Primitive Archer
Main Discussion Area => Bows => Flight Bows => Topic started by: Tuomo on October 13, 2016, 02:50:00 am
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Primitive bow classes (USA Archery rules) requires natural string materials. So, what kind of natural material strings you are using? Flax, silk or something else? What is average weight of the string? Length? Endless two loops, flemish two loops or flemish one loop. What is strength factor - two, three, four, five or something else? Straight strands, twisted strands or braided stands core of the string? What else you could tell? I am just curious...!
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ramie is interesting too
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I use flax string, 4 times draw weight, flemish most of the time occasionally endless. I think a material like silk can get away with less weight because it equals out the tension on the strands much better because of stretch. I have used nettle and found it slightly stronger than flax.
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Please, tell more, weight, length, etc.
I have been playing flax yarns. I have bought some well known Irish flax yarns, like Barbour's, Campbell and Patons. Every of these are quite good. Here is one example, Campbell 30/3 linen, 16 strands, 200 pounds, 165 cm (65"), tenacity 32,5 cN/tex, 83,7 grains without wax and center serving, 90,5 grains waxed and 96,5 grains waxed and with center serving. Servings are cotton. And this was old linen. With new and a bit better linen, about 75 grains string could be possible.
By the way, this is the best linen yarn I have now. My best silk thread (filament silk, not spun) has tenacity 41,20 cN/tex, so it is about 27 % stronger per mass than the Campbell linen yarn. Silk of course stretches but I don't think it is a problem, if the string is well prestretched.
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Do your plant fiber endless strings break at the loops? Apparently ramie strings for Turkic hornbows were made with something like flemish twist at the loops and plenty of serving because, if endless, the halving of # of strands at the loops resulted in breakage
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Loon, even though the strands are 1/2 in the loops they are still close to equal strength because the tension is divided bewtween two loops. About 150 grains is typical for a 65" string using a flemish twist. I have to use silk to go below 100 grains. 125 grains is about the least I can get by with and that will usually break in less than 6 shots. I think If I started using continuous loop I could get that number down but I am slow at making the continuos loop strings.
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Not a flight string but it is a linen string. This one is a 22 strand 16/2 Barbour linen with a 375# break strength, length 57". Weight waxed with serving is 140 grains.
(http://img.photobucket.com/albums/v355/Marc-St-Louis/ERC/Composite/ERC%20Recurve%20D%20Bow/375%20Linen.jpg)
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Mark, did you test the strands or is that the rating. You have always made great endless loop strings.
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I tested the strands Steve. They were breaking between 17 and 19 lbs
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Well made continuous loop string (endless) and two loop flemish string weight about the same.
Steve - is that 125 grain string with Pyrosupplies linen or something else? Where it breaks? Loop, nocking point or somewhere else? I have got some good Swedish linen, which is a way better than old Barbour's etc. 200 pounds, 65" endless string weights about 90 grains with servings.
But, how big factor string weight really is in flight shooting? With good flight bow and arrow, is 90 grains string really "much" better than for example 130 grains string? Yes, I know that it equals about 10-15 grains in arrow weight but does that really matter?
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Same as pyro supplies. Most of all our linen comes from the same mill. Mine usually break in the main body of the string usually toward one end or the other. I didn't break any last year as I got lazy and went to 125 grains, more strands.
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We spend all kinds of time trying to squeeze a little more performance out of our bows. It makes sense to try to get the most out of the string too. For maximum performance, a flight bow string should have minimal mass and maximimum stiffness. Rubber band-like elasticity hurts performance. I feel a couple extra strands of string may not be too bad a problem as long as the forces are evenly distributed to each strand because it makes the string stiffer.
Tuomo,
The last linen flight strings I made for a 50# bow (about 200# breaking strength) are 80-85 grains, fully silk served with reinforced loops. But these were shorter than yours at 54"-58" long. I use endless loop construction and no wax. I often use the thin Barbours 25/3 or 35/3 which has a strength-to-weight ratio almost as good or better than Dacron. I haven't had issues with these strings breaking at the salt flats for many years now.
I made a 400# string for a simple composite bow that Steve made for Jozsef Monus this year. I think the string was around 64" long, and weighed around 140 grains fully served with reinforced loops. The string was a bit long giving the bow a low brace height and I thought the resulting high forces would break the string to bits, but it held together without any issues.
Alan
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I would imagine that a shorter string would need to be stronger due to higher tension at brace?..
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Loon, the string angles of a lower brace put much higher strain on the bow than any other position it will be in. I have had string break right in half a few times when I had them a bit too long and marginal strength to start with.
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Here is one string made from Swedish 35/3 linen. Breaking strength is 200 pounds, length 57", 16 strands, little waxed and with 4" center serving. Weight is 68,8 grains. It weighted 63,8 grains without center serving and wax, and 66,2 without wax. I served it same material as the string body.
