Lesson 2, expanding on what we've done in starting out

I'm working on this next lesson now. I hope that you have become familiar with what we did in Lesson One, under the topic, "Starting out".

If you are real new to CAD, don't be afraid to play around in your system. It'll help you learn where, and what, the commands are.

Don't be afraid to post, in the thread, "Starting out", your experiences with lesson one along with the differences, and solutions in different systems.

We can all help each other out here if we try

I thought today would be a good day to start with the second lesson, so here goes.

You should have two lines, crossing 90 degrees to each other to start with.

The goal today will be to draw the nose ring, and the first two bulkheads, generally known as F-1, and F-2.

Since this is a generic set of bulkheads we will assume some demensions.

We will be using a 2" spinner.

The engine requires 1.25" between the mounts.

The motor mounts are 3/8" X 1/2" hardwood.



Let's begin.




We are going to start off with the command "Offset". This is about the most useful command in any Cad system. Some systems call it "parallel copy", or something like that.

In AutoCad, type "O", upper or lower cas, it doesn't matter, and hit enter, or right click your mouse. This is the default short cut to Offset. You can use your mouse if you prefer to click on the offset icon.

Look at the command line on the bottom of your screen. It should be asking you how far, or what distance to offset.

Let us assume that the line running horizontally is your thrust line, and we want to define the extent of the 2" spinner.

Enter 1, for 1 inch at the keyboard. and left click the mouse.

The command line now asks you tp pick the object, or line, you want to offset. Place your cursor on the horizontal line and left click. (pick)

The command line now asks you which side of the existing line you want to offset.

Move your mouse cursor to the side of the line you desire, and left click.

Now, you are still in the offset command lines, so, since we want two lines, 2 inches apart, move your cursor over the line again, Left click, and then move to the opposite side of the line, left click again, and you now have another line exactly 1 inch below the original horizontal line, for three lines total.

The top and bottom lines are exactly 2 inches apart.

Now, right click, to close out your command string. The command line should read simply "command", indicating that it is waiting for your next command.

Let's move the verical line to the left hand end of our horizontal line.

Type "M" and right click. Right click is about the same as enter. The command line now asks you to select objects, (You can move more than one object at a time.)Place your cursor on the line, in this case, and left click (pick). Follow with a right click, (execute).

The command line now asks you to pick a base point or displacement.

In this case, you want the intesection of the original two lines. Most system have default setting for intesection, and will try to set to the intersection automatically.

Left click, and the command line asks you to move the object to where you want it.

Move the line to the left hand side of the horizontal line, towards the end. Most systems will automatically pick to the end unless you tell it differently. Left click.

Your command line is now ready for the next command.

Let's draw the nose ring.

Type C, and hit enter. C is the shortcut command for Circle.

The command line is asking for several defining points for the circle, but we are going to use center, the default.

Place your cursor at the intersection of the thrust line and the line we just moved. It should highlight, showing it is set to the intersection. You can manually specify intersection, by typing int,enter, the shorthand for intesection.

Once the intesection is specified, left click.

The circle is started, but now we need to define the size of the circle. Since we have two lines 2 inches apart, we can stretch the circle up, or down, to the intersection of one of these lines, and left click. We now have a circle exactly 2 inches in dia.

The command line is now waiting for our next command.

There's another way. Remember in the first lesson, there's always more than one way to do something in a good Cad system.

Type C, or use your mouse over the icon, to select circle.

Use the cursor to select the intersection, or spot, where you want the center of the circle to be. left click, or hit enter on your keyboard.

The command line is asking for a radius, or diameter dimension. Type r, (for radius) hit enter. Type 1 (For the distance of the radius, 1 inch)Hit enter, and there's your circle,exactly 2 inches in diameter.

Let's make the nose ring with a 1.5" opening in the center.

Type O, hit enter, or right click. The command line is asking for a distance to offset. Since we have a 2 inch circle, and we want a 1.5 inch circle inside of the first one, we need to offset .25 inches.

Type .25, and hit enter, or right click.

Now, select the circle with your cursor, left click, The circle changes appearance, indicating it's status as selected, move the cursor to the inside of the circle, since you want a smaller circle inside the first one, and left click again. there's your new circle inside the first. Right click, or hit enter to finish the command.

Since this is a work drawing, and we are not trying to actually align up with proper offsets and moments as if we were drawing a model, we'll now draw a generic set of bulkheads.

Let's start with F-1, the firewall.

We will make the fuselage top line, .75 inch above the thrust line. The bottom of the fuselage will be 2 inches below the thrust line. In this case, we want to be able to slide the tank in and out, right behind the engine.

Let's clean up what we have first.

Erase the top and bottom lines, leaving just the thrust line.

You should know how to do this, we covered it in the first lesson.

let's extend the thrust line to the far side of the circle.

There are several ways to do this. AutoCad has a neat little function called "grips".

Set your cursor on the thrust line and left click with an empty command line.

The line takes on a dotted characteristic, and there are small blue boxes on the line, usually at both ends and the middle.

Place your cursor over the box closest to the dirction you want to go. In this case, that will be at the center of the circle.

Did you notice that your cursor sort of snapped into place when you were close to the proper point? Left click, and the bock changes color to red, which means it has been selected.

Now, drag the line to where you want it. If you want to be sure you are dragging it exactly horizontally, then make sure you've entered F8 to toggle ortho on first.

Grips is pretty handy, and can do several differnt functions, but it has some idiosyncransies that can catch you unawares. Go ahead and play with it a bit to see what it can do. remember undo, and oops can usually get you back where you started.

