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Discussion Starter · #1 ·
Anything goes as long as a main component is plastic. Scales / core etc. As long as the end result is functional and safe to use.

If using a brittle or impact 'unfriendly' material such acrylic, and I'd include styrene, PVC and ABS - even though plenty strong enough as a build material, allowances should be made so if fork hit there is no risk of frames coming apart.

Reinforced plastics such as G10, Micarta etc. are all welcome.

Same rules as always - completed, or first presented this month.
 

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Discussion Starter · #5 ·
Just note what I mentioned about acrylic - its great - but doesn't take fork-hits well. You would just need to address the safety aspect of that.

From experience PVC and ABS will shrug off hits for ages then suddenly fail...
 

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Yup yup yup, im well aware of how brittle it is, heck it frequently knaps small shards off as i cut it with a coping saw.

Thanks for the heads up though, ill be safe!
 

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Discussion Starter · #7 ·
If you were to add a layer of 1/4" micarta, G10 or even ply etc. on the shooters side should be all good :)

Though also check out polycarbonates like delrin or POM etc.
 

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All good. I just hapoened to find a 20mm thick slab of acrylic, so im using it up.
Ive had a full power frame hit with 8mm steel balls on 0.7mm bands on one acrylic frame i made, it knapped off a little slither but other than that was fine.

Big thick forks for the win!

But definately good advice.
Everyone, be careful with brittle materials, they will slice you up without a second though.
 

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Plastic slingshots? Hmm...here is an earlier post I found on this forum with a strong reality call from a 3-D maker: :hmm:

https://slingshotforum.com/topic/128852-dont-make-slingshots-out-of-plastic/

I would assume that most more experienced slingshot makers are reasonably familiar with the properties of hardwoods and common metals such as aluminium and steel, but very much doubt that this is the case with plastics - a fossil fuel-based substance that comes in all kinds of chemical formulas, some sturdy, others not when it comes to temperature variations and UV exposure in particular.

Unknown territory that I am definitely not so keen on when it comes to applying a significant force on forks made of a material, where you need to be absolutely certain that it is truly up to the task: broken fork limbs consisting of sharp plastic shards being flung back at your face within a split second is hardly a thrilling experience.

I suppose that a metal core will make most plastics safe enough in a homemade slingshot, but I would rather opt to buy a 100% plastic slingshot made by a reputable maker who fully understands the behavior of plastics under significant stress, especially once this multifaceted substance ages over time. Well, actually I would never buy a plastic slingshot.

I look forward to seeing what you guys come up with this month. Oh, get your safety glasses out before you shoot with your upcoming contraptions... :hmm: .
 

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Discussion Starter · #10 ·
PS - never said that the entire thing needs to be plastic ;-) Just as a main component. Though its quite possible to make something really beautiful from plastic (and even recycled HDPE).

Most reinforced plastics are plenty strong enough (though caution with working with them is always advised - esp. carbon/glass - less so with micarta). Also there are quite a few sheet formed plastics which are well up to the task - some have their own characteristics which are worth considering.

There are some awesome decorative plastics - many of which tend to be more of the brittle variety. But then again there are some ply woods which are phenolic infused (or you could infuse most woods with a vacuum system), I'd consider these as reinforced plastics in this case. Though Diamond wood and similar need to considered carefully as the wood grain tends to all run in the same orientation.
 

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Micarta and G10 are composite materials, as well as laminated wood. Plastic is plastic (see dictionary). I have been shooting with a 3D slingshot for two years and there are no signs of fatigue (aging). If you get her out in a nail, the sun will beat her and the frost will catch her, it's your job. Or if you shoot at it repeatedly (how do you want to hit it?
 

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Discussion Starter · #12 ·
Yes G10 and Micarta are composite materials. But for this month I'm accepting them as 'plastics'. As well as other phenolic infused materials. Its all about material choice and approach to application.

I personally have no concerns about 3D printed frames - and will accept them without any prejudice. They should last years - though I am aware of a few breaking after a single fork hit.
 

