how to fill checks in yew

[freke]

Hi
I working on yew bow with bamboo backing (not applied at this point), the wood is really poor quality so I have no big hopes but see it as a learning project, One limb has a year ring that check badly, I have seen it coming and after heat correction it has increase, or at least been more visible.

The layout of the bow is a flatbow 40 mm parallel 2/3 wide and 67-68"ntn, and I am not experienced enough with yew-boo to see how thick limbs needs to be to get a bow out of the stave but I hope the majority of this check will be gone during tilering although I am afraid I need to seal it some way if it goes too deep. I have only one successful yew-boo built before.

My question, is there any good method to fil it or at least stabilize?  It goes over two third off one limb starting in handle on one side, the other side is not as bad. Before II put some heat on the bow it was more a clearly visible hair line, but now is it easy to feel with the nail and too big to fill with cyanacrylat.

Thanks
Jonas

[Hamish]

Finish all heat treating, and corrections before gluing, as superglue will vaporise when heated.

I would use superglue, because epoxy won't get deep down into the cracks. You might also be able to clamp the sides to help close up the gap.

[freke]

Finish all heat treating, and corrections before gluing, as superglue will vaporize when heated.

I would use superglue, because epoxy won't get deep down into the cracks. You might also be able to clamp the sides to help close up the gap.

I will do all corrections and heat-treating and applying the Boo before I seal the crack anyhow hoping to be able to remove the worst part of the crack, super glue is handy and probably what I will use if nothing better comes up.


I have heard that there should be methods of apply epoxy deep in cavities but not find any easy way doing it?

[Hamish]

Even a runny type of epoxy is still very viscous compared with superglue.

You can sometimes run epoxy through a crack that goes through the belly out through the back. You set a vacuum cleaner hose on the back side and suck through the crack. It works in some cases.

Most of the time when you apply epoxy into your type of crack it only gets in to the first couple of mm. This gets removed during tillering and exposes the crack again.

I would heat treat, then glue the crack, and clamp it. It may totally close up. Then you can back it. Other wise if the backing is already on, it probababy won't close up.

You can always do a dry run and clamp it without glue to see how much it closes up.

[freke]

 right, it don't hurt try before backing  I will see if it can be done by clambs or bend the stave so it closing gap more and use super glue - it would at least close the bottom  that  worries be most if it start grewing.

[bownarra]

As you have seen dry heat and yew aren't really best friends....
You can heat epoxy to thin it but still best using a very thin wicking CA.
One thing however is that yew doesn't like being in wide thin bows. your layout isn't ideal for it. I would go narrow and thick. Certainly no wider than 1 1/4".

[Del the cat]

...
One thing however is that yew doesn't like being in wide thin bows. your layout isn't ideal for it. I would go narrow and thick. Certainly no wider than 1 1/4".

Eh? 
That's not my experience. My "go to" field bow is Yew 15/8" wide near the grip with a graceful curving width taper out to v slim tips.
Del

[freke]

If I could chose I would have done an english long bow  -but on opposed limb there was several violation the back, among one big knot 2/3 out of the limb so with the limb width I have at least something around the knot so design is pretty much decided my the quality of wood  - the shaping is maybe not the best but I try to keep both limb as equal as possible before glue up therefor has it been firs straighten with steam and then heat treated( lightly ) where I correct shape.

 
Dry heat was maybe not the best, but the crack/check was there before although it get way more visible - so I see the issue with dry heat but think I read somewhere that yew answer well to heat-treating?

There are loads of different CA / super glues on the market here - is there any better than the other and is there any specific to avoid? to look for, for example I use one bottle but some use with activator sparay etc) ?

[simk]

in my personal experience yew really likes dry heat a lot - it reacts quickly and this does need a significantly less heat compared to other woods for the same effect.
the problem with heat corrections before glueup is, that as soon as you scrape of the really heat treated top layers the bow will start to creep back when you tiller it. therefore I'd suggest a reallly long and deep heat treat in corrected areas. talking from experience here....

[gutpile]

appears your yew wasn't dry enough yet for the heat treat.. looks like you drove the moisture out of the wood causing the check.. JMO..gut

[freke]

pretty sure its dry and the check was there before although it may have become worse if it still wet but doubt it. The issue is the wood itself  - the forest is cursed but as yew is so rare here we build with everything we get hands on.

[bownarra]

...
One thing however is that yew doesn't like being in wide thin bows. your layout isn't ideal for it. I would go narrow and thick. Certainly no wider than 1 1/4".

Eh? 
That's not my experience. My "go to" field bow is Yew 15/8" wide near the grip with a graceful curving width taper out to v slim tips.
Del

just facts not talking about experience, this is an area that isn't subjective.
Yew has low bend resistance and high elasticity.
These characteristics of the wood allow elbs to be made from it. eg. narrow and thick
Of course you can make a wider bow but the best speed/efficiency will be had from the narrow and thicker limb. I've done it many times as well you know.

[freke]

I have progress with the build and at first the check seems to shrink and my hope rise, but I never made it to short string.
It has clearly delaminated in one year ring

So now my question is can it be saved? 
Was thinking about open it up as much I dare without damage it and use TB3 and clamp it.

[George Tsoukalas]

I am trying to figure out why that happened. I have never had it happen.
The obvious culprit is over heating but I learned not to go for the obvious.

You'd have to glue and wrap and you are not done tillering.
I would call it toast.
I've been hit in the head by bows more times than I can remember.
Jawge

[freke]

Bend it opposed direction and put in a wedge and it open up more, using some pressure and a needle pressing glue deep - risky project so it will be lighter bow if I make it finish