Need help on which rubbers to get for half-DIY speargun

[John Marr]

Hello people,
I will embark on a longer sailing journey through different ocean areas ( coastal, open and in between ) soon and I am staring to prepare my equipment for fishing.
Since space limitations ( especially when not on the boat and back packing ) are a big concern I opted to build a modular gun that can be used in a long and short configuration.
I have built it using a Rob Allen Vecta handle, matching aluminium rail barrel and open muzzle for double rubber configuration.
Now the long spear is a 6.5mm - length 115 cm which can be halved ( I did some precision milling and thread cutting ) to allow easy storage in a backpack.
The tube is split into three sections so I can take out the middle one and use the gun with a shorter ( 85 cm ) spear in different scenarios.
Now my big question is: What kind of rubbers ( length - diameter ) should I use?
Two different sets? Maybe with two rubbers for the 115 and one for the shorter one?

Thanks for all tips and suggestions.
Cheers!

 

[SubSub]

Sounds like a cool gun! Any pics on the build?


Bands: I dare to say there is a consensus nowadays that the Primeline small ID bands are the shit.

Band length: You've gotta measure the distances from the muzzle to the sharkfins/notches on your spear to calculate the stretch. You will definitely need to sets of bands, one for the long setup and one for the short.
115cm spear: I'd say 2 x 14mm small ID bands. Start @ 350% and work your way up to where you get the results you want.
85cm spear: Maybe go for a 14mm small ID band here too, but increase the stretch to 380%-ish. Otherwise just hop up in diam to 15-16mm small ID.

If you're using dyneema wishbone and you have good inserts, it's quite easy to switch bands from time to time.

Here's a pretty good calculator of band lenght. http://www.spearitco.com/speargun-band-length-calculator-s/1933.htm

 

[John Marr]

Awesome, thank you.
Since "Primeline small ID" is not something I could get my hands on here in Europe, I'd need to look for a similar style.
I can get Pathos, Imersion, Riffe, Rob Allen, Epsealon and Riffe bulk rubbers.
Any other tips to make the rig travel safe? spareparts, etc? I am going for dyneema wishbone especially since it reduces the risk of injury.
Here is a quick snap of the long version. The final screw-heads will be a bit flatter and rounder to minimize injury potential as well.

 

[SubSub]

I’m in Europe too and got mine shipped from the US. Easy peasy actually and since it is not a expensive nor bulky product it is not so much additional costs (shipping, customs, VAT).

Got mine from here: http://www.spearamerica.com/speargun-polespear-bands-rubber.html

MAKO spearguns also sell the Primeline bands. https://www.makospearguns.com/Speargun-Bands-by-Primeline-p/mbr-bk.htm

And if you’re going for dyneema wishbone, you are going to want these inserts! They are researched and developed by Majd / spearq8, a well known spearo/forum persona who also have a great YT channel: https://www.youtube.com/user/majdq8

I’ve tried them this summer and it has proven itself as being great for keeping water out of the rubbers (water in rubbers is a performance degrading occurance), as well as not slipping out. It has been picked up in production euro supplier Ermes Sub (although in Italian only. Hallelujah for Google translate) as well as MAKO (get some while you’re at it if you get rubbers from here!).

https://www.ermes-sub.net/accessori-vari.html

https://www.makospearguns.com/Q8-Stainless-Steel-Wishbone-Inserts-p/mq8sswi.htm

 

[John Marr]

Thanks SubSub. So after some consideration and googlification I opted for the 14mm Rob Allen bands whiyh seem to do more or less the same then the small ID ones.
Thanks for the inserts tip. I already build some who are very similar myself.
I will get back here once I have some results about how precise / powerful the rig is.

 

[John Marr]

all done...

 

[SubSub]

Nice! [emoji106] now we just need to hear how it works, and see some huge landed fish! [emoji16]

 

[Gab]

How did you manage the shafts? This is the main issue I faced when I wanted to make a travel speargun.

If the shafts don't also break up then it won't fit in a suitcase . If you can travel with full length shafts then there is no need to make a speargun that breaks down (other than to spare a bit of weight).

I ended up buying one but interested nonetheless.

Sent from my SM-G930F using Tapatalk

 

[John Marr]

Hello,
well: Its not that hard if you have access to a Lathe and some good drills and thread cutters or if you have a good local shop who can help you with that.
Cut the spear in two, drill holes in both ends, thread these holes, get a threaded rod to fit in the holes, use thread glue on one side, finished.
I carry two of these plus the extra shorter 85cm one.
Also: in case you mess up, usually you can find a spear locally if you are not far far far away from any kind of civilisation

 

[John Marr]

BTW: I also installed two »winglets« on the tip to make the gun more accurate. The two rubbers plus the relatively low weight gave the nozzle quite a jerk. These are made from wood and give the gun also a much better balance under water, because of the added buoyancy.

 

[Gab]

Hello,
well: Its not that hard if you have access to a Lathe and some good drills and thread cutters or if you have a good local shop who can help you with that.
Cut the spear in two, drill holes in both ends, thread these holes, get a threaded rod to fit in the holes, use thread glue on one side, finished.
I carry two of these plus the extra shorter 85cm one.
Also: in case you mess up, usually you can find a spear locally if you are not far far far away from any kind of civilisation

Thanks! Cool project I have to say, looks like you did an excellent job.

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[John Marr]

Here is a recent photo incl. my dinner, supper, dinner, supper and breakfast.

 

[popgun pete]

Here is a recent photo incl. my dinner, supper, dinner, supper and breakfast.

Did you cook him in cutlets as he looks good for chopping up?