SINEW GETS TOO DRY AFTER 6 MONTHS!

hi,

everything looks pretty fine! except the delaminated horn-body glueline. if all is done well, you should have parts of the wooden body in the horn and/or horn in the wooden body. horn and wood break more easy, than a well done glueline. body and horn have to be heated up before glueing with hide-, sinew- or fishbladderglue. too the glueline should be less than 0,5mm when dry.

Peter

Thanks,peter! except I am mostly having problem when I try to open the bow after 6 months drying time. The sinew gets to hard and dry, it be comes almost impossible to bend the bow with tepelik. Is it because not enough humid on the dry sinew? should I leave the bow outside in the humid more before I attempt to open it?

:shock: OMG what a pitty..

I agree your problem is the glue line.

what kind of glue do you use ?

did you coat both surfaces (wood+horn) with glue and let dry several times before you finally put it together ?

how fast did you open the bow (this may take some days) ?

keep cool : as long as the core and sinew is fine you can probably repair the bow by re-glueing the horn.

:wink:

Hi Uli, THANKS FOR RESPONDING,I used 30% tendon glue, 70% fish bladder glue. But the the real problem is when I try to open the bow the sinew was so dry like a bone!! it was very hard that I could not tie the tepeliks! I put so much pressure to it then off course the horn separated from the core. I believe it has something to do with humid on the sinew. Perhaps, I need to leave the bow in the humid until the sinew gets softer! I don't know? I still could not get the right answer :))) (my privious two bows were broken in to two pieces in the same exact process, the weird thing is after 6 months drying time my sinew gets from amber color to white color and extremely hard !! may be my glue has problem or sinew I am using is not healthy. I cook the glue as every body does, it is simple process so sinew I use is cattle which is ok too. THE MAIN THING IS THAT AFTER 6 MONTHS DRYING TIME IT BE COMES ALMOST IMPOSSIBLE TO TIE THE TEPELIKS BECAUSE THE SALS ARE SO HARD !!! AND NO FLEX IN THEM AT ALL, LIKE A METAL!!

No, The sinew is supposed to be as dry as possible. Most would probably agree that you can't get the sinew too dry.
Humidity is not good for a sinew backed bow.
It looks like it is strictly a horn/glue bonding problem and possibly your perception of the bows stiffness is because it is too strong for you or for what you are expecting.

thank you Patrick , when I read Adam books it says, "if the ambient humidity is very low, less then 30% RH, it is best to wait until a more humid season begins. Bow tend to be difficult to bend and materials are more brittle when very dry."

My previous two bow were broken like pencils in to two pieces last year while I was opening them. no horn strips were off.I do everything right until this point (I guess) when I open the bows they get broken because of to much of dryness and hardness.

That's interesting. I've never seen a sinew backing get brittle from low humidity. I regularly hang mine over a woodstove to get them as dry as possible.
Since these composite bows were used as war bows I can't imagine they were calling a halt in the action every time the humidity dropped.
The susceptibility of a composite to moisture is well known but this is the first I've heard that they have a window of optimum humidity as well.

hi Sado,

sounds the other way round with drying sinew -> normaly in drying prozess sinewlayer turns from white (wet) to translucent amber (dry). anyway, usual the sinewlayer never gets as hard to overstress the hornlayer.

you invested a lot of work and patience in all. please follow this way! open the bow with the "asa gezi", a tool to open the bow and do the first tiller until the bow has the shape nearly before sinewing. by the way, picture 3 -> perfect bow-shape, i love it! ok, give the bow step by step this form back! can take one month! after this use the tepeliks and leave it for at least 1 day before bracing! the bow needs time for his new form! remember: not only building a reflexbow needs patience, tillering and bracing need a lot of time!

wish you all the best
and hope this helps

Peter

Ulu; You need some success soon. I once knew of another man with this problem. His bows were too strong so he could not get them strung or they would self destruct. What are the dimensions of the horn, sinew and wood core at the middle of the limb?

You are definitely having a glue up process problem besides that. As Peter Kyudohund correctly states, there should be pieces of horn sticking to the wood core and wood core sticking to the horn. Since this has not happened, then I agree with Uli that this bow can be reworked, easily.

One should make a weak bow first or a child's bow to get an understanding of the process and feel.

I believe that you may be obsessing about the dryness of the glue. Put that out of your mind while you work on other issues. Post dimensions of thickness of the limbs.

Peter thanks again!! wow one month for only use ASA GEZI ? to open it for tepeliks? I wanted to open the bow,tepeliks,everything in two hours!!! Big mistake ha??
Thank you for the complement for #3 pictures that at less feels good after all:) I have one thing very good about me is that I can build a bow just like exact shape of antique ones!!
(IF I CAN, FINISH,OPEN ONE:)

Bye the way I am getting good advices so far, I wished I was in atarn net before!! then perhaps I could have achieve something until now.

Jack, thank you for respond also!!

my bow size is 117 cm ntn, kasan 19 cm, sal length I think is 25cm.
SAL thickness is, 5mm horn, 4mm wood core, 3mm sinew!! all together 12mm thick. Yes I also getting glue up problems besides the very dry sinew issue!! yes true!! and really really need some success!! gee, after 3 bow are broken yes!! I am really frustrated!!

I feel for you! At least the core didn't fracture - it looks like you can salvage it. Don't give up! :^)

Also, I am sending two bow pictures, one is white horn which was broke in the bloody same process last year, the other one is black horn bow also broke in the same process 2 years ago!!

I was practicing leather covering before I open it. it was paper not leather on it in the picture

I was practicing leather covering before I open it. it was paper not leather on it in the picture

I wanted to open the bow,tepeliks,everything in two hours!!! Big mistake ha??

EXACTLY, this was your problem !
do as Peter suggests.

your bows look perfect. (+ DARN white horn...)
the dimensions make a heavy bow of over 80lbs (rather 100).
I really hope to see it working.. keep us updated.
:D

Yep, as other did tell, glue problem. I have seen that when others use fishglue, I use hideglue.
Tepliks, I have seen others have problem with that also. I bend it over my knee first and then I use my bow press. Sometimes I put the bow in a wice and bend one limb at time and when they learn bending I take the bowpress.
And your bow can be strong maybe 100 lb. If there is a weak point it will break.
The first bending takes a lot of energy, but ones it has come around it will be lighter next time.
Nature all way find the weak point, I have break more bows then I made shooting :)
And I wrap the handle fade with sinew. Compression is so high that a bone insert can be crush. If it moves it will come of :(

what a petty - like Uli says, your bows look perfect! i can comfort you, my first 3 bows break too! don?t hasitate, please go on - we all want to see it braced!

i agree the advices from everybody in this topic. the form is perfect. there are different forces to take into consideration until the bow is shootable. when you open the bow, whole sal section tries to delaminate, because forces pull every layer apart. when sal is on tepeliks, in this section forces press all layers together. now the most endanged sections are near the grip and the kasaneye. at this point sal-glueline has only to resist sideforces. if the bow sirvived, this is half the way.

by the way, one of my broken bows had a 3cm bone insert as Celik; during bracing on pegboard to put the string on, this come off like a projectile, really dangerous. since this time i keep the Celik as thin as possible, max. 5mm. i saw big forces are in all sections of the bow, even in the stiffest one.

good luck, i am looking forward to see your bows braced!
Peter

You've had excellent advice. I must say I agree you definately had a glue problem. If it had only just delaminated then bit's of horn would be stuck to the core and vice versa.
My first couple of bows had horn/core delamination problems. Having everything nice and warm with good sizing is essential.
Good luck.