i have been asked various questions about making a hybrid so i though i'd start this thread to outline a step by step procedure for making of a high quality gun with the tightest tolerances possible using tools available in an average home shop, no mills, no cnc machines. i will try to provide everything from material and tool selection to pics with complete specs but be prepared this is not going to be much cheaper than buying one already made. also, it's not my intention to promote myself, i present this in the same spirit that some other guys (and you know who you are) on this and other forums have freely shared information in order to help fellow spearos and do it your self guys. i will post info in steps over a period of a few days to allow dialog. this is obviously not the only way to do it but it works for me and if you have any input please feel free to share.
teak has been the wood of choice for speargun making but it's not the only one, this site has good info in order to help you make a selection http://www.wood-database.com/l…ification/hardwoods/teak/. some of the important things that i look for in addition to durability and decay resistance are workability, specific gravity, hardness and overall beauty of the wood. some of the different types of wood i like are mahoganies other than philippine, padauk, lacewood, makore, sapele, sipo and others.
for hybrids it's not necessary to laminate, in fact i try to avoid lamination whenever possible because i think the end product looks better and to avoid problems later on. the dimensions of the wood vs pipe in order to have a gun that is well balanced is 50/50, for example, a 60'' gun will have a 30'' wood stock and 30'' pipe (including the muzzle). for a 60'' gun that shoots a 5/16'' shaft with three 5/8'' bands i start with a piece of wood that is 30lx3wx2h (final dimensions after straightening and squaring) for a gun than shoot a 9/32'' shaft it could be 30lx2wx2h.
after cutting the stock to about .25'' over the final dimensions i use my router table to straighten and square it. to do this i use a piece of laminate board the kind used for shelving which i mount camps every 12'' as shown in the pic bellow. i simply clamp the stock on the edge and use a flush trim template bit part# 45364 http://www.amanatool.com/route…ate-routerbits-45481.html to straighten and square the hight of the stock just a bit over the final dimension. i them use my drum sander to sand it smooth and bring it to the final dimension, my ryobi wds1600 is the most expensive tool in my shop at around $600 but it's one of my most use full. i do the same thing for the width and check to make sure the stock is straight and square using a dial caliper, a straight edge and a square. it is essential that the stock is within a few thousands of an inch straight and absolutely square or things will not line up properly as you go along. a table saw could be used to do this but i don't have room in my shop for a quality unit that takes precise cuts and this procedure gives me the precession that i need even though it's a little time consuming.
the next step is to setup the router table to take a center cut and once it's setup properly i don't move the fence till i'm done with all the cuts i need to take on the stock including, installing the pipe, cutting the track, the trigger mech pocket, the handle pocket and so on this insures that everything lines up.
i use a 1.125od carbon fiber pipe from rockwest composites part #45530 http://www.rockwestcomposites.com/index.php?p_resource=items&p_itc_pk=2,. it comes in 70'' lengths which is enough for 2 60'' guns. using the 50/50 wood vs pipe formula and assuming that we will make 2 60'' guns means that we will have 35'' of pipe for each gun. the muzzles i use are 3'' long so the amount of pipe that needs to be sticking out of the wood stock for a 60'' gun is going to be 27'' (27+3=30) which means that 8'' of the pipe will need to be inserted in the stock (27+8=35) which is plenty. i usually try not to use the same pipe for 2 long guns instead i try to make a 60'' and a 55'' or even a 50'' long gun which gives me a bit more pipe to insert into the wood but i think 8'' is ok. the same process is used for different pipes including aluminum railgun version, you simply have to find a router bit to match the pipes diameter.
i cut the channel for the pipe in three steps, first i use a .50'' straight plunge router bit, amana part #43422 http://www.amanatool.com/bits-fv/43200.html to make the 8'' cut that the pipe is going to be inserted into the wood and the trigger pocket at the same time. i never cut to the intended depth all at once instead i prefer to take severals cuts at a maximum of .50'' depth till i reach my intended depth which is 1.125'' for the trigger pocket (auto reseting neptonics trigger) and 1.250'' for the pipe channel as shown in the pic bellow.
second, i use a ball end bit on my router table, amana part #45970 http://www.amanatool.com/bits-fv/45960.html to cut the actual channel. for an 5/16'' enclosed track the depth of cut is 1.5925'' (1.125 of pipe + .3425 for the enclosed track + .0625 for the jbl track + .0625 above the shaft when loaded into the track). this is going to leave you with .375'' of wood bellow the pipe (remember the stock is 2.0'' thick) so if you're going to mount a reel on the gun make sure you insert the pipe into the wood only enough to allow you to drill holes for the reel mount without punching through the pipe. for an open track the process is the same but the depth of cut is 1.4675'' and for a 9/32'' shaft the depth 1.56125''. see pics bellow. to set the hight of the router bits buy a depth gage or simply make one of your own by taking repeated cuts and measuring the depth till you get to the what's desired. there's no way to get the precession of the numbers above on a router table so just give your self a little room (make a deeper cut) and use a drum sander to get the correct depth after.
the third and final step is to cover the cut left by the shank above the tube which is .50'' wide. cut a piece of matching wood to the length desires (remember the pipe is inserted 8'' into the stock) and using the drum sander bring it down to .50'' in width to match the slot cut into the stock, round off one corner to match the round end of the slot and make sure you have a nice and tight fit. now you need to make a round cut on the bottom of the piece so when installed over the pipe it matches it's contour and to do this i simply use the same ball end mill that i cut the pipe channel. it's a good idea to make this piece before you start so the router table fence is not moved. trim the piece to fit in length and now you are all set to glue in the pipe. see pic bellow.
you may think that this is a long and unnecessary way of doing it and you could do the same thing by sawing the piece in half and cutting two half circles in each for the pipe but doing it this way assures you that everything lines up to within a few thousands of an inch so the pipe is directly above the track and the track lines up exactly with the trigger mech and handle and so on. also, this is the only way i know how to assure that the pipe is inserted perfectly straight into the stock without having to make jigs or using expensive equipment not available to most do it your self guys. lastly, this way avoid laminations, especially ones that are in the center of the stock where screws will be added and the problem of delamination is a possibility.
it is essential that your tools are accurate, your router table should be completely flat and the fence straight. the router should be checked to make sure it cuts square and adjustments be made to correct things if necessary. work should be checked after every operation, it's easy to correct pretty much everything if detected early. always take light cuts and alway practice on a scrap piece before doing the real thing. have fun, alway use caution and follow all safety directions.
to be continued.
