Down&Dirty

I am drawing a 37% Extra in AutoCAD 2004. I have figured out how to draw complex shapes, such as the turtledeck, using the "ruled surface" function, but that only creates a "shell" of the correct shape. If I want to make a union of the turtledeck and the lower fuselage (which is a solid), I need to be able to draw the turtledeck as a solid. How do you 1: convert a surface shape into a solid, or 2: draw the complex shape as a solid from the start?

Also, I'm having a real difficult time modeling the cowl. Any tips or tricks?

Tall Paul

I draw parts like that seperately, and merge the parts along the join line. Still two parts.
Haven't done much AutoCad recently but for cowls I recall getting the basic shell, then exploding that into individual segments, and stretching those segments to fit the odd contours.
But that was years ago, I hope the process is simpler today.
RTFM and play around with the stuff. Sometimes work-arounds suggest themselves.

cappio777

My Feedback: (2)

As TallPaul mentioned, there are parts that cant be modeled in one shot so it takes the cleverness of the operator to figure out the easiest way to do it. I like to extrude the basic shape of the cowl then use the boolean operators to add or substract from that shape. Another way is to draw formers as to how you think the cowl (part) would look like at that point and extend it to the next one using the ruled surface. The problem with that is that if the part has an extensive amount of curves and contours the ruled surface transition will not give you the contours you want. Sometimes its a combination of many things. What kind of cowl are you trying to draw? Something like an Extra 300?

Down&Dirty

Thanks for the tips Tall Paul and Cappio.

I am modeling the parts separately, but I want to join them into one cohesive solid model. The reason for this is that a friend of mine is going to use the 3D model I am drawing to have mold plugs CNC machined out of foam. I'm not that familiar with CNC machining, but I think the drawing has to be one solid model rather than a bunch of component models that are not joined in any way.

Cappio: I am trying to model the cowl for the Extra 300 pictured in my first post. You are right about the ruled surface function not yielding the right contours. I'll keep messing around with it

Thanks

cappio777

My Feedback: (2)

Down, I dont know much about CNC specs but if thats the case just model the with the solid object comands. The boolean operators will let you join all the parts at the end to a single solid object. Converting a surface to a solid is something I havent done but I can check my books and will post and answer later.

jacs

Ask your friend if his CNC cutter program don't use surfaces only because overhere our's does. Either try to make a subtract on a solid with your surface and then subtract from another solid. Sometimes you need to use a tool to make complex shapes and I don't remeber if you can make a cut with a surface (In Unigraphics we only trim a solid with a surface and we are done).

Surfer Dude

Hey Down and Dirty hoy did you do the turtle deck and the Airfoiled Rudder? I can;t for the life of me figure out how to do it.
Thanks
Chris

OldRookie

My Feedback: (13)

I am just starting to learn AutoCad on my own. I am learning by trying to do the things that I'm use to doing with my CAD program at work. I'm starting to get the hang of using AutoCad, but it is going to be a wile before I am comfortable with it.
I was wondering, how much experience did you people have with AutoCad before you were doing the type of things you are discussing in this post?

Greg

Alex Titoff

Hi Down&Dirty.
I was using AutoCAD 2004 to recreate my Extra330L Electric for balsa after "one-point-land"[&o].
The cowl i created as solid using boolean operations on torus and cube.
I do not mind sharing this file? so if you what it give me you e-mail.

cappio777

My Feedback: (2)

Old Rookie, once you know the basics of 2-D design moving into 3-D solids and surfaces its not that hard. Learn how to use the solids menu (extrude, union, intersection...etc) creating basic shapes like boxes and cylinders. Learn how to use your UCS, make it work for you. Its easier to draw objects if you are looking at them perpendicularly, thats when UCS is your best friend. Then move on to draw a square box fuselage where you can SLICE away sections as if you are carving a piece of wood. Start simple and progress from one drawing to another. Dont complicate your first drawing with too many ideas and "curves"....you will learn that on the next design. In reality it took me a couple days to become proficient on 3-D after I understood the 3-D menu. Like anything else......practice practice practice.

Down&Dirty

Hover King-

Drawing the turtledeck and fin is pretty easy once you know the cross section shapes at either end of the part. For the turtledeck, just draw the bulkhead shape just behind the canopy in 2D and draw the shape of the fuse at the rudder hinge line (basically a rectangle because it tapers to the thickness of the rudder post. You also need to make the arc shape a "polyline" so that when you click on it the whole line is highlighted, not just one segment. Then in 3D space, set the two shapes you've drawn at the correct distance from one another. Then just use the "ruled surface" command (see help files), and select the two polylines you have created. The ruled surface function automatically creates the shape of the turtledeck for you.

One other thing: in AutoCAD the ruled surface function defaults to 6 sides which will give your part a faceted look. To smooth it out, type "surftab1" and reset it to 25 or higher, and then do the ruled surface. That will smooth out the contours of the part.

Tall Paul

.
AutoCad has a STEEP learning curve, especially when you go into 3D. Follow the rules, and it will be less painful. Nothing like doing a drawing in ISO, and then finding one of the points is over in Bakersfield, when it looked so good on the screen!
The only way to learn it is to use it, manual at the ready.