Primitive Archer
Main Discussion Area => HowTo's and Build-a-longs => Topic started by: Hillbilly Deluxe on April 19, 2010, 01:50:45 pm
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Hey everyone-
So I am attempting a yumi, and considering the limited amount of info. on building them I thought I would do a build along. Keep in mind that this is only my first yumi and third bow so take everything I say with a grain of salt.
For starters, I got the Boo from Frank's, (will post websites later), I ordered the 6"x8' (for a hansang-nobi) I ordered two and was glad that I did. Both were usable but I think that one would require some straightening and I didn't want to deal with that. So I split down some 2.5" strips out of the same piece so the nodes would match. I then knocked off the inner-walls and laid out the shape of the yumi.
I went 1.25" at the center and down to 1" at the tips. I got this from another post in PA and made mine slightly bigger because I was planning on making a little stronger yumi. So then I marked out the siyahs this way I could make sure that the nodes would not line up and get the proper length of the belly.
For the core I chose to go all bamboo. I couldn't find 8' wood and didn't want to have to splice it (which I did anyways). I used the straight and tempered fast-flex cores from Rudderbows. I am going to laminate three 1/8" pieces and then taper them as one. They only come in 6' pieces so I put the splice in the middle of the handle, not where the arrow will rest figuring that that should be the thickest part if the bow.
Enough talk here are some pics.
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Here is the back and belly after they have been cut to length and roughed out, next I will have to taper both.
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Here you can see the lams. in the core.
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Here is the three together. I am going to use the rope and wedge method to clamp and glue the core. Let you know how it turns out.
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Sorry here is the picture.
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Just a couple of comments: (I made a 'yumi' three years ago out of three pieces of bamboo that I had - it turned out OK and shoots great, but it is all wrong - I didn't know much back then and I did not shape it correctly - if I had, I wouldn't have been able to draw it. )
see http://www.primitivearcher.com/smf/index.php/topic,6634.0.html
At that width, that's going to be a very strong yumi...
I'll be interested to see how you attach the sayah.
Thanks, and good luck.
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Bhenders-
Thanks for the comments I just looked through your posts. I was wondering, (I didn't see it mentioned), how thick was your core at the handle and tips? Also what did you do your wrappings with I really like the colors.
On a personal note I tried the wedge method to clamp the core and you definitely want to use something like bailing twine. I used some small, 8# test hemp string and it got cut when I was pounding in wedges. Also keep the wedges fairly steep. There is another website where someone talks about making some from bamboo. I think it would be best to order yourself a piece of 2" boo with your bow boo just to make wedges. The cost would be really minimal and they would work very well.
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Here is the core after cooling off overnight in my "bow oven".
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DISASTER!!!
Well, I pulled the core out cleaned it up a bit thought I would bend it a little to see how strong it was and snap! Right in half, the single lam in the middle broke right at the joint that would have gone in the upper part of the handle. So now I have a six foot piece and a two foot piece.
I thought about gluing them together with another piece of possibly oak to thicken up the handle and make it into another bow. What do you think?
Getting back to the yumi. Any Suggestions? I am thinking of switching over to wood for the core. I was thinking red oak, because I could run to Lowe's and get one fairly easily. I know that I will have to really pick through them but I think I could find one. Any thoughts?
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Sorry, here are the pieces I have. I also have plenty of bamboo left. Bhenders, maybe it you could expound a little on ho you did yours?
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I think I had a long piece of glued bamboo from Franks, OR I just sanded down a piece of bamboo that I already had so that it was flat on both sides. My memory lately is like a steep sieve!!! I had been thinking of doing what you were going to do but was going to use vertical bamboo flooring. I bought 10 pieces of that last year, cut them in half and cut them into 1 1/4 inch widths. I made a 'horse' bow style bow from a couple of pieces and it works!. BUT - I was digging around my garage and found two lamanated bamboo planks that are 8 ft long (from Franks) that I forgot about so I'm going to use one of them for the center.
