Primitive Archer
Main Discussion Area => Bows => Topic started by: Ameer on October 09, 2015, 03:09:06 pm
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Hi guys, I'm new to Bowery and I've only ever done PVC bows before. My first attempt at making a self bow was a Sycamore sapling which I cut and air dried and it turned out horrible after month's of waiting and a lot of hard work, anyway I found a good few Mulberry trees growing too close to each other and the owner let me cut one of them down. I split it into staves and peeled the bark only to reveal many thorny like pin knots about 1 cm in diameter and 1 cm high protruding out of the stave, about thirty of them on just one stave , I'd like to know if I should go ahead and cut through them and maybe the earlier growth rings will be clean and if they carry through then can I apply sinew to back the bow? Or should I try to work around them? Altogether I have about twenty staves with the ends sealed some are branches so I could experiment a little but I'd hate to waste a stave so I'm open to any ideas.
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Oh man that is beautiful!
Just use it as back - it is ready!
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Oh man that is beautiful!
Just use it as back - it is ready!
What he said👆
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Thanks, I'll do that. What design should I go with? This is my very first bow.
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I agree with above, go for it!
What is your draw length, what draw weight are you looking for?
I'd say go 66" to 68"(since this is your first), 1 3/4" at the fades, out 8" with a straight taper to 3/4" tips(also because its your first). The tips should be narrowed to 3/8" later. This can give you a bow from 40# to 60# or more. Keep your first bow simple, learn proper tillering, go slow and keep in touch with pics and questions. ;)
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Thanks a lot, I've never really measured my exact draw length, how do I check it? I'll be sure to post pics as I go along. :)
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Mark an arrow like a ruler stick, starting from the crotch of the nock.
Pull it back on one of your other bows and see where you measure up.
From the crotch of the nock to the back of the bow
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Thanks, once I have my draw length how do I measure the length of the bow? I'm sorry if my questions sound naive, I've only ever built a few pvc bows from exact dimensions I found online, so I'm kinda new to this and I want to get it right the first time.
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The overall length of the bow does have a direct relation to your draw length. 2x your draw length plus about 10% to start but longer is a better option for a beginner. For a 28" draw (28"x2=56"+6"=62"). After you build a few bows this would be a good length for you. Until then I'd say go with 66" to 68".
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Shouldnt the sapwood ideally be removed for mulberry?
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If the wood was handled properly from the stump mulberry sapwood is a good back. I've made several mulberry selfbows with sapwood backs.
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I've heard the same, mulberry can be used with either a sapwood or heartwood back. I've got a few 4" red mulberry saplings I cut about a month and a half ago and they have little heartwood (finally found some straight mulberry and can't wait to try it out) I would go with practically the same design as PatB.
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B&A,FYI, you'll find a mulberry bow with mostly sapwood will be considerably thicker than an all heartwood bow.
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Interesting, I've read that that tends to be the case with all sapwood bows, wonder why that is? Since it makes a decent bow still, it can't be that it is significantly weaker wood, higher elasticity for less weight maybe?
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The sapwood is less dense than the heartwood.
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That's true, but density can't be the only factor, it must be a willingness to stretch under less strain than the heartwood, and since different density bow woods can make the same weight at practically the same dimensions, then it can't just be density.
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I think i would at least take the sapwood down to one growth ring. The problem with over doing the sapwood is that you can then get too much compression on the heart wood belly, especially if it is less thickness in ratio to the sapwood... you still have to imagine that the neutral plane is going to be the center of the limb's thickness, and i think that the sapwood tensile strength may possibly be more than the compression properties of the heartwood on mulberry.
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That's true, but density can't be the only factor, it must be a willingness to stretch under less strain than the heartwood, and since different density bow woods can make the same weight at practically the same dimensions, then it can't just be density.
Pat pretty much nailed the reason. It's true that the same front profile dimensions can be used for a wide variety of wood densities even though it's better to adjust the dimensions to best suit each particular stave. However, you will find that the thickness will for the most part have to be thicker to get the same draw weight on the lower density wood than it will be for heavier woods. Josh
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Who am I kidding, you all are probably right, who am I to argue with people who have been doing this for decades. but in my head it works out that a wood can have lower density and still retain tensile or crushing strength( I'm talking about 3 or 4 SG, which is what I assume the density difference on sapwood is) but then again, I'm just a 14 year old who likes bows!
Cheers!!!
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B&A, I never give it that much thought. ??? From experience I know the finished product is thicker when using sapwood over heartwood. My brain doesn't compute the whys but it does acknowledge the reality.
I've built mulberry bows that were all heartwood, heartwood with a sapwood ring back, 50/50 heartwood/sapwood and all sapwood and the more sapwood involved the thicker the limbs are for the same draw weight and design.
