Single and double band size comparisons.

[spaghetti]

Originally Posted by Pastor

Also the graph of "F = -kX" is not linear for rubber, the further you stretch it the less the proportional force needed to cause that extention

Spot on! That's exactly what the Maorisub engineer says in the article I linked above.

[Pastor]

I learned that 30 odd years ago in a Physics lesson at school

[Mr. X]

In other words, we don't know. Better ask forum members Miles or Rob Allen as they have probably shot both configurations and tell you the difference in reality. [My guess would be that althought the Tuna gun will be more powerful, there is little practical difference between the two configurations. Maybe a shorter 120cm Tuna gun with 2x16mm bands & thicker spear would have similar power/impact to the longer Caranx but it is a shorter gun, with a shorter spear and - depending on your rigging - shorter spear-line.]

Maybe we are missing out on something in the UK (it happens) but you don't hear of folk using twin band 80cm guns here instead of a 90cm gun, for example. I guess if I went to the med, I could put double bands on my 90cm to make it more like the ubiquitous 1m guns or a 1.1 even, but I probably wouldn't - it is powerful enough when it reaches the end of the spear-line already. ( I guess using an extra wrap or half wrap, or adding a reel, might allow for an increased range with the more powerful configuration - but not sure that's enough to justify having to load 2 bands).

[Jonny250]

I learned that 30 odd years ago in a Physics lesson at school

:-)
Ah you must have paid more attentian in school than i did - learn something new every day !! :-)

I've done a bit of google-reading on rubber properties now and it's really amazing stuff - strain varies with temperature, but also strain varies with strain-rate! so the faster you stretch it, the easier... apparently it's the heat change in the rubber that makes it non-linear (you can even feel the heat created when you stretch a rubber band!)

So an alternative way to TEST the best solution would be to hang weights on the bands, or use a strain guage, to see which can carry the most load. Of course you'd have to do this in the water so that any heat would be dissipated... ;-)

Do you have a translation for that article Spaghetti? Looks good.

OMD are you interested in rigging up a test - just for interest - we could hang some weights off a wishbone and measure/plot the extension? (i tried it but dont have enough weight)
I have 16mm and 18mm black and clear bands we could use..

[SinglerM]

I sort of figured the same would be the case Mr.X, it's more likely that some with a lot of experience would have a rough idea. It's probably too difficult to set up an actual test. I'm thinking that there must be a point where a double or single overlap in performance for given lengths.
On my gun the shaft still carries a lot of speed when it reaches the end of the shooting line. I like the quicker loading of a single band also.
it's possible that the reason the 1000 or 1100 double band models get recommended so often, is because they are at the sweet spot of performance for 16mm doubles. I certainly don't know. I'm curious where my 1300 single band fits within the scheme of things.

take care,
Mitch