composite cores ... pictures

the two 3 piece cores were made with the same form, the increased reflex gained by re-boiling the kasan/sal after the kasan/tip had cured for a day, and simply pressing the sal flat to the form. The other core, in the middle in the pictures, was made with the sal portion still in the air, about an inch from the form at the form's end.

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I think you make an error in the shape of the handle. very short and wide V-splices. look back at the book of mr. Karpowicz - page 77

For my bow I cut a 5" tapper from the end of the handle area into the sal. I have attached a picture that shows the two cores with a paper template of the handle with the v-splices. Note at the center the handle is 1" wide. The bow then tappers in and back out to a max width of 1 1/8".
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Made a little progress this week. I'm back at work after the holidays so not as much time available for the shop i'm afraid. I made a grooving tool, grooved the horn and core, and sized everything with two coats of thin hide glue. I shaped down the handle a little bit, to get that sharp point out of my way while i worked, but for now i'm going to leave it until after i have the horn glued on. So far i have just grooved the short recurve with no ears. It is gonna be my practice piece but will wind up to be a good bow, i think. I have plenty of sinew to put on the back, a combination of hide and sinew glue, and all i need now is a little scale to measure mass, so that i can calculate the amount of required sinew properly. Thanks for looking.

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Feels good. Combination of sinew and hide glue. Horn was not flat, but i heated the sal well before gluing, then began the process of attaching it to the core by using a spring clamp in the center. I then added oak strips and c-clamps and in a couple of minutes the thing was all glued up. I used an extravagant amount of glue and reasonable pressure. Thanks for looking.

Scott,
I am curious to know did u use concave horn/convex core method? I like the way how to form the concavity of horn by gluing flat heated strip onto convex core using rope binding. Anyway, i wish you good luck and hope it will be great bow.

Perhaps I am missing something... Aren't these cores very massive and thick? Will you plane them down after gluing the horn?

zoran: No the components are both flat.

stephen: yes the core is extremely thick! But the way i understood Adam K's instructions, the core is used as a skeleton and that is why it is bent in such a thick piece. It is much easier to steam-bend thinner wood, although this yew is pretty compliant.

I considered reducing the core before applying the horn, especially since the horn doesn't actually span the recurve. I guess the idea is that a thick core will hold its shape and force the horn to adhere. If the core is too thin, the horn can pull it out of the shape i so carefully made it take.

My next work, unless i'm totally wrong, is to reduce the core and clean up the horn, and get some movement in the limbs. After that, i apply the sinew and let the thing rest for 6 months.

If i'm out to lunch please let me know.

thanks

"...and get some movement in the limbs" - that may crack the core. Without sinew the core will not take the tensile stress, since the growth rings will be violated at the grip and the kasan.

Since you made the grips splice wide (as Pazuzu and bheggeseth noticed), once you trim the width, the splice will shorten rather dangerously. I suggest to either leave the grip wide or make it shorter. Plus keep the weight of the bow lighter to reduce the stresses at the splice.

I am worried about the length of horn as well. I understand the (later) tapered ends are still in the bending part of bow. That way the horns may slip off once the bow is flexed. Possibly sinew wraps will be required where the horns end (put on after the sinew backing).

Adam

Adam,

thanks, yeah i'm concerned about the length of horn as well. I thought as you do, that it may need sinew wrapping. Well, i am down with that, and will probably wrap the handle as well, since i bungled the splice-job. The pair of horn i got were twisted and this was all i could save, so that's why these horns go with this short recurve.

I don't mind making mistakes as it's all part of the learning process, but i am glad that some things have gone well.


You say not to flex the core. How do i know at which point to add the sinew, if i don't get the core bending at all first?

It isn't a selfbow. The weight can be estimated based on the total thickness of limbs. Subtract the sinew thickness (3mm) from the total to get the thickness of core + horn together. Then file the core down and the horn if necessary, trim the width, shape everything round and smooth and cut the grooves. At this point the thinned bow will flex, but do not do it.

Then layer the sinew until the total thickness is reached.

There is a table of old bows' dimensions which can be roughly followed.

Adam

(the core is best trimmed after the horns are attached to make the curves symmetrical, plus avoid damage to the core when clamped. Koreans do that too - see the video by Thomas)

Thanks Adam.

