This is a “spear" gun for playing in the pool. It shoots PVC pipe “spears”. I printed the spear tips in TPU to minimize the chances of injury. (I have 4 kids who will likely shoot each other.) I wanted a way to shoot my pool torpedos, but came up with this instead.

The tigger has a couple of rubber bands to ensure it automatically latches when you pull the spear back into position. The spears need to have a notch cut out of them about 1" from the tip for the trigger lock to catch on.

The design can be used with either surgical tubing or a bungee cord as shown in the pictures. To lock the surgical tubing in place jam a 10mm bearing into the tubing or print one of the 10mm tubing locks for each side. It stops the tubing from being able to pull back through the slots. If you go with the bungee cord I would suggest bending the hooks back to the body so you don't get caught on them.

The trigger and trigger lock are held in place with a 20mm and 25mm long M3 bolt respectively. I uses rainbow loom elastics because I have kids and they were all the craze at one point but any small elastic should do. PVC irrigation pipe comes in schedule 40 and schedule 80 where I am from. Both have ½" outer diameter but different wall thicknesses. I have made nocks and spear tips for each.

All parts were printed with 4 perimeters and 15% infill except the trigger lock which I suggest printing solid as it takes a lot of the stress. The action can be printed with very minimal supports as shown in the pictures and I just took a rounded bastard file to clean up the part where the spear slides through.

For surgical tubing/spear lengths that work I have tried:
Tubing: 14" (35 cm) Spear: 12" (30 cm)
and
Tubing: 18" (45 cm) Spear: 16" (40 cm)
both seem to work reasonably well.

I have shot myself point blank and didn't find it painful, but of course use at your own risk and I highly suggest eye protection. My family usually wears goggles in the pool anyway. I hope to get a chance to make some targets that float or sink once you hit them but wanted to get this out before pool season ends.

I haven't come up with a way to make “fletching” so that the spear shoots a little straighter. If anyone has ideas please feel free to remix. Oh and be sure to drain the air from the spears before you shoot or they will bob to the surface really quickly.

Have fun!