As we mentioned earlier, we are going to test for water-tightness at every stage of construction. This is just done by filling a sink with water, and putting the part of the model into the water until the water, is nearly at the lip, for a minute or two. We look carefully for any sign of water coming through the model. You can see this in the following image with the bottom-half of the duck before adding the ballast clay.
It's important to not only let the silicone sealant dry, but let it cure for at least 24 hours before doing this:
After the success of this test, we fill the ballast section with modeling clay, and do it again for two reasons:
- We want to make sure we didn't pack it with too firm a hand (breaking a seal)
- We need to make sure that the water line comes up to the right level
The bottom-half with the clay pack is shown in the following image:
Awesome! Now that our duck is packed with 2 lbs of clay, we're sure that there's no way it's going to capsize. Also...