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

I've been looking into this pretty seriously recently. I've used SolidWorks
a little and ProE quite a bit more. But did that at work where I didn't have
to pay for those programs. I cant afford either of those for my own use.
Alibre has a parametric modeller that is actually in my price range. And
then there is Rhino which I think can be had for about $300 with a student
ID. Havent decided either way, but my goal is designing a motorglider
fuselage so leaning heavily toward Rhino.

Mike Wills