Elasticity loss in an unused new band over time

[Lawrence of Iniquitity]

Newbie here. First post. Spearo returning to the ocean after a 30 year hiatus as a landlubber.

I recently bought a JBL Elite Woody Custom to use on reefs here on the Sea of Cortez. The gun had two 5/8 X 14" bands that looked like they had never been wet. The gun didn't have a mark on it so I'm sure it sat for 4-5 years without ever seeing water. Prior owner said as much.

I've never had difficulty loading a speargun but these bands seemed to have no elasticity. I replaced one with a 9/16 x14" band and loading that band is a piece of cake. This made me wonder if, over 4-5 years of no use, the 5/8" bands have lost much of their elasticity?

I considered adding a third band to the gun as even with both 5/8" bands cocked the gun seemed very low on power.

I contacted JBL today to ask if, since the shaft has only two shark fin tabs, I could load a third band and put two bands on one shark fin tab?

I was told by Shirley at JBL that they don't recommend two bands on one tab. She didn't say why.

An hour later I was looking at a number of online stores who sell JBL and on several of these websites it was stated: "All Woody Elite guns can accommodate a third power band." On all of the Woody Elite guns that featured this comment there were only two shark fin tabs.

Before I attempt shooting the gun with a third band, I'd appreciate comments as to whether the problem with low power and little elasticity of the bands on this gun might be a function of elasticity loss over a number of years?

Lawrence

 

[Bill McIntyre]

I've had bulk rubber stored in plastic bags in there dark for years with no loss of elasticity, but I'm not sure how that applies to your band situation.

However, I can tell you that I've used two bands on one tab on my Wong guns for years with no problem. I don't see why JBL would advise otherwise.

Many many years ago Wong provided shafts with pins instead of fins. A friend of mine wasn't very strong and couldn't get the second and third bands to their pins, so he loaded all three bands on the first pin and it broke off. Then he did the same with the second pin, and it broke too. But a properly welded fin should be able to hold two bands easily.

 

[Lawrence of Iniquitity]

Thank you, Bill.
JBL's comment is a mystery to me as well. The gun clearly has space for a third band, so I'll try this and see if it makes a difference.
Lawrence

I've had bulk rubber stored in plastic bags in there dark for years with no loss of elasticity, but I'm not sure how that applies to your band situation.

However, I can tell you that I've used two bands on one tab on my Wong guns for years with no problem. I don't see why JBL would advise otherwise.

Many many years ago Wong provided shafts with pins instead of fins. A friend of mine wasn't very strong and couldn't get the second and third bands to their pins, so he loaded all three bands on the first pin and it broke off. Then he did the same with the second pin, and it broke too. But a properly welded fin should be able to hold two bands easily.[/QUOTE

 

[cdavis]

The amber rubber I use in my slings for sure gets old, even if used very little. A new sling can be pulled hundreds of times over a couple of years. At 5 years, they would not last a week of light spearfishing. They snap when stretched.

How long they last depends a lot on the conditions of storage. My garage is hot and humid. Wetsuits deteriorate out there too.

 

[Lawrence of Iniquitity]

The amber rubber I use in my slings for sure gets old, even if used very little. A new sling can be pulled hundreds of times over a couple of years. At 5 years, they would not last a week of light spearfishing. They snap when stretched.

How long they last depends a lot on the conditions of storage. My garage is hot and humid. Wetsuits deteriorate out there too.

 

[Lawrence of Iniquitity]

Thanks CD. I'll change the bands and see how the new ones compare. I can save the older ones as backup.

 

[popgun pete]

Rubber dries out over a long period as it loses volatile chemicals from the rubber compound, that is why bands or bulk rubber stored in bags stay "fresh" for longer and maintain their elasticity. The volatiles build up in the sealed bag and then no more comes out of the rubber and there is a sort of equilibrium established. Amber bands over a period darken up as the rubber oxidizes and that makes the rubber become less flexible and susceptible to cracking. Unfortunately rubber is being attacked by oxygen from the day it is made, so while antioxidant chemicals are often added which slow the process, they do not eliminate it. Black bands have carbon black added which adds to their strength and abrasion resistance, but does not necessarily improve the elasticity. In the old days rubber was dusted with non-perfumed talc which sucked up chemicals until it formed a type of protective skin that slowed down further deterioration, but again did not eliminate it.

As for the gun taking another band, well it should handle three bands no problems as long as the extra wishbone does not pop off the shark fin tab. Could be the response you got from the company was prompted by the thought that maybe there was an opportunity to sell you a three tab shaft as they must have one if the gun also comes as a three bander. The M8 trigger mechanism will not be affected by three bands as it is geared to take even more.

Well I just checked the JBL website and they don't seem to offer a 3 tab shaft, not counting a third rest tab which may be an option. Two 5/8" bands should be enough. Often guns use smaller diameter bands, but more of them, to split the loading effort into smaller chunks.

 

[Pinniped72]

Great stuff Pete, many thanks for the info. I guess that keeping the bands in the fridge helps because lower temperatures generally slow down chemical reactions?

 

[Lawrence of Iniquitity]

Rubber dries out over a long period as it loses volatile chemicals from the rubber compound, that is why bands or bulk rubber stored in bags stay "fresh" for longer and maintain their elasticity. The volatiles build up in the sealed bag and then no more comes out of the rubber and there is a sort of equilibrium established. Amber bands over a period darken up as the rubber oxidizes and that makes the rubber become less flexible and susceptible to cracking. Unfortunately rubber is being attacked by oxygen from the day it is made, so while antioxidant chemicals are often added which slow the process, they do not eliminate it. Black bands have carbon black added which adds to their strength and abrasion resistance, but does not necessarily improve the elasticity. In the old days rubber was dusted with non-perfumed talc which sucked up chemicals until it formed a type of protective skin that slowed down further deterioration, but again did not eliminate it.

As for the gun taking another band, well it should handle three bands no problems as long as the extra wishbone does not pop off the shark fin tab. Could be the response you got from the company was prompted by the thought that maybe there was an opportunity to sell you a three tab shaft as they must have one if the gun also comes as a three bander. The M8 trigger mechanism will not be affected by three bands as it is geared to take even more.

Well I just checked the JBL website and they don't seem to offer a 3 tab shaft, not counting a third rest tab which may be an option. Two 5/8" bands should be enough. Often guns use smaller diameter bands, but more of them, to split the loading effort into smaller chunks.

Thank you for your input, Pete. Much appreciated.

 

[popgun pete]

Great stuff Pete, many thanks for the info. I guess that keeping the bands in the fridge helps because lower temperatures generally slow down chemical reactions?

Yes, that is exactly why they can go in the fridge, but don't freeze bands, especially wet ones as rubber absorbs water and ice crystals can form. Ever notice that bands feel cool and more floppy after a long dive, that is because they take up water into the material itself in very small amounts. Ditto for your fins and other rubber based products, in fact really wet fins can look new again as they skin with a continuous film of water as the beading effect of water on rubber breaks down as the rubber takes up water. My old spring heel Farallon "Farafin II" fins always look great, until they dry off!