Ahoy Martellus,

That looks pretty cool! It's been a while since I've heard about anyone attempting to develop electric-powered torpedoes for RC combat. Most people just want to put a few bottle rockets in their boat and call it a "torpedo", which we obviously cannot allow into battle for safety reasons. Your efforts have also gone far past most electric torpedo supporters, in that you have actually built a real physical prototype rather than just a sketch. So I will do everything I can to support you.

First, a quick summary of long-ranged torpedo development so far.

The basic efforts have been split between electric powered torpedoes, and gas powered torpedoes. Electric torpedoes have a potentially longer range, but are also more expensive and complex to produce. Furthermore, a sufficiently small electric-powered torpedo is almost impossible to get moving fast enough to penetrate balsa, so some sort of warhead must be used. Designing a useable warhead has stymied electric torpedo development so far, since the torpedo must be 1) able to penetrate balsa, 2) non-pyrotechnic, and 3) safe for humans to get hit. Nobody has yet to develop an electric torpedo warhead that meets all three requirements.

Gas powered torpedoes seem to have more potential. gas power allows a torpedo to achieve sufficient kinetic energy to penetrate balsa. Not harming people is a simple matter of regulating the pressure of the gas, so that the torpedo meets the same safety standards as all other cannons in the sport. One obstacle to overcome is miniaturizing the launching gear enough to fit in a 1:144 scale submarine or cruiser. The other problem that must be overcome is how to handle surfaced launches. Gas torpedoes work fine when launched from underwater, but how do they handle when launched from above the water? If the result is hazardous to humans, then it's a no-go. I have not experimented with this, nor have many other RC combat skippers. It is unfortunate, because the idea certainly deserves more development than it has currently received. Perhaps you could be the one to make it work in combat.

A third option that many newcomers overlook is to simply use more hydrodynamic shaped projectiles from ordinary torpedo cannons. This technique is already being used in RC combat today, and it provides a significant improvement over a single 1/4" ball bearing. There are several variations of this concept in use today.
1) multiple balls in one barrel. If you've ever ridden a bicycle behind a car, you are familiar with the concept of drafting. By loading two or three 1/4" balls into a single cannon barrel, you can get the 2nd and 3rd balls to draft of the 1st, increasing their underwater penetrating power. The cannon must still pass the 2-inch foam safety test (ie not completely penetrate 2" of white insulation foam from 1 foot away), but double- or triple-shotting a cruiser's torpedo cannons can boost underwater range from 1-2 inches to 2-3 inches. This may not seem like much but in practice it's the difference between sinking a target and scratching the target's paint.
2) a .24 caliber bullet, loaded so that the blunt end hits the target. This is only allowed in a few clubs and only for submarines. It is essentially a somewhat more massive projectile with a somewhat teardrop shape. This improves underwater range for submarine torpedoes, although the exact amount of benefit is unknown. There are very few submarines in the hobby, so nobody has done any empirical testing with .24 caliber bullets. As usual, the same safety testing applies, so the improvement is for a projectile that does pass the penetration test (not too much penetration).
3) solder a brass tube to a 1/4" ball. This technique reportedly works very well, but I have not seen it used since I joined the club. The idea is that a 1/4" ball plus a short length of brass tubing makes a much more hydrodynamic shape than a 1/4" ball by itself, and thus travels through water much better. In addition, the hollow inside of the brass tube traps a bubble of air, which helps submarine-launched torpedoes skim the surface to hit the penetrable area of a ship, rather than travelling too deep. From what I've heard, a 1/4" ball plus brass tube is able to penetrate balsa through up to 12" of water, although I am somewhat dubious. I have not had the fortune to see one of these projectiles in action so I cannot say for certain how well this method works.