Primitive Archer
Main Discussion Area => Bows => Topic started by: tattoo dave on June 19, 2014, 07:29:01 pm
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Just wanted to get everybodies thoughts. I've had a couple recent bows now where the poundage varied from long string to the short string. I checked weight at long string, was good, shortened string to low brace, maybe 4", and poundage went up about 5 pounds. I don't usually get super picky on weight for my own bows, but making some for trade. I'm wondering if that's normal, or if it's time to purchase a new scale :P
Tattoo Dave
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Dave, shorter string= shorter ntn= more load (draw weight) The brace height is like pre-load as the height increases so does the weight. Dont know what the books say just my take on it...sure somebody that knows will chime in.
rich
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I've only got half a bows worth of experience, but I found the same thing and my scales are new. Weight went up when I swapped to the short string.
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Sometimes the weight goes up and sometimes the weight goes down. It is usually close enough for me to determine when to brace a bow. I don't pay much attention to the lower inches when on a long string, but if I have a bow 50# on the long string@24" and then I brace the bow th bow ill still read pretty close to 50# on the short string. The bow will have a lot more stress on it than it had braced because it is bending much further but the string angles will be similar and thats the big determiner of draw weight once the starting point has ben established. If your bow is underbuilt or badly tillered it may loose weight at the same inches when braced because the wood gets crunched. But generaly speaking on the bows I build it is pretty close and I build a very wide variety of styles and lenghts and weights. Thats what I use to determine when to brace a bow unless I am just going by feel.
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I long string tiller out to 10 inches of string movement (not tip movement). I keep checking weight and also check for good bending
At that distance, I want target weight + 5#. I know that potentially at 26" (my draw) I will get 5 # over my target weight.
Then, I string it at a brace of 3 inches. I'll increase the brace as I proceed to full draw.
For example, if I want a 50# bow, I long string out to 10" and keep reducing weight until I hit 55# or so.
My long string is around 1.5 times longer than the bow for this method.
Your mileage may vary if you have a longer or shorter draw but can be calculated proportionally.
Jawge
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Jawge, I am going to slightly and respectfully disagree with you. I see where your method will work fine because you use a string of similar length. Botom line is that it really doesn't matter much how long the string is, just look and see how much it is pulling at so many inches draw. String cab be 1" longer than the bow or 12" longer, still reads close enough to know when to brace.
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You can disagree, Steve. I've used this method for many years. I do believe the length of the string impacts this method because of string angles but can't say for sure. I think that with a shorter string you are stressing the limbs more.
The 1.5 x longer was a ball park figure. I know that some bowyers like to use a long string equal to bow's length.
I've never tested with another differently sized string.
You know.
If it ain't broke don't fix it. :)
Jawge
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A few more words here. In my early days, I broke far too many staves at first stringing because they were just too heavy to be strung.
So I developed this method.
It is a slow careful approach to getting the stave ready for the short string.
I now many can go from floor tiller to stringing on a routine basis. More power to them but I've needed this crutch. It has served me well.
Jawge
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Jawge, not a crutch at all, you found a method that works. I have also found a method that works that is also slow and meticulous, probably more so than your mthod. Very easy to test.
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I am going to try and word this differently. I say that tip movement, string movement, and the weight you are actually pulling on the bow have no correlation to draw weight. The best indicator or current draw weight is simply to pull the string down to the draw length you are looking for or until the scale hits the draw wight and you check and see how many inches of draw you are at regardless of string length braced or unbraced. I am not saying it is 100% accurate but I am saying it is the best indicator.
The little flight bow I just did, I hit 50#@20 on the long string, I braced the bow and it was still 50#@20". The 100#@26 bow I did last week, was showing 100#24 on the lng string, I braced the bow and still showing 100#@24.
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All good info fellas. For the most part I've never seen much increase, a little, like a pound or 2. Just wondered. Thanks!!
Tattoo Dave
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Steve, weight of stave at 10 inches is correlated to weight of bow at 26".
Trust me. It is. I have used this method since the early 90's.
Further, I've taken tillered bows and drawn them 10 inches with the long string and have obtained draw weight.
I know it is hard to believe.
Once again this method is a rough guide to when to string the bow. Some can do it by feel. That's good.
I can see people running down to try it on finished bows.
That's good too. LOL.
Jawge
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Steve, I am not saying your method does not work. I am sure it does.
I've just never liked long stringing too far.
Jawge
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Jawge, I am sure your method works as well. The only thing I feel is important to prove and not for the sake of an arguement but for the sake of facts is that tip movement gives no reflection of draw weight unless you are using a very similar length string all the time. Just reading the draw length on your tiller board means you don't have to worry about how long your tiller string is.
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I don't know, Steve. Remember that in a finished bow, tips at best move a few inches. I think they are going to move a lot more with a really short string and strain limbs too soon for my tastes.
