Main Discussion Area > HowTo's and Build-a-longs
Winter project - Yew Recurve bow
Onebowonder:
--- Quote from: Bryce on March 12, 2012, 12:32:16 pm ---Iam no stranger to yew. But why not just add more sinew to raise the nuetral plane? To where the wood does the compressing and tue sinew works out the tension?
--- End quote ---
Just guessing here, ...but I'd think the answer would be something along the lines of, ...because the sapwood is already there, capable of doing the job, performs identically, costs nothing more in either effort or money, and saves both the effort and money that would be spent to remove the sap wood and add the additional sinew.
Gordon:
First let me be clear to all who are following this thread - I am not an expert at sinew backed yew bows. In fact, this is my first sinew backed yew bow. Regarding the question of the sapwood - my research was inconclusive on this point. I do, however, have the benefit of having an example of a well known bowyer's work in my possession. The bow was broken when the owner over-drew it (the bow is 48" and was pulled to 30"). Because the bow is broken I've been able to deconstruct it to learn something of how it was made. On this bow the bowyer left a very thin layer of sapwood under what appear to be 2 courses of sinew. I let this inform my decision to leave the sapwood on.
I also want to clear up any confusion as to how many courses of sinew I applied to this bow. I applied 2 1/2 courses of sinew, but I applied all the courses on the same day. I saw no particular advantage in waiting for the sinew to cure between courses, and evaluating the result now, I still don't.
I don't believe the edge knot will cause me any problem based on prior experience with similar knots, but if it does start to act up, I am prepared to wrap it.
It remains to be seen if these decisions are wise and I expect I will have my answers soon as I begin the tillering process.
Thank you all for your comments and for following this thread.
Bryce:
--- Quote from: Onebowonder on March 12, 2012, 01:16:49 pm ---
--- Quote from: Bryce on March 12, 2012, 12:32:16 pm ---Iam no stranger to yew. But why not just add more sinew to raise the nuetral plane? To where the wood does the compressing and tue sinew works out the tension?
--- End quote ---
Just guessing here, ...but I'd think the answer would be something along the lines of, ...because the sapwood is already there, capable of doing the job, performs identically, costs nothing more in either effort or money, and saves both the effort and money that would be spent to remove the sap wood and add the additional sinew.
--- End quote ---
I disagree. Sinew and yew sapwood are not the same. Sinews shinks 4% and stretches 10X farther than wood storing more energy. As far as time and effort. That's what being a bowyers is all about. If you dont want to put out time and effort into your bows just go buy one or string up a pvc pipe or something idk. Sinew is beyond cheap and 90% of the time free whether you harvest it yourself or someone on PA will gladly throw some your way.
So let me rephrase. Is there any performance advantages to leaving the sapwood on and sinew over the back?
Compared to just heartwood and sinew. Because that's how I was told to do it......
All of the bows that I have seen that had sinew backing in local museums had no sapwood.
and I apologize if I came off jerkish that's not my intent.
Oh boy wheres Jim hamm when yah need him.
Keenan:
Bryce,
Often people take things as a dogma or "The only way to do something". Not saying you are doing that, just saying sometimes we get in a mindset. I have also read Jim's an many other great bowyers books as well as having allot of hours on yew. If fact More yew experience then any other type woods. On some wood types the sapwood is worthless. I think there are some crossover thoughts to that as well, that may be a factor. Yet on yew it simply is the opposite. Yew sapwood is one of the most versatile and forgiving sapwoods that there is in. The tension strength is fantastic and it will hold the sinew very well. Probably better then the heart wood. I have not done side by side comparisons but that would be interesting.
My thoughts are that with the yew sapwood being left on there is double protection. Sapwood + Sinew for tension strength instead of just the sinew for tension.
Gordon:
--- Quote ---Is there any performance advantages to leaving the sapwood on and sinew over the back?
Compared to just heartwood and sinew. Because that's how I was told to do it
--- End quote ---
Bryce,
I really have no idea as I do not have sufficient experience with such bows to weigh in on your question. Frankly, for my first effort I'll be delighted if I simply end up with a decent build-a-long and a shootable bow.
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