Blue Water Hunting and Freediving - Digital Version 1 - Page 81
propulsion bands muzzle wooden barrel
spearhead adapter spearhead line release bolt-on ballast adds mass
The most suitable shaft material available is 17-4 PH stainless steel . The high-tensile strength provided by this heat-treatable material prevents most permanent bends . Fish weighing more than 100 pounds ( 45 kilograms ) are capable , however , of bending even this superior material . 17-4 PH stainless is expensive , and you must first machine it and weld it in its annealed ( soft ) state . The treatment process requires heat at 900 degrees Fahrenheit for one hour , followed by gradual cooling . Six feet ( 1.8 meters ) is a good length . The spearhead end of the shaft is machined with a thread pattern 5 / 16 inches by 24 threads per inch . These threads should end in a butt shoulder with the spear tip adapter bottoming on this shoulder . Welded tabs serve as attachment points for the propulsion bands . Select a
shaft with the front tab drilled to receive the spearshaft cable ; the hole needs to be high enough to clear the spearshaft guides . The rear of the shaft is machined to match the trigger mechanism .
Barrels are made of metal , carbon fiber or wood . Teak is the best choice for a wooden gun because its high oil content resists water absorption . Wood grain absorbs water irregularly , which leads to unequal swelling and , ultimately , to warping . Steve splits a piece of teakwood and laminates the two pieces together in a mirror-image relationship . He reasons that any tendency of the wood to warp in one direction is countered by its mate warping in the opposite direction .