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Band Poundage Question

Thread Status: Hello , There was no answer in this thread for more than 60 days.
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LiftAndShoot

New Member
Sep 11, 2016
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Hey guys -

I am infected at once both with the love of water I grew up in and a talentless love for DIY projects. It's a sickness, it really is.

That said, I have a question that I'm sure some of the veterans will see my purpose in.

I don't understand a lot about the bands that are strung on spearguns, but I do know that they come in various diameters and in multiple configurations (e.g. - multiple bands per gun). My JBL competition magnum (as yet unused) that I frankenbuilt has 3 bands and I don't know what their 'poundage' is.

So, here's my question - is there a way to determine what the poundage or energy in a band will be by knowing it's diameter and length? Obviously I want to translate this information into knowing if it's going to be stout enough for what I'd be spearing..

Thanks,
LaS
 
I don't know if this will answer your question, but some people use heavy duty fish scales to see the strength / lbs of force on the band. They do this by attaching the scales to the wishbones and pulling it all the way back to the notch- I believe

Cheers rock shooter
 
We generally estimate relative power from the cross-sectional area of the rubber - taking into account the cross-sectional area of the non-rubber hollow centre (which is much bigger from most scew-in bands). It's useful when comparing different options for a speargun with a barrel of a certain length.

e.g. 2x20mm > 2x16mm > 20mm > 2x14mm > 16mm > 14mm

It's just a rough guide though, real life is more complicated. In practice rubber diameters vary, "20mm" is often actually USA 3/4" which, in theory at least, should be 19mm.

As you are into DIY, you could try measuring it yourself. I expect the manufacturers might be able to provide some info - although I gather that speargun rubber is really manufactured for castrating cattle rather than spearing fish, so "poundage" & "energy" might not be of much interest to some manufacturers.

You might be overcomplicating things though: if your spear goes through the fish, you have enough power.
Also, it is not all about power tho'. Balance, accuracy and being in the right place at the right time are "right up there". You can miss opportunities if you have to spend a long time reloading.
 
Last edited:
Rock, X - thanks for the replies. I guessed it wouldn't be as simple as I hoped it would be.

For a piece of info, here's the deal - since I'm going to be in Texas for the next...bunch of years, I'm aiming to stalk down some big lake-and-stream dwellers out here. Namely, carp. But, I don't think I need a 3 band JBL to get there even though some of these fish are big. So, what I'm looking at doing is having my own home-built gun with ONE band.

-LaS
 
The problem with using only one band is usually the application. For example if you're strong enough for a 20mm mega band, you see a carp on a rock, there is almost no way to minimise the power so that if you miss, you don't hit the rock, as you'll end up blunting and bending heaps of spears. I personally would recommend 2x16 as you can always unload one for the tricky/risky shots, and it's a whole lot easier on the bruises to load, any higher double and it would be bordering on ridiculous . If you don't like it you could always not use it or remove it completely.

It's your choice really, you could probably shorten down a 16mm band, it depends on how strong you are.

Are you planning on making an enclosed or open track gun? This will determine what kind of power you can use preventing shaft whip.

Forgot to mention, band size should also depend on the thickness of the spear shaft.

Keeps us updated,

Regards
Rock Shooter
 
Rock -

That's clearly information my as-yet untrained brain hadn't considered. So, really appreciate it.

I think right now I don't know enough about guns and what their various configurations are 'best for' situations. Like I said, I'm wanting to build one (with my massive experience) because I have an Osage tree on my property that is just IN the way. So, that's my wood source. I can order the bands (2x16mm, thank you), and from there it's research. But, I don't know the best track for the gun or the length of the gun. Advice in that regard (knowing what my targets will be..) would be awesome.
 
What kind of tools do you have to work with? Router? Drill press?
I'm absolutely no expert on building guns, however there is a solution . On deeper blue there is a whole section on gun building.
here is the URLs for a great first build with limited enough tools:
http://southernfreedivers.org.au/forums/viewtopic.php?f=3&t=4162&p=36117#p36117

Like I said I'm no expert but I'll try and help you out!
Cheers
Rock Shooter
 
Reactions: Mr. X
If conditions are murky. I reckon a 70cm RA railgun (or similar Mako, etc.) with a single 16mm band (e.g. the RA Sparid model which comes with aluminium railed barrel, a 6.6mm spear & a spear & muzzle than can optionally accept a second band) would likely be more than powerful enough for even big carp. That's likely what I would go for. Although I'd be more than happy to use my 75cm Omer XXV with 6.3mm spear & 3/4" bulk rubber - it is a lot slimmer (& "hydrodynamic") & lighter too. It'd work fine with a single 16mm band too, perhaps better.

BTW RA will custom make railguns to pretty much any length if asked, you might want an even shorter speargun (e.g.60/50/40cm barrel). I have heard from an impeccable source that some folk use double bands on the very short guns in some of the former Soviet countries, presumably for carp and/or sturgeon and/or salmon (or James Bond type escapades).

Another rubber option would be 2 x 14mm. But then you'd have to load 2 bands. 1x16mm or 1x19mm would be my preference. But it is nice if the muzzle & spear can optionally accept another band -- it keeps your options open.
 
Bending a speartip in a rock is no biggie if you have a flopper shaft, just grind or file the point back onto it. With a sliptip of course hitting a rock will usually be goodbye to a $90+ tip.

If you want to go with a single band, you can also go with a thinner, lighter spear. Really big fish can bend your spear and while it can be restraightened it will bend easier next time.

Too many bands on a thin spear will lead to shaft whip, but on a short spear likesay 75cm and smaller, shaft whip is less of a problem.

For me the only problem with a fully powered gun for bottom hunting is burying spears into the reef, then it is a lot of bother to recover and sometimes impossible, even with a crowbar.

My 65cm gun was always loaded with two bands. It was used for holed up fish and night hunting; I regularly shot fish over 10 pounds and even a few over 20, but at near point blank range.
 
Reactions: Mr. X
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