Carbon Fiber Gun structures

[popgun pete]

Originally Posted by Diving Gecko

The gas inside is just air, and it's pressurized to quiet 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.

That is what I thought originally, but there would have to be an air feed attachment to the bladder and I cannot see any sign of where it was on the gun. The recessed feature in the front of the muzzle seemed like it could be that, but other C4 models don't have it, just a blanked off tip. The other possibility is inside the trigger mechanism pocket, however I think the gun stock parts forwards of the trigger are solid as the cross sections are thin. If the bladder was like a thick wall cucumber with longitudinal expansion ribs it could be pressurized and sealed and then used in the gun layup and the heat during cooking would expand it. Shaking the gun I don’t hear anything rattling inside it. I may try tapping it with a jeweller’s hammer and listen for any hollow sounds, but would need somewhere quiet to do it.

[Diving Gecko]

Originally Posted by popgun pete

That is what I thought originally, but there would have to be an air feed attachment to the bladder and I cannot see any sign of where it was on the gun. The recessed feature in the front of the muzzle seemed like it could be that, but other C4 models don't have it, just a blanked off tip. The other possibility is inside the trigger mechanism pocket, however I think the gun stock parts forwards of the trigger are solid as the cross sections are thin. If the bladder was like a thick wall cucumber with longitudinal expansion ribs it could be pressurized and sealed and then used in the gun layup and the heat during cooking would expand it. Shaking the gun I don’t hear anything rattling inside it. I may try tapping it with a jeweller’s hammer and listen for any hollow sounds, but would need somewhere quiet to do it.

Yeah, the tricky part is that we don't know whether C4 actually uses the more advanced method for their guns. I was once told by an Italian spearo that they use a more simplified method but he didn't elaborate on it and I have not been able to verify it or get any additional info.

If it really is bladder molding, then there would be an inlet somewhere on the mold. The opening doesn't necessarily show up in the finished part at all as it could have been closed later in the process - or as you say, could just be the trigger box.
The mold would often be placed in a heated press to keep it clamped together and for the higher curing temps needed for prepregs and faster turnaround. After that, the bladder (often made out of silicone) would be pulled from the part. Some alu molds also have heating elements built in. Others are placed in an oven but the industrial MO is a heated press.
There are variations of bladder molding. E.g. some DIY use "drop film" (the stuff that you cover floors in when painting) welded together with a soldering iron and then use a wet layup. So, still pressurized but rarely as high as the alu molds and not heated as much either.
In some cases, the bladder is left inside the part after curing but it is not that common to do as it adds weight.

[popgun pete]

Originally Posted by Diving Gecko

Yeah, the tricky part is that we don't know whether C4 actually uses the more advanced method for their guns. I was once told by an Italian spearo that they use a more simplified method but he didn't elaborate on it and I have not been able to verify it or get any additional info.

If it really is bladder molding, then there would be an inlet somewhere on the mold. The opening doesn't necessarily show up in the finished part at all as it could have been closed later in the process - or as you say, could just be the trigger box.
The mold would often be placed in a heated press to keep it clamped together and for the higher curing temps needed for prepregs and faster turnaround. After that, the bladder (often made out of silicone) would be pulled from the part. Some alu molds also have heating elements built in. Others are placed in an oven but the industrial MO is a heated press.
There are variations of bladder molding. E.g. some DIY use "drop film" (the stuff that you cover floors in when painting) welded together with a soldering iron and then use a wet layup. So, still pressurized but rarely as high as the alu molds and not heated as much either.
In some cases, the bladder is left inside the part after curing but it is not that common to do as it adds weight.

C4 Carbon do talk about their molding procedures, but it is only that used for their fin blades, they don’t say much about the guns at all. The "Urukay" gun came with no instructions, but I guess they expect you to look at the web-site where there is a rigging guide, but even then the photos shown there are not up-to-date as the barrel mounted line release is still being depicted.
The label on the gun says “No Joint Construction”, therefore that should be what it is. The Specs Sheet shown is now only for the "Graphite" and "Urukay" guns.

[Diving Gecko]

Originally Posted by popgun pete

C4 Carbon do talk about their molding procedures, but it is only that used for their fin blades, they don’t say much about the guns at all. The "Urukay" gun came with no instructions, but I guess they expect you to look at the web-site where there is a rigging guide, but even then the photos shown there are not up-to-date as the barrel mounted line release is still being depicted.
The label on the gun says “No Joint Construction”, therefore that should be what it is. The Specs Sheet shown is now only for the "Graphite" and "Urukay" guns.

This industry is not spared its sales BS. I can't recall which company it was that talked about how their fins had a shark skin pattern to make them more efficient. This is the most BS statement I've seen so far - anyone who has ever done a fiber layup using vac bagging or resin infusion will readily recognize the "shark skin" surface as that left behind by the peel ply. So, it's a completely "natural" byproduct of using a very common composites' manufacturing process.

This is all speculation and I'd be happy to be proven wrong, but I wouldn't at all be surprised if the Italian spearo who insisted that C4 uses a simpler bladder process is correct - but it doesn't harm C4 that we all think they are using something super expensive and proprietary. The heated press with alu molds make sense when you are trying to really save every last gram - which they are in racing bikes - and when you run high production numbers and need fast turnaround times. It's far from needed in spearguns where a voluminous design like any of the C4 guns offers you plenty of room for beefing up the laminate thickness.

