Where to cut yew

[tannhillman]

The cambium is a very thin un-barky looking layer, on your pic I can see inner bark along the bow back with a bit missing in the area of the dip, and I can see what looks like the yellowish cambium layer remaining on the dip? But hey its not always so easy interpreting a photo!    I have made a lot of yew selfbows and I always keep the cambium on as it, in my opinion, makes for a stronger bow as the sapwood remains unaffected, and it also protects the sapwood from future damage (like a natural integral backing).  I have never known it to come off during tillering or during subsequent use of the bow, but I have had pieces of inner bark in and around knots that I hadn't removed pop off during tillering as you describe.  I do remove the bark (inner and outer) early on in the process and leave the cambium on during seasoning.

The cambium is a very durable layer as illustrated by the fact that the majority of the MR bows had the cambium on, after tillering and then after another 400 years under water!!

[tannhillman]

Hi, have a look at this attachment which shows the cambium quite well.  I have been working with wood for many years and cambium has always been this term used for the thin layer just above the sapwood. If you scroll to the bottom of the last link you gave there is a pic of someone removing the inner bark (I have attached), and the cambium can be seen beneath. 

The references I have read in relation to MR bows have all used the term 'cambium' rather than 'bast' to describe the layer remaining on those bow backs, but different names can sometimes be used to describe the same thing.

I do think its important  to get terms right and avoid misinformation as you say, as there is already far to much of that around the subject of yew warbows already haha!

Iain

[DarkSoul]

(...)
The article says it is the Phloem which carries the nutrients (not the sapwood which your doc states), and that is what I had always believed.
After all the sapwood isn't wet and slippery, it's the layer just above it...
DAMN!
Here's an article about sugar Maple that says the sap does flow in the sapwood! http://maple.dnr.cornell.edu/produc/sapflow.htm
It appears even the academics can't agree. Or maybe I'm scan reading and missing the detail.

Sapwood transports water from the roots up the tree, to the leaves where it will evaporate.
Phloem transports nutrients (dissolved in water) produced by the leaves from the leaves to the growing tissues that require nutrients, such as buds, root meristems and cambium.

[tannhillman]

(...)
The article says it is the Phloem which carries the nutrients (not the sapwood which your doc states), and that is what I had always believed.
After all the sapwood isn't wet and slippery, it's the layer just above it...
DAMN!
Here's an article about sugar Maple that says the sap does flow in the sapwood! http://maple.dnr.cornell.edu/produc/sapflow.htm
It appears even the academics can't agree. Or maybe I'm scan reading and missing the detail.

Sapwood transports water from the roots up the tree, to the leaves where it will evaporate.
Phloem transports nutrients (dissolved in water) produced by the leaves from the leaves to the growing tissues that require nutrients, such as buds, root meristems and cambium.

With reference to Dels comment above, the document I attached (to show the position of cambium on a tree) actually said the following in relation to Sapwood -  "Sapwood is the tree's pipeline for water moving up to the leaves. Sapwood is new wood. As newer rings of sapwood are laid down, inner cells lose their vitality and turn to heartwood". It does not say that the sapwood carries nutrients!  Iain 

[PatM]

I think you're confusing the oxidation on the last layer of sapwood as "cambium". When you peel bark, the cambium comes off with it.

[tannhillman]

No, I have been working with wood for a long time. .no confusion, the thin layer between the sapwood and the bark is the cambium!  Have a look at the pics that I uploaded above, they both show the cambium layer, as does the document I attached  to an earlier message. 

 See Science Dictionary definition below:-

cambium   (kām'bē-əm) Pronunciation Key 
Plural  cambiums  or cambia 
 A cylindrical layer of tissue in the stems and roots of many seed-bearing plants, consisting of cells that divide rapidly to form new layers of tissue. Cambium is a kind of meristem and is most active in woody plants, where it lies between the bark and wood of the stem.

