Natural string: How strong?

[WhistlingBadger]

Would like to try my hand at making natural strings.  Have some sinew and some nice, long dogbane to work with.  I'm worried that it won't be strong enough, with natural materials being so variable.  Is there some way to know if a string is strong enough, other than just shooting it and hoping for the best?

[bjrogg]

I really don’t have any experience with natural strings. Not sure I can offer much.

You could probably make a string and test it by putting between two nails. Then like tillering tree pull with scale, rope and pulley.

See what weight it breaks.

Then put a string from one nail to rope. Test tension till it fails.

Be a lot of making and breaking string but would be interesting to see what you find

Bjrogg

[Aaron1726]

I feel the key to natural fiber strings (or any string for that matter) is consistency of strands (diameter, how tight the twist is, etc).  Once you are making quality, consistent string, then you can start to collect the data on breaking strength like bjrogg mentions. 

I've done a few natural fiber strings.  For my dogbane ones I twisted up some different diameter ones that I put to the test with a nail, the vise, and a scale and broke several to see how consistent my results were and to know how many of different sized strands were needed.  I'll have to dig up my notes, but the chosen strand size was breaking at some where in the order of 30lbs, so I then knew how many for the bow weight that was needed.

Then I've also done sinew without all the data collection and just twisted up a string that seemed about the right size for a string, and that's worked too.  But I still try to keep it very consistent along its length.

I'm sure others with a lot more experience will chime in too.  But just mess around with it learn as you go

[WhistlingBadger]

Thanks, guys.  Interesting stuff.  How strong should a string be, approximately, in relation to bow weight?

[pierce_schmeichel]

I personally love raw hide bowstrings. They are super easy to make. All you have to do is spiral cut a couple 3/8" string of raw hide. Then soak them, then twist them together and let them dry with a weight hanging from it.

Sinew makes an incredibly strong string...As long as you make it 1/8" to 3/16" thick string. Also a little truck I like to do with sinew strings is twist them up together into the string dry with a 3/16"-1/4" diameter  and then I soak it in a fairly diluted hide glue solution. Then hang it with a weight and let it stretch. The glue bonds all of the fibers together really well and makes it a little stronger. As it dries and stretches though it gains length and loses diameter.

But yeah raw hide is my go to for sure. It's super durable, super easy to make, and again super durable haha.

[WhistlingBadger]

I personally love raw hide bowstrings. They are super easy to make. All you have to do is spiral cut a couple 3/8" string of raw hide. Then soak them, then twist them together and let them dry with a weight hanging from it.

Sinew makes an incredibly strong string...As long as you make it 1/8" to 3/16" thick string. Also a little truck I like to do with sinew strings is twist them up together into the string dry with a 3/16"-1/4" diameter  and then I soak it in a fairly diluted hide glue solution. Then hang it with a weight and let it stretch. The glue bonds all of the fibers together really well and makes it a little stronger. As it dries and stretches though it gains length and loses diameter.

But yeah raw hide is my go to for sure. It's super durable, super easy to make, and again super durable haha.

I've heard that about rawhide.  I'll have to try it next time I kill a deer or antelope.

[JackCrafty]

I've made several natural bowstrings and they tend to break wherever there is an abrupt turn or kink in the string. This means it will break at the loops or where you tie off one end. It also breaks where you nock the arrow but much less frequently there.

Sinew is far stronger than any plant fiber I've tried except when it's wet. Sinew exposed to very high humidty can also be quite weak. Backstrap sinew is the best sinew for strings but you can use leg tendon if you're careful not to smash the fibers too much during the pounding phase of the processing.

I think the formula for the strength of the string is the draw weight x5. This means a 50lb draw bow needs a string that will hold 250 lbs of suspened weight. Sinew strings in this range will be 1/8" diameter at a minumum.

As a side note, waterproofing with oil, fat, tree sap, wax, or rosin on the natural strings has never worked for me. If I want to waterproof a sinew string, I use Tightbond III (waterproof wood glue). It makes the string look funny, it's not natural, and it's not 100% effective but it prevents a splash of water on your string from ruining your day. It also helps prevent breakage.