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#1
April 14th, 2006
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Guys, got a question..
I have a Gabbiano 100 gun with 20mm rubbers, I had some problems with it in the past, well...sometimes I still have  , but I like its accuracy and I kind of like it now.I need a little bit more power.. I have seen this italian dvd, where Donati, is his name, tests some rubbers on the same gun, and you can see..it is very obvoius..that the 16mm rubbers are more powerful then the 20mm..on a distance of 3meters.. The 20mm rubbers were cressis and the 16mm aswell.. Now...is it that he used, for example 16mm rubbers for a 90 gun on the 100? Could I put 16mm rubbers for a 90, on my 100 gun. I am not stupid  , ofcourse you can,...but is it effective?Anyone??
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The worst thing is to get involved with people who aren't passionate about what they're doing. Willem Dafoe 
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16mm RUBBERS..VS..20mm
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#2
April 14th, 2006
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well, ive used 16mm rubbers from a 75 on a 90 (beuchat) and it worked pretty good (you are talking about single bands right?) range was decent, loading was easy, not bad for the smaller fish, i figure it would be the same as if you took a 100cm gun and shortened the bands a bit, which a lot of people will end up doing anyways.
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#3
April 14th, 2006
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basically, thicker bands should have more power, so the 20mm should be more powerful than the 16mm. But you must consider that they're not all made of the same type of rubber. Parameters called "volumic mass" (the density of rubber) and "resiliency" (the elastic return of power) are the factors which make the difference: for instance, 16mm Dessaults are more powerful than Picasso 20mm, because Dessaults have a superior volumic mass and a better resiliency. So it's not a matter of numbers, but it's about the quality of rubber.
Another basic concept is that thicker bands require thicker shaft: too much power on a thin shaft would cause a loss of accuracy. But this is only relatively true, because shafts, too, are not all made of the same quality of steel... To make it end, it's a mess...good luck! (Me I wouldn't charge guns with too much power).
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#5
April 15th, 2006
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Dessault bands are the simply the best (and you know I always claim italian stuff to be the best, but in this case France rules)...
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Deeperblue.com Staff
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#6
April 15th, 2006
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Just fitted a set of screw in 20mm bands to my 90. They're immersion Mega boosters. Are these the same as Dessault? I think Immersion, Dessault and Escalapez are all the same company. Good old Jean-Baptiste.
Anyway, whatever. The thing is the gun is now more powerful than with the standard set of 16 mm bands. However, I can't seem to hit a barn door with it now. Only hit one of the 7 fish I've shot at in the last 2 days  . Hopefully I'll get used to it but I'm wondering if I've spoilt it by overpowering it  . If all else fails I'll have to find bigger fish to aim at.Dave
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#7
April 15th, 2006
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Quote:
About bands, shaft, and ballistics ther's a good technical article on maorisub website ("Balistica comparata delle ari subacquee"). Pity it's only in italian. Old Man again--Curioius about your shots misssed: where they short shots, with thick bands and thin shaft? If so, the explanation is in the above mentioned article (but still it's in italian ).
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#8
April 15th, 2006
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Okay, thanks for that. Got me designers in a twist.
 . At the start of the season I do find sometimes it takes a while to get my eye in but this year it does seem to be the bands as well. Most shots were at what I regard as medium range i.e. about 1 to 2 metres. At least one shot was high as I marked the dorsal fin and another shot was low as I saw the spear pass beneath the fish (just). The fish were all 2 to 4 lb (1 to 2 kg) so not big targets. The other shots I couldn't tell. If I had to guess I'd say the short shots were high and the longer ones low but by that reasoning I should have hit the mid range. .I did feel that the trigger was heavier and there is more of a kick (recoil) so it's more likely just to be inconsistencies. Spear is 6.5mm x 140cm and the gun is an old but top of the range Beuchat (no rail). I'm not looking for answers just passing on some experiences. More practice tomorrow - with luck. My mate had a 7.5lb bass today - wouldn't want to miss one of those. .buona caccia Dave Last edited by Old Man Dave; April 15th, 2006 at 21:04.
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#9
April 15th, 2006
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Hello Old Man. Well in this forst month of spring I could go spearing only once (due to bad weather, work, family, flu and then what else? The Pope?) and in that sole occasion I missed incredibly easy shots, as it's normal after months of no gun-in-hand. But I asked you for a specific reason.
I've learned that the accuracy on short shots of thin 6mm shafts is badly affected by overpowered bands, because thin shafts cant' absorb all of the power, so they flex and swing in the initial section of their tajectory. Which means: no accuracy on short range with 6mm. But if you used a 6,5mm (as I did: Seatec Diamant 6,4mm), I think it's simply human errors, and we will adjust our eye day by day (if it ever will stop raining and the Pope will let me go fishing ;-).
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Deeperblue.com Staff
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#10
April 16th, 2006
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Quote:
__________________
The worst thing is to get involved with people who aren't passionate about what they're doing. Willem Dafoe
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#12
April 17th, 2006
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Quote:
 They are pretty hard to catch, they always seem to come from above, the water is murcy here, so I had to react fast, not a lot of time... Look at shaneshac´s latest videos thread, shot here in Gibraltar... 2 weeks ago I thought that I had a small bonito, the viz was really bad, but unfortunately it was not a bonito, I had 2 horsemackerels on the tip of my spear, was still happy! You can see the pics http://forums.deeperblue.net/showthread.php?t=65568 Greets!!
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The worst thing is to get involved with people who aren't passionate about what they're doing. Willem Dafoe
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Re: 16mm RUBBERS..VS..20mm
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#13
April 18th, 2006
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Dave,
in my opinion 6.5mm is still small with 20mm either get a 7mm shaft for your 20mm rubbers or go back to 16mm 16mm with 6.5 should be fast enough 7mm and 20mm fast enough and still plenty of momentum at longer ranges 6.5mm will lose momentum too fast and especially with no rail be prone to flex under load when pushed by big rubbers Peter
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#14
April 19th, 2006
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On my 100cm open muzzle gun I use a combination of a stiff 18mm band with a 16mm band for more power.
I think its better than two 16mm or a single 24mm. Only have the gun for 1 week so dont have an opinion if using two different rubber diameters has any downsides..
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#15
April 19th, 2006
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Beginning to agree with you Poacher.
Been a few more times and fired quite a few shots with the 90cm gun, 140cm X 6.5mm spear and 20mm mega booster bands. Apart from one the fish of 6.5 lb I seemed to have missed all the other shots. On trying some target shooting I confirmed the impression I got from fishing. At 6ft (2 metres) range the spear hits 2 inches low and 3 to 4 inches left. That's quite a lot in terms of hits on small fish. Seems to be caused by the excess recoil. Just refitted the set of 16mm bands. Will try them later today just to make sure it's not me who's gone wonky in my old age. I wonder if the gun had a rail it would make much difference. Also am going to order a 130cm X 7mm diameter spear. Maybe that will work better. In the meanwhile I will stick to the 16mm bands as certainly in the last few years I was able to hit spot on every time even if i had to get a bit closer. Dave
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