60 Dahlgren 



alongside the ship. We tested a lot of those bombs in drops against a deck 

 target — one that had various thicknesses of lighter plate and then some 2-inch 

 plates as well. 



In other work with bombs, we had, on several occasions, reports that dive 

 bombers operating at steep angles were having the bomb tails, after release, flip 

 up and knock holes in the undersurface of the wing. To solve the problem, we 

 put a bomb out on a wing rack and then in another bomb case mounted a 

 camera. I went over to sick bay and got a roll of adhesive tape and a lot of string 

 and cut that into pieces about 6 inches long. I took the adhesive tape and stuck 

 lengths of string all around the surface of the bomb mounted on the rack. We 

 then had the pilot make a dive, without releasing the bomb, and took pictures to 

 see what the airflow was like around the bomb. It was easy to see that the airflow 

 wa^ coming down on the nose and up on the back of the bomb, so what we 

 needed was a little L-shaped piece sticking down on the tail so the tail couldn't 

 nip up. 



We also had problems with what were called flexible guns in airplanes. The 

 fixed guns are built so that when you aim the airplane, you aim the gun. Then, 

 in some airplanes there was a man in the rear seat, and he had a gun that would 

 pivot all around, and this was called a flexible gun. They were interested in 

 windage effects on flexible guns. We rigged up all sorts of camera techniques 

 for firing tracers, photographing them, and seeing how far they drifted. 



Of course there was a lot of work done in figuring out how much yaw a 

 projectile or a bomb had. On one of the first jobs I had, we had a report around 

 1935 or 1936 from Admiral Nimitz in the Pacific Fleet that in battle practice he 

 had seen projectiles coming down and hitting the water flat and bouncing at 

 battle range. That would have been very bad because they wouldn't have 

 penetrated armor, so we set up a program, fired projectiles, and took high- 

 speed motion pictures of them. The projectiles weren'tyawing that much at all. 

 Then we received another report and had to get some more pictures. That time 

 we found out what was really wrong. The projectile was an armor-piercing 

 projectile with a large combination windshield and cap on the front end, and 

 what happened was that when the projectile went into the water, the cap broke 

 off, and it was thecap that came out of the water, bounced a couple of hundred 

 yards, and entered the water again. 



There was a lot of work with the guns, too; for example, the original 

 development of the 3"/70 gun. We did the experimental firing and tried to get a 

 gun that was known to have high velocity and a reasonable operational life. 

 There was a lot of just getting pictures and devising means of producing sharp 

 photographs of projectiles coming out of the gun to see the condition of the 

 rounds and if they had full rotation. Had they taken their full spin or had the 

 rifling been stripped off the rotating band? How much did a gun jump when it 

 fired? How do you measure jump? 