[PatM]

So what happens as the tree actually lays down that yearly growth ring?  Look at the end profile of the log and look at each growth ring. If you work down a single growth ring perfectly, is there cambium on that layer as well?
 Your photo above also shows "dry rot" which doesn't actually exist.

[tannhillman]

The cambium is a layer between the inner bark and the first growth ring. If you season a log with the bark on then the cambium comes off with the bark when you remove it, and you are probably not aware of it (which is what I think is causing the confusion here as almost everyone makes their bows from seasoned staves with the bark on. However, if you peel off the bark on a freshly cut log then the cambium stays behind (as shown in the pic above). There is only one layer of cambium so if you remove a growth ring there will be not be any cambium, no.

I unploaded the photo to show the the position of the cambium on a log,  the 'dry rot', which is a term that is still commonly used, even though it tends to be called 'brown rot' today, is not relevant to the point I'm making about cambium.

The majority of the MR bows have the cambium on, demonstrating that the bark was removed prior to seasoning, which makes complete sense as in those days they did not have bench saws to cut up timber as we do today, so logs were split by hand, and it is much harder to split season logs so they would have ben split when fresh.   

[PatM]

 Not sure why you think it only comes off when seasoned versus when it is freshly peeled. Clearly it is not an attached layer.
 It may be parted somewhat when a log is freshly peeled but the majority of it is going to be on the inside of the bark rather than the outside of the actual wood.
 I have many freshly peeled elm logs and I can assure you that there is nothing but wood on the outside when the sap is running.
 If the sap is not running the cambium is stuck about the same as tape but it still comes off down to the wood.
 

[tannhillman]

I didn't say that it 'only comes off when seasoned versus when it is freshly peeled' ..I said that if you peel the bark off a freshly cut log then the cambium is left behind, whereas if you fully season a log with the bark on then it is virtually impossible to removed the bark without removing the cambium as well, (you certainly wont leave the cambium fully intact).  That  is my experience having done both methods ! I think that's enough said on the subject. Cheesrs

[PatM]

 I'm just not sure why you think it's going to be left behind on a freshly peeled log.

[tannhillman]

Because it IS left behind on a freshly peeled log, I do it that way all the time, have done for years and that's what happens !

[PatM]

 Since the cambium is actually a single layer of stem cells it seems unlikely that you can actually see if it's there or not.

[WillS]

I'm not sure why you think the MR bows have cambium on them.  Most were worked down slightly, to use the harder outer layer of a sapwood growth ring.  A couple had super tight thin sapwood and the bark was simply removed, in which case SOME tiny traces of inner bark can be seen, but certainly not on the majority.

Here are some pics I took last time I went.  If you can see any cambium/inner bark, point it out in these pics because I must also be mistaken on what "cambium" is.











When compared to this for example, which is a Pacific yew warbow I built recently and left most of the inner bark in place (or is this cambium?)

[Del the cat]

It states in the work done on the MR bows (by Hardy I believe)  that there are traces of cambium on the back of some of the bows.
Your picture of your Pacific Yew warbow is typical of a bow that hasn't had any the sap wood taken down to reduce it's thickness and....
a) Hasn't been meticulously cleaned up. No criticism is  implied as I believe that's exactly what they are talking about on the MR and many of my bows show the same, unless I am being obsessive in prettying them up.
or
b) Hasn't been tillered with the 'underbark' left on to allow it to pop off in one piece, which gives a virtually perfect surface.

I think the main problem with this thread is twofold... one the naming of the layer above the sapwood, as the Hardy MR reference refers to both bast and cambium and I take it the mean the stuff visible in your pic (which in my experience is homogeneous with the thicker corky layer which pops off). It doesn't really matter what we call it in terms of seasoning wood and making bows as long as we understand what we mean.
The other problem is the different experiences with Yew. It is up to the reader who's opinion and advice they take.
As always I only ever offer my first hand experience, and I have no problem with people ignoring it or preferring the experience of others.
I shall in future use a generic rather than specific name for the corky fibrous underbark stuff that pops off.
Del
BTW... nice looking back