Hi there I'm Matt and I am a geek. I love the RPG scene and intend on going to an event held in Derby but, for reasons of personal torment, I want to make the relevant equipment myself. In this case 1 sword two . . . well . . . let's say "ranged" weapons for now. The foam sword needed wasn't hard LD45 plastazote foam + 1m carbon fiber tube + dyed latex = done. Then I got a bit cocky and out of my depth with springs. Basically I know in events people use a bow (30lbs draw at 28") and arrow (with the head being a big lump of foam for obvious safety reasons) but that got me to wondering why not make something new? I'd already done so with the sword being a flammard to the traditional straight longsword affair. I looked at repeating crossbows and so on but the problem in this case was more with the arrows as, to make them safe, they had lost all of their aerodynamic capabilities. So I came up with the idea to have discs of foam fired by a launcher where the wooden leaf spring is replaced with a smaller metal one. This is where my ignorance starts to jump up and down waving flags as it goes. I tried to work out the amount of energy stored in the wooden bow by taking the draw length of 0.7112m (converted into m from 28") the draw weight of 13.6077711kg (as the force of 30lbs converted into kg) and by using the equation E=half the spring constant (which I got as 19.13 N/m) times the change of distance squared I only got 4.84 Joules? Is that right? If so can I just work out from there any spring (or combination of) that holds the same amount of energy and use that instead of a bow? Not to even get involved with the fun of seeing how the weight and shape difference of the projectile will affect it's flight. Or a firing mechanism. Or my ultimate hope that I could preload 6 such springs so I could fire off several shots before reloading. But first things first. Is my idea of using a metal spring which can store the same energy as a wooden spring viable? Is that amount of energy that I worked out correct? If not please baby step me through all which is wrong. It's the only way I'll learn. To finish will the use of a metal spring really reduce the size of the wooden bow down as much as I think? I mean I'm looking for a reduction of something almost the height of a person down to a mechanism that could fit on a forearm. Am I asking too much? Any input greatly appreciated. Matt.