With endless string, serving material and waxing is quite important factor. I have used quite thick silk servings (loops and center), which weighted 40-50 grains totally, plus about 10 grains wax. With this string, servings weighted only 7,5 grains and wax about 2,5 grains. Quite a remarkable difference! And more important than string body yarn qulity. For example, if the linen yarn would has 50 % more strength per mass, the string body mass saving would be 18 grains. And 10 % would equal about 4,5 grains. Linen, which has 10 % more strength per mass (compared for example to good quality Barbour's linen) is very difficult to obtain.
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That is a nice looking string and excellent weight!
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Tuomo,
That looks like a very well made string to me too! That must be some excellent linen. Is it still being manufactured? There are a couple of good articles in Archery the Technical side that lists strength properties of the best linen used for bow strings in the 1930's which I use to gauge against. Fortunately, I find it is pretty easy to obtain similar quality linen today. Your Swedish linen must be even better!
I think a large portion of my string weight ends up in the reinforced loops and heavy silk serving. I rarely use wax, but I am curious if there may be a benefit I am overlooking.
Next time I build a linen string, I will try to have someone take pictures of the process. I am curious to how it compares to how you & others make bow strings. I often learn something new each time I make a string with someone. The biggest problem for me is the amount of time it takes, but I feel it is much better spending some extra time to make one high performing string that is durable instead of quickly making several lower performing strings that break.
Alan
Alan
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Alan - sent you an e-mail.
The Swedish linen is Bockens Lingarna. You can order Bockens linen yarns (lace making threads) from here, it is also in English and they ships also to US and almost anywhere:
www lankava.fi/epages/lankava.sf/en_GB/?ViewObjectPath=%2FShops%2Fesito%2FCategories%2Fpellavalangat%2FNypl%C3%A4yslangat
Notice, put a period between www and lankava...
Pella is Finnish lace making linen but it is not as good as Bocken, unfortunately. In general, if you want good bow string linen, search lace making linen/thread/yarn. It has usually very good quality.
I have also calculated strenth coefficient for various materials. I have used SI-units and best de facto standard is cN/tex. cN is centinewtons and tex is yarns weight in grams per 1000 meters of yarn. In my test, old (at least 30-40 years) Barbour’s 35/3 linen has value 31,0 cN/tex. Best linen yarn, Bockens 35/3 has value 36,5 cN/tex and best filament silk has value 41,2 cN/tex.
Please, photograph your string making process. It would be great to see, how good flight shooting string is made. Two loop endless string is so easy and straightforward to make that it is hard to believe that there is any secrets. Equal strain to every strand, good servings and very little wax, that’s it. Ok, of course there is some fine nyances, which can be very important and which I don’t know yet. I have used natural material strings very little. My plan is to shoot flight shooting with natural material strings here in Finland next year. To the date I have used only modern string materials in flight shooting.
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Tuomo,
That's lots of good information!
I find I have to test every roll of thread I get. There can be such a wide range of properties even if it is different batches of the same product from the same supplier. Much of what I have is 20-100+ years old, so the variation may be due to how it is stored. Or, like any other natural material, it may depend on the conditions the thread grew and how it was rhetted & processed. I am sure there were better years and worse years, just like wine.
I'll put together a little pictorial of the next time I make one of these strings and focus only on the parts of the process I do different compared to the typical modern material string builder. I will probably learn more from the rest of you than you will from me!
I also look forward to hear how your strings perform for you compared to modern strings. My experience is that a great linen string will perform almost as well as a modern fast flight string.
Alan
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I go directly to the outlet and they allow me to test the individual rolls. I find in almost all cases the rated strength is almost exactly double the actual strength. They use a large circle and put a dowel through each end so they are actually testing two strands
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There is a standard test method for breaking strength, and it only tests the breaking strength of one strand. The measurement obtained is called the Breaking Tenacity, and it takes into account the linear density of the string to allow direct comparison regardless of differences in the thickness of the string.
www admet.com/how-to-perform-an-astm-d2256-thread-and-yarn-tensile-strength-test/
Alan
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I wonder how much difference using this method actually makes. I find even when I use a knot tied around two dowels it never breaks at the knot. Always in the middle of the string. I use a scale that records the highest reading and use a slow steady pull, it does seem consistent enough for being low tech. I always take several sample reading from each spool I buy.
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Steve,
My samples always broke at a knot. So I use a method similar to the one used by the textile industry. The only difference is that I use a longer length sample.
My digital scale didn't seem to handle the sudden breaking of the string and would sometimes give inconsistent results. So I still use the method of suspending a bucket from one end of the string and slowly filling it with water until it breaks. Then I weigh the bucket of water afterwards. Maybe I should invest in a better scale. It would sure be a lot more convenient to do it your way.
Do you also weigh the thread to get an idea of mass per unit length? If you divide the breaking strength by the mass per unit length, then it allows you to directly compare different sizes.
Alan
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Steve,
My samples always broke at a knot. So I use a method similar to the one used by the textile industry. The only difference is that I use a longer length sample.
My digital scale didn't seem to handle the sudden breaking of the string and would sometimes give inconsistent results. So I still use the method of suspending a bucket from one end of the string and slowly filling it with water until it breaks. Then I weigh the bucket of water afterwards. Maybe I should invest in a better scale. It would sure be a lot more convenient to do it your way.