Left click, and you now have the command line showing it's ready for your next command, and it is, but the line you picked still shows it's ready for grips. Any command you make will now be performed on the gripped line. type "e", the line is erased, 'U' for undo will get it back. this is not always good, so here's an easy way to get out of it.

On the upper left hand side of your keyboard, hit Esc.

Everything is now ready to go without affecting the line you gripped.

Ok, there's another way to do it. (Always is)

Type ex, shorthand for extend, right click, or use your cursor and pick the icon.

Notice the command line, it wants you to select a line or object to extend to. Place your cursor on the larger circle and right click. The circle changes appearance showing it is selected. Now place your cursor on the thrust line, and left click. the line will extend to the outer circle. right click, and a small box opens, cursor on enter, left click. Or simply enter from the keybopard once the line has extended.

To start out our F-1 bulkhead, we want a centerline first. We can offset, Copy, or simply draw a new vertical line. Since you know how to draw a line, and that's the easiest solution, we won't use that here, because I want you to learn a new command. Same goes for Offset now.

We are going to use copy. Another very useful command.

Type CP, enter, or right click, or use your cursor to pick the copy icon.
The command line is asking you to select the objects you wish to copy.

Select the vertical line with your cursor. Left click, and the line changes appearance, showing it has been selected.

Right click and the command line asks how far you want to move. We do not need an intersection since we are still in the ortho on (f8 toggled on) mode, so we can pick any point in space and the line will move in a straight line in the direction the cursor moves. Left click to select the base point, move the cursor to the right placing the line where you want it, left click again, and you are finished.

Since the bulkhead is symetrical, exactly the same both sides of the centerline, we only have to draw one half of the bulkhead.

First, let's offset the thrustline up .75 inches, and 2 inches down.

Do you remember how to do this?

Sure you do. If you have any questions, reread the directions above.

We need 1.25inches for the engine to clear, so half of that distance would be .625, or 5/8 inches. Let's offset the center line 5/8" to the right.

OK, did you do that?

Now, our normal hardwood mounts are 3/8" X 1/2", usually used with the widest dimension in the vertical plane. So, let's offset once more. This time we'll offset the inside of our motor mount, that line we offset 5/8 inches, 3/8" to the right. Autocad as well as many other systems will allow inputing numbers either as decimal, or fractions.

A little helpful trick when doing multiple commands.

Oftentimes, it is possible to go right back into the command by right clicking once more, after you get a new command line.

OK, for clarity, while you are learning, let's clean up some of the mess we are making. As you become more proficient, you may find that you can see what you are doing even with the mess.

Do you remember the trim command from the first lesson?

Trim off all lines to the left of the centerline, except for the thrust line. Next, trim all lines above and below the top and bottom of the bulkhead, except for the centerline.

Use fillet to square off the remaining upper and lower horizontal lines. Use a zero radius.

We can now offset the thrust line up .5 inches to allow for the motor mounts.

Trim the far right line, where the motor mounts will go, by using the thrust line, and the line you just offset as cut lines.
Once the cut lines are selected, take out the 1/2 inch long segment.

Let's next use fillet, with a zero degree radius to clean up the cutout for the motor mount.

You now have half of a bulkhead, and actually this half is good for F-2. Yes, but we were drawing F-1 weren't we?

Yes we are, and don't worry, we're almost done. Let me show you the magic.

We are going to first make sure we have enough room. Move the half bulkhead over about 3 inches to the right.

Remember the move command, it was one of the first we learned today.

Now, copy the half bulkhead, and set it between the nose ring and the first half bulkhead.

With the bulkhead in the middle, the one that will become F-1, we need to be able to slide the tank in and out from behind the engine. This means that the bulkhead will be cut short to the bottom of the motor mounts.

Use the extend command, and extend the bottom motormount to the centerline.

Use fillet to make a clean line returning to the centerline.

Erase the two remaining, unconnected lines.

You now have a half F-1, and a half F-2.

Let's use a new command called Mirror.

Type mi, the shorthand for mirror, right click, or use your cursor and pick the icon.

Using your cursor in a right to left dragging window, (Remember what that does, from the first lesson?)select all but the centerline of the small bulkhead.

right click, and the objects selected change appearaqnce.

The command line is asking you to select the mirror line.

Place your cursor on the intersection of the top line, and the centerline. left click, now move your cursor down to the intersection of the bottom line and the centerline, and left click again.

The command line asks if you want to delete the first items selected. In this case, and most cases, the default answer, No, is the correct answer, so, double right click. -1 bulkhead.

Now do the same thing to make your F-2 bulkhead.

You can leave your centerlines if you wish, or erase them at this time.

OK, you've learned some very good and powerful drawing commands in these first 2 lessons.

Your assignment.

Take what you've learned and see how much of an airplane you can draw using only the commands we've covered.

I'd like a report.

Good luck.

Hi John, would iot be possible for you to post a pic of your completed dwgs so we can see if we got it right

>Hi John, would iot be possible for you to post a pic of your
>completed dwgs so we can see if we got it right

A good idea,

Here's what I ended up with on this lesson.

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Attachment #1, (jpg file)

Got it.

I'm finding that Turbocad uses a quite different set of commands; generally fewer keystrokes--more streamlined. It'll be good once I learn more of it; right now it makes it sort of "hunt and peck" before I make a step work right.And it's more drop-down menu driven, rather than keyboard entries.

So far so good.

--Ray

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