I haven't thought about string lengths between those I've mentioned.
Jawge
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I'm puzzled(as usual). How are you guys measuring draw length on the long string? Where are you measuring from? If you are measuring from the back of the bow doesn't the length of the long string enter into it?
Thanks
Don
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I measure string travel. Mark where it starts and measure down ten inches. There are buildalongs on my site. I will find the right one ASAP.
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I measure just as if the bow is braced regardless of the length of the string or how far it is hanging down within reason. My string usually hangs down anywhere from 4" to 10". If I measure it at 50# at 24 with the loose string I get about the same measure if it were braced even though the limbs are moving much different amounts. Closest method I have found and easy to check using a long string and a finsihed bow.
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Thought I'd chip in.
All this is just how I do it, I've read all the other posts and of course all methods work and we all have our little quirks.
I don't claim it's right or original.
1. Long string should only be just long enough to get on the bow, this keeps the geometry closer to the braced geometry. (A very long string is almost pulling straight down rather than down and in towards the middle)
2. You have to measure something, I go by tip deflection. Once they are coming back about 7" or so (pulling to full target draw weight*), I'll go to a short string (low brace... say 4-5")...
After that it's business as usual.
* Full target draw weight on a long string is a lot less than the same weight pulled on a short (braced) string.
There is a long and tedious discourse on the subject of long string poundage needed to brace a bow on my blog here:-
http://bowyersdiary.blogspot.co.uk/2013/12/yew-stick-bow-and-draw-weight-to-brace.html (http://bowyersdiary.blogspot.co.uk/2013/12/yew-stick-bow-and-draw-weight-to-brace.html)
Don't come running to me if you regretted reading it! >:D
Del
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I have never weighted on on the long string,of course I use a tiller stick until I get it to brace with a long string just long enough to get it attached, I move down the stick 1 inch at a time and when tips look close I stretch a string tip to tip to simulate what it will look like at brace,when it is ready I brace maybe 4 inches and go to the tiller tree. Everyone has their way that works and this does for me. :)
Pappy
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Don C, here's my site where I go through long string tillering the way I do it. Jawge
http://georgeandjoni.home.comcast.net/~georgeandjoni/boardbowbuildalong.html
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Del, this could make a great topic for a video, we all have methods that work for us. I may prove myself wrong when I do this but I though of a simple test that could make a short but cool video. I take a finished bow and brace it. I check the draw weight at 3 different brace heights about 1" apart. Now I take that same bow and I hang 3 strings on it, one of them hangs down about 4" another 8" and another 12". I simply measure the weight at 28" or so with each one of these strings and see how much difference it makes. I have actually done this and I was surprised how close to the same they all read. A video will support or destroy what I said.
The only reason I would have for argueing this method is beause I feel like it is easy to explain and easy to repeat. We all have things we do that work that are hard to explain. I feel one of the worthwhile challenges of primitve bow making is finding ways to explain things that work so others can try it out and either shoot it full of holes or agree with it.
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Jawge, one thing I will never forget is reading your web site 15 or so years ago is what got me making bows that didn't break. I had been making bows for a few years and putting fiberglass cloth on the back of most of them to keep them from breaking. I read Jawges web sight and my whole world suddenly changed. So if you see us going back and forth it doesn't mean we don't respect each other, it just means we like to argue!
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Steve, thanks for the kind words.
Of course, I am not in any way offended.
I'm Greek we invented argumentative discourse!
I also have a science background and peer review is important.
Jawge
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Perhaps, the best piece advice I can give a beginner is to have a plan that will take one from a floor tillered stave to a strung stave. It can be a reduce the weight by feel approach or something else seen here.
It can be a plan obtained from someone or one developed specifically for that person.
Anything to avoid a willy nilly rush to the string is good.
Jawge
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I like vids. I think you should badger.
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Well this post went way beyond what I expected. :o Good stuff though fellas.
Tattoo Dave
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Del, this could make a great topic for a video, we all have methods that work for us. I may prove myself wrong when I do this but I though of a simple test that could make a short but cool video. I take a finished bow and brace it. I check the draw weight at 3 different brace heights about 1" apart. Now I take that same bow and I hang 3 strings on it, one of them hangs down about 4" another 8" and another 12". I simply measure the weight at 28" or so with each one of these strings and see how much difference it makes. I have actually done this and I was surprised how close to the same they all read. A video will support or destroy what I said.
I really would like to see the results of this! I would hypothesis that there would be little difference in draw weight between the 3 different brace height about 1" apart. However, as you unbrace the bow and allow the string to hang down from the bow the draw weight will progressively decrease as the "hang down" length increases. Of course as you approach a hang down length equal to your draw length (28"), the draw weight would be "0". I would be very interested in looking at a graph of the hang down length vs. draw weight - I bet it would be a nice "curve" that the smart math people could explain with some equation!