Yew longbow taking set while tillering

[WillS]

I'm tillering a 72" yew longbow at the moment, and while the stave already had about 3 inches of deflex before I started, I can feel the bow taking set as I tiller. 

I've not even reached brace yet, I'm still working the limbs on the long string but every time I draw a little bit further I can feel the bow going soft, almost as if it were chrysaling badly.  The moment I feel this I stop, check the set and it's got worse.  There are no chrysals anywhere in sight, and the set is evenly spread across the bow so no flat spots or hinges.

I've got it clamped to a 2x4 at the moment and I'm about to heat treat the belly to see if that will help, but I'm just wondering if this is a sign of something I've not picked up on?  I don't THINK the wood is green or even moist - it's been seasoned for over a year and a bit and when rasped or drawknifed it's crisp and there are no signs of moisture throughout. 

I had to use excessive heat straightening on this stave to take out twist and massive lateral bends - could this have weakened it too much?  I wouldn't have expected it to take this much string follow so early, so I'm a bit confused!

[Pappy]

Sounds like it is still wet to me,but just guessing,I would do the heat and straightening and then put it a very dry environment for a week or 2,at floor tillered it should dry quickly if that is the problem.  Yew is usually very springy.
   Pappy

[WillS]

Ok, will give that a go! Cheers!

[Del the cat]

I have had Yew that was a lot softer than expected. I'd say clamp it to a bit of 2x1 (narrow edge up) with the back against the 2x1 and a 1" block under the grip (e.g 1" of reflex). Put tape over the back first.
Heat treat the belly, this will do a heat bend to take out the deflex and temper/harden it all in one go. Expect it to take 30-45 mins each limb. Don't rush. Do it until you get a slight darkening of the belly. If you clamp some thin slats to the sides of the bow that will help keep the heat off the back and also direct the hot air along the belly giving a more even tempering and avoiding the brown stripe effect. A fish tail nozzle on the heat gun also saves waste heat, I reckon it speeds the proces up a fair bit too, but still expect to get bored rigid (have a cup of tea/coffee to hand;) )
See this post.
http://bowyersdiary.blogspot.co.uk/2013/02/yew-longbow-more-heat.html
Del

[WillS]

Thanks Del - I'd actually read your blog entry a while ago, so I was doing exactly as you'd said anyway! Trouble with this bloomin' stave is I've done so much heat straightening already, every time I heat an area, some random lateral bend comes back or it starts twisting!  It's gonna end up being lovely and reflexed but looking like a piece of tagliatelle at this rate.

What I wouldn't give at this point for a piece of yew that didn't need straightening....

[Del the cat]

If you clamp it laterally while you do the heat treatment and the leave it for a day at least, hopefully it should stay put.
(you just need a sack full of G clamps)
Del
(Have you got the clamps? No I always walk that way )

[vinemaplebows]

Got a pic of the stave?? That would be a help before I comment on something I can't see, have some a few things that come to mind considering yew, but must see the stave first.

VMB

[WillS]

Taken a couple of pics.  This is after the first run of heat straightening I've just done though.  You can still see the deflex kick in the lower limb that I need to take out, but it's much better than it was.

Looking down the front profile it's clear to see the twist and the lateral S-bend.  I'm not too worried about the lateral movement but the twist is a pain.  It was actually drawing nicely until I tried to remove the deflex and it all retwisted itself and the lateral bends got worse again.  I'll do as suggested and clamp it everywhere in both planes and try that. 

I'm starting to get a bit apprehensive about all this heating though.  There must be a point where it just weakens the yew so much that it's pointless making it bend!

[vinemaplebows]

 Looks as though this may have been from a branch? (although from the pic it is hard to tell)  If so it is ultra important to choose the right side. I would wrap it in a wet clothe over night and then either boil, or use direct heat if thats all you have. I personally use a microwave in these hard to deal with pieces. 2 1/2 minutes I am bending. Now here comes the crazy you are using a microwave......yeah I know

VMB

[WillS]

I believe it was from a branch, yes.  What do you mean by choose the right side?

How on earth do you get a bow into a microwave?!

[vinemaplebows]

Think how a tree branch grows on a yew tree (assuming you have seen one) Alot of times on yew only the ends of the branches have needles for light photosynthesis, branches will bend contort to reach the maximum amout of light it "can" cause twisting especially tward the ends of the branches. The upper part of the tree branch will be under tension because of holding up the weight, and like tension wood in vine maple, it would make a bow less likely to have string follow.

As to the micro-wave I have cut a hole through the front and back so the stave can go through it. I then place it as close to where I want heated by centering it in the nuke box, stuff wet rags around the stave where it meets both holes on the outside the nuke box......turn it on......walk outside and listen for the ding (around 2-4 minutes) then bend with clamps. Remember that micro waves heat by aggitating water molecules SO if the wood it wet, heats fast, not so wet think about wrapping a wet rag around it for a few hours the wood will obsorb enough water to have the wood heat easily. This causes drying to the wood so don't overdoe it, and don't zap the same spot too many times!

By the way I could fix that in about ten minutes!

VMB

[Del the cat]

There comes a point where sometimes you say..  "I'll just go with the flow". as long as the  two tips and the grip are in line the rest doesn't matter, twists bends whatever.
Slap a string on it, keep teasing it back, correct what you can in terms of sideways bend. The wood will tell you which way it wants to bend (or break if it doesn't want to be a bow).
Once it's about half way to full draw it should have established some sort of plane on which it's bending. Mark the grip and arrow pass to suit and call the face furthest from the string the back (if you're not convinced, write 'back' on it and a CE mark )
sometimes it will be as ugly as sin, sometimes it will look like gorgeous character, maybe it'll shoot like a dream, maybe it'll shoot like a pig.
Until then it's just a stick... so go with the flow and release the inner bow.
Del

[lesken2011]

As to the micro-wave I have cut a hole through the front and back so the stave can go through it.

I would love to see a picture of that! Would you mind posting one, or two, or three?

[George Tsoukalas]

Like Pappy I think it is wet too and I would not heat treat a wet stave. Water has to go somewhere so it  rushes out and causes cracks. Jawge

[WillS]

Thanks for the help guys.  Just a thought - I've never understood it, or found a description anywhere (I don't have TBBIV) but is this where the Mass Principle would help out?  If I can weigh the stave as it is, would the Mass Principle tell me if there was clearly too much moisture in it?