korean hornbow in process

...sorry for the long and incomplete link,3/3 is the correct video.

Stefan

I've never made a Korean bow before but what do you think is wrong? It looks fine to me. I would be using a longer stick now.

be sure to apply the tepelik the right way round (see Adams book).
:D you probably know that..

http://www.youtube.com/watch?v=o6qRnTVM2KU

Hi again,this should be the right link and here are my next steps.I decided
to continue the spreading.The little bump should not be to serious.As you
can see,the bending-zone starts to become visible at the left limb,the
right one is stiff like hell.
When is the right time to start to reduce horn?The korean master in the vid
is obviously reducing horn in the bending-zones.Should I do that also?

I have learned that it is not useful to use heat in the main Tillering-Process
because the tiller than is only temporary,for the correction of a tiller it is ok.
So I`d like to tiller this bow only by horn reduction,but again:
When do I have to start with it?

Any advice welcome regards Stefan

Hi everybody,
my Hornbow-Projekt ended in a katastrophe last night and I ?m still upset.
What happend? After I kept on spreading the bow with some little
scratching here and there the bending-zones became visible and everything
looked fine.In each spreading-stage I let the bow rest overnight.
Finally I put it in the Tepliks when a very light crackle occured.I decided to
heat the horn slightly.Everything fine,the crackle turned out to be 2 small
creases in the last layer of sinew that I put sidewards on the limbs.I let
the bow rest for 5 hours in the Tepliks,than wrapped the creases and set
it back to full circle by slight warming,to draw and tiller it under full tension.

When I had the bow on the drawing-board,everything seemed to be in
perfect order until I heard a slight wispering crackle... Immediately I tried
to loosen the bow but to late: it broke in a huge explosion.

The bow was 122cmNtN,12mm thick with 2,5cm wide limbs.I estimate
the drawweight far above 70lbs.Is that to much for a korean?

Please help for next time! Stefan

What a shame...
I can only suggest that the wood in the handle wasn't thick enough and some bending was occuring. What wood is the grip and how was the grain running in it?

From what I can see in a typical Korean bow some bending in the handle is rather plainly visible.
Is the significant "turkish" style lump on the back common?
To me it seems the korean bow works ever so slightly through the handle and that's why their "riser" seems like a stuck on feature rather than truly integrated in the belly side of the bow.

Stefan; You didn't do anything wrong. This is where a true Korean bow built by the masters breaks. Look at all the oldest bows any you may see wrapping, sometimes heavy , in this location. To have reduced in the limbs might have relieved the stress there but how could you know?

Build some weak bows and work up to a strong bow. This is my advice for everyone. First learn to walk and then to run. Don't let all that heavy bow talk affect you. Make a kid's bow.

oh pain..

if you put the bow on the pegboard like this
- after a "timar" process (!)
- without protecting tepeliks
- before its tillered
- before ever having strung it
every bow will break, preferably in this location

I suggest

1.) induce the bending in the right place
(which would more away from the grip)
with the help of the tepeliks
(note: pressing down the GRIP side not the TIP side)

2.) remove tepeliks on the pegboard or after stringing only if there is no dangerous deformation when releasing the tepeliks i.e. the bending section stays where you want it (more away from the grip) and keeps "balanced" over some cm. Typically the bending section will migrate towards the grip, then aggravate at the edge of the stiff handle section, form the "locus minoris resistentiae" and break.

I'm far from expert and haven't made such a strong bow like your attempt but still hope that helps

Oh no, I hope you?ll try it again!
I guess this would not have happened if you would have wrapped the whole handle section with sinew. I guess the limbs have bent to much close to the handle.
It looks like you can use the horn for the next trial and go for Jack?s advice.
Michael

Uli; "locus minoris resistentiae"; I like that. did you author this term? Spelling correct?

:D (latin "the point of least resistance") this is a technical term used in medicine (and probably other sciences too) so it is what comes to my mind first ;-)

...thank you all for your advices and suggestions!The next bow will come
up soon...Well,I really think I?ve learned something from this accident!
I am aware now that the fade of the korean handle is a real "hot spot",
in danger to delaminate!In comparison to the ottoman bow where you don?t
find a part like this,because the whole grip is spliced,not glued!
So I managed to make 2 koreans in the same manner,same handle,
same tepliks,same pegboard,but they got only 55lbs and the fades were
wrapped!Shame on me,when I recognized in the video,that they didn?t
use any wrapping while tillering,I decided to leave it away.Bad mistake!
I guess,what actually happened to the bow was,that the fade started to
delaminate and levered the sinew til it broke.That might be as well the
reason for the shape of the korean handle:a flat angle at the fade means
less stress,the higher the handle ,the sharper the angle,the bigger the
danger to delaminate!

Another point is the way how to use the pegboard.Next time I will put the
bow with tepliks on the pegboard until I can string it. I took the shape of
my tepliks from my hwarang bow and also the distance to the grip should
be all right.But when I had the bow on the pegboard without the tepliks ,the bending zones started to move towards the grip,as Uli said!

A little bit wiser for the next try.... Stefan