# Taper & band life - I have measured the differential stretching



## mike160304 (Aug 10, 2018)

Further to the thread:

https://slingshotforum.com/topic/115254-why-taper-and-does-band-life-decrease-as-taper-inceases/

I cut a 12-9mm taper (25%) in Precise 0.75mm and marked 5" of it in inches with a ballpen, leaving short ends spare for clamping. I stretched the 5" to 20" - 4x overall stretch - and measured the stretched length of each 1" section:

1 2 3 4 5

Stretched length, inches: 3.65 3.75 4.0 4.25 4.45

This means that I am stretching sections 4 and 5 more than I want to. A bit of schoolboy maths told me to try an overall stretch of 3.6x, so I did, and got this:

1 2 3 4 5

Stretched length, inches: 3.3 3.4 3.6 3.8 4.1

i.e. max stretch 4.1x, near enough to my 4x target.

The current slingshot project is rebuilding my Altoids Tin competition entry ("Curiously Strong" aka "Curiously Altoid") for the second time, to see what accuracy I can get at 10 metres with 7 or 8mm steel ball.

So now I shall taper the Precise 0.75mm rubber from 12 to 9mm (25%) and cut the band length to give me 3.6x overall stretch, knowing that I can shorten the bands if I need more stretch.

Mike


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## Grandpa Grumpy (Apr 21, 2013)

I don't understand what you're going for here. If you looking for performance you need to go more than 3.6 X stretch. If you are looking for band life, then don't taper. 5X stretch will give you a compromise between power and band life whether you taper or straight cut.


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## Nicholson (Sep 25, 2012)

Or you could switch to tubes. McMaster Carr sells good rubber tubes


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## KawKan (May 11, 2013)

Grandpa Grumpy said:


> I don't understand what you're going for here. If you looking for performance you need to go more than 3.6 X stretch. If you are looking for band life, then don't taper. 5X stretch will give you a compromise between power and band life whether you taper or straight cut.


I think it's a interesting and fun trial to find a setup that matches the light ammo (narrow width), features light draw weight (taper) and good life (lower stretch).

This would be interesting to see draw weight and chrony results with all these options.

I might use a cut with less than 4X stretch for target bands if it dropped my point of impact closer to my aiming reference.


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## mike160304 (Aug 10, 2018)

Grandpa Grumpy said:


> I don't understand what you're going for here. If you looking for performance you need to go more than 3.6 X stretch. If you are looking for band life, then don't taper. 5X stretch will give you a compromise between power and band life whether you taper or straight cut.


Thanks - that's fine, and is a crisp, clear statement of the generally accepted wisdom, I think.

I usually wander off-piste with my projects, while knowing about the main road. Just my curiosity. This Altoids Tin slingshot is very off-piste and is not about velocity.

Mike


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## mike160304 (Aug 10, 2018)

Nicholson said:


> Or you could switch to tubes. McMaster Carr sells good rubber tubes


Thanks, yes, I use tubes too, I have replied to you about this in the previous thread.

One of my other slings has 2050 single tube and I use it for 5-gramme ammo, it is quite lively at 4x stretch, but will of course do 5x stretch if I want.

Mike


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## mike160304 (Aug 10, 2018)

KawKan said:


> Grandpa Grumpy said:
> 
> 
> > I don't understand what you're going for here. If you looking for performance you need to go more than 3.6 X stretch. If you are looking for band life, then don't taper. 5X stretch will give you a compromise between power and band life whether you taper or straight cut.
> ...


Thanks, yes. I really enjoyed this test.

I usually take the received wisdom on board, but my curiosity takes me off-piste into eccentric areas too. Occasionally, this works better than expected. Mostly, of course, it doesn't. But I learn a lot.

I meant to add, yes, a chronograph is needed to quantify the results, and to help to decide what to do next.

I did not get on very well with my last chronograph and I have put it on Ebay and ordered a new one from Danking, it was on special offer.

My recent special offer purchase from Dankung, the Toucan Agile Rosewood (Phew!!!) slingshot, is really interesting, and I have not spent enough time with it yet. So I hope that their chronograph will be fun too.

Mike


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