Do you also weigh the thread to get an idea of mass per unit length? If you divide the breaking strength by the mass per unit length, then it allows you to directly compare
different sizes.
Alan
I always make that comparison. The only thing I have never been sure of is the effect of having more or less strands.
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I recently received some of the Swedish Bockens unbleached linen thread and ran into a perplexing issue that makes me question how I've tested and ranked all my linen so far.
Without much thought, I ran the sample from my house, to my work shop to do a series of break tests, where I noticed a very interesting trend. Due to random interruptions, it took me about an hour and a half to complete five breaking strength tests. The first test broke at 9.8#, and each successive test yielded a slightly higher breaking strength than the one before. The last test broke at 12.2#. I wondered what was going on here? I used a very consistent method, where the sample supports a large bucket that was slowly filled with water until the string snapped. The bucket of water was then weighed on a recently calibrated and certified scale to obtain the breaking strength of the sample. I threw out any results where the test sample may have broken at one of the supports.
I then decided to re-test my best performing 35/3 Barbours material and was shocked when it performed less than 60% as strong as the last time I tested it! The thread felt very brittle and I could break it by hand without too much effort. Something seemed very wrong. I sat this information aside, not sure what to make of it.
A couple days later, I was back in the workshop and tried breaking the Barbour's sample again by hand, but this time it felt completely different. It wasn't going to let go without cutting my fingers! How can this be? It was then I realized that the last time I used this Barbour's thread was in an air conditioned room in extremely dry conditions at the Bonneville Salt Flats, and I had sealed it in a plastic bag before returning home in Oregon. This may have kept the thread in a very dry condition, leaving it very brittle.
It is well known that linen loses significant strength as it becomes very dry. The humidity next to the air conditioner unit at Bonneville may have been just a few percent when I sealed the Barbour's thread in the plastic bag. Something similar may have been happening when I was testing the unbleached Bockens thread. Prior to my break tests, the Bockens thread was stored in the house near a de-humidifier. I then moved it to my workshop (without climate control) to conduct the tests, which was near 100% humidity level during our cool misty-rainy weather. My theory is that the increasing break strengths that I measured were due to the thread gradually becoming acclimated to the higher humidity environment in my workshop!
So this throws all the data I have collected on various linen samples in doubt. They were all tested in different conditions at different times of the year. How do I compare one against another in a meaningful way?
Alan
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The only condition that you would be able to duplicate accurately would be soaking wet. My humidity where I live is more consistent than most at about 60% give or take a few, but even at that I have never bothered to check the humidity when testing. Excellent observation.
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Very interesting results. I suspect that humidity change was the reason. I have at least three humidity meter, in every room I store wood or other materials. It is easy to check relative humidity. For example, I store my linen threads in the basement, where the relative humidity is always about 50-70 %, depending of the season.
Bocken's breaking strength was 13,1 # (min. 11,4, max 15,5) with short sample (30 cm, n=17) and 10,8 (min. 9,7, max 12,2) with long sample (150 cm, n=12). Relative humidity 55 %, 20 C. So, if you use longish samples, we are getting just the same results.
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Badger makes a good point: the only way everyone around the world can meaningfully compare results is to have wet thread.
Which begs the question: do those that shoot flight competitively, do you moisten your strings prior to shooting, or otherwise keep them in a sealed humidity environment before taking them out onto the salt flats?
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I wipe the string down with a lightly damped cloth before i shoot in very low humidity. It isn't enough moisture to add much mass but it sure makes a difference in the life of the string.
Alan
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Someone sent me a link to this mob:
http:/www.pyrosupplies.com/shop/page/category/Category/647698bcca6b92aff582ef0260d5adfd.html
suggesting the imported seven strand linen makes about a 130 gr string for about a 50 lb bow of 70" long.
Has anyone experimented with the other stuff available here?
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Ok so what kind of mass weight should I look for in a 69" 50# bow that only breaks2out ten times? :-\ Arvin
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Arvin I don't follow that line of thinking that a good all wood flight bow is 90% broke. Wood is not the same as fiberglass. Wood performs best if you stay within its elastic limits which puts it all the way down in the 70% broke class. I would say with 3" of reflex between 24 and 25 oz.
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Ok ;D as usual misunderstood. What I want to know is what should the string weigh. So I can try to build string for the mass of the bow. I am sure I am showing my ignorance here. Did not get there in math. Maybe 85 grains? Just a guess. Arvin
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Arvin 85 is good, I quite weighing them because I know mine are always heavier than I want. 8 strands is about the best I have been able to get by with on the 6 strand linen. I heard you mention 6 strands, thats good!
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85 grains for a durable finished linen string would be very good for a 50# 69" long bow.
Alan
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Ok guys . I'll see how close I can get. I feel I am in the right crowd already. It's not about who's name is on the record it's how can we beat the previous distance. It all boils down to who can make the best set of limbs. Arvin