Skinny Strings & Silencers
This article should really be called "taking the crap off the bow". At pretty much every shoot I went to last year I had Andy standing behind me on the range and inevitably at some point he would berate me for having 4 spider silencers and 2 limb saver dampers on my bow, he was convinced all the stuff was sapping the speed from my bow. I had put it all on almost the day I got the bow just to see what it looked like and it looked super - I don't need silencers when shooting 3D, it was purely a decision based on what it looked like, they stayed on the bow all year. Partly it was me just being perverse and part of it was that I was shooting pretty well and if I was missing out on a small amount of speed - so what ?
So a couple of weeks ago I thought I would make a few new strings for this year and tune them in to the bow, at the same time I figured to see exactly how much speed the "stuff" was costing me.
First though I ran a speed test with the standard arrows I generally use to test bows with the current set up.445gn 11.12gn/# 174fps500gn 12.50gn/# 168fps530gn 13.25gn/# 159fps565gn 14.12gn/# 146fps
Currently on the bow was a 12 strand DF97 string, the figures didn't look too bad so I was interested to see what the chrono had to say. The string prior to the one I currently used had been a 10 strand and that was what I intended to make, whilst I was at it I went back to a project I had been experimenting with at the start of '09.
It always seemed arbitrary that string makers put 10, 12 or 14 strands of material into a string so I tried to find out why. It turns out that at some point years ago folks decided that to be safe they needed a string that was 4 times as strong as the bow weight, so a chap with a 50# bow should use a string with a breaking strain of at least 200#, sounds pretty sensible. With the materials available at the time this meant a string of around 12 to 14 strands.
However, since those days things have changed, there have been advances in string materials with the invention various formulas of Dyneema and Vectran and stuff that doesn't even have a name, just a number. What impact have they made on the world of strings ?
You would think a huge amount and in truth they do, they perform better, have less stretch characteristics and offer higher arrow speeds, not least of their properties is the higher breaking strains, where before one might expect a single strand to offer a breaking strain of under 40#, there are now materials which offer a thinner diameter and yet will take 165# on a single strand.
Yet still we are offered and recommended to use 12 strands, which can equate to 780# breaking strain, far in excess of what the average archer draws ( even when times'd by 4)
Back last year I had made myself several skinny strings, initially I had used 10 strands of D75, then moved down to 8 strands, 6 strands and finally 4 strands.
Each strand has a breaking strain of 125# and comes in at a diameter of .016 - at 4 strands you have a very skinny string, more like a cheese wire.
Now putting 4 strands on my current bow of choice, an ACS CX 45#@28" on an RC 16" riser could prove to be a very costly experiment if it should go pear shaped. I decided to take as many precautions as possible - 4 strands gives me a breaking strain of 500# - using the 4X rule I only need 188# so the theory says I am safe. However the effect of 4 strands on the limb tips would no doubt be noisy if not catastrophic so I padded the loops out to 18 strands with Dacron which I felt would offer some additional cushioning rather than use D75 for padding.
Once served and string on the bow you have a bizarre looking set up with what appears to be a string at each limb tip and a centre serving and nock point hovering in mid air, I like to serve in my nock points and to my eye the skinny little string in black & white looked beautiful.
After tuning I was sure I could feel a marked improvement in performance but before I had a chance to test it out over the chrono I noticed that after an hours shooting or so the nock had moved - despite being advertised as "no stretch" it appeared that the string had grown, only to be expected on a new string as even at 12 strands a string needs to be shot in. After putting in a few twists I set about shooting again. By the end of the shoot the nock had moved once again. This happened again the next time I shot so I left the bow strung overnight before my next shoot, reset the brace and went off to a 3D shoot, by lunch I had lost yet another 1/4" - the string seemed to be "creeping". By this time I was fed up with it and a little worried that something more sinister than just creeping or stretching was going on so I took off the string and put it to one side.
Over the year though, I hadn't forgotten that the skinny string appeared to have improved the performance by a noticeable margin, so as I said two weeks ago I returned to the project and now that the "crap was coming off the bow" this would be the ideal time to test out another skinny string.
This Flemish string was made with the utmost care and again padded out at the loops with Dacron to 18 strands, this time to avoid any nonsense on the bow I pre stretched it on a little home made jig and then the bow was strung, it was left for 3 days strung and shot intermittently. Stringing a modern Longbow for long periods of time is not an issue given the materials they are made with - I would feel very differently about leaving a wooden bow strung but I have many hunter friends in the States who leave thier modern bows strung for the whole season with no ill effect.
There was some small amount of creep but once the brace had been reset just twice in that time it appeared to settle.
