Cores breaking problem

fusizoli · Post by **fusizoli** » Fri Sep 26, 2014 5:38 pm

Think the problam made those thing I ve mentioned before. This is not a wood fault.

4mm horn 6mm core 2mm sinew is not a good proportion

4mm horn 4mm core schould work with 2mm sinew

or

5mm horn 5mm core 3mm sinew....

Schould put a thicker sinew layer on it but it will push the neutral plane to the horn glue line. Especially if the horn is thin.
6mm core is good for warbows well ower 100#

But waiting for what the pro bowyers say ;)

Kviljo · Post by **Kviljo** » Fri Sep 26, 2014 6:45 pm

I'd say the kiln dried wood can be part of the problem too. It is really quite a bit more brittle compared to air dried. More sinew would in any case solve it though.

On the other hand, small cracks in the core is probably quite acceptable. Peter Dekker washed off the sinew layer of a manchu original, and there was lots of little cracks along the bending sections.

Which way do you orient the growth rings in the limbs? Flat, or standing? If they are standing, it is quite difficult to know how the real fibre direction is. Flat rings are safer, as you will see the fading growth rings which should be avoided.

mikekeswick · Post by **mikekeswick** » Sun Sep 28, 2014 6:44 am

Thanks for the advice. I was limited to the horn thickness at maximum of 4mm due to the thickness of the horns before working them so the wood thickness was kind of determined for me.....I suppose I will have to use much thicker sinew if this happens again.
The wood is all flatsawn not on the bias or quatersawn as per Adam's recommendation regarding lateral stiffness.
This problem is very frustrating because all the work and waiting has already been done.... I really want to get better at making these bows but I must be doing something consistantly wrong. As has been suggested it must be the sinew thickness or ratio of horn/wood/sinew.

Alessi Francesco · Post by **Alessi Francesco** » Wed Oct 01, 2014 5:46 pm

I fully agree with Fusizoli: less wood and more sinew. Plus, I think that cherry could be quite brittle in tension. What was the min radius of bending?

Zoran Pavlovic · Post by **Zoran Pavlovic** » Thu Dec 04, 2014 6:47 pm

A pity for bows Mike, i am not expert but Francesco, Kviljo and Zoltan have interesting and useful points.
I would only ask is there any exemple to use cherry for the grip for Ottoman bows or any other bow where splice is in bending part? We saw in one exemple that cornel doesn't work well.
I do experiment with other kind of bow but i use same specie of wood for the grip/splices as limbs wood species (one acer campestre, second one ash, made several raw cores but am still not satisfied so i don't dare to glue the horn and do other stuff, my budget isn't for game.
Also, there are great advices here such as your bad experiences shown here are worth learning about possible failures. I shall use equal proportion of horn/wood. And what i've learnt now is to use more sinew for security (as i remember Adam suggested it for less experienced makers as i am -3 layers).
Thank you for showing details (i know what i can expect in the future ).
Cheers and wish you luck with next attempts!

mikekeswick · Post by **mikekeswick** » Sun Dec 07, 2014 7:20 am

Thank you Zoran.
I have managed to get some hornbeam that has perfect grain. It bent perfectly and has been sat on the forms for over a month now. I will be doing the splices soon.
I will be putting all the above advice to use and really concentrating on making this next bow as close to perfect as possible.

scemdonmez · Post by **scemdonmez** » Sun Dec 07, 2014 11:20 am

Air dried wood are best for sure but my first bows are made by kiln dry,I do not lived any problem. I believe form and proportion of cross section are more important. 3 mm snew is too much for, 4-4 wood-horn, I think it can easy twisted.
Gluing line is very important where it placed on center line.
I believe glue absorbing of snew and backing methot are very important.

Cem