Bowmonk, I think all the pins on the back were of concern to Ameer so I was letting him know that if the sapwood is sound he could use it as the back. As it is now the sapwood is physically unblemished so therefore the best possible back for his bow...if the sapwood is sound.
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It looks like the mulberry I have in Florida. It grows very fast here. Growth rings are huge. I always use just under the bark for my back. In fact the biggest piece I've found was maybe 5 or 6 inches but I've never seen heartwood on this type of mulberry I have around here. The wood has good properties though (not Osage good) but good none the less.
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Does heartwood have to be a different colour to sapwood on Mulberry wood? Where exactly does the heartwood start on this stave?
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The sapwood is creamy color and the heartwood is caramel color.
All of the mulberry I've seen had large growth rings.
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Wow Mulberry has a lot of sapwood.
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How big(diameter) was the tree?
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About 12 inches the bottom was thicker though.
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That is a very typical stave from my experience with mulberry. You shouldn't worry about those little pin-knots. Mulberry is resilient bow wood. Just be careful about it twisting. If it isn't fully seasoned before use, you might find your tips move on you...even in straight-grained wood I've seen it do some strange stuff while drying. You can heat treat it as well! It will end up very light and have excellent cast.
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Can I please see a picture of one your mulberry bows?
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Sure, I'm working on one right now. I am splicing it out of billets. When it is done, I'll send you some pics!
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I understand why you recommended that he use what he had for the back of the bow Pat B, and just looking at the surface of what he had I agree, it looked great already. I will still say though that if that is a photo of the stave he is using, considering the thickness of the rings and the depth of the sapwood, and the fact he has a nearly 3 to 1 ratio on sapwood to heart wood... I think it would still be advisable to work the back down to the last sapwood (white) ring leaving one growth ring of sapwood.
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I agree Bowmonk but if he's new at this chasing a clean ring with all the pins could be a daunting task. If Ameer doesn't mind the challenge having a heartwood belly would be the preferred.
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Okay I managed to split the stave again on a growth ring for most of stave and get two staves out. Hopefully two bows.
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Nice, I see one sapwood bow and one sapwood backed bow!
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I get the feeling that b&a473 is looking at the question of thickness from the physics and Josh and Pat are making their recommendations for more thickness when using sapwood, from experience.
In my book, experience trumps theory. Would Josh or Pat try try to estimate just how much extra thickness they allow for lighter woods? And are we comparing designs with the same over-all set? or permitting more set for the stronger but otherwise equal bow?
thanks
willie
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Oh no, I know that the sapwood bow will be thicker, I trust PatB and JOSH, they know what they're doing. But I was saying, that the sapwood might not be weaker when it comes to compression/tension, but that it is more stretchy, kind of like a thick rubber band and a thinner one, thick = more strength but the same bendability as a thinner rubber band.
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Willie...those are very good questions. I'm not sure I'll have good answers for them, but I'll try. When we say that all else being equal(length, width, profile, tiller etc.) that the sapwood bow will be thicker in comparison to one of heartwood to achieve the same draw weight, it's not really a matter of allowing for more thickness. The thickness is established as you tiller. After making a few of various combinations, you notice that the more heartwood there is, the thinner the bow will be to achieve your desired weight. I can't give you a set percentage of increase in thickness, I can just report that is noticeable. Also, if you take for instance the two splits that Ameer got out of this stave and you make two bows of identical dimensions(except thickness), tiller, draw weight and length, the sapwood only bow will take just a little more set and be slightly lighter in mass than the heartwood bow. That's if all else is the same. However, if you increase the width of the sapwood bow in proportion to the difference in density(I usually go a 1/4" wider) the mass and set become nearly identical even though the sapwood only bow will still be slightly thicker. I've only actually played with this kind of in depth study a few times and not always with mulberry, but the results have been pretty consistent. I wish that I had more time to do such experimentation, but I don't. I'm sure others have though. I don't know if that answered your questions or not, but it's the best I can do. Also remember, wood is not created equal. Any experimentation is subject to skewed results due to variances in not only the species, but even from one end of a stave to the other. A lot of the time, regardless of how careful and controlled your experiments are, the results are little more than best guess and assumptions. There are certainly noticeable patterns though. And this is one of them. Josh
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Josh
thanks for taking a few moments write in detail. Sometimes folks come here to "just get the anwsers", (nothing wrong with that approach), But I appreciate the time you have taken to explain your experience, It helps to understand the basic principles of what we enjoy
willie
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I agree with Josh 100%. To make a mulberry bow that is the same draw weight as an osage bow I go about 10% over the dimensions of the osage bow. A mulberry bow of the same draw weight as an osage bow can be a faster bow because the mulberry, even 10% bigger that the osage, will probably be lighter physically thus less tip mass. Mulberry reacts well to belly tempering too with adds a bit more zip.
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I'm learning a lot on this thread, the least of all that I need to get some mulberry.