7.5mm + Shaft not a Good option for a 110 cm Wooden Speargun ?

[Ed_Camino]

Hey Guys, I had been using a 6.5mm (145cms) Shaft on my 110 Wooden Speargun for about 5 motnhs and it was great... I hardly missed any shots and I was happy with the results I was getting considering I've only been spearfishing for 8 months But I lost the Shaft and I now have been using a 7.9mm (138cms) Shaft and well, the story has changed like you wouldn't believe .missing very easy shots . Shots I didn't miss before . From a very close range even and it is very Frustrating .I figured it was gonna be a heavier Shaft than the 6.5mm (145cms) Shaft I had before that's why I thought it was gonna be best to get it a bit shorter (138cms). So guys , any thoughts as to why That is happening ? any suggestions ? things I should know about Shafts other than the Longer the Shafts the more range I'd get or the thicker the shaft the more momentum stuff etc. I'd appreciate any help or any suggestions !

thanks guys

 

[Mr. X]

Not surprised. You changed the spear size - didn't you expected things to change as a consequence, else why change it? I would suggest getting another 6.5mm/145cm spear: the obvious/simple route back to factory spec. perfection

My 2 cents worth on your thickness v. length question:

THICKNESS (Yes! And mass.):
If you want to stick with the fat shaft, you need to analyze what is happening but most likely you will need more power (e.g. more bands and/or thicker rubber). If you are using, say, a single 16mm/19mm band now, you could try running with two 16mm bands - assuming you spear has notches/fins for two or more rubbers.

You could also check out, say, Rob Allen configurations to see what spear diameters they use for different band configurations (it'll likely be 2x16mm bulk rubber loop bands or more).

LENGTH (No, probably not):
Shortness can be a factor, spears are normally 40cm longer than the barrel on a eurogun but 7cm is probably not going to be huge problem. Here is why I say that:

1. My Omer XXVs (75sm & 90cm) run spears 5cm shorter than normal and that is factory configuration and they don't have rails to (some XXVs have rails, mine don't) - they work great.

2. Rob Allen reckons you can run spears upto (if I recall correctly) 10cm short on their railguns if necessary - the rail probably offsets the spears tendency to sag in the middle between supports that you'd get on non-railguns.

3. You are using a 7.9mm shaft on, what, a 100cm barrel - it ain't gonna droop much in the middle. Do you have a supporting rail/groove - if so, see #2 above.

4. If you barrel length really is 100cm, the recommended spear length (for a eurogun/railgun) would normall be 140cm, so 138cm is pretty darn close to normal.

Other considerations:
The barb/flopper can sometimes need adjustment.

Like I said: I would suggest getting another 6.5mm/145cm spear.

 

[Ed_Camino]

Hey Mr x, the reason why I went from a 6.5 to a 7.9 was bc I couldn't find another 6.5 at the moment...they didn't have it in stock at the stores so I figured you know, ( the genius that I am) if I get a 7.9mm it should harder to bend and more resistant overall. My 110 wooden spear gun has 2 19mm Rubber bands from omer and the new 7.9 mm is pinned and I've ven been loading it to the last two pins for more power bc I figured I'd need all the power I could get to that shaft moving. I had mini shark fins on my 6.5 and the 7.9 pinned. I even moved the flopped from the top to the bottom to see if that could help with the flight of it helping keeping it straight . the barrel is really 110cm and yes, I have and been told the correct way should be having your shaft 40cms longer than the barrel but I had no problems with the one I had...even with another Shaft I have that was 142cms long...But of course, they were both 6.5mm. So with that said...is there any possible way to correct this or should I try getting another 6.5mm x 140cms + ? And btw if you would please...could you or anybody on this forum try to explain to me with every possible detail you can think of and all the pros and cons of having a 6.5 mm Shaft..the pros and cons of a 7.5mm+ Shaft on a 110 wooden Speargun loaded with ( 2) 19mm R bands Thank you Mr x and please excuse my ignorance on the matter... I'm just try to learn everything and anything I can..!

 

[foxfish]

Spear gun ballistics can be complicated but one factor you don't mention is the overall balance of the gun.
Manufacturers take time to address this issue and match the length & weight of the spear to match the guns buoyancy.
If the gun is now muzzle heavy (or light) this can effect accuracy.
I would suggest you discover why your gun is not hitting your aim point, it might still be shooting straight just not going where you expect!
Set up a target & take some practice shots to see what is happening...