I found the chart you mean, on page 41 of your book. The average draw weight is 127 #. Too much for me. I'm going to make this one pull 60# or so, trying for a 28" draw. I see there is a 50 and a 70 on the list, i'll examine those and interpolate.

One thing i noticed right away: some things don't make sense. No criticism to your chart, i just don't get the findings in this one respect.

160# bow, wider by 3 mm and only 1 mm thinner than a 180# bow, and even shorter. I'd have thought the draw weights would be the other way around.


Anyway, i wanna thank you for all your time and research, and also for adding advice when newcomers like me show up. How did you manage to gain access to the Turkish bows in the first place, which are listed in this chart? Rub a magic lamp?

Zoran Pavlovic wrote:

I like the way how to form the concavity of horn by gluing flat heated strip onto convex core using rope binding.

I thought that might be a good idea too. It was not. The horns cracked along the limb, even if the core was only slightly convex. It's of course possible I did not heat the horns enough, but from that experience I would advice caution.
On the other hand, using a heatgun to get the damaged horns off the core, as suggested here somewhere, was a good idea. Worked a charm, thanks

1mm less thickness is a lot. The weight goes down with the cube of thickness, while only in proportion to the width. Do you have the Trad. Bowyers Bible? All that must be well explained there.

Adam

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I have progressed a bit farther than this, to the point of transitioning the kasan into the sal, even though the whole thing is still far too thick. I am at the stage in doing things which i call "walking in the dark" where i have no real idea where my next step is going to land, but i must move forward.

Adam told me that at this stage the "bow" becomes bendable but that i must not bend it until after the sinew is applied and cured. Gonna be tough.

This is the simple recurve bow.

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Here you can see the limbs are straight before sinewing.
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Thick layer of sinew.
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I sinew wrapped the handle because of the added-in bits of horn, and the end of the horn. We shall see.

After 5 days the straight bow has pulled into considerable reflex, each tip being about 2.5 " off the straight line. This is natural, as you can see i didn't tie the tips together.

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It is not quite clear how far the sinew goes onto the siyah bend? I think it should cover the inner curve of the heat-bent part, or else they might straighten out again.

The average grip thickness for the turkish bows is around 33,8mm (Karpowicz 2008, 41). I think it is better to make it rather short like you have, than too long. I made mine too long for my first try, and it made the bow stack more than it could have with a shorter one.

Are you going to put more sinew on this bow? If so you really should pull it into a lot more reflex before adding the sinew. You need to strain the materials more. Yew can easily handle this reflex by itself (without the horn). When the sinew is applied pull it into more reflex to 'press' the sinew into the back as described in Adam's book.

How long is it?

it's approximately 49" overall. measures 42" between the tips in a straight line.

mike, as for whether i'll be adding more sinew, i dunno yet. As mentioned, it has 2 thick layers on it already. my intended draw weight is 60#. I think i have enough sinew on it for that.

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the white sinew is not suck more glue cause you are not separate sinew to fine equality thread, maybe these sinew on bow will be fine thread by press/shake and no glue

it's true that much of the sinew was still in strands up to 1/8" acrss.

Here is the first sinew layer on the turkish style composite.

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This time i properly applied the sinew first to the edge, around the belly. Then i used wide clumps about 6" long, deer leg sinew, to cover the back from the grip outwards to the tips. These were almost wide enough to cover the limb completely all the way to the edge strips. Here and there i had to put in filler strips.

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This work was done yesterday. I learned from the sinew job i did last week on the composite shortbow, and kept the first layer simple. Rather than trying to fill in every little gap, i will just let the thing cool and cure, and besides i almost got it covered completely.

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Have you reduced the tips width yet? They still look too wide?

the tips are still 2" too long, and yes they are still a little oversized

made some more progress. This bow has been curing with 2 layers of sinew for 6 weeks or so. yesterday i inlaid the nock reinforcements and today i braced and drew the bow.

It's 48" overall length. so far drawing 55 at 24. very high early string tension. the cracking of the glue scared the crap out of me!

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not finished yet, and i just added a better sinew wrapping over the ends of the horn, but this bow kicks ass so far. the arrows fly out fast and hit hard. Can't wait to see how it finishes!

http://www.youtube.com/watch?v=lTaM4vKkhtU

that is a short vid of the first drawing of the bow

Your upper limb is stiff and I would correct the twist in the strung position before pulling it. Good luck.