Euro Riffe...Changing to 20mm band

[ihab]

Greetings,

I know this was probably discussed before…but I’m a bit lost.:head

I have a 90 cm Euro Riffe (which is actually 110 cm long) with a 6.75 mm shaft, 130 cm long.

The gun comes stock with 2 x 16 mm bands and I want to change this setting to a single 20 mm band for faster loading.

The choice of length for the 20 mm band is a bit confusing when reading this forum.

Some on this forum advise on using the 3:1 stretch rule, making the band length needed approx. 43 cm.
Others swear by the fact that any spear, 130 cm long, using a 20 mm band, band must be 48 cm long.

So what rule do we follow……!!:t

Thank You
Ihab

 

[OregonSpearo]

The following table for the correspondence between tube length (first column) and circular band length (third column):

 

[getawayFK]

Ihab, why would you want to change it to a single 20mm band? because with the 6.75 and heavy shaft, I guess that would even be bit underpowered (I already noticed that even with the standard 2*16mm bands the euro riffe is slightly underpowered starting at mid ranges, where the shaft starts dropping earlier. So i guess with the 20mm bands, that might destroy the accuracy and range of this gun...

I advise you to stick with the standard bands, and simply change them to slightly shorter ones if u want even better accuracy on longer shots.

Best regards

 

[ihab]

You know getawayFK, I think you're quite right.:martial

I actually did try the 20 mm single band setup and it was a disaster:vangry ...total disaster....The gun was underpowered, it was difficult to load the gun with a relatively short 20 mm rubber....and accuracy was a joke.
So, I guess I will go back to the original setup...which I also agree it is a bit underpowered....any suggestions are welcomed.rofl

Ihab, why would you want to change it to a single 20mm band? because with the 6.75 and heavy shaft, I guess that would even be bit underpowered (I already noticed that even with the standard 2*16mm bands the euro riffe is slightly underpowered starting at mid ranges, where the shaft starts dropping earlier. So i guess with the 20mm bands, that might destroy the accuracy and range of this gun...

I advise you to stick with the standard bands, and simply change them to slightly shorter ones if u want even better accuracy on longer shots.

Best regards

 

[ihab]

Are you sure this table is for 20 mm bands....the original band lenth on an RA 100 cm gun is 77 cm....looking at you table, it say 60 to 65...........more than 11 cm difference....what do you think.:head

The following table for the correspondence between tube length (first column) and circular band length (third column):

 

[foxfish]

Use a mamba rofl

 

[apnea_beast]

2 18mm bands work great. thats what i've got on mine. that riffe mech was designed to handle up to 2 20mm bands and the teak is super strong. they can be the same length as the stock 16's or one or three centimeters shorter. make them yourself otherwise your going to waste a lot of money trying to figure this out. remember you can always go shorter if you don't have enough zap.

 

[ihab]

Thanks apnea_beast....I'll try the 18mm setup...problem is the wishbone dynema cord on the original 16mm bands are relatively long compared to the ones I have in stock.

How do you suggest I go around this.
Cheers:friday

2 18mm bands work great. thats what i've got on mine. that riffe mech was designed to handle up to 2 20mm bands and the teak is super strong. they can be the same length as the stock 16's or one or three centimeters shorter. make them yourself otherwise your going to waste a lot of money trying to figure this out. remember you can always go shorter if you don't have enough zap.

 

[getawayFK]

Btw apnea_beast, i added an extra 16mm band to my riffe 110cm, but added the 24' band instead of the 26.5' that should be used with... So now I have 3 16mm bands, the two standard 26' 16mm bands, and one 24' 16mm band... Anyway, it's hard to add the 3rd band, and u must at least load 1band (dry) in order to get some space in the muzzle area and fit the 3rd band...

Now to test: I only had few opportunity to shoot in water with 3bands, and I had 2 bad misses on large fish (big baracuda and king mackerel). Not sure if the problem was due to the loss of accuracy of the gun, or because I missed the shots myself (as visibility was really bad that day and those fish were on the edge of visibility). On another trial, I shot from like 2m distance (from the tip of the spear) at a medium sized seabream (those are like 20-30cm max and fast moving) and it was like a lazer... So im not sure yet about its accuracy with the 3bands, as I'll have to do some pool testing with it.... Another note: with 3 16mm bands, the recoil is pretty strong so u must really shot with firm arm or both hands otherwise u could injure urself...

