Author Topic: Flight shooting strings  (Read 3844 times)

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Offline Badger

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Re: Flight shooting strings
« Reply #15 on: October 18, 2016, 08:55:44 am »
  That is a nice looking string and excellent weight!

Offline avcase

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Re: Flight shooting strings
« Reply #16 on: October 18, 2016, 11:45:13 am »
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

Offline Tuomo

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Re: Flight shooting strings
« Reply #17 on: October 18, 2016, 11:21:54 pm »
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) Barbourís 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, thatís it. Ok, of course there is some fine nyances, which can be very important and which I donít 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.

Offline avcase

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Re: Flight shooting strings
« Reply #18 on: October 19, 2016, 03:54:17 pm »
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

Offline Badger

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Re: Flight shooting strings
« Reply #19 on: October 19, 2016, 06:04:29 pm »
  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

Offline avcase

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Re: Flight shooting strings
« Reply #20 on: October 20, 2016, 01:53:54 pm »
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
« Last Edit: October 20, 2016, 07:24:53 pm by avcase »

Offline Badger

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Re: Flight shooting strings
« Reply #21 on: October 20, 2016, 05:13:02 pm »
   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.

Offline avcase

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Re: Flight shooting strings
« Reply #22 on: October 20, 2016, 07:17:35 pm »
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

Offline Badger

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Re: Flight shooting strings
« Reply #23 on: October 20, 2016, 08:24:14 pm »
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.

Offline avcase

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Re: Flight shooting strings
« Reply #24 on: November 01, 2016, 12:00:17 pm »
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

Offline Badger

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Re: Flight shooting strings
« Reply #25 on: November 01, 2016, 12:21:41 pm »
  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.

Offline Tuomo

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Re: Flight shooting strings
« Reply #26 on: November 01, 2016, 11:31:09 pm »
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.

Offline Aussie Yeoman

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Re: Flight shooting strings
« Reply #27 on: December 25, 2016, 07:25:27 pm »
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?
Articles for the beginning bowyer, with Australian bowyers in mind:

http://www.tharwavalleyforge.com/articles/tutorials

Offline avcase

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Re: Flight shooting strings
« Reply #28 on: December 25, 2016, 09:50:17 pm »
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

Offline Aussie Yeoman

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Re: Flight shooting strings
« Reply #29 on: December 26, 2016, 11:21:46 pm »
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?
« Last Edit: December 27, 2016, 07:08:33 am by Marc St Louis »
Articles for the beginning bowyer, with Australian bowyers in mind:

http://www.tharwavalleyforge.com/articles/tutorials