since i have been absent for a while i decided to go ahead and add some ideas here for those that are curious on methods to create a fiberglass stock.
here is what i have learned from my work experience in fabrication over the years. one of my former jobs was in the prosthetics industry, and fiberglass resin is used a lot when they make artificial limbs.
the thing about this stuff is it is not solid fiberglass. first there has to be a form, and usually the form is made of plaster ans broken out later, so to start off i would suggest making a half stock form by sawing a donor in half and then modifying it to your needs, to get the stock profile you want.
next take the halves of the stock and embed them in a type of impression foam set in two large cardboard boxes big enough to hold each half. suspend them on each end by putting a dowel in each end using a drill to make sure you have a nice even and level donor in each box and get good impressions in the foam. now the fun part. pour your plaster into the foam forms and make sure at least one end of the stock has a stick embedded in it soemwhere that you can afford to lose material, like the butt of it which will later be filled with a higher impact foam and epoxy. you can also use other hard setting mixes similar to epoxy like dental compound. but that comes later.
once the plater sets up hard, and is still somehwat workable, use a shure form to smooth out any deformations in the stock and then sand then down with sandpaper and water while the cast is suspended in a vice. this will make for a nice smooth surface to laminate the fiberglass over top of. you also need to take a tad bit more material off of the plaster than the
actual size of the stock because that will be filled in by the
laminated layers. so i would not remove any more than 1/8 to 1/4 inch of
the surface all the way around.
once it has been sanded to perfection or to your liking, you can use the cast right away as the form for the lamination.
you will need some tubes of fiberglass mesh, preferably the kind woven sort of like a braid or basketweave, and that can be found on amazon easily enough. it should be carbon fiber and just large enough to fit over the cast without a lot of overhang, but if you cant find any that is perfect, you can always cut and staple what you need in place for the first layer since it is not going to see any skin contact ever. if you must have overhang, then make sure it is placed somewhere that will be trimmed out later, like the butt or the top side where the barel sits. then sew or staple or glue (whatever workd the best) the overhang together and trim it up so there is no more than an inch sticking out. it is much easier to work this way. really the method of putting the two halves of overhang together is up to the type of carbon fiber you could find, and not necessarily what you think wil work. those that have a tighter weave and resemble stretchy cloth are probably more easy to staple or sew. anything more like braided line will need a good glue of some kind to tame, because those dont like to behave with staples or sewing.
the resin is going to be some kind of poly resin that is two part mix, and you dont want to mix it until you are ready to pour it. to prep the cast for pouring and lamination, first take a stocking of some sort like old pantyhoes with no runs or some new ones and some baby powder and cover the plaster cast. you should pull the carbon fiber tube over the cast and make sure it is evenly pulled and smooth over the surface, it is ok to have a few wrinkles in it because those will be eliminated later, but get as many of them out as you can, and dont worry about a little bunching up around the ends. next you put a snug fitting plastic bag over the cast and leave an opening on one end (the top or in this case the front end of the stock not the butt) but you tie the opening off with a rubber band or twist tie til you need it opened. next you must have a suction fixture, which you can make from regular black plumbing pipe and a reverse compressor or some other way to pull suction, and you rest the stick inside the pipe with the front of the stock facing up, this makes it easier to pour the resin. drape the bottom or butt end of the plastic bag around the pipe and tape it off generously, there should be no leaks. make sure you have latex or nitrile gloves on before you do the next part. and keep a box of them handy for these foams and resins.
once you are ready with the resin mixed, turn on the suction to draw out all the air, and open the top of the plastic bag and pour the resin in the funnel it makes then close it off again and tie it. use the suction and your hands to work the resin into the carbon fiber evenly as possible so that there are no bubbles and try to work the bubbles toward the ends where you will have material to remove. this depends on speed because there is a small window of about two minutes that you have before it sets up too much and the project is ruined, so work as quickly as possible and make sure even if the resin is not impregnated perfect, that it is spread around with no voids. follow the instruction per the bottle on cure time and let it cure. now it may be that you dont have a fast fure resin which is probably better for you if this is something you want to try and not worry about having to scramble.
