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All About Guns What's your weapon of choice, and why? Discuss the beloved speargun here!

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Old 07-17-2019, 05:29 AM   #1
popgun pete
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Carbon Fiber Gun structures

It would be interesting to see carbon fiber guns sectioned longitudinally to check out the various thicknesses in the walls of the gun body and how the masses are distributed along the gun, with possibly cross sectional cuts as well to show the lateral distributions moving from front to rear of the gun. Now gun owners are not going to shove their gun through a band saw to find out, but manufacturers must check their guns out by cutting the first prototypes up, especially to check the influence of the internal molding bladder in pushing the gun to shape in the mold. Another source of info would be cutting up guns that have had a fatal accident and are beyond repair.

We tend to think of carbon fiber guns as lightweights, that is certainly true of spearguns that are basically re-barrelled tube guns where the alloy barrels are replaced with carbon fiber tubes, however monocoque construction guns can be quite heavy and that must be down to the sidewall thickness of their bodies if they don’t have strategic lumps of lead in certain positions.

Without spear, line or bands my C4 Carbon "Urukay" 120 cm weighs 2.57 kg which is reasonably heavy. That is the weight reading on a portable digital scale used for weighing luggage.
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Old 07-17-2019, 07:57 AM   #2
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Re: Carbon Fiber Gun structures

Pete, if you are intending to slice that Urukay in half, it would be pretty cool to see.
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Old 07-17-2019, 08:43 AM   #3
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Re: Carbon Fiber Gun structures

In C4 spearguns some weights are added in strategic areas, for what I know. Carbon fiber by itself would be too light
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Old 07-17-2019, 05:02 PM   #4
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Re: Carbon Fiber Gun structures

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Originally Posted by Behslayer View Post
Pete, if you are intending to slice that Urukay in half, it would be pretty cool to see.
At the sticker price of $1,599.00 RRP I will not be doing that, but it would be possible to X-ray it if one had access to an industrial X-Ray machine, or maybe an ultrasonic scanner. Medical X-Ray units are in hard pressed use, so access there is virtually unobtainable (I have worked in the X-Ray department of a large hospital as a technician, my first work experience job as a student).

If there is metal inside it and the metal is ferromagnetic then a magnet may locate it. I have some powerful magnets, maybe a fridge magnet may work. If it is lead, brass or titanium used as ballast then a magnet will not work.
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Old 07-17-2019, 07:20 PM   #5
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Re: Carbon Fiber Gun structures

An ultrasonic thickness gauge should be able to detect the wall thickness if you can calibrate it to the speed of CF, but will only work on relatively flat surfaces.

I've used ground penetrating radar (GPR) to find hidden lead ballast in a wood gun.
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Old 07-17-2019, 08:45 PM   #6
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Re: Carbon Fiber Gun structures

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Originally Posted by manoa matt View Post
An ultrasonic thickness gauge should be able to detect the wall thickness if you can calibrate it to the speed of CF, but will only work on relatively flat surfaces.

I've used ground penetrating radar (GPR) to find hidden lead ballast in a wood gun.
Yes, that is a handy gadget as the reflectance from metal is much stronger and wave propagation changes compared to the plain wood. A wall stud finder may work, but my experience with them is they are not particularly accurate or discriminatory and it can come down to an educated guess on the device readings and the quantum of known spacing’s in actual building practice.
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Old 07-18-2019, 03:43 AM   #7
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Re: Carbon Fiber Gun structures

I don't know if any manufacturer is going to disclose this information as I believe is a big part of the design of their guns. It would be like releasing the blue prints of the guns.

Cool to see? Yes, absolutely. Unlikely? Definitely.

I recently saw a sectional cut of the the Cressi Yuma tube (by the manufacturer) where you can see how the bottom of the barrel is thicker (as well as the top thanks to the integral shaft track), which essentially works as an I beam. The difference is that instead of a single centered web, you have two (one on each side) to conform a closed shape (which is our tube).

You can see it here: https://www.cressi.es/es/apnea_fusil_yuma

26mm barrel, meant for fishing in the current, extreme lateral maneuverability, surf fishing, etc. I don't think the US will be importing many of them, given the kind of spearfishing donde there. In the North of Spain (Cantabric Sea and Atlantic Ocean), fishing in the surf is common.

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Old 07-18-2019, 04:13 AM   #8
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Re: Carbon Fiber Gun structures

I modified an Urukay 120 a while back, and I needed information on where I could drill in the CF and not worry about damaging inner voids. If I remember correctly the front muzzle area and the back handle area are solid CF with no voids. The midsection has a void that has trapped air. Some of the older models had problems with water infiltration but that seems to not be a problem in later versions. To be honest, I really think that the gun is way over designed by a factor of 4 or more. Even 4 thick bands at full stretch would never get close to stressing that structure.


In its original configuration the gun did not shoot very well. But after modding the muzzle and the handle the gun shot extremely well with 8mm shaft. it would be a great platform to test out new ideas in speargun setup where you really want to push things either in classic or roller or invert roller setup. The muzzle has robust front and side screws that allow for adapting many different designs to take roller, invert or classic. You can play with all sort of ideas using a 3D printer and just screw it on.
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Old 07-18-2019, 10:56 AM   #9
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Re: Carbon Fiber Gun structures

Solid lumps of resin will be reasonably heavy and the C4 spearguns being of “No Joint Construction” I don't see how any metal will be inside it as a bladder acts as the internal part of the mold and that squeezes the resin composite body outwards to press against the external mold halves. A magnet does not stick on the gun anywhere, including all the metal parts. I assume the bladder stays inside the finished product and is a sealed item that expands with heat when the gun is "cooked" in the mold.

