Yumi Build Along

[Hillbilly Deluxe]

   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.

[Hillbilly Deluxe]

Here is the back and belly after they have been cut to length and roughed out, next I will have to taper both.

[attachment deleted by admin]

[Hillbilly Deluxe]

Here you can see the lams. in the core.

[attachment deleted by admin]

[Hillbilly Deluxe]

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.

[Hillbilly Deluxe]

Sorry here is the picture.

[attachment deleted by admin]

[bhenders]

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.

[Hillbilly Deluxe]

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.

[Hillbilly Deluxe]

Here is the core after cooling off overnight in my "bow oven".

[attachment deleted by admin]

[Hillbilly Deluxe]

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?

[Hillbilly Deluxe]

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?

[attachment deleted by admin]

[bhenders]

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.

[Hillbilly Deluxe]

   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?

[Hillbilly Deluxe]

   By the way I really appreciate your input.

[bhenders]

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

[bhenders]

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.