CAD Tool For Design Tiny Aircraft

Hi All,

I have never really used a CAD program to design anything. I toyed
with AutoCAD back in 1987 but nothing more.

I'd like to design a small model aircraft, about one meter in length.
Even though it's small, it's still complex. There are many mechanical
pieces.

The most important feature I need, by far, is interdependencies of
paramters. [There is probably a fancy name for this]. In other words,
if I change an artifact of the aircraft from one material to the
other, I would like the change to manifest in every aspect of the
aircraft that depends on the material. I guess this is standard
feature. I would like to be able to program interelationships also,
preferrably in C++, but a scripting language will do.

The other important feature is that I need the tool to be "3D-aware"
from the outset. I'm hearing others in rec.aviation.piloting that
AutoCAD is not entirely 3D-aware. I don't know what that means, and I
am definitely not interested in finding out by trial and error.

I post to CCS because the presentation of SolidWorks on its website
gives me the feeling that they understand these issues and attacked
them head on, but any CAD package would do.

Finally, I prefer cheap over expensive.

-Le Chaud Lapin-

On Tue, 25 Sep 2007 21:17:19 -0700, Le Chaud Lapin wrote in
om:

I have never really used a CAD program to design anything. I toyed
with AutoCAD back in 1987 but nothing more.

I'd like to design a small model aircraft, about one meter in length.
Even though it's small, it's still complex. There are many mechanical
pieces.

RCCad? It's 3-D.

http://www.rccad.com/

The most important feature I need, by far, is interdependencies of
paramters. [There is probably a fancy name for this]. In other words,
if I change an artifact of the aircraft from one material to the
other, I would like the change to manifest in every aspect of the
aircraft that depends on the material. I guess this is standard
feature. I would like to be able to program interelationships also,
preferrably in C++, but a scripting language will do.

I don't know whether it supports scripts.

The other important feature is that I need the tool to be "3D-aware"
from the outset. I'm hearing others in rec.aviation.piloting that
AutoCAD is not entirely 3D-aware. I don't know what that means, and I
am definitely not interested in finding out by trial and error.

A design program from a different standpoint:

http://www.davincitechnologies.com/AirplanePDQ.htm

It is CAD. I don't know whether it does 3-D.

Marty
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On Sep 25, 9:17 pm, Le Chaud Lapin wrote:
Hi All,

I have never really used a CAD program to design anything.
I am definitely not interested in finding out by trial and error.

I post to CCS because the presentation of SolidWorks on its
website gives me the feeling that they understand these issues
and attacked them head on, but any CAD package would do.

Finally, I prefer cheap over expensive.

-Le Chaud Lapin-

My recommendation is to get an overview introduction through a
school's CAD training class. CAD is only one small part of any design
& engineering project.

Cheap: As is commonly said, you get what you pay for. SolidWorks at
$4000 US may be considered expensive. A more important consideration
in the end, is when you have to supply 3D Solids files to people you
collaborate with and manufacturing companies for CNC work. You will
need to send them files in the format they need to do their work.

Learning to model in a 3D CAD program will NOT give you the elements
of mechanical engineering, design, & aircraft engineering specifics.
I would expect you to spend even more time learning engineering
issues, than the CAD side of the project.

Bo

The word you are looking for is parametric. SolidWorks fits this bill.
There are several ways to make components in SW work together. At the
most basic level geometry in one part can be tied to that in another.
To this can be added equations that relate different dimensions. To
this can be added design tables which are nothing more than
spreadsheets built into a part or assembly of parts that drives part
dimensions. And to this can be added control from an external program
like Excel (the most common) to Access to a custom written API
program.

As to cheap, well the question there is whether this is a hobby
interest or a business interest. If it is a hobby, no doubt the cost
of SW at 3,995 plus yearly maintenance might be a bit high, but for a
business it isn't much at all. In addition SW requires a fairly high
end PC to do the kind of thing you are talking about.

As with anything as complex as airplane design (you didn't say it had
to fly, but I am guessing it will) to do the things mentioned in the
first paragraph will require some training, some practice and probably
more questions on this forum.

TOP

"Le Chaud Lapin" wrote in message
ps.com...
I'd like to design a small model aircraft, about one meter in length.
Even though it's small, it's still complex. There are many mechanical
pieces.

Finally, I prefer cheap over expensive.

If your model plane doesn't require very organic shapes, then Alibre might
be a good choice and is cheaper than SolidWorks. If you need more organic
shapes and smooth transitions, SolidWorks would be a better choice, but it
can take a lot of work to get it right and the models will be less robust.
(You'll change a parameter and some feature far away may break.) If you need
really nice shapes, and don't have the time or patience to mess around, you
might need to go to the expensive guys, like CATIA and UGS. Jumping into
them from a non-CAD background would be really scary.