The front barrel sections and the rear handle sections are much the same and the bulbous parts which provide mass and buoyancy change on the various models of the C4 spearguns. If you did not need to be concerned with the last two then the guns could have a skinny thick barrel solid right through. In a way they are like a hybrid pipe gun as the main feature is that slim forward barrel and the rear end is a very slim and compact eurogun handle with the trigger mechanism sunk into the top of the grip handle.

The slim ends of the gun are only possible in carbon fiber as otherwise the guns would bend and break, although they could be done in metal, but would then have no hope of floating. There are guns with stainless steel spines buried in an outer foam and fiberglass covered jacket, but they are going to have gaps and joins where the components are fitted together, unlike the carbon fiber bodied guns.

Last edited by popgun pete; 07-18-2019 at 11:16 AM.
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Old 07-18-2019, 01:23 PM   #10
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Re: Carbon Fiber Gun structures

The bladder is surrounded by layers of carbon, during the layering process, you can vary the thickness and layer some heavier material in between. Then the bladder is expanded at high pressure into the mold and the cooking happens. I guess deeper details are protected, but this is how it was explained to me .
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Old 07-18-2019, 05:12 PM   #11
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Re: Carbon Fiber Gun structures

It is logical to assume that the bladder will have a particular shape and be like a football in a sense. When it is heated the gas trapped inside it will expand and provide pressure that forces the bladder outwards. The gun will be layered up on the bladder and then put into the clamshell mold. Bear in mind that heat can be applied by electrically heating the mold and or a combination of microwave and thermal sources such as steam. Microwave will heat items that have a polar component such as water, but microwaves will not penetrate a metal vessel, therefore cooking may be a two stage process. "C4 Carbon" are not the only bike frame company that makes monocoque constructions and a year or so back we looked at another company that did reveal aspects of their process, a search here should find it. From memory it was "Trek".

Found it here: http://www.spearboard.com/showthread...nocoque&page=3

One thing for sure is the gun is one piece, the faint mid-line is a mold joint line that has been virtually erased on my example. A few C4 guns have exhibited some careless fettling in this respect with chatter marks and thin scrapes around the more curved sections, but my gun going over it with a magnifying glass looks perfect. The muzzle tip shows a buff colored depressed shallow pit that must have something to do with how the gun is made, you can see it in some of their advert photos.
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Last edited by popgun pete; 07-18-2019 at 07:48 PM. Reason: added reference
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Old 07-18-2019, 07:55 PM   #12
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Re: Carbon Fiber Gun structures

Something to read about carbon fiber bicycle frames which are relatively similar to a hollow carbon fiber unitary construction speargun.

MONOCOQUE MANUFACTURING

A term commonly used to describe modern carbon fibre bicycle frames, monocoque design effectively means the item handles its loads and forces through its single skin. In reality, true monocoque road bike frames are extremely rare, and the majority of what is seen in cycling only feature a monocoque front triangle, with the seatstays and chainstays produced separately and later bonded together. These, once built into a complete frame, are more correctly termed a semi-monocoque, or modular monocoque, structure.

https://cyclingtips.com/2018/01/how-...ames-are-made/

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Old 07-18-2019, 11:45 PM   #13
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Re: Carbon Fiber Gun structures

Some photos of the C4 "Urukay" 120 cm.
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Old 07-18-2019, 11:48 PM   #14
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Re: Carbon Fiber Gun structures

Quote:
Originally Posted by popgun pete View Post
Some photos of the C4 "Urukay" 120 cm.
.....and after its been cleaved with the band saw?

thanks Pete!
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Old 07-19-2019, 02:03 AM   #15
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Re: Carbon Fiber Gun structures

Quote:
Originally Posted by popgun pete View Post
It is logical to assume that the bladder will have a particular shape and be like a football in a sense. When it is heated the gas trapped inside it will expand and provide pressure that forces the bladder outwards. The gun will be layered up on the bladder and then put into the clamshell mold. Bear in mind that heat can be applied by electrically heating the mold and or a combination of microwave and thermal sources such as steam. Microwave will heat items that have a polar component such as water, but microwaves will not penetrate a metal vessel, therefore cooking may be a two stage process. "C4 Carbon" are not the only bike frame company that makes monocoque constructions and a year or so back we looked at another company that did reveal aspects of their process, a search here should find it. From memory it was "Trek".

Found it here: http://www.spearboard.com/showthread...nocoque&page=3


One thing for sure is the gun is one piece, the faint mid-line is a mold joint line that has been virtually erased on my example. A few C4 guns have exhibited some careless fettling in this respect with chatter marks and thin scrapes around the more curved sections, but my gun going over it with a magnifying glass looks perfect. The muzzle tip shows a buff colored depressed shallow pit that must have something to do with how the gun is made, you can see it in some of their advert photos.
The gas inside is just air, and it's pressurized to quite high pressures from a compressor. Not just by heating of the air
This is one of the reasons the molds have to be very strong.

Last edited by Diving Gecko; 07-20-2019 at 01:05 AM.
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