sinew cracked

[puscica]

Dear all,

I come from Slovenian alps, I am new on this forum. I like this hobby and I made bows since 2004, when I succesfully made first yew longbow for my daughter. After this I build for myself and my friends more than 50 bows. Few of them reflex-deflex laminated with Gordon glass, but mostly primitive bows with or with out of sinew backing.
My last challenge it is horn bow and there I have 5 years long trip with out of reall succes.
- first I have troubeles with joint horn-wood, but this is ok now, I know how to do it. In fact I am use lo less glue and start to use heat for straiting to fast.
- now I have bigg troubeles with sinew. I am try with ostrich sinew. deer and elk sinew taked from local hunters, Dictum Issinglass and hide glue and at the end with home made glue from sinew.

My troubeles:
- to thin glue and sinew become white, separate and start to cracking.
- to thick glue and all surface start to cracking deeper and deeper.

By my last bow I am use issinglass and elk sinew. It is work like in dreams and I put on leather cover. After 14 days I try it again and I hear thousands of cracks. It work, but tru the leather is visible lot of cracks.

What to do? Perhaps change upper surface of sinew...?

[Pat B]

Welcome to PA, puscica.
I haven't made a horn bow but I have made a few sinew backed bows. Sounds to me like you used too much glue. That is the only part of the sinew/glue matrix that I think would crack.

[JNystrom]

I think what is adviced commonly is to use thin glue in the first layer and thicker glue in the last layers. Glue cracking in the surface isn't that serious and actually it allways happens. The sinew/glue layer will get a bit white and generate tiny crosswise cracks, but the main thing will be that the sinew should be safe/intact underneath.

Personally i've never had problems with too concentrated glue if the adhesion to the earlier sinew layer was good. BUT, i've had plenty of problems with too thin last layer, because the sinew will separate and start to lift from the glue.

[puscica]

Nice answer!

a.) I try to avoid small crachs and put to less glue. Than happen exact what you write: Sinew start to separate, lift from glue etc.
b.) I want toawoid separating of sinew and than come thousands of small cracks, plus white colour. Nobody mention this and I was totally scary and confused.
Last bow it is stop to cracking and it keep arround 60#.

How to put fotos on this forum? I made smallest format, but when try I get answer: To long time or to high resolution.


br from Slovenia!

[Pat B]

Br, most folks use photo hosting sites like "Imgur". They store your pics and resize them so they can be posted on other sites. It is free and easy to work with.

[loefflerchuck]

I thought it best to start with thicker glue in the first layer and go thinner after that