Jerry Steiger

On Tue, 25 Sep 2007 21:17:19 -0700, Le Chaud Lapin
wrote:

I'd like to design a small model aircraft, about one meter in length.
Even though it's small, it's still complex. There are many mechanical
pieces.

The most important feature I need, by far, is interdependencies of
paramters..

The other important feature is that I need the tool to be "3D-aware"
from the outset. I'm hearing others in rec.aviation.piloting that
AutoCAD is not entirely 3D-aware...

Autocad is NOT the program you want for something like an aircraft
design. "3D aware" is meaningless; even a program is 3D or it isn't.
Autocad is 3D nowadays, but its interface dates back to days when it
wasn't, and it shows. And parametrics (where one change can
automatically send changes rippling through the design) is highly
overrated (I'm sure I'll hear from the guys on CCS about this), though
it can also be very useful.

A fully 3D program is, IMHO, a must for any kind of design, anything
else is silly. A parametric modeler, however (like SWX and many
others) can be very cumbersome to use... and I've used a lot of them
over the years. Yes, if the design constraints are set up correctly
from the start, minor changes can be ridiculously easy... but if not,
or if you don't have a clear idea of where you're going from the
start, you can find yourself boxed into a corner and have to start
from scratch.

Personally, I prefer a pure geometry based modeler. Simple
dimensional changes affecting many components may take longer, but
it's far easier to make large sweeping changes if necessary, or switch
to an alternate design approach. Most of my work nowadays is large
machine design (though my degree is in aero engineering), for which I
use KeyCreator (formerly Cadkey). Same price range as SWX, though,
which I don't define as "cheap".

-Dana
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Personally, I prefer a pure geometry based modeler.

Users should have the option to use "a pure geometry based approach"
or a parametric approach in one package. Unfortunately at this point
they don't have this option. There is no reason KeyCreator shouldn't
add parametrics. Using parmetrics is often faster when creating parts
from scratch. Why Kubotek refuses to do this for KeyCreator is beyond
me.

The just announced KeyCreator V7 looks very disappointing because not
enough progress appears to have been made on direct dimension editing.
From what I can tell the only progress in this area is that faces can
now be angled when making direct dimensioning editing changes.

How robust do you feel "direct dimension" editing in KeyCreator is
now?

Where do you feel improvements need to be made?

Simple dimensional changes affecting many components may take longer, but
it's far easier to make large sweeping changes if necessary, or switch
to an alternate design approach.

Probably true but depends a lot on the skill of the user.

BTW, it appears to me that SpaceClaim is far ahead in regards to "pure
geometry" changes compared to KeyCreator. Too bad SpaceClaim insists
on a licensing scheme that will never work in machining job shops.
Same deal think3 tried. There is also no demo of SpaceClaim to try. At
least KeyCreator has a downloadable demo.

Has Bob Bean been removed yet? He's really holding KeyCreator back.


Jon Banquer
San Diego, CA
http://worldcadaccess.typepad.com/bl...mment-76366100

I am currently designing an aircraft to compete in a competition with
a specific goal and the way I'm proceding is as follows:

1) Select a published airfoil with characteristics that meet the
design goal/s. Use a free program like xfoil to help in the analysis.

2) Create a spreadsheet to compute the mass of the various components
based on material densities which is then tied to the airfoil lift
coefficient and vehicle speed to size the wing. It will calculate the
required moment arms to keep the MAC, aerodynamic center and CG where
they should be in relation to each other and size the wing and tail.
The wieght can also tie to the aircraft performance issues important
to you to size the power requirement which determines engine weight to
loop back through the previous calculations with the weight
correction. You could carry it further to cover strength analysis.

3) Create a model in the 3d modelling software you have access to (I
used Solidworks) and import it into a 3d CFD program to verify the
validity of your design (I used Ansys). You could probaly get a local
university student to take care of this step for you for next to
nothing.

4) Build and fly the prototype.

5) Repair the prototype and make adjustments.

I saw no need to create an executable. The spreadsheet was fast and
easy to adjust as required along the way.
There are quite a few programs available to do this that are not very
expensive but I personally didn't care for any of the ones I saw.



On Tue, 25 Sep 2007 21:17:19 -0700, Le Chaud Lapin
wrote:

Hi All,

I have never really used a CAD program to design anything. I toyed
with AutoCAD back in 1987 but nothing more.

I'd like to design a small model aircraft, about one meter in length.
Even though it's small, it's still complex. There are many mechanical
pieces.

