When do you change your rubbers? 20mm vs. 16mm

[Mr. X]

Hi,
I'm curious as to how long speargun rubbers last typically. Also, when do you change them - do you wait until the rubber perishes or tears?

I already replaced the Dyneema wishbone this year when the wear went beyond the protective sheath & started to cut into the core.

I was planning to eventually replace the 16mm rubber on my Rob Allen railgun with similar 16mm rubber, however I ended up with some 20mm bulk rubber. I am not that keen to use it though as I fear it will (1) it may be a pain to load & (2) it may screw up the excellent accuracy of my gun (which is just as it left the factory). I know it is normal practice to use a longer length of 20mm than 16mm ... to ease loading. Any thoughts, experiences, insights or suggestions?

(I think I might be inclined to try a smaller diameter spear rather than thicker rubber, if I wanted more speed. I am really just looking to keep the gun performing as it left the divefactory).

 

[spaghetti]

Rubbers must be changed immediately if they have cracks in the portion near the fittings of the muzzle or wishbone: that means they can get broken any moment, and if it happens while the gun is loaded, they can smash your face.
Me I change rubbers once in a year, generally early in summer: I store them in the fridge inside a plastic bag during winter, "finish" them in spring and change in summer. But it basically depends on how often you use them AND on your sensation: if you feel like they got feeble, you will feel the need of new bands on.
---16 or 20? it's not just a matter of sizes because not every manufacturer uses the same quality of rubber. In any case, mind that band thickness and shaft thickness must be balanced. For example, I wouldn't use 20mm bands for 6mm shaft: that would probably turn to very bad accuracy, especially in short range shots.
You may also read this article by Mark Laboccetta:
http://www.deeperblue.net/article.php/443/42
and this forum topic:
[ame="http://forums.deeperblue.net/showthread.php?t=65743"]16mm RUBBERS..VS..20mm[/ame]

 

[roy_nexus_6]

When do you change your rubbers?, long speargun rubbers, protective sheath,
I think this thread has a potential for some good posts ...........

rofl rofl rofl

 

[Mr. X]

When do you change your rubbers?, long speargun rubbers, protective sheath,
I think this thread has a potential for some good posts ...........

rofl rofl rofl

Oh no, here we go again! Walked right into it:duh

Spaghetti for the record, my railgun has a 6.6mm spear & the rubbers are, I believe, all genuine Rob Allen. The existing rubbers currently appear fine & the gun is stored in a cool dark place.

 

[Dobs]

Hi Mr. X,
I second Spaghetti's opinion on the bands change.
As for the 16mm vs. 20mm question, there is a big difference between the two set ups. I have tried both on my wooden guns and the thicker rubbers give more range with the same accuracy. This is valid as long as you have a rail (and you do have one on your Rob Allen). With the 16mm band the 6.25mm shaft hits spot on for up to 2 m., but then it starts falling down, while with the 19mm (or 20mm) bands it flies straight until the end of a single wrap, which is about 3 m (I'm talking about a 90 cm gun).
On another gun (110 cm), I use 6.5 mm shaft with 19mm rubbers and it also flights straight to the end of the single wrap.
I have even tried 6mm shaft with 19mm bands and it is accurate enough.
All these set ups are tested on wooden guns with integrated rail, though. If you try this on a standard euro gun, with no rail, it is different story.
I never tried a 7mm shaft, but I guess it will be better with thicker bands than 16mm.
As for the loading, it is more technique than strength so you will get used to loading 20mm bands in no time.
Cheers!

 

[Griff]

hey there guys.
in my opinion, unless you have super short rubbers, the biggest difference between the 16mm and 20mm rubbers is the durability. 20mm last a lot longer because the perishing affects the area much less in relative terms. i've been using thicker rubbers for the last few years now and wouldnt choose a 16mm for single rubber gun just because you have to toss them out sooner. with time all rubbers loose their power at a particular stretch and so i've just kept on chopping them shorter, doing this you extend their life, untill they start looking well dodgy and its time for a replacement. keep in mind that this is for a rob allen muzzle where the worst wear happens at the wishbone, the part that gets cut off when you shorten your rubber. the black rubber stands up to nicks very well, and one of my guns has small two nicks which i can see when loaded. however, they dont seem to be growing and the gun still shoots fine. these cuts are different to the normal perishing and are probably reef related.

I dont like loading a 20mm gun because of the lack of give and which makes getting into position for the big pull that much harder. a good compromise for me has been the 18mm rubber in terms of durability and loadability.

in terms of the physical difference, 16mm rubber can get to the point outside of its elastic range which isnt good, but it takes a big big pull to load it at that sort of range. thicker rubbers would be impossible to load to outside its elastic range, at least by normal people. i think thicker rubbers are also more resistant to creep (slow increase in length due to continual load, ie decrease in power for a speargun) because the material is less strained which is also a plus.

also remember that with thinner spears you loose penetration power. IMHO for a 110 gun, a 7mm spear and a single 18mm rubber is the best setup.

 

[Mr. X]

Getting some really good insights from this thread. Grif, thanks, I think you answered my questions and also given me several ideas for things I should do. Excellent.

By the way, where did you get your 18mm rubbers from - RA? I've never even seen 18mm rubber; saw 19mm rubber mentioned on, I think, a Rabitech chart somewhere. (It's hard to find bulk rubber over here).

 

[Huw]

Hiya Foxfish,

Just browsing this thread, and it was a debate that i found myself in the center of a while back. I eventually concluded that i was hitting more fish than i was missing, and that i had become so used to my 16mm rubbers on my 90cm with a 6.35mm shaft that there was no need for more power. I felt that with each size, of rubber, shaft etc, there would be both positives and negatives, and therefore since i was used to my set up i couldnt do better that staying with what i had.

Just my ten penneth, and it would be great to hear what differences you notice between the 20mm and 16mm bands, should you decide to stick with the change.


Huw.

PS: sorry i cant offer you any help on finding bulk rubber over here!

 

[Griff]

Hey X

ya, got the 18 from rob allen. not sure where its produced, but i'm sure its available around europe. I first heard of 18mm from some european site if memory serves me. and its not the 19mm, or what we call 20mm. you also used to get 20 with a bigger hole in the middle. that may also be pretty cool cause in the end its all about area. cheers