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Carbon Fiber Monocoque Spearguns conventional/roller/inverted

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GRAPHITE SPEARGUNS

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Oct 29, 2023
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Hi all I am new to the forum and wanted to post a couple builds maybe get some tips to what could be done better and join the collective knowledge source.

I have made a few wood spearguns but quickly moved onto carbon spearguns as i feel there are many advantages and my setup to rapid prototyping is now quite streamline.

Guns shown (left to right) are 2 banded 14mm (350%) 900mm from tip to butt 7mm shaft / 16mm banded roller (320%) 1150 tip to butt 7mm shaft / triple 16mm banded (320%) 1100mm tip to butt 7,5mm shaft.

After testing all platforms i find the inverted roller has the most potential for myself, the lack of recoil and clean line of sight make my shots much more accurate and the power in the gun looks to be similar to other platforms.

Couple questions
Best way to attach a reel to a inverted roller?
Horizontal reel or vertical preferences?
Why do speargun manufacturers have one band that is longer usually the first band (for inverted)?
Best way to stop inverted roller line at the muzzle without using a riser?
Is band friction a big loss in an invert?
 
Reactions: Mr. X
There is more than one type of inverted rollergun, so answers are going to vary. You can see the basic types of rollerguns here.
Inverted Rollerguns have a band battery on the underside and rear of the gun with only cables running on the muzzle rollers or they can have bands that run all the way around the gun when cocked. The former need side pulleys to run the cable drive, the latter usually have stretched limited bands that run on the top deck and draw against Y connection or split bands that run to different anchor positions. An example of the latter is the Salvimar Tomahawk.

Maybe you can tell us which type you are thinking of. Despite the interest on forums most people use standard band guns as they are simple to use and re-band in the field.
 
For my invert I attach the reel to the handle guard. I prefer vertical reel, free spool type. All my bands (3 to 4 pairs) are the same length. I use knots at the muzzle end to stop the the line. I can definitely over power my invert if I choose to. Meaning, if there is any significant band friction loss (which I don't see), the gun can power past it.
 
Hi Pete the inverted roller gun is exactly as you described band battery on the bottom, using a pulley system so only cables run on the muzzle as well as top deck. I personally think if only cables go through the muzzle call it an invert if bands to through the muzzle call it a roller.

 
Thanks for the answers musubi. I may have to redesign my handle to suite a reel on the trigger guard. do you mostly use tube guns how do you attach your bands at the handle area.

I have an idea currently to have rear roller so band 1 is attached on top deck band 2 is attached just in front of rear roller and 3 is attached onto the reel bracket, i wonder how hard it will be to pull a band over a horizontal reel?
 
I use pipe/tube guns with the MVD Zeso speargun handle. See here: https://mvdspearusa.com/products/mvd-zeso-speargun-handle
It has an integrated hook on the handle portion. I hook two pairs to this hook. My bands don't lay nicely, but I haven't noticed any performance issues in my guns.

Depending on how much band stretch you want, it may be difficult to loop that 3rd band over the reel. Take a look at Ermes's offering on their hooks for the bands. https://ermessea.com/collections/roller-zone-hooks
They have a hook setup that hooks beneath the reel. I think that's a neat idea in combination with a horizontal reel.

What trigger mech you thinking of going with?
 
The inverted rollerguns, which technically are cable guns, have different length bands to space out the band anchor locations. The idea of any rollergun is to obtain full band drive for the length of the gun barrel. The downside of this is you have to pull right from the muzzle to load it. The use of two stage loading helps out by reserving the harder pulls for the bottom of the gun where you don't have so far to reach and all the anchors are at the rear. As for the reel you see a lot of vertical pin, horizontal drum reels where one of the band anchors goes around and or under the reel. I think the Briante gun has a good system as it leaves room for the anchors by pushing the reel back as far as it can go. The reel is basically a line retrieval device for after the victim is dispatched, you never want too much line in the water if you can help it.
 
Reactions: Mr. X
The Ermes systems look very nice i may recreate something like that out of carbon and give it a go.

I plan on not using massive amounts of band stretch maybe something like 320% i guess i could mount a stand in and actually try to load it.

Ermes double roller mech.
 
I have also thought about placing the reel in this location but i dont like how the reel line will lay. In nz we typically dive to the bottom and there is seaweed to get tangled into thus anything like reel line not laying near the body on the gun may become a hazard. a vertical reel may fix this problem as the line can lay flat against the body.

I feel as thought the bands could have been put back even further, I wonder what that boxy bit at the rear of the gun does.

 
That boxy part may be to add buoyancy at the rear. The gun body has rear windows for band wrapping bands and rear rollers, so that all adds weight, plus you have the weight of the mechanism and reel. The Ermes Sub and similar mechanisms have short sear box roofs, that is what can allow the spear tail to jump out, extend the roof by a couple of centimetres and that problem goes away. The main advantage of the floating roller tooth is it effectively flattens the mechanism in terms of its gearing, but the tooth does not need to be a roller.
 
For example the roof could be made much longer, however the extension shown here is going overboard just to make the point. Windows could skeletonize the longer roof, in fact we see that in the Sigal Sub handle.

 
Reactions: Mr. X
Depending on your preferences and design idea, a vertical reel would allow a bit less of an angle for your reel line. You could also lessen it if you sloped the front part of the trigger guard down and mounted the reel to that, and tuck it as close to the barrel as possible. I wouldn't want the reel line too far away as well.
 
Great info guys, @popgun pete do you think that small amount of "roof box" will have a dramatically better out come to tail lift? or would you need say 1/3 of the track to be enclosed to capture tail lift at the trigger.

@musubi I think i may try a few different options maybe 3d print some parts to see which method fits the build a bit better.

This is the current stage of the inverted roller build with rear rollers, Computer vs real life.
 
Well it used to, for example Sea Hornet guns have a long tunnel and they are reverse mechanisms. The only problem for that layout is it is too tall for a eurogun, but fine for a cocking stock gun. I have shot plenty of them. This cut back roof came about when folded metal cassettes were being built and no one thought of pushing the guns much in terms of power, guns only needed to shoot about 12 to 15 feet and that is where many still shoot at. Many comments you read on boards are echoes, when repeated enough they become the truth, but are no such thing.
 
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Yes shots are generally only 2 or 3 meters but, i always like to have in my minds that i have a gun capable of slinging a hunk of metal accurately to 5m or so instead of worrying about penetration, less to think about better for diving.

i may try add a detachable tunnel to the end of my gun and see if there are any improvement.
i guess i should move along and make said gun first.
 
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