 

[Ed_Camino]

Hey Foxfish, you are right I didn't mention that part. The gun felt pretty balanced with the 6.5mm x 145cms I had before and to be honest I don't know if it was as balanced as a good Speargun needs to be but I had no problems. I was right on the money with most of my shoots. Even on moving targets. Yes, with the new 7.9mm x 138 cms Shaft the Speargun does feel heavier than it did before. Muzzle heavy and even the Shaft felt heavy by it self felt heavier more so loaded on the the gun..yesterday I did set up a target and I was missing down on every single shot . I set up the target at about 12 feet. Some might say that the target was too far away but the same target at the same distance I was right on point with the 6.5mm x 145cms . Thoughts and suggestions are welcome and much appreciated!

 

[Bill McIntyre]

I think the most likely cause is muzzle flip. The shaft is too heavy in relation to the weight of the gun, so you have more recoil. Since your grip on the handle is probably lower than the line of recoil, the gun rotates around your hand and the muzzle rises. As it rises, it pushes up the rear end of the shaft as it leaves the gun, causing the shaft to hit low.

Adding more power would just make it worse, since it would increase recoil. If you want to use a heavier shaft and/or thicker bands, you need a bigger gun to go with them.

 

[myfish]

I would add spear drop and a drop in energy transfer from whatever bands you had, now driving something MUCH heavier. If anything, with bands staying the same, I wouldn't blame recoil and muzzle flip/spear being diverted down as a consequence. That's usually a symptom of overpowering.

 

[Ed_Camino]

I Think after using that 7.9 mm shaft a couple of times and seeing how it travels after its released from the gun I'd have to agree with you . yes, its a fact the muzzle flip has something to do with it bc its a much heavier shaft but in my humble opinion seeing what i've seen so far I'm pretty sure that the main issue ts the weight ...even out of the water I pick it up and hold it and of course you can tell the difference and how much heavier than the 6.5 mm it is but I didn't think it was going to make much of a difference Obviously I guess its one of those mistakes you make as a rookie but you all had great points and were a big help .I've learned the Shat selection has a lot to do with the Accuracy when it comes down to spearfishing so if you all can thin think of something else , things you might have missed or not said please feel free to share Knowledge

Thanks a lot guys.!

 

[mariusshobo]

Here is my calculation regarding the mass of the two shafts:

1. dia 6.5mm, 145cm lenght
8050.00kg/cubic meter x 3,14x(0.00325m x 0.00325m)x1,45m = 0.38714405kg

2. dia 7.9mm, 138cm lenght
8050.00kg/cubic meter x 3,14x(0.00395m x 0.00395m)x1,38m = 0.54425046kg

The difference of weight between the shafts : 157 grams, the thicker shaft being heavier.
More mass on shaft, more recoil. And you had increased the mass of the shaft with almoust 50%. I guess it is it.

 

[doyenofcastle]

Hey Guys, I had been using a 6.5mm (145cms) Shaft on my 110 Wooden Speargun for about 5 motnhs and it was great... I hardly missed any shots and I was happy with the results I was getting considering I've only been spearfishing for 8 months But I lost the Shaft and I now have been using a 7.9mm (138cms) Shaft and well, the story has changed like you wouldn't believe .missing very easy shots . Shots I didn't miss before . From a very close range even and it is very Frustrating .I figured it was gonna be a heavier Shaft than the 6.5mm (145cms) Shaft I had before that's why I thought it was gonna be best to get it a bit shorter (138cms). So guys , any thoughts as to why That is happening ? any suggestions ? things I should know about Shafts other than the Longer the Shafts the more range I'd get or the thicker the shaft the more momentum stuff etc. I'd appreciate any help or any suggestions !

thanks guys

how much the band stretch % you are using ?in your previous 6.5mm did you use 2*19mm?

 

[Bill McIntyre]

There are so many variables that I'm questioning everything that I think I used to know, but the best bet is to go back to what was working in the first place.

F

For instance you said you have a 110 cm wood gun. Two days ago I shot this yellowtail with a Abbelan 110 cm wood gun with an 8 mm shaft and two 14.5 mm small ID bands stretched to about 370%. I would never have believed that s small gun like that could handle a shaft that thick and use bands that small, but in a pool it was very accurate at a range of 20 feet. I think its at least partly a function of gun design. The bands are perfectly aligned with the shaft, and the handle is very high.

 

[doyenofcastle]

370% two band give theoretical force of 94Ib , it's enough for 8 mm spear ,if U use 16mm regular at 310% may be you get same results but band last for longer time ,i think main factors here is (spear weight (not length or dia.)/band force/gun weight ) ,SS spear vs spring spear both same dimension under same force behave differently ,I'm not expert at all but this what I think .