Building my hybrid barrel

My goal here is to build a gun for open water. Not blue water for tuna and such, but hefty enough to handle three 5/8" bands for longer shots on mid water snapper, cobia, AJs, etc. Possibly upgradable with a fourth band if I have the chance to hunt wahoo or something.

So I opted for a hybrid design for good maneuverability, but with a little more heft to handle the extra band load. My logic was that if I could make the tube a little larger and thicker, but with a built in open track, then I could keep the height about the same as a RA barrel, and maybe even less than a typical 1-1/4" barrel with a stuck on track.

Well, for better or worse, here's what I got so far. It ended up just a hair over 1-3/8" OD (1.420"), with a built in track for a 5/16" shaft that is close to half the shaft deep, and a wall thickness that is just a little over 1/8" (about 0.140"). Sitting next to a Rabitech barrel, you can see that the height to the top of the shaft is just about the same.

I'm sure that it isn't as perfect as a production carbon fiber tube, but hopefully the extra diameter and wall thickness can compensate.

Here's the process, if anyone else has the itch.

You'll need a core of wood, foam, or something else. I tried a couple of different approaches, but the one that ultimately worked best was using one of those router bits that cut half a circle in one pass. Just make SURE that the square piece you start with is accurately planed square. Cut a groove in the top, that will help form the open track. You will also need a little "dummy" piece, wrapped in tin foil, and temporarily screwed to the end of the dowel. This will be pulled out later, leaving a recess to fit a muzzle.

You will need a half round piece to form the outside of the open track. I played with both teflon and delrin, and found that the delring works just fine and is much cheaper. Go with white, as it will be much easier to see against the black carbon fiber later when laying everything up. I built a little jig out of scrap plywood that makes it easy to cut this in a mill or drill press. You feed the rod from the left. It passes under the cutter, which removes the top half of the rod. The screw pushes down on the flat, and keeps everything from rotating as you push the rod through.

Next post, putting it all together.

The carbon fiber comes in sleeves. I got mine from Soller composites, and they have lots of color blends if you want something other than black. The blue will be a pole spear for the up and coming spearfishermen in the family. Also, the weave can fit a variety of diameters. I used four layers of 1.5" sleeve on this tube, with each adding about 1/32" of final wall thickness. Tie a knot in the end, and roll each sleeve inside out like a sock. This will make it easy to roll onto the dowel.

I used West 105/206 epoxy for this, blended with a liberal amount of graphite powder to make the track slick. Since I used the same recipe for all four of the layers, the black color can never scratch off. I found that 4 pump squirts, mixed with one big tablespoon of graphite, worked well for a single layer of my 36" long tube.

Do two layers first, and clamp everything in both directions to a strongback to keep it all straight. If you use a bull nose router to make a curved piece, you can avoid the worst of the flat spots. A piece of clear heat shrink tubing wrapped around the outside of the dowel, sleeve, and half round, will form everything to shape. I really like using the clear heat shrink, because you can see the epoxy run as you shrink it, making sure that all voids are filled. Then clamp it from the outside to force the half round down, making the track. I showed this with the track on top for clarity, but it works better upside down. That way, epoxy runs down and insures that there are no voids in the track. There's no epoxy in the pic, just for illustration.

You can do this by yourself, but you've really got to think through all the steps. For example, run a string through the heat shrink, so you can tie it to the carbon fiber wrapped dowel and pull it through.

After you do the first two layers, let it cure and sand it nice and round. For subsequent layers, you won't need to clamp it from the sides (because everything should be straight).

I also tried a bunch of ways to make it perfectly round when the tube was fully cured. In the end, the lathe was more trouble than it was worth, and I just sanded it by hand. If you use two-sided tape to stick sandpaper to the round piece of wood that you clamped with earlier, you can sand with surprising precision. Use calipers, and check the diameter often to make sure that everything is even. It took me about two hours, but this tube is round within +/- 0.005", and the diameter is between 1.420" and 1.430" over the whole length. Using the heat shrink approach, you will get some spots that appear to be voids. But most of the time, it is only because the areas around them have excess epoxy. For my tube, I never had to fill in any low spots. Just remove the high spots around them.

The epoxy sands beautifully with the addition of the carbon fiber. Sure makes a mess though. Overall, I'm pretty happy with how it turned out. It has a little flex, which surprised me, but that's with me supporting it at the ends and leaning in the middle. Hopefully not so much when the gun is finished.

So far, so good.

Thanks.

Seaweed - I'm not sure on the angle of the bi-axial sleeves. Soller composites offers uni-directional sleeves as well. Maybe my tube would have turned out a little stiffer with a combination of the two? One thing that I noticed is that clamping the little half round piece down into the track pulls the orientation of the fibers into a more circumferential direction, instead of lengthwise along the barrel. As I understand it, circumferential is good for resisting torque, but aligned with the barrel would better resist bending.

Hau - Overall length of the gun will be 58"-60". And don't give up on that enclose track euro barrel . . .

Seaweed got me thinking about the orientation of the carbon fiber weave, so I ordered some different carbon fiber sleeves, which have almost all the fibers running lengthwise. I'll make up a second tube, and compare the two to see which layup produces a stiffer tube.

The second tube will have three layers of uni-directional sleeves, topped off by a single layer of biaxial sleeving.

Hau - This will be a "Heavy Hybrid", weighing in at around 50% more than a typical Wong or similar hybrid gun. Overall length will be about 58-60", split evenly between a 2-3/8" square wood stock, and the carbon fiber barrel. Because I am short, it is a modified mid handle, with the grip positioned a little rearward at about 11"-12" forward of the butt.

This is a prototype in more ways than one. Having tested the techniques a little, I think that it might be possible to extend the concept even further to produce an enclosed track CF barrel.

Just beginning to understand how much I don't know . . .

I've been talking to a guy who has done some tubes before, as well as some comparitive testing. He says that the tube is MUCH stiffer if the great majority of the fibers run lengthwise.