The most important feature I need, by far, is interdependencies of
paramters. [There is probably a fancy name for this]. In other words,
if I change an artifact of the aircraft from one material to the
other, I would like the change to manifest in every aspect of the
aircraft that depends on the material. I guess this is standard
feature. I would like to be able to program interelationships also,
preferrably in C++, but a scripting language will do.

The other important feature is that I need the tool to be "3D-aware"
from the outset. I'm hearing others in rec.aviation.piloting that
AutoCAD is not entirely 3D-aware. I don't know what that means, and I
am definitely not interested in finding out by trial and error.

I post to CCS because the presentation of SolidWorks on its website
gives me the feeling that they understand these issues and attacked
them head on, but any CAD package would do.

Finally, I prefer cheap over expensive.

-Le Chaud Lapin-

On Sep 27, 6:16 pm, Dana M. Hague
d(dash)m(dash)hague(at)comcast(dot)net wrote:
A fully 3D program is, IMHO, a must for any kind of design, anything
else is silly. A parametric modeler, however (like SWX and many
others) can be very cumbersome to use... and I've used a lot of them
over the years. Yes, if the design constraints are set up correctly
from the start, minor changes can be ridiculously easy... but if not,
or if you don't have a clear idea of where you're going from the
start, you can find yourself boxed into a corner and have to start
from scratch.

Personally, I prefer a pure geometry based modeler. Simple
dimensional changes affecting many components may take longer, but
it's far easier to make large sweeping changes if necessary, or switch
to an alternate design approach. Most of my work nowadays is large
machine design (though my degree is in aero engineering), for which I
use KeyCreator (formerly Cadkey). Same price range as SWX, though,
which I don't define as "cheap".

I read all the responses and looked around the 'Net, and it seems that
SolidWorks, if not what I'm looking for, is create by people who had
the mindset I was looking for.

But now I am confused. I thought parametric modeling was good.

I program computers from time to time, and being able to change the
structure of a component and have everything that depends upon it
change accordingly is simply invaluable, so I cannot see why this
would be bad. That's precisely the behavior I want.

For example, in my miniature aircraft I envision, there is only one
fuel tank, and it's cylindrical, but its radius and length are a
function of several other parameters.

I am guessing that, like in programming, there is an art to
structuring the interdependencies so as to minimize likelihood of
running into dead-end that you mention.

Finally, I was really surprised to learn that parametric modeling was
not fundamental in all CAD programs. I cannot imagine what it would
be like to try to optimize a design without it. What do people do
without parametric modeling? Tweak every single component manually
during optimization phase?

[I am going to give Alibre a look also.]

-Le Chaud Lapin-

On Sep 30, 7:27 pm, Le Chaud Lapin wrote:
On Sep 27, 6:16 pm, Dana M. Hague





d(dash)m(dash)hague(at)comcast(dot)net wrote:
A fully 3D program is, IMHO, a must for any kind of design, anything
else is silly. A parametric modeler, however (like SWX and many
others) can be very cumbersome to use... and I've used a lot of them
over the years. Yes, if the design constraints are set up correctly
from the start, minor changes can be ridiculously easy... but if not,
or if you don't have a clear idea of where you're going from the
start, you can find yourself boxed into a corner and have to start
from scratch.

Personally, I prefer a pure geometry based modeler. Simple
dimensional changes affecting many components may take longer, but
it's far easier to make large sweeping changes if necessary, or switch
to an alternate design approach. Most of my work nowadays is large
machine design (though my degree is in aero engineering), for which I
use KeyCreator (formerly Cadkey). Same price range as SWX, though,
which I don't define as "cheap".

I read all the responses and looked around the 'Net, and it seems that
SolidWorks, if not what I'm looking for, is create by people who had
the mindset I was looking for.

But now I am confused. I thought parametric modeling was good.

I program computers from time to time, and being able to change the
structure of a component and have everything that depends upon it
change accordingly is simply invaluable, so I cannot see why this
would be bad. That's precisely the behavior I want.

For example, in my miniature aircraft I envision, there is only one
fuel tank, and it's cylindrical, but its radius and length are a
function of several other parameters.

I am guessing that, like in programming, there is an art to
structuring the interdependencies so as to minimize likelihood of
running into dead-end that you mention.

Finally, I was really surprised to learn that parametric modeling was
not fundamental in all CAD programs. I cannot imagine what it would
be like to try to optimize a design without it. What do people do
without parametric modeling? Tweak every single component manually
during optimization phase?

[I am going to give Alibre a look also.]

-Le Chaud Lapin-- Hide quoted text -

- Show quoted text -


Suggest you find your way ASAP to www.kubotekusa.com and view their
video on direct dimension editing to see what can be done without
parametrics.

Jon Banquer
San Diego, CA
http://worldcadaccess.typepad.com/bl...mment-76366100