The previous two blogs looked at the ogive shape and its use in describing bullet shapes. While cruising around the web, I noticed a rather large ogive shape that I thought was interesting. I am a big fan of anything having to do with battleships, and the 16-inch projectiles fired by the Iowa-class battleships are an excellent example of a large ballistic ogive. They have an ogive radius of 9 calibers (i.e. 144 inches/ 16 inches = 9 caliber). For those interested in a modern discussion of these projectiles and how to improve them, I suggest this forum discussion.
During WWII, the Iowa-class ships fired two types of projectiles:
- Mk 13 HC (High Capacity)
A shell designed to carry the maximum amount of explosive. It was used for shore bombardment against "soft" targets. It weighed 1900 lbs. It is shown in Figure 1.
- Mk 8 AP (Armor Piercing)
This projectile is designed to destroy structures made of reinforced concrete or armored ships, like other battleships. This projectile weighed 2700 lbs. It is shown in Figure 2.
Figure 4 is a good illustration of the differences between the HC and AP projectiles. Notice how the AP shell is basically a big slug of metal that has a windshield on the front of it to make it aerodynamically friendly.
Figure 5 shows the actual pieces of an AP shell.
Figure 6 shows a dimensioned drawing of the HC projectile. Note that the fuze, which attaches to the nose, is not shown. The full length of the projectile with fuze is 64.00 inches.
To illustrate that these projectiles have 9 caliber ogives, I fitted a couple of 9 caliber radii circles to one of the photos (see Figure 7).
In this post, I showed that even large projectiles use the ogive shape. I collected some useful historical information into a single spot and will use this data in posts to come on ballistics.
See Figure 8 for a snippet from a US Navy manual that describes this projectile.