once the thing has cured, then you can put more layers on it until you get a shell for each half. i would say no more than three is good enough for now. after each individul layer is done and cured, you have to sand the surface of it for optimal bonding with the next laminated layer and to get all the imperfections out. dont worry if there are wrinkles, you can sand them out, whether by hand or by a power tool. the choice is yours depending on the quality you want in the sanding and the urgency of your build.
once the third layer is done, grab your cured carbon fiber laminated casts and cut them off using a vibratory cutter or dremel tool just on the flat side of the cast, and then use a chisel or some kind of tool to carefully chip the plaster out. any thing left over can be washed out in the sink with common dish soap and water. trim both halves til they mate up flush and there is just a slight seam between them. this has to be done carefully so for some you may want to factor in the need to leave a bit of the flat side with just a lip there for the two surfaces to mate together and make the halved into one piece. but it really is preference and skill level. if you can sand both halves on the inside to perfection for mating, then by all means do it that way. it will look good too.
once the two halves are finished cleaning up and ready to join, then it is time to start thinking about the inside surfaces, where the barrel or other receiver parts are going to need a snug fit, and those have to be done a bit differently. there are a lot of ways it can be done, but i think it is best to take cues from those who glass bed their stocks. take your gun parts and coat them in some kind of grease or other agent to keep from bonding with anything and use those as the inner form.
now make sure you have enough opening cut in the halves of your shell for the assembly to pass through as needed. you need some blocking of some kind to hold everything square, whatever you choose, pieces of poluymer, or light wood or even aluminum, it doesnt matter, that is fine, just try to choose something that is light and also durable because it will be embedded inside the stock body. why blocking? it is easier to relocate the parts to the same place later. i would also reccomend blocking in the butt of the stock to make it easier to attach a butt pad or plate to the stock later. once the blocking is cut to the correct size to locate the gun parts correctly, and fit snugly on the inside of the shell halves, then tape all of them together so it stays together
now you need something called marine foam to fill the interior of the stock and keep it from collapsing and keep the two halves together. this is also easily found on amazon but it can be pricey if you buy it in quantity.
mix up the foam and dont worry about mixing too much if you dont know how much you need, it will expand and ooze all over the place, but expect a mess cause it will get messy. it is also pretty workable so you can wire brush it away or sand it off if you need to.
put the whole assembly in a gun vice so it faced the way you normally shoot, if you dont want to tape it together, you can use clamps to hold the halves together just snug but not overtight, and pour the foam in the stock openings til it fills all the gaps and oozes all over the place. let it sit to cure for as long as the bottle directions say and just forget it for a while.
once it is cured for sure, then you can remove your barel and the recever components from the stock. a light cleaning will get the foam off if there is any. if not then you might want to use a blasting medium or brush on them that wont mar the finish.
the next part is a bit odd i admit, but the only way i can think of finishing it off. you have to fill the openings with clay or plaster, and only fill them just barely below the surface so they leave a nice depression where you need to cut out openings again. then chuck your stock back into the suction fixture on a stick again, and prep it for a couple more layers of carbon fiber. this is just to keep the halves together and make sure it doesnt split. it wont, unless you skip this step. but the other thing it is for is to make a nice smooth surface with no visible seam.
put a couple more laminations of carbon fiber and resin over top of everything (minus the barrel and the other parts of course) and cure.
once it is cured, use a dremel or cutter just on the inside of the depressions and access the plaster. chip it out as much as you can and again wash the rest out in the sink with dishsoap and water. dont worry if you damage the foam because that will be fixed and you also have those location blocks in the foam to hold your parts again.
once it is all cleaned up, then use the same method they use glass bedding a stock to finish off the interior
the next thing you do after "glass bedding" the stock is to take the carbon fiber stock after it is all cured up, and sand it all down again. you can fill the end where the stick was on the butt with epoxy, or with resin, or whatever is durable enough to do the job, or you can drill a hole in the foam and put a tube inside for storing a cleaning kit. but this does work pretty well. any way you choose it needs to have some kind of epoxy or resin to seal the gaps.
the final finish is up to you, but it should probably be some kind of compatible spray on finish that does not require it to be baked on. it is pretty much up to you whether you want to put laquer on it so it looks like carbon fiber, or paint it so it looks like polymer. choice is yours.
hope this helped out.