Confusing sideways bend

[joachimM]

Could the wood of that yew tree be too dry?

[WillS]

Well that's something I don't know enough about to say, really.

I did do a quick sapwood bend test just now, and the sapwood (without any heartwood) broke at very little bend, into extremely short fibres quite unlike usual yew sapwood.  If I can chalk this up to the wood and not me I'll be much happier, but I think it's more likely to be user error than anything else!

[WillS]

This is the result of bend-testing just the sapwood from this particular tree.  Have to say, it doesn't look particularly good in terms of tension material 

[George Tsoukalas]

As you proceed on your bowyer journey, WillS, you develop a feel as to when the bow is ready to get pulled a little further. You have to coax a tiller and take your time.

I can't really tell why your bow broke from those photos. I can speculate that you pulled it too far too fast before it was ready.

Did you long string tiller?

That stave did not even look ready to be braced. Just speculating.

Here's my site.

http://traditionalarchery101.com/

I broke a lot more than 5 before I got a hunting weight shooter.

Jawge

[WillS]

Thanks George.  I've actually made probably about 50 or 60 at this point, most of them over 100lb and normally when this sideways bending occurs it's either an easy fix, or I ignore it and the bow resolves itself.  I made a nice 115lb ash bow last year which has very similar twist and it's fine at full draw.  The 140lb ash bow I posted in the warbow section actually has some slight sideways bend to it as well.  This particular batch of yew just doesn't seem to be able to cope with the sideways forces, however.  I'm wondering if it's down to the sapwood just not being elastic enough to hold together.

This one actually blew up at brace height (or just beyond) while long string tillering which is pretty unusual for me!  Mine normally go pop at around 32" when I've done all the finishing work 

[George Tsoukalas]

Sorry, Will. I thought I read that 5 blew up on you. That's what I get for typing before my 2nd cup of coffee. Jawge

[WillS]

Yeah you read it right, it was 5 in a row!  But all from the same tree. 

The question is - am I doing something wrong when it comes to correcting this twisting problem, or is it a problem with the wood itself?  I'd like it to be the latter

[George Tsoukalas]

Well, Will, then, it still looks like you bend it too far too fast.

Are we talking a twist or a dog leg?

I don't know about war bows and such but that stave looked capable of 50# anyway.

When I make bow, first I floor tiller 2-3 inches.
After floor tillering, I go to the rope and pulley and long string tiller out to 10 inches of string movement where I want good bending and around target weight. Then I string it.

My early days I'd break staves while stringing because they were too heavy.

The above method puts the stave about 10# over target.

Jawge

[WillS]

This was going to be around 130lb which is just a bit too heavy for floor tiller.  You can floor tiller them at that weight, but its easier to use long string tillering instead.  It broke at 50lb, but that wasn't the end goal for the bow.

I do pretty much as you described, regardless of draw weight.

To be honest I still don't know if its twist or something else.  Not dog leg, because the staves are dead straight when I start bending them.  The sideways bending happens almost immediately, and the back and belly of the bow stay level, while the actual limb itself bends outwards then back again, forcing an S shape down the whole bow.  When you take it off the tiller and look down it, its still dead straight.

[DC]

Do you know the history of the stave? I'm looking at your sapwood bend test and wondering if the sapwood has started to decay?

[WillS]

It was cut about 4 months before I got to it, and was left outside without the ends being sealed.

Not the best recipe for success!

[WillS]

We're talking about three or four BIG logs by the way, that I split and shortened dramatically to get around 13 staves from.  I assumed that reducing them so much would remove any problem areas, but perhaps not?  Would that be a logical reason for every single one so far to fail?

[DC]

I really have no idea how rot resistant yew sapwood is but I do know it's not as resistant as the heartwood. I don't think 4 months in the rain would bother it. I've worked yew that was on a slash pile longer than that. Maybe if it was laying on the ground and the staves you're working were on the bottom? I'm just guessing here. Maybe it's just bad karma. Have you pissed anybody off lately

[wizardgoat]

I think you just answered your question. Yew heartwood will not rot in that time, but the sapwood will easily. Even if it just started too, the outside growth rings under the most tension have been compromised.
On the 4 or 5 salvage yew staves I've worked, the sapwood was dry and powdery when scraped.  It should be creamy and carve like butter.
Maybe make an all heartwood bow, or back with rawhide.
I'd try to get a bow or 2 from that batch still

[WillS]

It doesn't feel any different to what I've worked before, and certainly doesn't feel powdery.  Perhaps it's just started to go, and that's enough?

Still doesn't explain the sideways bending in every single stave however.  My plan now is to rip it all into boards and make laminated warbows out of it, but if it still tries to pull into an S shape I'm not sure what the answer is.