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Dan - Are you trying to smooth the surface because it is uncomfortable against the foot, or just to make it look good?

I know that the simultaneous application of heat and pressure can smooth some rubber surfaces. I remember this from the old vulcanizing rubber patches for bike inner tubes. That might be applicable for a place where you can get a heated piece of smooth metal on each side and clamp, but probably won't work on the complex curvature of a foot pocket.

I don't know of any way to restore the factory shine though.

The threading in the cut away is only about half as long as in the real thing. The gray material is PVC, which is pretty strong as plastics go.

This one is admittedly a prototype, just to try a few different approaches. But I think the connection could be made quite strong by making the whole arrangement longer, and providing for lots of threads, with a substantial length of unthreaded shaft inside the plastic.

Some pictures would probably help, so I made a little cut away model.

A standard tap has a tapered nose, and therefore does not cut fully formed threads all the way to the bottom of a hole. Because of this, a threaded shaft, screwed in completely, will jam itself into the area at the end of the hole where the threads are incomplete. Maybe not the best idea with metal to metal contact, but a stainless shaft in a plastic bushing ends up working like one of those lock-nuts with nylon inserts. It can be removed, but it's very tight for the first full turn or so.

Secondly, you can see from the cut away model, that we drilled out the threads near the openning of the hole. This allows the shaft to remain its full diameter at this point, which is where any bending stresses are greatest.

If you ever need to cut threads very nearly all the way to the bottom of the hole, ask for a "bottom tap", like the lower of the two here:

My son has been dying for us to try our hand at building a pole spear for him to use around Wood Guy's place this summer, so today we gave it a shot. Not a home run, but useable, and we learned a few things.

The construction is two layers of carbon fiber / blue fiberglass sleeve over a 1/2" PVC pipe. We turned pieces of PVC for each end, which we glued in place with standard PVC cement. This isn't a big game spear, and we figured the PVC cement should handle the flounder or small mangroves. On the business end, we threaded the shaft and screwed it into the PVC end piece. It actually screws in further than the threaded area on the shaft, so that the shaft is the full 5/16" thickness at the entry. Overall length is 5', and the diameter is just over 7/8".

Things that went well:

Hanging it from the ceiling with a weight kept it nice and straight.
The heat shrink left a perfect finish. Zero sanding.
The threaded shaft can be removed, but it's a tight threaded fit. I don't think it will come loose unintentionally.

On the downside, I would have liked it to be stiffer. The composite layer is less than 1/32" thick. We considered ordering a few more sleeves to add thickness, but the 10 year old member of the design team was anxious to see the finished version . . .

Dan - Might need to hit you up for a couple floppers and pins if you still have some.

I'll throw in two cents from a grasshopper. One thing that I've learned from trying to hold my breath while walking, etc. is the value of slowing down. For me, being new, one of the impulses underwater is to move too quickly. Doing a little dynamic apnea out of the water has helped me to realize when I am moving unnecessarily quickly, and not getting the most out of the breath.

I don't quite follow how you will lock the washer in position, but how will you reach it if it is under the head of the screw?

Exactly.

I think the spring could easily be fastened to the head by driving the screw through a plastic bushing, of the same diameter as the screw head, but having a slot along the length similar to the old bushing. Once the bushing was screwed on all the way against the head, it couldn't move. Simple. That would allow a longer piece of the spring end to be engaged than would be possible with just a hole through the head. And the little plastic bushing could easily be cut to length to fit guns of different heights.

Definately could be a "Mark II" version here.

Hmmm. You are right that a longer spring would have to be of a larger wire diameter to have enough torque. It could be done, but looking through the McMaster catalog, I don't see any stock springs that would work.

The slotted idea may have potential. I have a tiny cutter that would allow me to make such a slot. It might actually be easier to install, as the hardest part with the present design is stabbing the end of the spring into the tiny hole. I'll have to try that.

Quote from Toledo970

Is the sleeve necessary? If instead of putting a groove in the sleeve, you make a hole in the head of the screw, wouldn't this also work? I know that while screwing in the screw you would load the spring(or overload it) but couldn't this be figured out too. Wouldn't that also reduce the width?

If the sleeve could be eliminated, then the diameter of the spring could be reduced to the point that the spring was just large enough to fit around the screw. You just gave me an idea. There is another way, but the installation would be a little more delicate. Ponder this:

Reading the pics below from left to right. Start with two holes. A larger 3/16" hole (for the screw and spring) and a smaller, overlapping 1/16" hole. When installing the screw, the end of the spring is pushed off into the smaller side hole, so the spring does not get tightened as the screw is turned. When the screw is almost tight, allow the end of the spring to snap into a slot cut in the head of the screw. Rotate the screw a little more to properly tension the spring. The top end of the spring would have to be left a little longer, so that it could be manipulated, and then cut flush when the installation was complete, but it might work?

What you were looking for (and found) is called "shim stock" in industry. Thin pieces of aluminum, stainless, and brass are available from McMaster.com and other places in almost any size from 0.002" through 0.100". If you can get an accurate measurement of the inside tube diameter, and the outside of the male piece, then you can subtract to get the difference and order the proper thickness for any application. They have thin nylon and UHMW plastic as well, but not in quite so many sizes. Hobby shops that cater to remote control model airplane builders are often a good place to get thin pieces of metal too.

Or you can just cut the bottom out of a shopping bag.

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.

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

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.

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.

Bienvenido willy en que parte de la isla pescas

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 . . .

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.

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.

It seems different to you because you have first hand knowlege. You know that part of being a successful diver requires you to relax, instead of exerting yourself. But most people don't have that first hand knowledge of either mountain climbing or freediving. To many people, they both seem to require some superhuman ability.

I think that they do have one thing in common in that they both embody things that most people fear. In mountain climbing, it's the idea of hanging over a cliff by your fingertips. In spearfishing, it's the idea (for most people) that you are one breath from drowning. Remember too that many people won't even wade in the knee deep water for fear of sharks. For most people that I have talked to, the idea that a freediver might describe a massive hammerhead or even white shark encounter as a once in a lifetime experience seems foriegn to the point of insane.