Now i am only using 2 16mm bands (shorter than the normal bands) and I noticed improvement in distance accuracy, and not much recoil as compared with 3bands...

I hope that was useful.

Best regards

 

[panosb]

Hi mates,

The length of the bands depend on the max. loadind length (MLL) of the gun and not on the gun length. It also depends on the stretch ratio of each band type.The MLL is the distance from the muzzle of the gun up to the notch or sharkfin we intend to load each band. (This means that for 2 or more bands these must not necessary be of the same length!)The MLL depends on the type of mech the gun has (inverse or normal) as well as the shaft used.

The stretch ratio is differs among the manufacturers of bands as well as among various thicknesses. The ratios usually are between 3 and 4, with usual figures being 3.2-3.4.

Regarding the 6.75mm shaft, you can get the maximum perfromance using 2X17.5mm bands a little longer than suggested (smaller ratio) With one band,even thick, this shaft is usually underpowered. 3X16mm bands is too much for 6.75mm and for Eurogun as well.

Hope I have helped.

Panos

 

[sbooker]

Hey ihab, what type of bridles/wishbone do you have on that Riffe? I find the dynema bunches and spoils the view down the shaft.

 

[Amphibious]

I use a single 20mm band and a 6.75mm shaft on my 90cm Master America, shoots great, don;t find it under powered at all. I use the 3:1 rule.

 

[sbooker]

is that an open muzzle gun?

 

[ihab]

Hello Amphibious,

Could yoy elaborate more on the 3:1 rule.....and give an example for a 90 cm gun, with 2 x 16 mm bands.

Thanks

I use a single 20mm band and a 6.75mm shaft on my 90cm Master America, shoots great, don;t find it under powered at all. I use the 3:1 rule.

 

[Amphibious]

bands should be cut so they stretch to 300% when nocked.

hard to give an example without haveing the gun here to put a tape measure on

 

[ihab]

Do you measure the distance for any gun from the nozzle to the notch on the spear to determine the length of the rubber to be used?
Or else, from where do measure gun to determine length of rubber :martial

 

[apnea_beast]

just cut your 18mm bands the same length as the stock 16mm's and then try it out. you can always shorten them if you feel it needs more power. your going to need to use 1.75mm or 2mm cord to make wishbones(dyneema or spectra, maybe even vectran). to make the end knots in the wishbone double up the end part of the line and then tie a figure-eight knot. a single strand knot won't be thick enough and it will pull through. you could also use some sort of beads like the brass ones that some companies use. the knot to secure the wishbones within the rubber is the double constrictor knot. search for an image of the knot and you'll get some results with illustrations. you can buy a wishbone insertion tool from rob allen ( i bought mine from florida free divers).

the length of the gun is irrelevant. you want to measure the amount of stretch which will be from the muzzle to the notches.

 

[Marwan]

wow this thread is kicking, my friend ihab's quest for ultimate power
in my humble opinion, if you feel that 6.75 is underpowered on a single 20mm, you need to get a mamba i use the 6.75 with single 18mm and never felt it to be underpowered...but these things are a bit up to personal preference i guess, it would also be influenced by things like the type/size of fish you hunt...

 

[ihab]

Okay Guys...and Marwan:hmm ...thanks for all who put in their notes on this subject, but...UNTIL now......no one has come forward to explain exactly, how to determine the length of a rubber band…in relation to the gun’s length.

Everyone seems to have a different view….so let’s hear it from someone involved preciously in the rigging of rubber bands for spearguns….or we are back to square 1

To make it easy….let’s take a 90 cm gun….as an example….. and try to rig 2 x 16 mm rubber bands.

Or whatever is easier.

Thank you .............and it is hot in Cairo

 

[Amphibious]

measure from thr point of attachment, to the last nock point on the shaft. divide by 3. for circular bands take this # and multiply by 2. take off a few cm's for wishbone lenth.