books on airframe structural analysis, so be it. (Try a
search using 'fundamentals of aircraft structural analysis.' The books
are out there and fairly cheap, too -- apparently because nobody reads
them :-)
and all you get from that is a guessed set of figures which tell you
nothing about the oversights in design or the plain errors in
calculation that have crept through.
the design book that I was working through yesterday(Vogel) turns out
to have pages of stuffed up calculations in it. I learnt a lot from
working out that there must have been errors and correcting them but I
could have learnt far more with some valid example calcs to work
through.

if we are not to repeat all the mistakes and inefficiencies of the
last century of aviation, ie to progress to really efficient
homebuilts in the future, we really need to get the designs and the
calculations discussed not the bloody paint schemes.

think also on the consequences for safety. would all those guys have
died aerobatting in RV3's for instance if they had been able to see
the calcs for themselves? ...and to see how close they were pushing
it.
Stealth (working on it and I'm eaa712250 ) Pilot

On Mon, 09 Jan 2006 22:13:59 GMT, Richard Lamb
wrote:

I did some basic calculations on the wing used on the Chuckbird/Texas
Parasol
before building my first one. I came up with a shade over 4 G's at 650
pounds.
(seemed like a good idea before selling plans)

Then got Nuked by several guys who claimed the wing was "weak" - because
they
were building 650 pounds - EMPTY.(and it was my fault!?!)

E-bleepin'-nough!

Richard

wings should have a 1.5 margin of safety so if your wing is 4g's at
650 lbs ultimate strength then you actually designed a 2.6g working
strength wing at that weight.
2.6 x 1.5 = 4

you make my point exactly. by publishing your figures others who are
interested can check your numbers and point out errors that you might
have missed.
60 degree banked turns would be ok but steepen up the bank angle a
little, hit some turbulence, .... poof, tinsel time.

got a sweat up? :-)


look at the rest of usenet. if you made an honest effort and stuffed
up someone would almost certainly post details of a more suitable
design.

I think that this is an area that we enthusiasts should be devoting
some attention to in the future.
Stealth Pilot

On Mon, 09 Jan 2006 18:43:22 -0800, Ron Wanttaja
wrote:

On 9 Jan 2006 12:16:29 -0800, "Lou" wrote:

I have to admit he does bring up a good point. I have often wondered
what the difference in strength's and weakness would be if I used
different wood in my plane, or enlarged the components for a larger
pilot.

Which is probably one reasons designers don't provide the equations. Many hate
it when folks make changes.

Ron Wanttaja

your honour I sold the guy the plans, I provided him with the worked
design calculations showing how the design was arrived at. the
comments in the calculations show how the material sizes were arrived
at. he has made changes to the aircraft which are neither in the
original designs nor show any validating calculations so my conclusion
is that he just guessed at the changes and proceeded blindly.
I cannot see how I can be held responsible for the stupidly
incompetent actions of others.

sounds like a defense to me.

Stealth Pilot

No sweat, just a basic misunderstanding.

We design to a 4 G _yiield_ limit.

This is where the wing, after being stressed, no longer
returns to the original shape
It has reached the "plastic" limit and has deformed.
Yes, it has failed, but it did not break.

The 1.5 G safety factor then gives a 6 G _ultimate_ limit.
THIS is where the wing breaks.

mo better?

Richard

Stealth Pilot wrote:


your honour I sold the guy the plans, I provided him with the worked
design calculations showing how the design was arrived at. the
comments in the calculations show how the material sizes were arrived
at. he has made changes to the aircraft which are neither in the
original designs nor show any validating calculations so my conclusion
is that he just guessed at the changes and proceeded blindly.
I cannot see how I can be held responsible for the stupidly
incompetent actions of others.

sounds like a defense to me.

Stealth Pilot

Don't get me wrong, Stealth, I hear what you are saying.

But I think the kind of analysis you imply is beyond anybody
but Boeing (even Airbus seems to have problems getting it right).


Igor Sikorsky was quoted as saying:

There are good designers with good designs and
good designers with bad designs,

And there are bad designers with good designs
and bad designers with bad designs.

If all designers flew their own designs, there would
eventually be only good designers with good designs.


A little old Russian arrogance, but an interesting point.

On Wed, 11 Jan 2006 14:23:18 GMT, Richard Lamb
wrote:

No sweat, just a basic misunderstanding.

We design to a 4 G _yiield_ limit.

This is where the wing, after being stressed, no longer
returns to the original shape
It has reached the "plastic" limit and has deformed.
Yes, it has failed, but it did not break.

The 1.5 G safety factor then gives a 6 G _ultimate_ limit.
THIS is where the wing breaks.

mo better?

Richard


your brow not mine :-)

muchos mo betta.

Stealth Pilot

On Wed, 11 Jan 2006 14:38:02 GMT, Richard Lamb
wrote:



Stealth Pilot wrote:


your honour I sold the guy the plans, I provided him with the worked
design calculations showing how the design was arrived at. the
comments in the calculations show how the material sizes were arrived
at. he has made changes to the aircraft which are neither in the
original designs nor show any validating calculations so my conclusion
is that he just guessed at the changes and proceeded blindly.
I cannot see how I can be held responsible for the stupidly
incompetent actions of others.

sounds like a defense to me.

Stealth Pilot

Don't get me wrong, Stealth, I hear what you are saying.

But I think the kind of analysis you imply is beyond anybody
but Boeing (even Airbus seems to have problems getting it right).



no! simple aeroplanes like we're involved in dont have that
complicated a set of calcs. Evans did his for the vp1 in 25 pages.


Igor Sikorsky was quoted as saying:

There are good designers with good designs and
good designers with bad designs,

And there are bad designers with good designs
and bad designers with bad designs.

If all designers flew their own designs, there would
eventually be only good designers with good designs.


A little old Russian arrogance, but an interesting point.

he's absolutely right.

methinks itteration and access to other designs is what improves the
ante
Stealth Pilot

On Wed, 11 Jan 2006 22:08:05 +0800, Stealth Pilot wrote:

On Mon, 09 Jan 2006 18:43:22 -0800, Ron Wanttaja
wrote:

On 9 Jan 2006 12:16:29 -0800, "Lou" wrote:

I have to admit he does bring up a good point. I have often wondered
what the difference in strength's and weakness would be if I used
different wood in my plane, or enlarged the components for a larger
pilot.

Which is probably one reasons designers don't provide the equations. Many hate
it when folks make changes.

your honour I sold the guy the plans, I provided him with the worked
design calculations showing how the design was arrived at. the
comments in the calculations show how the material sizes were arrived
at. he has made changes to the aircraft which are neither in the
original designs nor show any validating calculations so my conclusion
is that he just guessed at the changes and proceeded blindly.
I cannot see how I can be held responsible for the stupidly
incompetent actions of others.

sounds like a defense to me.

And by the time you get to tell your side of the story to the judge, you're out
$20,000 or so in attorney's fees. Burt Rutan never lost a lawsuit...but he got
tired of defending himself and got out of the homebuilt business twenty years
ago. One homebuilt company in the '80s was destroyed defending itself against a
suit where the customer drilled into his engine case to install a gauge but
didn't bother to remove the metal chips. They won the case...but went bankrupt
doing so.

Ron Wanttaja