I think that the oak will get crushed in the middle if you try to use it. How thick was the 'center' strip going to be?
I was going to measure my bow for you but from memory (at work now) my bow is less than 1 inch wide and about 1/2 thick. I'll measure it tonight when I get home.
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I was going to make the core go from 3/8 in the handle down to 1/4 at the top knock and just slightly thicker at the bottom knock. Someone on another yumi post said that I would probably want some form of wood in the core to give it more "spring".
Could you explain "crushed" better. Sorry I'm new to the bowyer world and don't understand all the lingo yet. My thoughts were that if I used Oak it would be something like a "board bow" with a boo back and belly making it that much better, no?
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By the way I really appreciate your input.
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Well, the first bow I made was an oak board and I put bamboo on both sides. Very bad tiller and eventually the oak got crunched and finally broke... I believe the actual term is crystalised??? It just can't take the bending and the wood cells and fibers get crushed and finally fail.
I keep meaning to measure my yumi style for you but keep getting sidetracked by yard work. Like I said before it's was a "yumi style" becuase everything was wrong about it... except it looks ok when shooting. I still like to shoot it but I'm going to try to do a more authentic one this spring or summer. Check out the build along on paleoplanet.
From reading about yumi making, everything is shaped before the glue up and the bow is glued and then it's done. They have been doing it so long that they don't 'tiller' the bows at all. The only wood pieces are the two wood strips on the sides of the bamboo core which MAY leave them some room to adjust things.
I'm thinking 3/8 for the core is way too thick. Yumi bows are 'backwards' when unstrung and with a core that thick, it's going to take an elephant to string it. Check out http://www.yumi-bows.com/yumi.html for how a bow should look when it's being glued and wedged (is that a verb?). That's Koppendrayer's web site. I would love to get to his place sometime to see how he does things.
btw: I'm far from a expert on these things. There are a couple of other threads about making a yumi. I seem to recall one on here a while ago that was very good. Do a search on it... found it http://www.primitivearcher.com/smf/index.php/topic,11083.0.html very good write up.
also look at http://www.kougei.or.jp/english/crafts/0707/f0707.html
here's a build along on paleoplanet
http://paleoplanet69529.yuku.com/topic/22774/t/Yumi.html?page=1
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I should add that yumi are shot with a thumb draw and the arrow on the 'outside' of the bow. Very different from the 'English' style. The Japanese use a glove with a stiff thumb (that costs an arm and a leg) so I just use the thumb from a heavy duty glove ( attach a leather strap and wrap that around your wrist to keep it on). You could also use a thumb ring like they use on horse bows. I've made a couple of thumb rings but shooting with them seems to introduce Quantum effects in my shooting (random scatter).
I've found that I never get string slap when shooting this way (and I always do when using an English release). It is also more like using a mechanical release because I think you get a cleaner release of the string.
One more .... the draw on a yumi is REALLY long. Typically past your ear. One should be careful not to get inside the draw.. LOL Might be problematic if anyone's ears stick out too far...
Once you get the next one done, go to youtube and watch someone shoot a yumi. For them, it's all about the procedure of getting ready to shoot. The 'zen' of doing. It's not even supposed to matter if you hit the target. I'm too western, I WANT to hit the target - but good form is nice because it makes shooting easier and it's kinda cool when the arrow hits the target and the bow flips around all by itself.
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Thanks for all of the web-sites, they are all very helpful for anyone else planning on starting a yumi. These were essentially a majority of the info that I found as well on yumi construction which is why I thought I would do the build along.
The web-site for Frank's where I got the boo is: www.franksupply.com they have all different sizes. I got the glue and core bamboo from: www.rudderbows.com they have a tremendous amount of bow and arrow making supplies and are very professional.
