More fun with Carbon Fiber - Lost Wax Barrel?

Quote from Toledo970

. . . an inflatable form to put the CF around

If you use an inflatale inner core, I think that you would need something rigid around the outside to limit the exansion. Added complexity.

Quote from Toledo970

. . .or just making a thin innercore out of 2 parts(same mold) gluing together and laying the rest on top of that.

Not quite sure I have my brain wrapped around this. Are you talking two pieces glued end to end, or a top piece / bottom piece glued along a horizontal seem? What is the advantage to that?

Hmmm. I see your point, and like the general direction. But I see a potential problem, based on conflicting properties of the wax. To get a wax that has minimal shrinkage when it solidifies, I have ordered a "casting wax". Because this stuff is normally used for casting jewelry and such, it flows like water to capture the tiniest details. I suspect that it will pour through the holes and fill the inside of the pipe.

I guess that one possibility might be to dip the pipe in a thicker wax first, to seal the holes.

Hau,

I had kind of intended this type of barrel for use iin a hybrid construction. But I think that it would be possible to adapt a standard handle. Tough to say for sure though, unless I had one in my hands to play with.

Anyone have an extra handle that they would be willing to donate to science?

I may have misunderstood.

Hau - Were you talking about the Aimrite handle like is used on their Venom guns? Or were you thinking of adding an american trigger and the plastic aimrite handle to a CF barrel?

Well, I've made a little more progress. I finally gave up on trying to mold the wax to the final shape. For this one, I just cast a rectangular brick in an open top mold. Once cool, I just cut of the top 1/4" where the shrinkage voids were.

I've learned that it is much easier to see the surface of the wax, and identify any imperfections, if the wax is colored by adding some candle wax to the paraffin. I also learned that it is easy to fix minor chips by dripping melted candle wax in the chip, and then smoothing with a knife.

I've learned that wrapping with tape is easier, and squeezes out the excess resin better, than the heat shrink tubing approach. Don't use scotch tape like the pic, though. It is impossible to remove from the cured epoxy. But electrical tape, wrapped with the sticky side OUT, works great. It leaves some tiny spiral lines in the epoxy, but these are easily sanded off.

My prototype barrel section is 1-7/16" wide, by 1-5/8" tall. I kept the bottom relatively flat to mount reels and handles and such, and rounded the top more. Wall thickness is about 0.100", achieved with an inner biaxial sleeve, three wraps of uni fabric, and one outer biaxial sleeve.

My intent here is that a barrel of similar dimensions could strong enough to be used for everything from a rear handle or rear handle plus, to mid sized hybrids, to larger blue water guns, all with consistant sight picture and aiming. It would be super easy to make a hybrid, because the openning in the wood can be rectangular and open at the top, so much easier to cut.

I don't know if all that will ultimately work out, but my next step is to make a full length piece for a 52-54" rear handle plus gun. The reel / handle / trigger section will be layed up around a core of teak, while the forward half of the barrel will be hollow. I'll add ballast up front to get the trim just right. Stay tuned.

Quote from Dan

Very neat. I'm having trouble visualizing how this tube would work with a euro handle. I'll understand better what you're planning to do when I see the finished product.

The gun design is still evolving in my head while I experiment with the processes. I only post the pics to taunt Hau . . .

Quote from Wood Guy

Very cool. I've only been casually interested in carbon fiber hybrids, but this experiment has got me pumped! How did you end up melting the wax out?

For barrel sections up to about 36" long, you need a crappy old barbeque grill. I have one you can use.

Quote from Wood Guy

Would you use a delrin muzzle, and if so, how would you make the shape that fits inside the barrel?

Think simpler. Fill the last 1-1/2" of the barrel with epoxy, poured around the largest cylindrical "dummy" piece that will fit inside the barrel. In this case, about 7/8" in diameter. When the epoxy is cured, remove the dummy piece, which leaves you a perfectly round bore inside the epoxy filled end of the CF tube. Now, it's a simple matter of turning the male end of the muzzle to fit inside the round female bore. Much easier than trying to accurately fit the inside of the CF shape.

Quote from Wood Guy

How would you envision the transition between the cf and the wood of the stock?

Part of what could make this so nice for a hybrid is that there is no need for a transition. You could run the tube all the way to the butt of the gun. Use the CF for what it's best at - strength in a small package. Now the wood exists only to add mass, attach the handle, etc. There is no loss of strength where you join the CF to the wood as in a normal hybrid.

Quote from Wood Guy

I wonder how a wooden muzzle matching the wood on the handle would work? It could be epoxied into the end rather than pinned like the delrin is. I realize most guys would probably prefer the look of the delrin, but teak might look pretty good as well.

I wouldn't make a bolt-on muzzle from wood. But you could certainly plug the last 3-4" of the barrel with wood during the layup, and then cut the band slot / holes through the CF and wood as Chad does on some of his guns. The strength of the CF allows smaller shapes, or higher band holes, while the wood inside simply provides a smooth inside surface and plugs the end of the barrel.