to all those brains out there-help!!!     i don't have time or
money to waste on weak cad programs. i need a great cad program to
design a twin rotary amphibian. i am a newbie at cad. (no habits to
break) i will also be purchasing a dedicated laptop for the job.
suggestions on brand? thanks george g. on the vote for rhino. does
anyone else have experience they would like to share?

--
flyboy


I like Rhino.

Paul Lamar


A lot depends on what you want to do.  In the CAD world there are many
flavors of programs, but they usually are categorized into either
parametric
and non-parametric.

In very general terms, parametric programs allow the user to create
designs
where some dimensions are related others such that one can change one
dimension and have related dimensions automatically change.  For
example,
one might create a shaft with a bushing around it.  One could
specify that
the clearance between the shaft and bushing must always be a
specific value.
If you later elect to increase the size of the shaft, the bushing will
automatically increase in dimension so that the specified clearance is
maintained.  This is just one (simplified) example of parametric
behavior.

Non-parametric programs, do not respond as noted above.  If one
wishes to
increase the size of one part, the user is often required to
manually redo
the other parts.

SolidWorks is one example of a popular parametric design program
while Rhino
3D is an example of a non-parametric program.  Each has its respective
strengths and tradeoffs.

In addition to this feature, some CAD programs permit designers to
create
very smooth, very complex surfaces while others are more limited in this
capability.  Arguably, Rhino 3D currently permits users to create much
"nicer" surfaces as opposed to SolidWorks.  In this context, one
simplistic
example of "nicer" refers to how smoothly one surface blends into other
surfaces.  Imagine sighting down a car's body.  "Nicer" surfaces
will not
display kinks and obvious transitions while less nice ones may have
noticeable surface transitions.  This surfacing capability is one of the
reasons Rhino 3D has grown so popular among industrial designers,
and others
wishing to create smooth, nice looking shapes.  But don't misunderstand;
SolidWorks creates nice surfaces, but Rhino 3D does it better...at
least for
the moment.

If one accepts, for the sake of argument, that Rhino 3D has a more
powerful
surfacing capability, as compared to SolidWorks, and one is more
interested
in form design, it might be a better choice than SolidWorks.  On the
other
hand, if one is designing mechanical assemblies with a great number of
anticipated dimensional changes, SolidWorks might be the program to
choose.
Of course there are other programs out there and other criteria to
consider,
and there are certainly other features to consider, even between
Rhino 3D
and SolidWorks.  One should also not forget popular programs like
AutoCAD.

More recently, McNeel (producers of Rhino 3D) have addressed this
parmetric
issue by providing a well behaved path such that nice looking,
non-parametric shapes can be designed in Rhino 3D and then imported into
SolidWorks where the internal mechanical components of the user's
design can
better be designed to fit into the Rhino 3D shape.  Unfortunately,
if the
user later elects to change the size or layout of his mechanical
assembly,
such that it no longer fits inside the Rhino 3D shape, one has to go
back
into Rhino 3D to resize the enclosing shape.

Now, if cost is not a major issue, one can always use Catia from
Dassault
Systemes.  It is parametric and has very powerful surfacing
capabilities.
Catia is the standard for companies such as Lockheed and Boeing.
 But you
had better think it over.  A single user commercial (retail) version of
Rhino 3D lists for $995.  A single user commercial version of SolidWorks
lists for about $4,000.  And Catia goes out the door for $10,000 to
$14,000.


Then there is the issue of ease of use or the learning curve.
 Clearly, the
more features a program has, the steeper that curve may be for
people new to
CAD design programs.  Rhino 3D is alleged to have an easier learning
curve
as compared, say, to SolidWorks.  And some would argue that Catia is
even
more difficult to learn.

I happened to use SolidWorks for a lot of my mechanical designs, but
I am
also very familiar with Rhino 3D and often recommend it to those more
interested in esthetics.  I know that Paul likes Rhino and feels
that, up
until now, it has satisfied all his needs.  But Rhino would not have
permitted me to design the things I have, such as gearboxes for turbine
engines and other mechanical assemblies.

So, where does this all lead.  Personally, I would recommend SolidWorks
unless you are primarily interested in producing things with very
complex
surfaces.  Most amateur aircraft, however, do not involve such
surfaces.  I
know of one aircraft design being done by a close friend using
SolidWorks
which is outstanding.  I doubt that it could have been done in Rhino 3D.
There were many dimensional revisions which would have been
exhausting to do
in Rhino.

I don't know much about AutoCAD, so I'm in no position to comment
intelligently about it.  But I have used earlier versions of Catia
and think
that, for most amateur designers, it is overkill.

I'm sure that Paul has other views and know he will be responding to
this
message.  If he doesn't I'd be quite surprised.

George Lazik
Woodland Hills / Santa Paul California

I designed this gear box in Rhino and had it made in the same NC shop
George had his made :) I will say one thing about Rhino Ver 3. It
doesn't  do variable radius fillets worth a damn. version 5 is out
so I don't  know if they fixed this.

Cowls in aircraft are very important because you must fit all the
parts inside. Rhino does cowls much better than Solid Works.
It is tricky to do cowls but I can help. It took me about
a month to learn how to do them. Not 24/7 just off and on
for a month.

IMHO it is not worth $4000 for Solid Works.

Paul Lamar


Hi Paul

I have SolidWorks and it's very good but the learning curve is steep.

If Flyboy only wants' to design an airplane what about Aerologic link
attached.

http://www.aerologic.com/index.html

Might be worth a look?

Clive      England


Flyboy, I don't reccommend trying to use a laptop on any of the
better CAD systems. The screen size is too small and you will spend more
time resizing viewports than designing just to get things big enough to
see what points you  are picking. The second consideration is processing
power. The typical laptop is about 1.8 Ghz and dual core with 2Gb of
ram. This will operate the program as long as your model is small and
not very detailed or finely meshed. Using a desktop allows adding a
graphics card such as the asus 9800 or nvidia 9500 which have in excess
of 120 processor cores.( For some reason the radeon based Ati cards have
issues with CAD.) This shifts the on screen display processing to the
pci express-16  based graphics card for processing with a transfer rate
of 3 Gb/second. Anytime you zoom in or out the active viewport has to
regenerate. My current drawing is 230 mb which for the 4 viewports is
approaching 1 GB of display points.
  If you know where you are heading with a design and are using
more  of the editing type commands it doesn't take much to overheat a
laptop. If you find yourself waiting for the command line to display the
computer is maxed out during those times. If you use a laptop for
microsoft office or surfing the internet there is much more time for it
to dissipae the heat.  I have problems with any desktop having power
supply failures. 500 watts is the minimum that will survive and 650 is
more reliable.While running CAD or gaming programs the power supply is
at 350 to 400 watts output and that is a lot of heat to dissipate.  If
you run CAD on a laptop it will have to be plugged into the wall to stay
on for more than 20 minutes just like a deshtop.
   The best deal on the computer would be a used gaming computer
from craigs list or e-bay which are often priced at what I spend on
just the ram to build one. One with an nvidia (not ATI) video card and 4
GB of ram that is not running overclocked which can overheat the
northside bridge, the processor, and the video card.

george grimes