Core:
So for the core I decided to go with the oak. I got a 1x3 with really good grains and then chased a ring all the way down the back, then tapered the belly down to the widths I wanted. I was also thinking 3/8 might be a little thick. I will post the final dimensions I came up with when I get it sanded down and ready to glue up. I am shooting for around 10mm in the handle. I also used the 1x3 so that I could lay it out so that it had a little bit of bend to the right at the bottom, allowing the bow to spin in your hand when shot. I am also planning on heat tempering the core and belly this should help keep it from crysalizing. I am also thinking that with the exceptional length of the yumi that will help spread out some of the stress.
Back / Belly:
For the back I will not heat treat it and here are the dimensions; handle: 5mm, upper tip: 3mm, lower tip: 2mm. For the belly, once again I will temper it and the dimensions are as follows; 5mm the entire length.
Here is some information I found on lengths from another web-site. I then put the English equivalent down for all of us Yankees.
Archer's Height Arrow Length Bow Length
150 cm- 59" 85 cm - 33.5" Sansun-tsumari 212 cm 83.5"
150-165 cm 65" 85-90 cm 35.5" Namisun 221 cm 87"
165-180 cm 71" 90-100 cm 39" Nisun-nobi 227 cm 89.5"
180-195 cm 77" 100-105 cm 41" Yonsun-nobi 233 cm 91.7"
195-205 cm 81" 105-110 cm 43" Rokusun-nobi 239 cm 94"
205 cm+ 85" 110 cm+ 45" Hassun-nobi 245 cm 96.5"
Hope all of this helps, I will post some pics. as well. I have to make some wedges and get some pieces for the syahs before I can glue it up bit I will post as soon as I can. Until then shoot straight!
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Here is a pic. of the core after being roughed out, showing the grains.
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Reverse the words for the last two pics.
Here is the core looking down the belly and shows the curve to the right.
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Here are the end of the belly and back after they have been planed down using a belt sander and some 60 grit.
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I just ordered some ebony for the tips, here is the web-site: www.exoticwood.biz they have a lot of selections and most of there stock is turning blanks, so I think that it will work excellent for this application. I think that I am going to do a black handle that fades into red with the black ebony tips again, then finish it all off with tru-oil. I think this will somewhat emulate a urishi finish.
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Here is a picture of the bow after being glued. As well as a closer shot of the knocks partially finished.
I started bending it a little and it is definitely going to be a strong bow, which on one hand is good because that is what I was going for, but on the other hand I think that it may be a little too strong. I am going to try and train the bottom some more because almost all of the bend is in the upper limb right now. I think that I should have planed the lower tip to the same as the top.
I also planed the ends of the tips down to approx. 2mm for the length of the knock, as per another build along. I don't know that I would recomend this for a beginner because it make the tips a lot weaker and it is harder to bend to shape.
I was also wondering if anyone knew where to get a yumi string?
And also if anyone wanting to comment on my shaping feel free, I won't get my feelings hurt. I used the rope and wedge method and ended up with about 30cm of reflex when it was all said and done.
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Sorry I have not had time to post on this in a while, the core of the bow is too thick. lol ;D so i am going to grind off the belly and thin it down a little. :'( I had it bending nicely and enough to get it braced, however i think that it would have ended up a 150# bow which I thought was kind of excessive. I am also getting ready to go back to work in the rock-slides on I-40 back in TN / NC so i won't have as much time to work on it but will keep you updated.
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Id love to make a yumi one day, no one around my area has one and i bet it would be sick to use, i have a 28 inch draw lol
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There is a couple very good videos on how a traditional yumi bow is made. If you go straight across the bow from the back to the belly starting at one node you should end up in the middle of two nodes, hope that makes sense. It will if you watch the youtube vids. And you'll need a specific shape for a mold when your curing the bow
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There is a couple very good videos on how a traditional yumi bow is made. If you go straight across the bow from the back to the belly starting at one node you should end up in the middle of two nodes, hope that makes sense. It will if you watch the youtube vids. And you'll need a specific shape for a mold when your curing the bow
I agree there are alot on youtube about yumi bows