The Rocket’s Fins
Now it’s time for the fins. For the fins, you’ll need to use an interesting little trick to create the curves, but once you’ve made one basic fin, you’ll be able to make two exact copies of it to save time. The trick to the fins involves creating what’s called a hole object and using it like a cookie cutter to remove unwanted areas of a solid object.
You’ll find as you continue to work with Tinkercad that the application sometimes requires you to be a bit creative in order to get the shapes you want. As you can see by browsing the Geometric section of the toolbar, there is no fin shape. But that’s not going to stop you. You can first focus on the outer curve of the fin shown in the sketch in Figure 4.17.
FIGURE 4.17 A fin will be a small sliver of a larger object.
As you can see, the outer edge of the fin is actually a piece cut out of a stretched circle. You’ll first create a flattened cigar-shaped oval that has the curve you want for the outer edge. You’ll do this by dropping a thick tube object on the workplane, as shown in Figure 4.18.
FIGURE 4.18 Start with a thick tube object.
Flatten the tube to 2mm in height and stretch the tube to get the curve you want. Figure 4.19 shows that I’ve flattened the tube to 2mm and dragged one of the other white dot controls to give the finished oval dimensions of 18mm wide by 35mm long.
FIGURE 4.19 The flattened oval is the start of a fin.
Next, cut the tube object in half vertically by creating a 2mm-thick rectangle to cover half of the tube. Figure 4.20 shows that I’ve dropped a box object onto the workspace, shrunk it to 2mm in height, and matched its width and length to that of the tube object. (The width is 18mm and the length is 35mm.)
FIGURE 4.20 The flat rectangle will help cut the oval in half.
Now, here’s the trick: Select the rectangle object and then click on the Hole button indicated in Figure 4.21. Notice that the rectangle will change from a color to a clear outline.
FIGURE 4.21 Turn the rectangle into a hole object.
Now, drag the rectangle so that it covers half of the oval object. Figure 4.22 shows the rectangle object overlapped over the oval.
FIGURE 4.22 Overlap a solid object with a hole object.
Finally, drag and select both objects so they are outlined. Likewise, you can hold down the Shift key and click on each object to perform a multiple-select action. Figure 4.23 shows that the clear hole object and the orange oval are selected.
FIGURE 4.23 Select both objects to be combined.
Click the Group button. This instructs Tinkercad to combine the two objects into a single object (see Figure 4.24).
FIGURE 4.24 Group two or more objects together to create a single object.
As you can see, the outer hole objects will be treated as empty space and will delete or erase any solid objects they encounter. This means that half of the oval object will disappear. Keep in mind that Tinkercad must perform some calculations to determine where solid material and a hole intersect, and this can sometimes take a minute or two for complex combinations. When the calculations are done, the final piece that is left exists as a single object, as shown in Figure 4.25.
FIGURE 4.25 The final object consists of material not combined with the hole object.
Now take a look at Figure 4.26, and you’ll get an idea of how the final shape of the fin will be accomplished.
FIGURE 4.26 A sketch of how the final fin will be made.
To make the inner curve of the fin, you need to create another unique object on the workplane and then convert it to a hole object. Then you will group the new hole object with the half oval in Figure 4.25, which will yield the final desired fin shape. The dimensions of this second oval piece are 49mm x 64mm. Figure 4.27 shows a new oval object, flattened to 2mm and shaped to get the desired inner curve.
FIGURE 4.27 A fin will be a small sliver of a larger object.
After selecting the new shape and clicking the Hole button, drag the two objects together, as shown in Figure 4.28. You can see that the final shape of the fin will be the bit that’s not covered by the hole object.
FIGURE 4.28 Creating the final fin requires another hole object.
When you’re happy with the fin shape, select both objects and click the Group button again. The hole object disappears, along with any solid sections of the oval object, leaving only the final fin shape, as shown in Figure 4.29.
FIGURE 4.29 The final fin shape.
Now all that’s left is to create two more fins. The fin should already be selected because when you group two objects, the final object is always selected when the grouping task is complete. You can simply make a copy of the object by pressing Ctrl+C on a Windows computer or Command+C on a Mac. You can also click on the Edit menu, as shown in Figure 4.30, and then click the Copy option.
FIGURE 4.30 Copy the fin object and make two more.
Select the Edit menu again and click the Paste option to have a copy of the fin object placed on the workspace. Instead of using the menu, Windows users can press the Ctrl+V shortcut, and Mac users can press Command+V.
A pasted copy usually overlaps the original by a small amount. Just click the copy and drag it to a blank area of the workplane. Figure 4.31 shows my three final fin objects.
FIGURE 4.31 Three fins, ready to be attached to the rocket.
Zoom out a bit, and you can see all your parts ready for assembly to make the rocket and the launchpad, as shown in Figure 4.32.
FIGURE 4.32 All the objects are ready for assembly.
Up next in Chapter 5, you’ll learn how to combine the parts. This will involve some stacking and centering of objects as well as some rotating of parts (such as the fins).
Before you leave this chapter, think about some of the new skills you have acquired in Tinkercad:
- Dragging an object around on the screen—This involves simply clicking and holding on an object and placing it where you want it on the workplane.
- Zooming in and out—This will be useful when you want to get closer to a particular piece (such as one of the fins) for detail work or to view all your work at once.
- Resizing objects—By using the white dot controls, you learned how to modify an object’s width, length, and height.
- Changing color—Changing the color of an object can make distinguishing parts of the larger model easier. Once parts are combined, a single color can be selected.
- Converting an object to a hole object—By creating an object and turning it into a hole object, you can remove material from a solid object.
- Selecting multiple parts—You can select more than one part at a time by holding down the Shift key and picking them one by one or else dragging a rectangle around them.
- Copy and paste—Copying and pasting copies of an object will save you lots of time when you begin making more complicated models.
You’ll be learning many more Tinkercad skills in the chapters to come, but for now, feel free to create a new design of your own and play around with the other shapes available in the Geometric section. Take some time to experiment and use the skills you’ve acquired so you’ll feel confident using them throughout the remaining chapters. See you in Chapter 5.