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Plastics come in a large number of forms as shown in the list below (bottom of the web page). Which ones would be suitable for slingshots is the question here (any chemistry people out there?):

https://omnexus.specialchem.com/polymer-properties/properties/strength-at-break-tensile

My chemistry classes date back to roughly 1981, so my knowledge is a bit sketchy to say the very least :hmm: . However, if I take standard steel as a reliable reference to compare the so-called tensile strength at break with that of plastics, I get a clearer picture:

Sourced from Google: "Tensile strength is measured as a force per unit area - the unit being a pascal (Pa)/megapascal(MPa), a newton per square metre (N/m2) or pounds-force per square inch."

OK...steel has a tensile yield strength of 350 MPa. Most of the plastics in the list of the above link have value far lower than that. Plastics reinforced with glass fiber seem to do quite well, though.

I don't know anything about Micarta and in what forms it is available on the market, but this random search result gives me a rough idea as a comparison with steel:

https://www.norplex-micarta.com/wp-content/uploads/2017/07/TDB_NP625.pdf

The values of relevance for Micarta: a tensile strength of 85 MPa.

G10 is quite interesting with a tensile strength of 262 MPa, so quite a strong material in itself.

https://www.norplex-micarta.com/wp-content/uploads/2017/07/TDB_NP625.pdf

As a hobbyist maker of slingshots, all this tells me that I would in any case opt for a birch plywood or metal core when using any type of plastic or Micarta from a safety point of view. I would assume that one needs to be careful with any glass fiber reinforced plastics and composites in terms of the dust generated while processing and sanding these. Not my cup of tea, fur sure.
 

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Discussion Starter · #14 ·
Glass and especially carbon fibre need care with working - the dust is a real health issue.

Micarta (or any other paper/cloth) reinforced plastic - is less of an issue, however the dust can be an irritant and does has some health concerns - so again care should be taken. Then again this is true for bone or horn and some woods etc. Even ply is often glued with phenolic based adhesives...

Fork hits with composite plastics isn't a major concern - in most cases a simple sanding and its good to go. The reinforcing material protects the structure to a large degree, and damage is localised.

But don't discount HDPE- its readily available in sheet form - and can be recycled from milk jugs or buckets (often used in food grade containers). Its also easy to work with hand tools, and we've seen some awesome routered frames in some of the last few months.

Fact is many builders here use plastics for many of their frames. If you want to use say kirinite or acrylic on a ply or metal core - its perfectly acceptable.
 

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You scold mikarta! Very durable material, yet easy to process. Not so long ago, micarta gears were used in internal combustion engines. In terms of strength. I periodically buy a Soviet-made micarta, it is already 30 years old, and it is still just as durable. But about the various HDPE, I am always tormented by doubts.
 

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Discussion Starter · #16 ·
I use 'silk' micarta' (paper) in most of my own frames - stuff is tough as.

Also look for brands such as tufhol. Works pretty much like a hardwood. Saws/machines/files/sands perfectly.
 

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Catching up on the SOTM activities, May was a busy month for me. Congrats to the May winners. June looks interesting and I have several rolls of plastic filaments. I should be able to contribute something of interest.
 

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Ok.....I'll start off by saying, I totally understand if this does not fit in the parameters of this competition, but this is as plastic as I get. And I'm totally fine if this one is not counted! That said.......here goes.

Here is my latest "Jaguar" my Jaguar design is the "re vamped" version of my heavy hitter design which is the flag ship of my signature "2-piece" designs. The Jaguar name comes from the fender Jaguar. The Jaguar was the "new and improved" model to follow the strat and tele. (Altho it's never gained the popularity that the iconic strat and tele did)

This one has bronze forks and a canvas phenolic handle, 90mm fork tip to fork tip and 11mm thick forks. So it's nice and slim for the pocket. But with the pommel handle it locks in the hand and has the support of a full size frame.

Thanks for checking it out guys and thanks again to Matt man for hosting this monthly contest.

Shane. https://youtube.com/shorts/t5RaQdUeV1U?feature=share 325731F0-BDCE-4A23-BB16-B84C9C7E5353.jpeg 14A87721-8754-4B56-85AC-516A41E4CD94.jpeg A9B56B1D-8431-4842-9DE6-0F7EAD72567D.jpeg
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