So to the test - the first set of figures show the bow with "crap on", the second with the same string but "crap off" the third with a naked 4 strand D75 string and the bow retuned to the lowest possible brace with good tuning, drawn to 28"450gn 11.12gn/# 174fps 180fps 190fps500gn 12.50gn/# 168fps 174fps 178fps530gn 13.25gn/# 159fps 167fps 173fps565gn 14.12gn/# 146fps 159fps 166fps
If you are looking at those figures and thinking "yeah right" I don't blame you, I had to go and sit down and then do the test all over again, same bow, same limbs, just silencers off and most notably with a heavy arrow you gain 13fps !, with a light one 6fps.
Once changed to the skinny string I gained 10fps with a light arrow and 7fps with a heavy one - I would have to add that this is not a scientific test, this is me with my chrono trying to get to the bottom of what the hell is going on - Obviously the weight of a string will have an effect on the speed at which it returns to the bow, there may also be an issue with resistance, more surface area of a fat string vrs a skinny string, with regard to the weight, a brass nocking point or even a couple could have a significant effect of string speed - all very interesting and warrants further investigation. This is a topic I am sure we will re-visit before too long. I would be very interested to hear from anyone else who has experimented with skinny strings especially if they might have some light to shed on the whole matter and any correlation between string weight and arrow speed.
What I can tell you with out any shadow of a doubt is that the 4 strands of D75 outperforms anything I have ever shot before. The difference between the bow I had with crap on and the one I have now with the new tune is 16fps with a light arrow and 20fps with a heavy one - that equates to 7.5# to 10# of draw weight - the ACS was a fast bow anyway and I may have dampened down it's capability a little with the addition of the crap but the increase in performance just by changing the string is still worth 5# to 8# of draw weight that you don't need to hold, over and above the standard string - INCREDIBLE.
I am not suggesting that everyone rush out and start cutting their strings but for me the experiment will continue over a longer period and for the foreseeable future I will be using a skinny string. Just for fun I put an Easton legacy arrow at 420grns and 4" very low profile feathers on through the chrono to see if I could get 200fps from a 45# bow ( this weight is still well within the minimum recommended weight (8gpp) of an arrow at 9.4gpp. 196, 196, 197 was as close as I could come at 28"of draw.
There are several things to note regarding this whole experiment serving a skinny string will leave you with a skinny knock point, the way around this would be to either double serve which to my mind is a little daft if you have gone to the trouble of making a skinny in the first place, perhaps just double serving the area of the nock could be a solution but not one I would favour. You could use tie on nocks which I do like and maybe use some dental floss to build the actual nock between the tie on's or search for a nock with the slimmest groove - something I should really check out.
The next thing is pre-stretching strings, I usually give my fatter strings a moderate stretch and let the bow take care of it over the next hundred arrows or so, with the first skinny I made I found that it was stretching all over the place, however this had more to do with the number of twists in it than anything else, using my usual formula for length I actually found the string to be a little long once made - this was because there was less bulk in the whole thing to take up the length. Because it was too long it had more twists in it I am assuming they had the effect of a coiled spring in that once the string was taut they added a sponginess, leaving the bow braced seemed to cure it but taking it on and off the bow meant that the whole process started again. The second string took an age to make and had to be re started twice, when I eventually did get it right with the right number of twists that's when I started the chrono test.
On the first string I served the nock in, which turned out to be a pain because it stretched much more than I anticipated, on the one used for this test I actually stretched it before serving and then used tie on's which I served over - I took a chance the brace wouldn't change drastically and I was right - perhaps luckily, that the nock point ended up exactly where I thought it would - in future I would not serve over the nock point but just use tie on's after it had been served.
The next thing was that the string made virtually no noise, I say virtually becasue I thought it made no noise and those who I asked to listen to it said it was silent, but I am not going to claim it made NO noise whatsoever but it did seem to make the bow almost quieter, with just that lovely low dull thud of a well tuned bow.
I am almost tempted to say it reduced any "noise" in the hand too - I mean an ACS is just about as shock free as you could get and I was worried that the skinny would introduce some kind of shock or feedback through the hand, however the addition of the Dacron padding must have really done the job as there was no feedback at all.
A skinny string won't make you a better archer but it will add some speed to your arrow which can only be a good thing - I really couldn't say what extra stresses it put on the bow limbs and I would have to advise anyone thinking of using one to perhaps talk to the bowyer first, I actually can't see many bowyers saying " sure, stick a skinny string on" unless with the caveat " .. oh and by the way if it breaks the limbs then it's your problem and not mine !"
By no means is this the end of the story on this particular topic, in the process of this whole experiment it's only fair to say the bow probably wasn't in a state of "super tune" when I had all the gear on the string and in the process of re-tuning I was able to lower the brace height considerably whilst getting excellent flight and that probably added a little something to the speed. I must now go back and test the strings I used, I want to get them weighted, I want to compare the number of twists per inch and also test the draw weight of the bow with each string and at each stage. Stu's new and improved calculator with the tweak for skinny strings is fortuitous and timely as I will also need the work out the spine for the bow now that it has been "super-tuned". So I shall look forward to another few days in the workshop playing with bows and arrows.... what a chore !