[popgun pete]

Originally Posted by Diving Gecko

This industry is not spared its sales BS. I can't recall which company it was that talked about how their fins had a shark skin pattern to make them more efficient. This is the most BS statement I've seen so far - anyone who has ever done a fiber layup using vac bagging or resin infusion will readily recognize the "shark skin" surface as that left behind by the peel ply. So, it's a completely "natural" byproduct of using a very common composites' manufacturing process.

This is all speculation and I'd be happy to be proven wrong, but I wouldn't at all be surprised if the Italian spearo who insisted that C4 uses a simpler bladder process is correct - but it doesn't harm C4 that we all think they are using something super expensive and proprietary. The heated press with alu molds make sense when you are trying to really save every last gram - which they are in racing bikes - and when you run high production numbers and need fast turnaround times. It's far from needed in spearguns where a voluminous design like any of the C4 guns offers you plenty of room for beefing up the laminate thickness.

I will write and ask them and see if we receive an answer. Message in Italian has now been sent.

[popgun pete]

The company have replied and they say that the gun is pressurized via a hole in the bottom of the stock which is plugged by the reel mounting where they fit a threaded cap. So the access point is hidden by the reel which you see on all the C4 guns which means that the extreme ends of the gun are solid, only the bulbous parts are hollow.

My "Urukay" gun has no surface pin holes or blemishes and is perfectly smooth all over, so that is a benefit of hot molding under pressure and that also makes the guns very strong.

[Diving Gecko]

Hey Pete,
Nice to hear they shared that bit of info and thanks for asking for us

[Behslayer]

Interesting bit of Detective work Pete

[Mikel_24]

Great work Pete!

[popgun pete]

Although spearguns are needed in different lengths for different jobs, and that has always been the case, it seems to me that modular bodyweight guns could be made for different shooting powers and the corresponding ballast/buoyancy requirements changed for each application.

The gun could basically be a barrel rail with integral rear grip and muzzle and be fitted with different bellies to provide the mass and buoyancy required for the different shaft weights and the number of bands needed to power them. Thus in the case of a C4 the “Graphite”, “Urukay” and “Mr Dark”, etc. could all be essentially the same gun sub-structure, but with a different lower “hull” indexed by a lower rail system slid and fixed onto the gun barrel which would also carry the reel in the same way that the carbon fiber guns are made now.

[popgun pete]

When rigging the “Urukay” for a shot you have a rather elaborate line wrapping sequence to sort out. On most open muzzle guns, e.g. a Riffe, the line running forwards from the shaft wraps a short pin at the muzzle then goes over the shaft to hold it down onto the muzzle track section by wrapping into a slot in the muzzle nose on the opposite side, or around another pin, before the line heads rearwards to the line release lever or finger back at the trigger mechanism. After that you can do another wrap forwards to the muzzle over a front line wrap hook and then back again to the line release finger after which you snug the remaining line up with your reel. When you shoot the line length to the spear attachment point comes forward and immediately loosens the line bridging across the spear which was holding it onto the muzzle track so that any shaft tabs will not be collecting that transverse run of line on the way out. That is not what happens on the “Urukay” as there you have a full wrap of line length on the gun before the line crosses over to hold the spear in the muzzle and then a second wrap running under the barrel to cross back to the line release finger side of the gun. Under some circumstances the first shaft tab has a chance to pick up the shooting line which is crossing over the muzzle as it is not being pulled away by the spear departing because about 3 spear lengths of line have to be pulled out straight first before it can pull that section away. This is probably why C4 state that their guns work best with slotted rather than tabbed shafts. I bought an 8 mm tabbed shaft for my “Urukay” and as I was installing the shooting line this all became readily apparent.

The problem with this twin plate, strut supported muzzle is the first line run from the spear has to go over the muzzle struts as if you go under instead in order to wrap upwards over the spear and hold it down on the other side then the shooting line will lasso the strut on the way out and pull the shot up very short. Springy mono might help by popping off all the wrapping points once the line release unlocks, but woven line may not when using this type of muzzle.

The side struts are being used in place of pins and hooks, but the problem is that unlike muzzle wrapping pins they are all on the bottom of the gun, not on the top.

[popgun pete]

The new "Gladius" has addressed this problem by providing some conventional line wrapping hooks. The spear now has shark fins, which is also a change as before you had to source your own shafts.

Interestingly C4 line wrap on the left hand side of the gun, whereas most of my guns line wrap on the right, although some of the bigger guns wrap on both sides as does the "Urukay", but it only has one line release finger.

[popgun pete]

The "Urukay" could be modified by adding line wrap hooks on the forward mounting screws where now there are nylon spacers and shooting line routing rings. Another hook could depend from underneath as a lower wrap hook and all three could be made as one component "saddled" underneath the barrel nose.

[popgun pete]

It is possible to hang a set of line wrap pins out the front end of the gun, but they need to hold the shaft onto the track as can be seen here on one of Kosta's (Seal) guns.

[popgun pete]

Currently an Easter sale on C4 Graphite models here at 33% off retail: https://spearfishing.com.au/collecti...uro-speargun-1
https://spearfishing.com.au/collecti...-euro-speargun

Although the gun photos show the line release on the barrel, I think that is just because they don't update the photos. My "Urukay" was similarly displayed, but was in fact the Auto-R model with the line release lever on the mech.